The asymmetric synthesis of terminal aziridines by methylene transfer from sulfonium ylides to imines.

PubMed

Kavanagh, Sarah A; Piccinini, Alessandro; Connon, Stephen J

2013-06-07

A new ylide-based protocol for the asymmetric aziridination of imines via methylene transfer has been developed involving the use of a simple chiral sulfonium salt and an organic strong base. A systematic study identified triisopropylphenyl sulfonylimines as optimal substrates for the process. Unexpectedly, hindered C2-symmetric sulfonyl salts incorporating bulky ethers at C-2 and C-5--which had previously been useful in the corresponding epoxidation chemistry--decomposed in these aziridination reactions via competing elimination pathways. Under optimised conditions it was found that a simple salt derived from (2R,5R)-2,5-diisopropyl thiolane could mediate asymmetric methylene transfer to a range of imines with uniformly excellent yields with 19-30% ee. Since this is a similar level of enantiomeric excess to that obtained using these same salts in epoxidation chemistry, it was concluded that if more bulky sulfonium salts could be devised which were resistant to decomposition under the reaction conditions, that highly enantioselective aziridine formation by methylene transfer would be possible.

Stereoselective construction of the 5-hydroxy diazabicyclo[4.3.1]decane-2-one scaffold, a privileged motif for FK506-binding proteins.

PubMed

Bischoff, Matthias; Sippel, Claudia; Bracher, Andreas; Hausch, Felix

2014-10-17

A stereoselective synthesis of a derivatized bicyclic [4.3.1]decane scaffold based on an acyclic precursor is described. The key steps involve a Pd-catalyzed sp(3)-sp(2) Negishi-coupling, an asymmetric Shi epoxidation, and an intramolecular epoxide opening. Representative derivatives of this novel scaffold were synthesized and found to be potent inhibitors of the psychiatric risk factor FKBP51, which bound to FKBP51 with the intended molecular binding mode.

Selected Publications by the NCI Director

Cancer.gov

Dr. Norman Sharpless's written work on cancer research appears in many leading scientific journals, as well as a variety of other publications. This page lists some of the articles published by Dr. Sharpless since becoming NCI director.

Asymmetric epoxidation of unsaturated ketones catalyzed by heterobimetallic rare earth-lithium complexes bearing phenoxy-functionalized chiral diphenylprolinolate ligand.

PubMed

Qian, Qinqin; Tan, Yufang; Zhao, Bei; Feng, Tao; Shen, Qi; Yao, Yingming

2014-09-05

Four novel heterobimetallic complexes [REL2]{[(THF)3Li]2(μ-Cl)} stabilized by chiral phenoxy-functionalized prolinolate (RE = Yb (1), Y (2), Sm (3), Nd (4), H2L = (S)-2,4-di-tert-butyl-6-[[2-(hydroxydiphenylmethyl)pyrrolidin-1-yl]methyl]phenol have been synthesized and characterized. These readily available complexes are highly active in catalyzing the epoxidation of α,β-unsaturated ketones, while the enantioselectivity varies according to the ionic radii of the rare earth center. A series of chalcone derivatives were converted to chiral epoxides in 80 → 99% ee at 0 °C using TBHP as the oxidant in the presence of 10 mol % of 1.

Maximizing the Prospects for Progress Against Cancer

Cancer.gov

The 2018 American Society of Clinical Oncology annual meeting featured numerous, potentially practice changing research findings, according to NCI Director Dr. Norman Sharpless. In this Cancer Currents post, Dr. Sharpless discusses the rapid pace of progress in cancer research.

Blog Posts by the NCI Director Dr. Norman Sharpless

Cancer.gov

NCI Director Dr. Norman Sharpless writes posts regularly for NCI's Cancer Currents Blog that highlight his vision for NCI, meetings with and partnerships in the cancer community, and strategic and scientific initiatives to advance cancer research and care.

Enantioselective syntheses and biological studies of aeruginosin 298-A and its analogs: Application of catalytic asymmetric phase-transfer reaction

PubMed Central

Fukuta, Yuhei; Ohshima, Takashi; Gnanadesikan, Vijay; Shibuguchi, Tomoyuki; Nemoto, Tetsuhiro; Kisugi, Takaya; Okino, Tatsufumi; Shibasaki, Masakatsu

2004-01-01

Aeruginosin 298-A was isolated from the freshwater cyanobacterium Microcystis aeruginosa (NIES-298) and is an equipotent thrombin and trypsin inhibitor. A variety of analogs were synthesized to gain insight into the structure–activity relations. We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogs, in which all stereocenters were controlled by catalytic asymmetric phase-transfer reaction promoted by two-center asymmetric catalysts and catalytic asymmetric epoxidation promoted by a lanthanide–BINOL complex. Furthermore, serine protease inhibitory activities of aeruginosin 298-A and its analogs were examined. PMID:15004282

Enantioselective syntheses and biological studies of aeruginosin 298-A and its analogs: application of catalytic asymmetric phase-transfer reaction.

PubMed

Fukuta, Yuhei; Ohshima, Takashi; Gnanadesikan, Vijay; Shibuguchi, Tomoyuki; Nemoto, Tetsuhiro; Kisugi, Takaya; Okino, Tatsufumi; Shibasaki, Masakatsu

2004-04-13

Aeruginosin 298-A was isolated from the freshwater cyanobacterium Microcystis aeruginosa (NIES-298) and is an equipotent thrombin and trypsin inhibitor. A variety of analogs were synthesized to gain insight into the structure-activity relations. We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogs, in which all stereocenters were controlled by catalytic asymmetric phase-transfer reaction promoted by two-center asymmetric catalysts and catalytic asymmetric epoxidation promoted by a lanthanide-BINOL complex. Furthermore, serine protease inhibitory activities of aeruginosin 298-A and its analogs were examined.

Novel stereocontrolled approach to syn- and anti-oxepene-cyclogeranyl trans-fused polycyclic systems: asymmetric total synthesis of (-)-Aplysistatin, (+)-Palisadin A, (+)-Palisadin B, (+)-12-hydroxy-palisadin B, and the AB ring system of adociasulfate-2 and toxicol A.

PubMed

Couladouros, Elias A; Vidali, Veroniki P

2004-08-06

A new stereocontrolled method for the formation of trans-anti cyclogeranyl-oxepene systems is described. The demanding stereochemistry is secured by stereoselective coupling of a cyclogeranyl tertiary alcohol with a 1,2-unsymmetrically substituted epoxide, while the formation of the highly strained oxepene is achieved employing ring-closing metathesis. Since the stereochemistry of the trans-fused 6,7-ring system is determined by the epoxide, the method also allows the construction of trans-syn 6,7-ring systems. This approach leads to the synthesis of the AB fragment of Adociasulfate-2 and Toxicol A, for the first time. The flexibility and efficiency of the presented strategy is demonstrated by the total asymmetric synthesis of (-)-Aplysistatin, (+)-Palisadin A, (+)-12-hydroxy-Palisadin B, and (+)-Palisadin B, employing two similar key intermediates.

Enantioconvergent biohydrolysis of racemic styrene oxide to R-phenyl-1, 2-ethanediol by a newly isolated filamentous fungus Aspergillus tubingensis TF1.

PubMed

Duarah, Aparajita; Goswami, Amrit; Bora, Tarun C; Talukdar, Madhumita; Gogoi, Binod K

2013-08-01

An effort was made to isolate biocatalysts hydrolyzing epoxides from various ecological niches of northeast India, a biodiversity hot spot zone of the world and screened for epoxide hydrolase activity to convert different racemic epoxides to the corresponding 1, 2-vicinal diols. Screening of a total of 450 microorganisms isolated was carried out using NBP colorimetric assay. One of the strains TF1, after internal transcribed spacer sequence analysis, identified as Aspergillus tubingensis, showed promising enantioconvergent epoxide hydrolase activity. The hydrolysis of unsubstituted styrene oxide (1) occurred to give 97 % ee of R-(-)-1-phenylethane-1, 2-diol (6) with more than 99 % conversion within 45 min incubation. It is shown to be a cheap and practical biocatalyst for one step asymmetric synthesis of chiral R-diol. The other representative substrates (2-5), although underwent hydrolysis with more than 99 % conversion beyond 15 h, exhibited poor enantioselectivity.

Total synthesis and stereochemical assignment of the spiroisoxazoline natural product (+)-calafianin.

PubMed

Bardhan, Sujata; Schmitt, Daniel C; Porco, John A

2006-03-02

Synthesis of the spiroisoxazoline natural product (+)-calafianin is reported using asymmetric nucleophilic epoxidation and nitrile oxide cycloaddition as key steps. Synthesis and spectral analysis of all calafianin stereoisomers led to unambiguous assignment of relative and absolute stereochemistry.

NCI Director Norman E. Sharpless on the Future of Cancer Research | Poster

Cancer.gov

Last week, Director Norman E. “Ned” Sharpless spoke with Paul Goldberg, editor and publisher of The Cancer Letter, regarding his six-month “listening tour,” a project he embarked on after being named the new director, as well as his vision for the National Cancer Institute (NCI).

Sharpless Outlines His Plans for NCI During Spring Town Hall | Poster

Cancer.gov

At the National Cancer Institute (NCI) Spring Town Hall, new director Norman E. “Ned” Sharpless, M.D., summarized his goals for NCI’s role in cancer research. The event, which was held at NCI Shady Grove and livestreamed to eight other major NCI locations, was Sharpless’ first town hall since his six-month “listening and learning tour” concluded.

High specific activity enantiomerically enriched juvenile hormones: synthesis and binding assay.

PubMed Central

Prestwich, G D; Wawrzeńczyk, C

1985-01-01

A stereoselective total synthesis of chiral juvenile hormone I is described that allows stoichiometric introduction of two tritium atoms in the final step. Both optical antipodes of the pivotal epoxy alcohol intermediate were prepared in 95% enantiomeric excess by the Sharpless epoxidation of a (Z)-allylic alcohol. Elaboration of the hydroxy-methyl group to a vinyl group followed by selective homogeneous tritiation affords optically active juvenile hormone I analogs at 58 Ci/mmol. Competitive binding of the labeled 10R, 11S and 10S,11R enantiomers with unlabeled enantiomers to the hemolymph binding protein of Manduca sexta larvae was determined by using a dextran-coated charcoal assay. The natural 10R,11S enantiomer has twice the relative binding affinity of the 10S,11R enantiomer. The availability of such high specific activity optically pure hormones will contribute substantially to the search for high-affinity receptors for juvenile hormones in the nuclei of cells. Moreover, the chiral 12-hydroxy-(10R,11S)-epoxy intermediate allows modification of juvenile hormone for solid-phase biochemical and radioimmunochemical work without altering either the biologically important carbomethoxy or epoxy recognition sites. PMID:3860862

UNC Cancer Center Director to Lead NCI.

PubMed

2017-08-01

President Donald Trump has selected Norman "Ned" Sharpless, MD, director of the University of North Carolina Lineberger Comprehensive Cancer Center, to lead the NCI. The news was met with widespread approval among cancer researchers, who view Sharpless as a strong communicator who can ably represent the needs of the cancer community in the face of proposed funding cuts. ©2017 American Association for Cancer Research.

Progress in aminosugar derived asymmetric organocatalysis.

PubMed

Agarwal, Jyoti

2016-11-22

In the last decade aminosugars, especially d-glucoamine based organocatalysts, have been applied to catalyze various asymmetric reactions such as aldol reactions, Michael addition, Strecker reactions, Biginelli reactions, epoxidation, fluorination, and imine reduction, and for the synthesis of various biologically important molecules such as 3-alkylnitro-2-hydroxynaphthoquinones, trans-dihydrobenzofurans etc. Immense growth has been also observed in the structural modification of aminosugar based organocatalysts to obtain the best results from them. This review sheds light on such organocatalytic transformations reported in last the decade including the effect of the structural modification of sugar amines on their catalytic efficiency and the stereoselectivity of the reaction.

A general protocol for creating high-throughput screening assays for reaction yield and enantiomeric excess applied to hydrobenzoin

PubMed Central

Shabbir, Shagufta H.; Regan, Clinton J.; Anslyn, Eric V.

2009-01-01

A general approach to high-throughput screening of enantiomeric excess (ee) and concentration was developed by using indicator displacement assays (IDAs), and the protocol was then applied to the vicinal diol hydrobenzoin. The method involves the sequential utilization of what we define herein as screening, training, and analysis plates. Several enantioselective boronic acid-based receptors were screened by using 96-well plates, both for their ability to discriminate the enantiomers of hydrobenzoin and to find their optimal pairing with indicators resulting in the largest optical responses. The best receptor/indicator combination was then used to train an artificial neural network to determine concentration and ee. To prove the practicality of the developed protocol, analysis plates were created containing true unknown samples of hydrobenzoin generated by established Sharpless asymmetric dihydroxylation reactions, and the best ligand was correctly identified. PMID:19332790

Molecular recognition and self-assembly special feature: A general protocol for creating high-throughput screening assays for reaction yield and enantiomeric excess applied to hydrobenzoin.

PubMed

Shabbir, Shagufta H; Regan, Clinton J; Anslyn, Eric V

2009-06-30

A general approach to high-throughput screening of enantiomeric excess (ee) and concentration was developed by using indicator displacement assays (IDAs), and the protocol was then applied to the vicinal diol hydrobenzoin. The method involves the sequential utilization of what we define herein as screening, training, and analysis plates. Several enantioselective boronic acid-based receptors were screened by using 96-well plates, both for their ability to discriminate the enantiomers of hydrobenzoin and to find their optimal pairing with indicators resulting in the largest optical responses. The best receptor/indicator combination was then used to train an artificial neural network to determine concentration and ee. To prove the practicality of the developed protocol, analysis plates were created containing true unknown samples of hydrobenzoin generated by established Sharpless asymmetric dihydroxylation reactions, and the best ligand was correctly identified.

Efficient asymmetric hydrolysis of styrene oxide catalyzed by Mung bean epoxide hydrolases in ionic liquid-based biphasic systems.

PubMed

Chen, Wen-Jing; Lou, Wen-Yong; Zong, Min-Hua

2012-07-01

The asymmetric hydrolysis of styrene oxide to (R)-1-phenyl-1,2-ethanediol using Mung bean epoxide hydrolases was, for the first time, successfully conducted in an ionic liquid (IL)-containing biphasic system. Compared to aqueous monophasic system, IL-based biphasic systems could not only dissolve the substrate, but also effectively inhibit the non-enzymatic hydrolysis, and therefore markedly improve the reaction efficiency. Of all the tested ILs, the best results were observed in the biphasic system containing C(4)MIM·PF(6), which exhibited good biocompatibility with the enzyme and was an excellent solvent for the substrate. In the C(4)MIM·PF(6)/buffer biphasic system, it was found that the optimal volume ratio of IL to buffer, reaction temperature, buffer pH and substrate concentration were 1/6, 35°C, 6.5 and 100 mM, respectively, under which the initial reaction rate, the yield and the product e.e. were 18.4 mM/h, 49.4% and 97.0%. The biocatalytic process was shown to be feasible on a 500-mL preparative scale. Copyright © 2011 Elsevier Ltd. All rights reserved.

Natural Optical Activity of Chiral Epoxides: the Influence of Structure and Environment on the Intrinsic Chiroptical Response

NASA Astrophysics Data System (ADS)

Lemler, Paul M.; Craft, Clayton L.; Vaccaro, Patrick

2017-06-01

Chiral epoxides built upon nominally rigid frameworks that incorporate aryl substituents have been shown to provide versatile backbones for asymmetric syntheses designed to generate novel pharmaceutical and catalytic agents. The ubiquity of these species has motivated the present studies of their intrinsic (solvent-free) circular birefringence (CB), the measurement of which serves as a benchmark for quantum-chemical predictions of non-resonant chiroptical behavior and as a beachhead for understanding the often-pronounced mediation of such properties by environmental perturbations (e.g., solvation). The optical rotatory dispersion (or wavelength-resolved CB) of (R)-styrene oxide (R-SO) and (S,S)-phenylpropylene oxide (S-PPO) have been interrogated under ambient solvated and isolated conditions, where the latter efforts exploited the ultrasensitive techniques of cavity ring-down polarimetry. Both of the targeted systems display marked solvation effects as evinced by changes the magnitude and (in the case of R-SO) the sign of the extracted specific optical rotation, with the anomalously large response evoked from S-PPO distinguishing it from other members of the epoxide family. Linear-response calculations of dispersive optical activity have been performed at both density-functional and coupled-cluster levels of theory to unravel the structural and electronic origins of experimental findings, thereby suggesting the possible involvement of hindered torsional motion along dihedral coordinates adjoining phenyl and epoxide moieties.

Synthesis of the ABC tricyclic fragment of the pectenotoxins via stereocontrolled cyclization of a gamma-hydroxyepoxide appended to the AB spiroacetal unit.

PubMed

Halim, Rosliana; Brimble, Margaret A; Merten, Jörn

2006-04-07

The stereocontrolled synthesis of the C1-C16 ABC spiroacetal-containing tricyclic fragment of pectenotoxin-7 6 has been accomplished. The key AB spiroacetal aldehyde 9 was successfully synthesized via acid catalyzed cyclization of protected ketone precursor 28 that was readily prepared from aldehyde 12 and sulfone 13. The syn stereochemistry in aldehyde 12 was installed using an asymmetric aldol reaction proceeding via a titanium enolate. The stereogenic centre in sulfone 13 was derived from (R)-(+)-glycidol. The absolute stereochemistry of the final spiroacetal aldehyde 9 was confirmed by NOE studies establishing the (S)-stereochemistry of the spiroacetal centre. Construction of the tetrahydrofuran C ring system began with Wittig olefination of the AB spiroacetal aldehyde 9 with (carbethoxyethylidene)triphenylphosphorane 10 affording the desired (E)-olefin 32. Appendage of a three carbon chain to the AB spiroacetal fragment was achieved via addition of acetylene 11 to the unstable allylic iodide 39. Epoxidation of (E)-enyne 8 via in situ formation of L-fructose derived dioxirane generated the desired syn-epoxide 36. Semi-hydrogenation of the resulting epoxide 36 followed by dihydroxylation of the alkene effected concomitant cyclization, thus completing the synthesis of the ABC spiroacetal ring fragment 6.

Advancing Patient Care Through Focused Innovation

Cancer.gov

In this Cancer Currents post, NCI Director Dr. Norman Sharpless describes the key areas of opportunity he has identified that, with enhanced attention from NCI, he believes can accelerate progress in cancer research and care.

Concise Stereocontrolled Formal Synthesis of (±)-Quinine and Total Synthesis of (±)-7-Hydroxyquinine via Merged Morita-Baylis-Hillman-Tsuji-Trost Cyclization

PubMed Central

Webber, Peter; Krische, Michael J.

2010-01-01

Concise stereoselective syntheses of (±)-quinine and (±)-7-hydroxyquinine are achieved using a catalytic enone cycloallylation that combines the nucleophilic features of the Morita-Baylis-Hillman reaction and the electrophilic features of the Tsuji-Trost reaction. Cyclization of enone-allyl carbonate 11 delivers the product of cycloallylation 13 in 68% yield. Diastereoselective conjugate reduction of the enone 13 (>20:1 dr) followed by exchange of N-protecting groups provides the saturated N-Boc-protected methyl ketone 19, which upon aldol dehydration provides quinoline containing enone 15, possessing all carbon atoms of quinine. Exposure of ketone 15 to L-selectride enables diastereoselective carbonyl reduction (>20:1 dr) to furnish the allylic alcohol 16. Stereoselective hydroxyl-directed epoxidation using an oxovanadium catalyst modified by N-hydroxy-N-Me-pivalamide delivers epoxide 17 (17:1 dr). Cyclization of the resulting amine-epoxide 17 provides (±)-7-hydroxyquinine in 13 steps and 11% overall yield from aminoacetaldehyde diethyl acetal. Notably, highly stereoselective formation of five contiguous stereocenters is achieved through a series of 1,2-asymmetric induction events. A formal synthesis of (±)-quinine is achieved upon deoxygenation of the N-Cbz-protected allylic acetate 22 to provide olefin 23, which previously has been converted to quinine. Thus, (±)-quinine is accessible in 16 steps and 4% overall yield from commercial aminoacetaldehyde diethyl acetal, making this route the most concise approach to quinine, to date. PMID:18989927

[4 + 3] Cycloaddition of aromatic α,β-unsaturated aldehydes and ketones with epoxides: one-step approach to synthesize seven-membered oxacycles catalyzed by Lewis acid.

PubMed

Zhou, Yu-Qiang; Wang, Nai-Xing; Zhou, Shu-Bao; Huang, Zhong; Cao, Linghua

2011-01-21

A novel intermolecular [4 + 3] cycloaddition method to construct 1,4-dioxide seven-membered oxacycles was developed. This one-step method was carried out in the presence of catalytic amount of (C(2)H(5))(2)OBF(3) under mild conditions. Seven-membered oxacycles and some natural compounds could be easily synthesized via this protocol. Control experiments were carried out and possible mechanism for the reaction was proposed. Asymmetric reactions were proceeded and 3e was obtained with moderate ee value.

Incidence of Cancers of the Lower Stomach Increasing among Younger Americans

MedlinePlus

... by Disqus. blog comments powered by Disqus Featured Posts Advancing Patient Care Through Focused Innovation April 16, 2018, by Norman E. Sharpless, M.D. Study Tests Way to Lower Dose of Prostate Cancer Drug ...

H II REGIONS, EMBEDDED PROTOSTARS, AND STARLESS CORES IN SHARPLESS 2-157

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Chian-Chou; Williams, Jonathan P.; Pandian, Jagadheep D., E-mail: ccchen@ifa.hawaii.edu, E-mail: jpw@ifa.hawaii.edu, E-mail: jagadheep@iist.ac.in

2012-06-20

We present arcsecond resolution 1.4 mm observations of the high-mass star-forming region, Sharpless 2-157, that reveal the cool dust associated with the first stages of star formation. These data are compared with archival images at optical, infrared, and radio wavelengths, and complemented with new arcsecond resolution mid-infrared data. We identify a dusty young H II region, numerous infrared sources within the cluster envelope, and four starless condensations. Three of the cores lie in a line to the south of the cluster peak, but the most massive one is right at the center and associated with a jumble of bright radiomore » and infrared sources. This presents an interesting juxtaposition of high- and low-mass star formation within the same cluster which we compare with similar observations of other high-mass star-forming regions and discuss in the context of cluster formation theory.« less

Asymmetric Synthesis of 1,2,9,9a-Tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI)

PubMed Central

Lajiness, James P.; Boger, Dale L.

2011-01-01

A short, asymmetric synthesis of the 1,2,9,9a-tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI) analogue of the CC-1065 and duocarmycin DNA alkylation subunits is described. Treatment of iodo-epoxide 5, prepared by late-stage alkylation of 4 with (S)-glycidal-3-nosylate, with EtMgBr at room temperature directly provides the optically pure alcohol 6 in 87% yield (99% ee) derived from selective metal–halogen exchange and subsequent regioselective intramolecular 6-endo-tet cyclization. The use of MeMgBr or i-PrMgBr also provides the product in high yields (82–87%), but requires larger amounts of the Grignard reagent to effect metal–halogen exchange and cyclization. Direct transannular spirocyclization of 7 following O-debenzylation of 6 provides N-Boc-CBI. This approach represents the most efficient (9-steps, 31% overall) and effective (99% ee) route to the optically pure CBI alkylation subunit yet described. PMID:21192653

Retooled Award Supports Budding Cancer Researchers

Cancer.gov

In this Cancer Currents post, NCI Director Dr. Norman Sharpless discusses how NCI is retooling a grant mechanism, called the MERIT R37 Award, to help early-stage investigators by extending the length of time they can receive funding under their first independent NIH grant.

NCI Director Norman Sharpless’s ASCO 2018 Remarks

Cancer.gov

In this video, NCI Director Dr. Norman E. Sharpless discusses the future of cancer research at the 2018 American Society of Clinical Oncology (ASCO) annual meeting in Chicago. Learn more about his focus on basic science, workforce development, big data, and clinical trials.

Development of an enantioselective synthetic route to neocarzinostatin chromophore and its use for multiple radioisotopic incorporation.

PubMed

Myers, Andrew G; Glatthar, Ralf; Hammond, Marlys; Harrington, Philip M; Kuo, Elaine Y; Liang, Jun; Schaus, Scott E; Wu, Yusheng; Xiang, Jia-Ning

2002-05-15

A convergent, enantioselective synthetic route to the natural product neocarzinostatin chromophore (1) is described. Synthesis of the chromophore aglycon (2) was targeted initially. Chemistry previously developed for the synthesis of a neocarzinostatin core model (4) failed in the requisite 1,3-transposition of an allylic silyl ether when applied toward the preparation of 2 with use of the more highly oxygenated substrates 27 and 54. An alternative synthetic plan was therefore developed, based upon a proposed reduction of the epoxy alcohol 58 to form the aglycon 2, a transformation that was achieved in a novel manner, using a combination of the reagents triphenylphosphine, iodine, and imidazole. The successful route to 1 and 2 began with the convergent coupling of the epoxydiyne 15, obtained in 9 steps (43% overall yield) from D-glyceraldehyde acetonide, and the cyclopentenone (+)-14, prepared in one step (75-85% yield) from the prostaglandin intermediate (+)-16, affording the alcohol 22 in 80% yield and with > or =20:1 diastereoselectivity. The alcohol 22 was then converted into the epoxy alcohol 58 in 17 steps with an average yield of 92% and an overall yield of 22%. Key features of this sequence include the diastereoselective Sharpless asymmetric epoxidation of allylic alcohol 81 (98% yield); intramolecular acetylide addition within the epoxy aldehyde 82, using Masamune's lithium diphenyltetramethyldisilazide base (85% yield); selective esterification of the diol 84 with the naphthoic acid 13 followed by selective cleavage of the chloroacetate protective group in situ to furnish the naphthoic acid ester 85 in 80% yield; and elimination of the tertiary hydroxyl group within intermediate 88 using the Martin sulfurane reagent (79% yield). Reductive transposition of the product epoxy alcohol (58) then formed neocarzinostatin chromophore aglycon (2, 71% yield). Studies directed toward the glycosylation of 2 focused initially on the preparation of the N-methylamino --> hydroxyl replacement analogue 3, an alpha-D-fucose derivative of neocarzinostatin chromophore, formed in 42% yield by a two-step Schmidt glycosylation-deprotection sequence. For the synthesis of 1, an extensive search for a suitable 2'-N-methylfucosamine glycosyl donor led to the discovery that the reaction of 2 with the trichloroacetimidate 108, containing a free N-methylamino group, formed the alpha-glycoside 114 selectively in the presence of boron trifluoride diethyl etherate. Subsequent deprotection of 114 under mildly acidic conditions then furnished the labile chromophore (1). The synthetic route was readily modified for the preparation of singly and doubly (3)H- and (14)C-labeled 1, compounds unavailable by other means, for studies of the mechanism of action of neocarzinostatin in vivo.

NCI Partners with VA, DoD for Cancer Research

Cancer.gov

Partnerships and collaborations are an important component of NCI’s success. In this Cancer Currents blog post, NCI Director Dr. Norman Sharpless describes three efforts made possible by a memorandum of agreement with three US military institutions: the APOLLO network, NAVIGATE, and BD-STEP.

NCI Director Norman Sharpless’s ASCO 2018 Remarks-The Power and Promise of Cancer Research

Cancer.gov

NCI Director Dr. Norman E. Sharpless discusses the future of cancer research at the 2018 American Society of Clinical Oncology (ASCO) annual meeting in Chicago. Learn more about his focus on basic science, workforce development, big data, and clinical trials.

NCI and the Cancer Community: Focus on Patients Through Innovative Research

Cancer.gov

At the 2018 AACR Annual Meeting , NCI Director Norman Sharpless describes the key focus areas where NCI can be particularly important to the cancer research enterprise on advancing progress and explains how addressing the challenges of the cancer research landscape requires innovative thinking.

Recent progress in asymmetric bifunctional catalysis using multimetallic systems.

PubMed

Shibasaki, Masakatsu; Kanai, Motomu; Matsunaga, Shigeki; Kumagai, Naoya

2009-08-18

The concept of bifunctional catalysis, wherein both partners of a bimolecular reaction are simultaneously activated, is very powerful for designing efficient asymmetric catalysts. Catalytic asymmetric processes are indispensable for producing enantiomerically enriched compounds in modern organic synthesis, providing more economical and environmentally benign results than methods requiring stoichiometric amounts of chiral reagents. Extensive efforts in this field have produced many asymmetric catalysts, and now a number of reactions can be rendered asymmetric. We have focused on the development of asymmetric catalysts that exhibit high activity, selectivity, and broad substrate generality under mild reaction conditions. Asymmetric catalysts based on the concept of bifunctional catalysis have emerged as a particularly effective class, enabling simultaneous activation of multiple reaction components. Compared with conventional catalysts, bifunctional catalysts generally exhibit enhanced catalytic activity and higher levels of stereodifferentiation under milder reaction conditions, attracting much attention as next-generation catalysts for prospective practical applications. In this Account, we describe recent advances in enantioselective catalysis with bifunctional catalysts. Since our identification of heterobimetallic rare earth-alkali metal-BINOL (REMB) complexes, we have developed various types of bifunctional multimetallic catalysts. The REMB catalytic system is effective for catalytic asymmetric Corey-Chaykovsky epoxidation and cyclopropanation. A dinucleating Schiff base has emerged as a suitable multidentate ligand for bimetallic catalysts, promoting catalytic syn-selective nitro-Mannich, anti-selective nitroaldol, and Mannich-type reactions. The sugar-based ligand GluCAPO provides a suitable platform for polymetallic catalysts; structural elucidation revealed that their higher order polymetallic structures are a determining factor for their function in the catalytic asymmetric Strecker reaction. Rational design identified a related ligand, FujiCAPO, which exhibits superior performance in catalytic asymmetric conjugate addition of cyanide to enones and a catalytic asymmetric Diels-Alder-type reaction. The combination of an amide-based ligand with a rare earth metal constitutes a unique catalytic system: the ligand-metal association is in equilibrium because of structural flexibility. These catalytic systems are effective for asymmetric amination of highly coordinative substrate as well as for Mannich-type reaction of alpha-cyanoketones, in which hydrogen bonding cooperatively contributes to substrate activation and stereodifferentiation. Most of the reactions described here generate stereogenic tetrasubstituted carbons or quaternary carbons, noteworthy accomplishments even with modern synthetic methods. Several reactions have been incorporated into the asymmetric synthesis of therapeutics (or their candidate molecules) such as Tamiflu, AS-3201 (ranirestat), GRL-06579A, and ritodrine, illustrating the usefulness of bifunctional asymmetric catalysis.

Chirality transition in the epoxidation of (-)-alpha-pinene and successive hydrolysis studied by Raman optical activity and DFT.

PubMed

Qiu, Shi; Li, Guanna; Liu, Peng; Wang, Changhao; Feng, Zhaochi; Li, Can

2010-03-28

Characterization of the chirality evolution involved in chemical and biochemical reaction processes is extremely important to the understanding of the chiral catalysis mechanism. In this work, the chiral transition from the epoxidation of (-)-alpha-pinene to alpha-pinene oxide and successive hydrolysis to (-)-pinanediol has been studied as an archetype of the asymmetric catalysis by Raman optical activity (ROA) and the DFT calculation. Minor changes of the absolute configuration of the chiral products from (-)-alpha-pinene to (-)-pinanediol lead to the dramatic variation in ROA spectra indicating that the chirality is delocalized in the whole molecule rather than only concentrated on the chiral centers. The oxygen atom of alpha-pinene oxide contributes strong ROA signals while the two hydroxyl groups of (-)-pinanediol give no apparent contribution to the chirality in terms of ROA signals. Isolation of the two symmetric anisotropic invariants shows that the predominant contribution to the ROA signals stems from the electric dipole-magnetic dipole invariant, and the bond polarizability model is indeed found to be a good approximation for molecules composed of entirely axially-symmetric bonds in alpha-pinene oxide and (-)-pinanediol. This study demonstrates the feasibility of using ROA to sensitively monitor the variation of the chirality transition during the chiral reactions either in the chemical or biological system.

Web-Based Instruction: A Guide for Libraries, Third Edition

ERIC Educational Resources Information Center

Smith, Susan Sharpless

2010-01-01

Expanding on the popular, practical how-to guide for public, academic, school, and special libraries, technology expert Susan Sharpless Smith offers library instructors the confidence to take Web-based instruction into their own hands. Smith has thoroughly updated "Web-Based Instruction: A Guide for Libraries" to include new tools and trends,…

Methods for polymer synthesis

DOEpatents

Allen, Scott D.; Simoneau, Christopher A.; Keefe, William D.; Conuel, Jeff R.

2016-12-06

The present invention provides methods for reducing induction periods in epoxide-CO.sub.2 copolymerizations. In certain embodiments, the methods include the step of contacting an epoxide with CO.sub.2 in the presence of two catalysts: an epoxide hydrolysis catalyst and an epoxide CO.sub.2 copolymerization catalyst. In another aspect, the invention provides catalyst compositions comprising a mixture of an epoxide hydrolysis catalyst and an epoxide CO.sub.2 copolymerization catalyst.

Regio- and enantiofacial selectivity of epoxyeicosatrienoic acid hydration by cytosolic epoxide hydrolase.

PubMed

Zeldin, D C; Kobayashi, J; Falck, J R; Winder, B S; Hammock, B D; Snapper, J R; Capdevila, J H

1993-03-25

The hydration of cis-epoxyeicosatrienoic acids to the corresponding vic-dihydroxyeicosatrienoic acids by cytosolic epoxide hydrolase demonstrates moderate regioselectivity with rates of hydration highest for the 14,15-epoxide and lower for the 11,12- and 8,9-epoxide (4.5, 1.6, and 1.5 mumol of product/mg of protein/min, respectively). Incubations of the 8,9- and 14,15-epoxides with cytosolic epoxide hydrolase show stereoselective formation of diols (7:3 and 4:1 ratio of antipodes, respectively) and concomitant chiral enrichment of the remaining unmetabolized substrate. In contrast, hydration of the 11,12-epoxide is nonenantioselective. The Km value of the enzyme for the 14(R),15(S)-epoxide is 3 microM. Incubations of the enantiomerically pure 8,9- and 14,15-epoxides with lung or liver cytosol, followed by chiral analysis of the resulting diols demonstrate selective cleavage of the oxirane ring at C9 and C15, respectively. On the other hand, cleavage of the 11,12- oxirane ring was less selective. The stereochemical preference of the cytosolic epoxide hydrolase, together with the known chiral composition of the endogenous arachidonate epoxide pools, suggests a functional role for this enzyme in the metabolism of these important compounds.

Swelling behaviour in n-pentane and mechanical properties of epoxidized natural rubber with different epoxide content

NASA Astrophysics Data System (ADS)

Kinasih, N. A.; Fathurrohman, M. I.; Winarto, D. A.

2017-07-01

Epoxidized natural rubber (ENR) with different level of epoxidation (i.e. 10, 20, 30, 40 and 50 mol% indicated as ENR ENR10, ENR20, ENR30, ENR40 and ENR50, respectively) were prepared. They were then vulcanized by using efficient system vulcanization. The effect of epoxide content on curing characteristic, swelling and mechanical properties in N-pentane was investigated. The Attenuated Resonance Fourier Transform Infrared (ATR-FTIR) and H-Nuclear Magnetic Resonance (H-NMR) were used to determine the epoxidation level. Glass transition (Tg) of ENR samples was determined by using Direct Scanning Calorimetry (DSC). The result revealed that the resistance of ENR in N-pentane increased with increasing epoxidation level, which indicated by decreasing equilibrium mol uptake and diffusion coefficient. The compression set of ENR and aging resistance increased with increasing epoxide content, except ENR50 was due to ENR 50 have two Tg value. However, the value of hardness and tensile strength were not effected by epoxidation level.

Enzyme-catalyzed cationic epoxide rearrangements in quinolone alkaloid biosynthesis.

PubMed

Zou, Yi; Garcia-Borràs, Marc; Tang, Mancheng C; Hirayama, Yuichiro; Li, Dehai H; Li, Li; Watanabe, Kenji; Houk, K N; Tang, Yi

2017-03-01

Epoxides are highly useful synthons and biosynthons for the construction of complex natural products during total synthesis and biosynthesis, respectively. Among enzyme-catalyzed epoxide transformations, a reaction that is notably missing, in regard to the synthetic toolbox, is cationic rearrangement that takes place under strong acid. This is a challenging transformation for enzyme catalysis, as stabilization of the carbocation intermediate upon epoxide cleavage is required. Here, we discovered two Brønsted acid enzymes that can catalyze two unprecedented epoxide transformations in biology. PenF from the penigequinolone pathway catalyzes a cationic epoxide rearrangement under physiological conditions to generate a quaternary carbon center, while AsqO from the aspoquinolone pathway catalyzes a 3-exo-tet cyclization to forge a cyclopropane-tetrahydrofuran ring system. The discovery of these new epoxide-modifying enzymes further highlights the versatility of epoxides in complexity generation during natural product biosynthesis.

Prediction of metabolites of epoxidation reaction in MetaTox.

PubMed

Rudik, A V; Dmitriev, A V; Bezhentsev, V M; Lagunin, A A; Filimonov, D A; Poroikov, V V

2017-10-01

Biotransformation is a process of the chemical modifications which may lead to the reactive metabolites, in particular the epoxides. Epoxide reactive metabolites may cause the toxic effects. The prediction of such metabolites is important for drug development and ecotoxicology studies. Epoxides are formed by some oxidation reactions, usually catalysed by cytochromes P450, and represent a large class of three-membered cyclic ethers. Identification of molecules, which may be epoxidized, and indication of the specific location of epoxide functional group (which is called SOE - site of epoxidation) are important for prediction of epoxide metabolites. Datasets from 355 molecules and 615 reactions were created for training and validation. The prediction of SOE is based on a combination of LMNA (Labelled Multilevel Neighbourhood of Atom) descriptors and Bayesian-like algorithm implemented in PASS software and MetaTox web-service. The average invariant accuracy of prediction (AUC) calculated in leave-one-out and 20-fold cross-validation procedures is 0.9. Prediction of epoxide formation based on the created SAR model is included as the component of MetaTox web-service ( http://www.way2drug.com/mg ).

ZINClick: a database of 16 million novel, patentable, and readily synthesizable 1,4-disubstituted triazoles.

PubMed

Massarotti, Alberto; Brunco, Angelo; Sorba, Giovanni; Tron, Gian Cesare

2014-02-24

Since Professors Sharpless, Finn, and Kolb first introduced the concept of "click reactions" in 2001 as powerful tools in drug discovery, 1,4-disubstituted-1,2,3-triazoles have become important in medicinal chemistry due to the simultaneous discovery by Sharpless, Fokin, and Meldal of a perfect click 1,3-dipolar cycloaddition reaction between azides and alkynes catalyzed by copper salts. Because of their chemical features, these triazoles are proposed to be aggressive pharmacophores that participate in drug-receptor interactions while maintaining an excellent chemical and metabolic profile. Surprisingly, no virtual libraries of 1,4-disubstituted-1,2,3-triazoles have been generated for the systematic investigation of the click-chemical space. In this manuscript, a database of triazoles called ZINClick is generated from literature-reported alkynes and azides that can be synthesized within three steps from commercially available products. This combinatorial database contains over 16 million 1,4-disubstituted-1,2,3-triazoles that are easily synthesizable, new, and patentable! The structural diversity of ZINClick ( http://www.symech.it/ZINClick ) will be explored. ZINClick will also be compared to other available databases, and its application during the design of novel bioactive molecules containing triazole nuclei will be discussed.

40 CFR 721.2675 - Perfluoroalkyl epoxide (generic name).

Code of Federal Regulations, 2010 CFR

2010-07-01

... Substances § 721.2675 Perfluoroalkyl epoxide (generic name). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as perfluoroalkyl epoxide (PMN P... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Perfluoroalkyl epoxide (generic name...

40 CFR 721.2675 - Perfluoroalkyl epoxide (generic name).

Code of Federal Regulations, 2011 CFR

2011-07-01

... Substances § 721.2675 Perfluoroalkyl epoxide (generic name). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as perfluoroalkyl epoxide (PMN P... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Perfluoroalkyl epoxide (generic name...

40 CFR 721.2675 - Perfluoroalkyl epoxide (generic name).

Code of Federal Regulations, 2013 CFR

2013-07-01

... Substances § 721.2675 Perfluoroalkyl epoxide (generic name). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as perfluoroalkyl epoxide (PMN P... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Perfluoroalkyl epoxide (generic name...

40 CFR 721.2675 - Perfluoroalkyl epoxide (generic name).

Code of Federal Regulations, 2012 CFR

2012-07-01

... Substances § 721.2675 Perfluoroalkyl epoxide (generic name). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as perfluoroalkyl epoxide (PMN P... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Perfluoroalkyl epoxide (generic name...

40 CFR 721.2675 - Perfluoroalkyl epoxide (generic name).

Code of Federal Regulations, 2014 CFR

2014-07-01

... Substances § 721.2675 Perfluoroalkyl epoxide (generic name). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as perfluoroalkyl epoxide (PMN P... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Perfluoroalkyl epoxide (generic name...

Research Results

NASA Astrophysics Data System (ADS)

2012-12-01

Achievements in Sino-German Interdisciplinary Major Research Project Published by Small A Conserved Proline Switch on the Ribosome Facilitates the Recruitment and Binding of trGTPases Air Pollution Contributes in Sunshine Dimming in China Role of Lymphatic Trafficking and Biodistribution Soft Fibrin Gels Promote Selection and Growth of Tumorigenic Cells Targeted Therapy: The New Lease on Life for Acute Promyelocytic Leukemia, and Beyond The Structural Basis for the Sensing and Binding of Cyclic di-GMP by STING Research on Atomic-Scale Investigation of Li Storage Mechanism in Spinel Li4Ti5O12 NSFC Funded Project Made Significant Progress in Intelligent Nanomaterial and Device Palaeobotany and the Evolution of the Monsoon in China Non Heme System Asymmetric Epoxidation Reaction Made Progress Rapid Advancement of Immunology Study in China Chinese Experts Successfully Produced Transgenic Animals from Haploid Embryonic Stem Cells

Preferential glutathione conjugation of a reverse diol epoxide compared to a bay region diol epoxide of phenanthrene in human hepatocytes: relevance to molecular epidemiology studies of glutathione-s-transferase polymorphisms and cancer.

PubMed

Hecht, Stephen S; Berg, Jeannette Zinggeler; Hochalter, J Bradley

2009-03-16

Bay region diol epoxides are recognized ultimate carcinogens of polycyclic aromatic hydrocarbons (PAH), and in vitro studies have demonstrated that they can be detoxified by conjugation with glutathione, leading to the widely investigated hypothesis that individuals with low activity forms of glutathione-S-transferases are at higher risk of PAH induced cancer, a hypothesis that has found at most weak support in molecular epidemiology studies. A weakness in this hypothesis was that the mercapturic acids resulting from the conjugation of PAH bay region diol epoxides had never been identified in human urine. We recently analyzed smokers' urine for mercapturic acids derived from phenanthrene, the simplest PAH with a bay region. The only phenanthrene diol epoxide-derived mercapturic acid in smokers' urine was produced from the reverse diol epoxide, anti-phenanthrene-3,4-diol-1,2-epoxide (11), not the bay region diol epoxide, anti-phenanthrene-1,2-diol-3,4-epoxide (10), which does not support the hypothesis noted above. In this study, we extended these results by examining the conjugation of phenanthrene metabolites with glutathione in human hepatocytes. We identified the mercapturic acid N-acetyl-S-(r-4,t-2,3-trihydroxy-1,2,3,4-tetrahydro-c-1-phenanthryl)-L-cysteine (14a), (0.33-35.9 pmol/mL at 10 microM 8, 24 h incubation, N = 10) in all incubations with phenanthrene-3,4-diol (8) and the corresponding diol epoxide 11, but no mercapturic acids were detected in incubations with phenanthrene-1,2-diol (7), and only trace amounts were observed in incubations with the corresponding bay region diol epoxide 10. Taken together with our previous results, these studies clearly demonstrate that glutathione conjugation of a reverse diol epoxide of phenanthrene is favored over conjugation of a bay region diol epoxide. Since reverse diol epoxides of PAH are generally weakly or nonmutagenic/carcinogenic, these results, if generalizable to other PAH, do not support the widely held assumption that glutathione-S-transferases are important in the detoxification of PAH in humans.

Formation of furan fatty alkyl esters from their bis-epoxide fatty esters

USDA-ARS?s Scientific Manuscript database

Epoxidation of vegetable oils and consecutive epoxide ring-opening reaction is a widely investigated path for producing biobased lubricants and polymers. The reaction mechanism and products are considered well-studied and known. In the current study, the reactions of epoxidized alkyl soyate with fou...

40 CFR 721.10210 - Soybean oil, epoxidized, reaction products with diethanolamine.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Soybean oil, epoxidized, reaction... Significant New Uses for Specific Chemical Substances § 721.10210 Soybean oil, epoxidized, reaction products... chemical substance identified as soybean oil, epoxidized, reaction products with diethanolamine (PMN P-09...

Epoxide hydrolases: structure, function, mechanism, and assay.

PubMed

Arand, Michael; Cronin, Annette; Adamska, Magdalena; Oesch, Franz

2005-01-01

Epoxide hydrolases are a class of enzymes important in the detoxification of genotoxic compounds, as well as in the control of physiological signaling molecules. This chapter gives an overview on the function, structure, and enzymatic mechanism of structurally characterized epoxide hydrolases and describes selected assays for the quantification of epoxide hydrolase activity.

Sulfuric acid as a catalyst for ring-opening of biobased bis-epoxides

USDA-ARS?s Scientific Manuscript database

Vegetable oils can be relatively and easily transformed into bio-based epoxides. Because of this, the acid-catalyzed epoxide ring-opening has been explored for the preparation of bio-based lubricants and polymers. Detailed model studies are carried out only with mono-epoxide made from methyl oleate,...

Cu-catalyzed cross-coupling reactions of epoxides with organoboron compounds.

PubMed

Lu, Xiao-Yu; Yang, Chu-Ting; Liu, Jing-Hui; Zhang, Zheng-Qi; Lu, Xi; Lou, Xin; Xiao, Bin; Fu, Yao

2015-02-11

A copper-catalyzed cross-coupling reaction of epoxides with arylboronates is described. This reaction is not limited to aromatic epoxides, because aliphatic epoxides are also suitable substrates. In addition, N-sulfonyl aziridines can be successfully converted into the products. This reaction provides convenient access to β-phenethyl alcohols, which are valuable synthetic intermediates.

The effects of metyrapone, chalcone epoxide, benzil, clotrimazole and related compounds on the activity of microsomal epoxide hydrolase in situ, in purified form and in reconstituted systems towards different substrates.

PubMed

Seidegård, J; DePierre, J W; Guenthner, T M; Oesch, F

1986-09-01

The influence of metyrapone, chalcone epoxide, benzil and clotrimazole on the activity of microsomal epoxide hydrolase towards styrene oxide, benzo[a]pyrene 4,5-oxide, estroxide and androstene oxide was investigated. The studies were performed using liver microsomes from rats, rabbits, mice and humans; epoxide hydrolase purified from rat liver microsomes to apparent homogeneity; and the purified enzyme incorporated into liposomes composed of egg-yolk phosphatidylcholine or total rat liver microsomal lipids. All four effectors were found to activate the hydrolysis of styrene oxide by epoxide hydrolase in situ in rat liver microsomal membranes, in agreement with earlier findings. Epoxide hydrolase activity towards styrene oxide in liver microsomes from mouse, rabbit and man was also increased by all four effectors. The most striking effect was a 680% activation by clotrimazole in rat liver microsomes. However, none of the effectors activated microsomal epoxide hydrolase more than 50% when benzo[a]pyrene 4,5-oxide, estroxide or androstene oxide was used as substrate. Indeed, clotrimazole was found to inhibit microsomal epoxide hydrolase activity towards estroxide 30-50% and towards androstene oxide 60-90%. The effects of these four compounds were found to be virtually identical in the preparations from rats, rabbits, mice and humans. The effects of metyrapone, chalcone epoxide, benzil and clotrimazole on purified epoxide hydrolase were qualitatively the same as those on epoxide hydrolase in intact microsomes, but much smaller in magnitude. These effects were increased in magnitude only slightly by incorporation of the purified enzyme into liposomes made from egg-yolk phosphatidylcholine. However, when incorporation into liposomes composed of total microsomal lipids was performed, the effects seen were essentially of the same magnitude as with intact microsomes. When the extent of activation was plotted against effector concentration, three different patterns were found with different effectors. Activation of epoxide hydrolase activity towards styrene oxide by clotrimazole was found to be uncompetitive with the substrate and highly structure specific. On the other hand, inhibition of epoxide hydrolase activity towards androstene oxide by clotrimazole was found to be competitive in microsomes. It is concluded that the marked effects of these four modulators on microsomal epoxide hydrolase activity are due to an interaction with the enzyme protein itself, but that the presence of total microsomal phospholipids allows the maximal expression leading to similar degrees of modulation as those observed in intact microsomes.(ABSTRACT TRUNCATED AT 400 WORDS)

Regiospecific Epoxidation of Carvone: A Discovery-Oriented Experiment for Understanding the Selectivity and Mechanism of Epoxidation Reactions

ERIC Educational Resources Information Center

Mak, Kendrew K. W.; Lai, Y. M.; Siu, Yuk-Hong

2006-01-01

This article describes a discovery-oriented experiment for demonstrating the selectivity of two epoxidation reactions. Peroxy acids and alkaline H[subscript 2]O[subscript 2] are two commonly used reagents for alkene epoxidation. The former react preferentially with electron-rich alkenes while the latter works better with alpha,beta-unsaturated…

In Silico Study and Cytotoxicity of the Synthesized Open-chain Analogues of Antimycin A3 Against HEP-2 Laryngeal Cancer Cells

PubMed Central

Arsianti, Ade; Fadilah, Fadilah; Kusmardi, Kusmardi; Sugiarta, Gede Y.; Tanimoto, Hiroki; Kakiuchi, Kiyomi

2017-01-01

Background: Laryngeal cancers affect one quarter of all head and neck cancers. Chemotherapy is a standard method in treatment laryngeal carcinoma. How-ever, cancer chemotherapy is often a failure due to the appearance of drug resistance. This fact suggests that the search for novel, safe, and more effective laryngeal cancer drugs are required. Antimycin A3 is a fit ligand of anti-apoptotic Bcl-2. While Bcl-2 is known to be over-expressed in laryngeal cancer cell, it is quite reasonable to expect an-timycin A3 and its analogue to induce apoptosis in those cells. Methods: With this viewpoint, we decided to conduct research that is aimed to evaluate cytotoxic activity of the synthesized open-chain analogues of antimycin A3 against HEP-2 laryngeal cancer cells, as well as to conduct in silico study of the analogues on receptor binding target Bcl-2 of laryngeal cancer. Results and Conclusion: Open-chain analogues of antimycin A3 were successfully syn-thesized in a good yield from Boc-L-Threonine by esterification, amidation, and Sharp-less asymmetric dihydroxylation. Consistent with in silico study, the analogues exhibited a greater anticancer activity against laryngeal HEP-2 cells than the original antimycin A3 with IC50 ranging of 31.6 µM to 46.3 µM. Our results clearly demonstrate that the open-chain analogues of an-timycin A3 as a promising candidates of new anti-laryngeal cancer agents.

Copper-catalyzed cross-coupling reactions of epoxides with gem-diborylmethane: access to γ-hydroxyl boronic esters.

PubMed

Ebrahim-Alkhalil, Ahmed; Zhang, Zhen-Qi; Gong, Tian-Jun; Su, Wei; Lu, Xiao-Yu; Xiao, Bin; Fu, Yao

2016-04-07

Herein, we describe a novel copper-catalyzed epoxide opening reaction with gem-diborylmethane. Aliphatic, aromatic epoxides as well as aziridines are converted to the corresponding γ-pinacolboronate alcohols or amines in moderate to excellent yields. This new reaction provides beneficial applications for classic epoxide substrates as well as interesting gem-diborylalkane reagents.

Sharpless-76E: astrometry and outflows in a protostellar cluster

NASA Astrophysics Data System (ADS)

Chibueze, James O.; Hamabata, Hideo; Nagayama, Takumi; Omodaka, Toshihiro; Handa, Toshihiro; Sunada, Kazuyoshi; Nakano, Makoto; Ueno, Yuji

2017-04-01

Using VLBI Exploration of Radio Astrometry, we have conducted multi-epoch observations of the H2O masers associated with Sharpless 76E. The measured annual parallax is 0.521 ± 0.024 mas corresponding to the distance of 1.92^{+0.09}_{-0.08} kpc. From the parallax measurement, we obtained the peculiar motion of Sh2-76EMM1 (UMM1, VMM1, WMM1) to be (-9 ± 3, 10 ± 4, 6 ± 4) km s-1and Sh2-76EMM2 (UMM2, VMM2, WMM2) to be (-5 ± 12, 3 ± 14, -21 ± 22) km s-1, where U, V and W are directed towards the Galactic Centre, in the direction of Galactic rotation and towards the Galactic north pole, respectively. The internal motion of the H2O masers trace two separate bipolar outflows, one associated with Sh2-76EMM1 and the other with Sh2-76EMM2. The spectral energy distribution (SED) of Sh2-76EMM1 suggests it to be a class I YSO. We have only limited data points for the SED fit of Sh2-76EMM2, therefore can only speculate it to be probably a class II based on its comparative K-band and H-band magnitudes.

Versatile Synthesis of Stable, Functional Polypeptides via Reaction with Epoxides.

PubMed

Gharakhanian, Eric G; Deming, Timothy J

2015-06-08

Methodology was developed for efficient alkylation of methionine residues using epoxides as a general strategy to introduce a wide range of functional groups onto polypeptides. Use of a spacer between epoxide and functional groups further allowed addition of sterically demanding functionalities. Contrary to other methods to alkylate methionine residues, epoxide alkylations allow the reactions to be conducted in wet protic media and give sulfonium products that are stable against dealkylation. These functionalizations are notable since they are chemoselective, utilize stable and readily available epoxides, and allow facile incorporation of an unprecedented range of functional groups onto simple polypeptides using stable linkages.

Epoxide hydrolase-lasalocid a structure provides mechanistic insight into polyether natural product biosynthesis.

PubMed

Wong, Fong T; Hotta, Kinya; Chen, Xi; Fang, Minyi; Watanabe, Kenji; Kim, Chu-Young

2015-01-14

Biosynthesis of some polyether natural products involves a kinetically disfavored epoxide-opening cyclic ether formation, a reaction termed anti-Baldwin cyclization. One such example is the biosynthesis of lasalocid A, an ionophore antibiotic polyether. During lasalocid A biosynthesis, an epoxide hydrolase, Lsd19, converts the bisepoxy polyketide intermediate into the tetrahydrofuranyl-tetrahydropyran product. We report the crystal structure of Lsd19 in complex with lasalocid A. The structure unambiguously shows that the C-terminal domain of Lsd19 catalyzes the intriguing anti-Baldwin cyclization. We propose a general mechanism for epoxide selection by ionophore polyether epoxide hydrolases.

Substrate specificity of the violaxanthin de-epoxidase of the primitive green alga Mantoniella squamata (Prasinophyceae).

PubMed

Goss, Reimund

2003-09-01

The substrate specificity of the enzyme violaxanthin de-epoxidase (VDE) of the primitive green alga Mantoniella squamata (Prasinophyceae) was tested in in vitro enzyme assays employing the following xanthophyll mono-epoxides: antheraxanthin (Ax), diadinoxanthin (Ddx), lutein-epoxide (LE), cryptoxanthin-epoxide (CxE), 9- cis neoxanthin (cNx), all- trans neoxanthin (Nx), and xanthophyll di-epoxides: 9- cis violaxanthin (cVx), all- trans violaxanthin (Vx), cryptoxanthin-di-epoxide (CxDE). The data presented in this study show that the VDE of M. squamata not only exhibits a low affinity for the mono-epoxide Ax, as has been reported by R. Frommolt et al. (2001, Planta 213:446-456), but has a reduced substrate affinity for the mono-epoxides Ddx, LE, CxE, and Nx as well. On the other hand, xanthophylls with a second epoxy-group (Vx, CxDE) can be de-epoxidized with a higher efficiency. Such a preference for xanthophyll di-epoxides cannot be observed for the higher-plant VDE, where, in general, no marked differences in the pigment de-epoxidation rates between xanthophyll mono- and di-epoxides are visible. Despite this substantial difference between the VDEs of M. squamata and S. oleracea there are also features common to both enzymes. Neither VDE is able to convert xanthophylls with a 9- cis configuration in the acyclic polyene chain and both rely on substrates in the all- trans configuration. Both enzymes furthermore exhibit a dependence of enzyme activity on the polarity of the substrate. Highly polar (Nx) or non-polar (CxE) xanthophylls are de-epoxidized with greatly reduced rates in comparison to substrates with an intermediate polarity (Vx, Ax, LE, Ddx). This dependence on substrate polarity becomes more obvious when the higher-plant VDE is examined, as the substrate affinity of the VDE of M. squamata is more strongly influenced by the existence or absence of a second epoxy-group. In summary, the data presented in this study underline the fact that different VDEs, although in general catalyzing the same reaction sequence, are functionally diverse.

Modeling of Toxicity-Relevant Electrophilic Reactivity for Guanine with Epoxides: Estimating the Hard and Soft Acids and Bases (HSAB) Parameter as a Predictor.

PubMed

Zhang, Jing; Wang, Chenchen; Ji, Li; Liu, Weiping

2016-05-16

According to the electrophilic theory in toxicology, many chemical carcinogens in the environment and/or their active metabolites are electrophiles that exert their effects by forming covalent bonds with nucleophilic DNA centers. The theory of hard and soft acids and bases (HSAB), which states that a toxic electrophile reacts preferentially with a biological macromolecule that has a similar hardness or softness, clarifies the underlying chemistry involved in this critical event. Epoxides are hard electrophiles that are produced endogenously by the enzymatic oxidation of parent chemicals (e.g., alkenes and PAHs). Epoxide ring opening proceeds through a SN2-type mechanism with hard nucleophile DNA sites as the major facilitators of toxic effects. Thus, the quantitative prediction of chemical reactivity would enable a predictive assessment of the molecular potential to exert electrophile-mediated toxicity. In this study, we calculated the activation energies for reactions between epoxides and the guanine N7 site for a diverse set of epoxides, including aliphatic epoxides, substituted styrene oxides, and PAH epoxides, using a state-of-the-art density functional theory (DFT) method. It is worth noting that these activation energies for diverse epoxides can be further predicted by quantum chemically calculated nucleophilic indices from HSAB theory, which is a less computationally demanding method than the exacting procedure for locating the transition state. More importantly, the good qualitative/quantitative correlations between the chemical reactivity of epoxides and their bioactivity suggest that the developed model based on HSAB theory may aid in the predictive hazard evaluation of epoxides, enabling the early identification of mutagenicity/carcinogenicity-relevant SN2 reactivity.

Probing Competitive and Co-operative Hydroxyl and Ammonium Hydrogen-Bonding Directed Epoxidations.

PubMed

Brambilla, Marta; Brennan, Méabh B; Csatayová, Kristína; Davies, Stephen G; Fletcher, Ai M; Kennett, Alice M R; Lee, James A; Roberts, Paul M; Russell, Angela J; Thomson, James E

2017-10-06

The diastereoselectivities and rates of epoxidation (upon treatment with Cl 3 CCO 2 H then m-CPBA) of a range of cis- and trans-4-aminocycloalk-2-en-1-ol derivatives (containing five-, six-, and seven-membered rings) have been investigated. In all cases where the two potential directing groups can promote epoxidation on opposite faces of the ring scaffold, evidence of competitive epoxidation pathways, promoted by hydrogen-bonding to either the in situ formed ammonium moiety or the hydroxyl group, was observed. In contrast to the relative directing group abilities already established for the six-membered ring system (NHBn ≫ OH > NBn 2 ), an N,N-dibenzylammonium moiety appeared more proficient than a hydroxyl group at directing the stereochemical course of the epoxidation reaction in a five- or seven-membered system. In the former case, this was rationalized by the drive to minimize torsional strain in the transition state being coupled with assistance from hydrogen-bonding to the ammonium moiety. In the latter case, this was ascribed to the steric bulk of the ammonium moiety disfavoring conformations in which hydrogen-bonding to the hydroxyl group results in direction of the epoxidation to the syn face. In cases where the two potential directing groups can promote epoxidation on the same face of the ring scaffold, an enhancement of epoxidation diastereoselectivity was not observed, while introduction of a second, allylic heteroatom to the substrate results in diminishment of the rate of epoxidation in all cases. Presumably, reduction of the nucleophilicity of the olefin by the second, inductively electron-withdrawing heteroatom is the dominant factor, and any assistance to the epoxidation reaction by the potential to form hydrogen-bonds to two directing groups rather than one is clearly unable to overwhelm it.

The rabbit liver microsomal biotransformation of 1,1-dialkylethylenes: enantioface selection of epoxidation and enantioselectivity of epoxide hydrolysis.

PubMed

Bellucci, G; Chiappe, C; Cordoni, A; Marioni, F

1994-01-01

The rabbit liver microsomal biotransformation of alpha-methylstyrene (1a), 2-methyl-1-hexene (1b), 2,4,4-trimethyl-1-pentene (1c), and 1,3,3-trimethyl-1-butene (1d) has been investigated with the aim at establishing the enantioface selection of the cytochrome P-450-promoted epoxidation of the double bond and the enantioselectivity of microsomal epoxide hydrolase(mEH)-catalyzed hydrolysis of the resulting epoxides. GLC on a Chiraldex G-TA (ASTEC) column was used to determine the enantiomeric composition of the products. The epoxides 2 first produced in incubations carried out in the presence of an NADPH regenerating system were not detected, being rapidly hydrolyzed by mEH to diols 3. The enantiomeric composition of the latter showed that no enantioface selection occurred in the epoxidation of 1c and 1d, and a very low (8%) ee of the (R)-epoxide was formed from 1b. Incubation of racemic epoxides 2b-d with the microsomal fraction showed that the mEH-catalyzed hydrolysis of 2c and 2d was practically nonenantioselective, while that of 2b exhibited a selectivity E = 4.9 favoring the hydrolysis of the (S)-enantiomer. A comparison of these results with those previously obtained for linear and branched chain alkyl monosubstituted oxiranes shows that the introduction of the second alkyl substituent suppresses the selectivity of the mEH reaction of the latter and reverses that of the former substrates.

Sequential enzymatic epoxidation involved in polyether lasalocid biosynthesis.

PubMed

Minami, Atsushi; Shimaya, Mayu; Suzuki, Gaku; Migita, Akira; Shinde, Sandip S; Sato, Kyohei; Watanabe, Kenji; Tamura, Tomohiro; Oguri, Hiroki; Oikawa, Hideaki

2012-05-02

Enantioselective epoxidation followed by regioselective epoxide opening reaction are the key processes in construction of the polyether skeleton. Recent genetic analysis of ionophore polyether biosynthetic gene clusters suggested that flavin-containing monooxygenases (FMOs) could be involved in the oxidation steps. In vivo and in vitro analyses of Lsd18, an FMO involved in the biosynthesis of polyether lasalocid, using simple olefin or truncated diene of a putative substrate as substrate mimics demonstrated that enantioselective epoxidation affords natural type mono- or bis-epoxide in a stepwise manner. These findings allow us to figure out enzymatic polyether construction in lasalocid biosynthesis. © 2012 American Chemical Society

Epoxide reduction with hydrazine on graphene: a first principles study.

PubMed

Kim, Min Chan; Hwang, Gyeong S; Ruoff, Rodney S

2009-08-14

Mechanisms for epoxide reduction with hydrazine on a single-layer graphene sheet are examined using quantum mechanical calculations within the framework of gradient-corrected spin-polarized density-functional theory. We find that the reduction reaction is mainly governed by epoxide ring opening which is initiated by H transfer from hydrazine or its derivatives. In addition, our calculations suggest that the epoxide reduction by hydrazine may predominantly follow a direct Eley-Rideal mechanism rather than a Langmuir-Hinshelwood mechanism. We also discuss the generation of various hydrazine derivatives during the reduction of graphene oxide with hydrazine and their potential contribution to lowering the barrier height of epoxide ring opening.

Catalytic Efficiency of Titanium Dioxide (TiO2) and Zeolite ZSM-5 Catalysts in the in-situ Epoxidation of Palm Olein

NASA Astrophysics Data System (ADS)

Yunus, M. Z. Mohd; Jamaludin, S. K.; Abd. Karim, S. F.; Gani, A. Abd; Sauki, A.

2018-05-01

Titanium dioxide and zeolite ZSM-5 are the commonly used heterogeneous catalysts in many chemical reactions. They have several advantages such as low cost and environmental friendly. In this study, titanium dioxide and zeolite ZSM-5 act as catalyst in the in-situ epoxidation of palm olein. Epoxidation of palm olein was carried out by using in-situ generated performic acid to produce epoxidized palm olein in a semi-batch reactor at different temperatures (45°C and 60°C) and agitation speed of 400 rpm. The effects of both catalysts are studied to compare their efficiency in catalyzing the in-situ epoxidation. Epoxidized palm olein was analyzed by using percent of relative conversion to oxirane (RCO%) and fourier transform infrared spectroscopy (FTIR). Surface area of the catalysts used were then characterized by using BET. The results indicated that titanium dioxide is a better catalyst in the in-situ epoxidation of palm olein since it provides higher RCO% compared to Zeolite ZSM-5 at 45°C.

Epoxidation of Short-Chain Alkenes by Resting-Cell Suspensions of Propane-Grown Bacteria

PubMed Central

Hou, Ching T.; Patel, Ramesh; Laskin, Allen I.; Barnabe, Nancy; Barist, Irene

1983-01-01

Sixteen new cultures of propane-utilizing bacteria were isolated from lake water from Warinanco Park, Linden, N.J. and from lake and soil samples from Bayway Refinery, Linden, N.J. In addition, 19 known cultures obtained from culture collections were also found to be able to grow on propane as the sole carbon and energy source. In addition to their ability to oxidize n-alkanes, resting-cell suspensions of both new cultures and known cultures grown on propane oxidize short-chain alkenes to their corresponding 1,2-epoxides. Among the substrate alkenes, propylene was oxidized at the highest rate. In contrast to the case with methylotrophic bacteria, the product epoxides are further metabolized. Propane and other gaseous n-alkanes inhibit the epoxidation of propylene. The optimum conditions for in vivo epoxidation are described. Results from inhibition studies indicate that a propane monooxygenase system catalyzes both the epoxidation and hydroxylation reactions. Experiments with cell-free extracts show that both hydroxylation and epoxidation activities are located in the soluble fraction obtained after 80,000 × g centrifugation. PMID:16346338

Ultrasound-assisted chemoenzymatic epoxidation of soybean oil by using lipase as biocatalyst.

PubMed

Bhalerao, Machhindra S; Kulkarni, Vaishali M; Patwardhan, Anand V

2018-01-01

The present work reports the use of ultrasonic irradiation for enhancing lipase catalyzed epoxidation of soybean oil. Higher degree of unsaturated fatty acids, present in the soybean oil was converted to epoxidized soybean oil by using an immobilized lipase, Candida antarctica (Novozym 435). The effects of various parameters on the relative percentage conversion of the double bond to oxirane oxygen were investigated and the optimum conditions were established. The parameters studied were temperature, hydrogen peroxide to ethylenic unsaturation mole ratio, stirring speed, solvent ratio, catalyst loading, ultrasound frequency, ultrasound input power and duty cycle. The main objective of this work was to intensify chemoenzymatic epoxidation of the soybean oil by using ultrasound, to reduce the time required for epoxidation. Epoxidation of the soybean oil was achieved under mild reaction conditions by indirect ultrasonic irradiations (using ultrasonic bath). The relative percentage conversion to oxirane oxygen of 91.22% was achieved within 5h. The lipase was remarkably stable under optimized reaction conditions, later was recovered and reused six times to produce epoxidized soybean oil (ESO). Copyright © 2017 Elsevier B.V. All rights reserved.

Epoxide Hydrolase Conformational Heterogeneity for the Resolution of Bulky Pharmacologically Relevant Epoxide Substrates.

PubMed

Serrano-Hervás, Eila; Casadevall, Guillem; Garcia-Borràs, Marc; Feixas, Ferran; Osuna, Sílvia

2018-04-06

The conformational landscape of Bacillus megaterium epoxide hydrolase (BmEH) and how it is altered by mutations that confer the enzyme the ability to accept bulky epoxide substrates has been investigated. Extensive molecular dynamics (MD) simulations coupled to active site volume calculations have unveiled relevant features of the enzyme conformational dynamics and function. Our long-timescale MD simulations identify key conformational states not previously observed by means of X-ray crystallography and short MD simulations that present the loop containing one of the catalytic residues, Asp239, in a wide-open conformation, which is likely involved in the binding of the epoxide substrate. Introduction of mutations M145S and F128A dramatically alters the conformational landscape of the enzyme. These singly mutated variants can accept bulky epoxide substrates due to the disorder induced by mutation in the α-helix containing the catalytic Tyr144 and some parts of the lid domain. These changes impact the enzyme active site, which is substantially wider and more complementary to the bulky pharmacologically relevant epoxide substrates. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct Epoxidation of Propylene over Stabilized Cu + Surface Sites on Ti Modified Cu 2O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, X.; Kattel, S.; Xiong, K.

2015-07-17

Direct propylene epoxidation by O 2 is a challenging reaction because of the strong tendency for complete combustion. Results from the current study demonstrate the feasibility to tune the epoxidation selectivity by generating highly dispersed and stabilized Cu + active sites in a TiCuO x mixed oxide. The TiCuO x surface anchors the key surface intermediate, oxametallacycle, leading to higher selectivity for epoxidation of propylene.

An unexpected epoxidation of benzil derivatives in their reaction with a germene.

PubMed

El Kettani, Sakina Ech-Cherif; Lazraq, Mohamed; Ouhsaine, Fatima; Gornitzka, Heinz; Ranaivonjatovo, Henri; Escudié, Jean

2008-11-07

The germene Mes(2)Ge=CR(2) (Mes = 2,4,6-trimethylphenyl, CR(2) = fluorenylidene) reacts with various benzil derivatives to lead to germanium-containing bicyclic epoxides by an unexpected new type of epoxidation reaction.

Di-epoxides of the three isomeric dicyclopenta-fused pyrenes: ultimate mutagenic active agents.

PubMed

Otero-Lobato, María José; Kaats-Richters, Veronica E M; Havenith, Remco W A; Jenneskens, Leonardus W; Seinen, Willem

2004-11-14

To rationalize the high bacterial mutagenic response recently found for the (di-) cyclopenta-fused pyrene congeners, viz. cyclopenta[cd]-(1), dicyclopenta[cd,mn]-(2), dicyclopenta[cd,fg]-(3) and dicyclopenta[cd,jk]pyrene (4), in the presence of a metabolic activation mixture (S9-mix), their (di-)epoxides at the externally fused unsaturated five-membered rings were previously proposed as the ultimate mutagenic active forms. In this study, cyclopenta[cd]pyrene-3,4-epoxide (5) and the novel dicyclopenta[cd,mn]pyrene-1,2,4,5-di-epoxide (6), dicyclopenta[cd,fg]pyrene-5,6,7,8-di-epoxide (7) and dicyclopenta[cd,jk]pyrene-1,2,6,7-di-epoxide (8) were synthesised from 1 to 4, respectively, and subsequently assayed for bacterial mutagenicity in the standard microsomal/histidine reverse mutation assay (Ames-assay with Salmonella typhimurium strain TA98). The di-epoxides 6-8 are present as a mixture of their cis- and trans-stereo-isomers in a close to 1:1 ratio ((1)H NMR spectroscopy and ab initio IGLO/III//RHF/6-31G** calculations). The direct-acting mutagenic activity and the strong cytotoxicity exerted by 5-8 both in the absence or presence of an exogenous metabolic activation system (+/-S9-mix) demonstrate that the ultimate mutagenic active forms are the proposed (di-)epoxides of 1-4.

Quantitation of enantiomers of r-7,t-8,9,c-10-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]-pyrene in human urine: evidence supporting metabolic activation of benzo[a]pyrene via the bay region diol epoxide.

PubMed

Hecht, Stephen S; Hochalter, Jon Bradley

2014-09-01

Benzo[a]pyrene (BaP), a potent polycyclic aromatic hydrocarbon carcinogen, is widely distributed in the human environment. All humans are exposed to BaP through the diet and contact with the general environment; cigarette smokers have higher exposure. An important pathway of BaP metabolism proceeds through formation of diol epoxides including the 'bay region diol epoxide' 7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [BaP-(7R,8S)-diol-(9S,10R)-epoxide] and the 'reverse diol epoxide' 9S,10R-dihydroxy-7R,8S-epoxy-7,8,9,10-tetrahydrobenzo [a]pyrene [BaP-(9S,10R)-diol-(7R,8S)-epoxide]. The bay region diol epoxide is considered a major ultimate carcinogen of BaP based on studies in cell culture and laboratory animals, but the available data in humans are less convincing. The bay region diol epoxide and the reverse diol epoxide react with H2O to produce enantiomeric BaP-tetraols that are excreted in the urine. We used chiral stationary-phase high-performance liquid chromatography and gas chromatography-negative ion chemical ionisation-tandem mass spectrometry to quantify these enantiomeric BaP-tetraols in the urine of 25 smokers and 25 non-smokers. The results demonstrated that the BaP-tetraol enantiomer representing the carcinogenic bay region diol epoxide pathway accounted for 68±6% (range 56-81%) of total BaP-tetraol in smokers and 64±6% (range 46-78%) in non-smokers. Levels of the major BaP-tetraol enantiomer decreased by 75% in smokers who quit smoking. These data provide convincing evidence in support of the bay region diol epoxide mechanism of BaP carcinogenesis in humans. © The Author 2014. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Complex Cure Kinetics of the Tertiary Amine activated Reaction in DGEBA Epoxy Hardened with Diethanolamine

NASA Astrophysics Data System (ADS)

Ancipink, Windy; McCoy, John; Clarkson, Caitlyn; Kropka, Jamie; Celina, Mathias; Giron, Nicholas; Hailesilassie, Lebelo; Fredj, Narjes

The curing of a diglycidyl ether of bisphenol-A (DGEBA) epoxy with diethanolamine (DEA) involves a well understood fast amine-epoxide reaction followed by a more complicated slower hydroxyl-epoxide reaction. The time scale of these two reactions are well separated and can be studied independently from one another. The initial amine-epoxide reaction results in a tertiary amine adduct which is a product of the direct reaction of a secondary amine from the DEA reacting with a single DGEBA epoxide. The second hydroxyl-epoxide reaction results in a highly crosslinked glassy epoxy resin. The deviation in the mechanisms between high and low temperatures are discerned through the use of differential scanning calorimetry (DSC), infrared spectroscopy (IR), and isothermal microcalorimetry (IMC) data. Observations of reaction rates at temperatures ranging from 30° C to 110° C have led to the determination that the hydroxyl-epoxide reaction is temperature sensitive. The hydroxyl-epoxide reaction occurs through two different mechanisms: at low temperatures, the reaction is catalyzed by the tertiary amine adduct; at higher temperatures, the reaction does not appear to be catalyzed. Sandia National Laboratories, Albuquerque, NM.

Epoxidation of Alpha-Methylstyrene and its Lewis Acid Rearrangement to 2-Phenylpropanal

NASA Astrophysics Data System (ADS)

Garin, David L.; Gamber, Melissa; Rowe, Bradley J.

1996-06-01

This undergraduate organic lab experiment includes procedures for the peracid epoxidation of an olefin and the Lewis acid rearrangement of an epoxide to a carbonyl compound. Product mixtures and transformations can be readily analyzed by several spectroscopic techniques.

Mechanism of olefin epoxidation in the presence of a titanium-containing zeolite

NASA Astrophysics Data System (ADS)

Danov, S. M.; Krasnov, V. L.; Sulimov, A. V.; Ovcharova, A. V.

2013-11-01

The effect of the nature of a solvent on the liquid-phase epoxidation of olefins with an aqueous solution of hydrogen peroxide over a titanium-containing zeolite is studied. Butanol-1, butanol-2, propanol-1, isopropanol, methanol, ethanol, water, acetone, methyl ethyl ketone, isobutanol, and tert-butanol are examined as solvents. A mechanism of olefin epoxidation with hydrogen peroxide in an alcohol medium over a titanium-containing zeolite is proposed. Epoxidation reactions involving hydrogen peroxide and different olefins are studied experimentally.

Vibrational Excitations and Low Energy Electronic Structure of Epoxide-decorated Graphene.

PubMed

Mattson, E C; Johns, J E; Pande, K; Bosch, R A; Cui, S; Gajdardziska-Josifovska, M; Weinert, M; Chen, J H; Hersam, M C; Hirschmugl, C J

2014-01-02

We report infrared studies of adsorbed atomic oxygen (epoxide functional groups) on graphene. Two different systems are used as a platform to explore these interactions, namely, epitaxial graphene/SiC(0001) functionalized with atomic oxygen (graphene epoxide, GE) and chemically reduced graphene oxide (RGO). In the case of the model GE system, IR reflectivity measurements show that epoxide groups distort the graphene π bands around the K-point, imparting a finite effective mass and contributing to a band gap. In the case of RGO, epoxide groups are found to be present following the reduction treatment by a combination of polarized IR reflectance and transmittance measurements. Similar to the GE system, a band gap in the RGO sample is observed as well.

Vibrational Excitations and Low Energy Electronic Structure of Epoxide-decorated Graphene

PubMed Central

Mattson, E.C.; Johns, J.E.; Pande, K.; Bosch, R.A.; Cui, S.; Gajdardziska-Josifovska, M.; Weinert, M.; Chen, J.H.; Hersam, M.C.; Hirschmugl, C.J.

2014-01-01

We report infrared studies of adsorbed atomic oxygen (epoxide functional groups) on graphene. Two different systems are used as a platform to explore these interactions, namely, epitaxial graphene/SiC(0001) functionalized with atomic oxygen (graphene epoxide, GE) and chemically reduced graphene oxide (RGO). In the case of the model GE system, IR reflectivity measurements show that epoxide groups distort the graphene π bands around the K-point, imparting a finite effective mass and contributing to a band gap. In the case of RGO, epoxide groups are found to be present following the reduction treatment by a combination of polarized IR reflectance and transmittance measurements. Similar to the GE system, a band gap in the RGO sample is observed as well. PMID:24563725

Combinatorial evolution of site- and enantioselective catalysts for polyene epoxidation

NASA Astrophysics Data System (ADS)

Lichtor, Phillip A.; Miller, Scott J.

2012-12-01

Selectivity in the catalytic functionalization of complex molecules is a major challenge in chemical synthesis. The problem is magnified when there are several possible stereochemical outcomes and when similar functional groups occur repeatedly within the same molecule. Selective polyene oxidation provides an archetypical example of this challenge. Historically, enzymatic catalysis has provided the only precedents. Although non-enzymatic catalysts that meet some of these challenges became known, a comprehensive solution has remained elusive. Here, we describe low molecular weight peptide-based catalysts, discovered through a combinatorial synthesis and screening protocol, that exhibit site- and enantioselective oxidation of certain positions of various isoprenols. This diversity-based approach, which exhibits features reminiscent of the directed evolution of enzymes, delivers catalysts that compare favourably to the state-of-the-art for the asymmetric oxidation of these compounds. Moreover, the approach culminated in catalysts that exhibit alternative-site selectivity in comparison to oxidation catalysts previously described.

Enantioselective epoxidation with chiral MN(III)(salen) catalysts: kinetic resolution of aryl-substituted allylic alcohols.

PubMed

Adam, W; Humpf, H U; Roschmann, K J; Saha-Möller, C R

2001-08-24

A set of aryl-substituted allylic alcohols rac-2 has been epoxidized by chiral Mn(salen*) complexes 1 as the catalyst and iodosyl benzene (PhIO) as the oxygen source. Whereas one enantiomer of the allylic alcohol 2 is preferentially epoxidized to give the threo- or cis-epoxy alcohol 3 (up to 80% ee) as the main product (dr up to >95:5), the other enantiomer of 2 is enriched (up to 53% ee). In the case of 1,1-dimethyl-1,2-dihydronaphthalen-2-ol (2c), the CH oxidation to the enone 4c proceeds enantioselectively and competes with the epoxidation. The absolute configurations of the allylic alcohols 2 and their epoxides 3 have been determined by chemical correlation or CD spectroscopy. The observed diastereo- and enantioselectivities in the epoxidation reactions are rationalized in terms of a beneficial interplay between the hydroxy-directing effect and the attack along the Katsuki trajectory.

Polyisoprenoid epoxides stimulate the biosynthesis of coenzyme Q and inhibit cholesterol synthesis.

PubMed

Bentinger, Magnus; Tekle, Michael; Brismar, Kerstin; Chojnacki, Tadeusz; Swiezewska, Ewa; Dallner, Gustav

2008-05-23

In our search for compounds that up-regulate the biosynthesis of coenzyme Q (CoQ), we discovered that irradiation of CoQ with ultraviolet light results in the formation of a number of compounds that influence the synthesis of mevalonate pathway lipids by HepG2 cells. Among the compounds that potently stimulated CoQ synthesis while inhibiting cholesterol synthesis, derivatives of CoQ containing 1-4 epoxide moieties in their polyisoprenoid side chains were identified. Subsequently, chemical epoxidation of all-trans-polyprenols of different lengths revealed that the shorter farnesol and geranylgeraniol derivatives were without effect, whereas the longer derivatives of solanesol enhanced CoQ and markedly reduced cholesterol biosynthesis. In contrast, none of the modified trans-trans-poly-cis-polyprenols exerted noticeable effects. Tocotrienol epoxides were especially potent in our system; those with one epoxide moiety in the side-chain generally up-regulated CoQ biosynthesis by 200-300%, whereas those with two such moieties also decreased cholesterol synthesis by 50-90%. Prolonged treatment of HepG2 cells with tocotrienol epoxides for 26 days elevated their content of CoQ by 30%. In addition, the levels of mRNA encoding enzymes involved in CoQ biosynthesis were also elevated by the tocotrienol epoxides. The site of inhibition of cholesterol synthesis was shown to be oxidosqualene cyclase. In conclusion, epoxide derivatives of certain all-trans-polyisoprenoids cause pronounced stimulation of CoQ synthesis and, in some cases, simultaneous reduction of cholesterol biosynthesis by HepG2 cells.

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

PubMed Central

2013-01-01

Summary Enantioselective desymmetrization of meso-aziridines and meso-epoxides with various nucleophiles by organocatalysis has emerged as a cutting-edge approach in recent years. This review summarizes the origin and recent developments of enantioselective desymmetrization of meso-aziridines and meso-epoxides in the presence of organocatalysts. PMID:24062828

Derivatization of castor oil based estolide esters: Preparation of epoxides and cyclic carbonates

USDA-ARS?s Scientific Manuscript database

Estolides that are based on castor oil and oleic acid are versatile starting points for the production of industrial fluids with new properties. A variety of unsaturated estolides were derivatized by epoxidation with hydrogen peroxide. The epoxidized estolides were further modified using supercritic...

Ring opening of epoxides with C-nucleophiles.

PubMed

Faiz, Sadia; Zahoor, Ameer Fawad

2016-11-01

Ring opening of epoxides has been an area of interest for organic chemists, owing to their reactivity toward nucleophiles. Such reactions yield important products depending on the type of nucleophiles used. This review article covers the synthetic approaches (1991-2015) used for the ring opening of epoxides via carbon nucleophiles.

Epoxidation catalyst and process

DOEpatents

Linic, Suljo; Christopher, Phillip

2010-10-26

Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

Industrially relevant epoxy-acrylate hybrid resin photopolymerizations

NASA Astrophysics Data System (ADS)

Ajiboye, Gbenga I.

Photopolymerization of epoxy-acrylate hybrid resins takes advantages of inherent properties present in the free-radical and cationic reactions to reduce oxygen inhibition problems that plague free-radical reactions. Similarly, the combined reaction mechanisms reduce moisture sensitivity of the cationic reactions. Despite the advantages of epoxy-acrylate hybrid resins, problems persist that need to be addressed. For example, low conversion and polymerization rate of the epoxides are a problem, because the fast acrylate conversion prevents the epoxide from reaching high conversion. Controlling phase separation is challenging, since two moieties with different properties are reacting. The physical properties of the polymer will be impacted by the availability of different moieties. High shrinkage stress results from the acrylate moiety, causing buckling and cracking in film and coating applications. The overall goal of this study is to use the fundamental knowledge of epoxy-acrylate hybrid resins to formulate industrially viable polymers. In order to achieve this goal, the study focuses on the following objectives: (I) determine the apparent activation energy of the hybrid monomer METHB, (II) increase epoxide conversion and polymerization rate of hybrid formulations, and (III) control physical properties in epoxy-acrylate hybrid resins. In order to increase the epoxide conversion and rate of polymerization, the sensitivity of epoxides to alcohol is used to facilitate the activated monomer (AM) mechanism and induce a covalent bond between the epoxide and acrylate polymers through the hydroxyl group. It is hypothesized that if the AM mechanism is facilitated, epoxide conversion will increase. As a result, the resins can be tailored to control phase separation and physical properties, and shrinkage stress can be reduced. In pursuit of these objectives, the hybrid monomer METHB was polymerized at temperatures ranging from 30°C to 70°C to obtain apparent activation energy of 23.49 kJ/mol for acrylate and 57 kJ/mol for epoxide moeities. Then, hybrid systems pairing hydroxyl-containing acrylates with epoxides were formulated to promote the faster AM mechanism. Monomer composition was changed in the presence of hydroxyl-containing acrylate, and initiators were carefully selected in order to control phase separation. The conversion of acrylate and epoxide was monitored in real time by Raman spectroscopy. The physical and mechanical properties were monitored using dynamic mechanical analysis. Epoxide conversion and rate of polymerization in epoxide-acrylate hybrid monomer systems were shown to increase through the introduction of a hydroxyl group on the meth/acrylate monomer, taking advantage of the faster AM mechanism. In addition, this covalent bond linking the epoxide network to the meth/acrylate polymer chains resulted in little or no phase separation and a reduction of the Tg for the hybrid polymer compared to the neat epoxide. Fundamental knowledge gained from this research will enable the use of epoxy-acrylate hybrid resins in variety of applications. For instance, shrinkage may be reduced in dental fillings, noise and vibration problems in aircraft and other machinery may be controlled, and photopolymerization cost could be reduced in thin film applications.

Physio-pharmacological Investigations About the Anti-inflammatory and Antinociceptive Efficacy of (+)-Limonene Epoxide.

PubMed

de Almeida, Antonia Amanda Cardoso; Silva, Renan Oliveira; Nicolau, Lucas Antonio Duarte; de Brito, Tarcísio Vieira; de Sousa, Damião Pergentino; Barbosa, André Luiz Dos Reis; de Freitas, Rivelilson Mendes; Lopes, Luciano da Silva; Medeiros, Jand-Venes Rolim; Ferreira, Paulo Michel Pinheiro

2017-04-01

D-limonene epoxidation generates (+)-limonene epoxide, an understudied compound in the pharmacologically point of view. Herein, we investigated the anti-inflammatory and antinociceptive potentialities of (+)-limonene epoxide and suggested a mechanism of action. The anti-inflammatory potential was analyzed using agents to induce paw edema, permeability, and myeloperoxidase (MPO) activity. Pro-inflammatory cytokines and cell migration of peritoneal cells were also assessed. Antinociceptive effects were evaluated by writhing test induced by acetic acid, formalin, and hot plate assays and contribution of opioid pathways. Pretreated animals with (+)-limonene epoxide showed reduced carrageenan-induced paw edema in all doses (25, 50, and 75 mg/kg) (P < 0.05). At 75 mg/kg, it suppressed edema provoked by compound 48/80, histamine, prostaglandin E 2 , and serotonin and reduced permeability determined by Evans blue and MPO activity. It also reduced leukocytes, neutrophils, and IL-1β levels in the peritoneal cavity in comparison with carrageenan group (P < 0.05). (+)-Limonene epoxide diminished abdominal contortions induced by acetic acid (78.9%) and paw licking times in both 1 (41.8%) and 2 (51.5%) phases and a pretreatment with naloxone (3 mg/kg) reverted the antinociceptive action in morphine- and (+)-limonene epoxide-treated groups (P < 0.05). Additionally, it enlarged response times to the thermal stimulus after 60 and 90 min. In conclusion, (+)-limonene epoxide inhibited release/activity of inflammatory mediators, vascular permeability, migration of neutrophils and displayed systemic and peripheral analgesic-dependent effects of the opioid system.

Epoxide-mediated differential packaging of Cif and other virulence factors into outer membrane vesicles.

PubMed

Ballok, Alicia E; Filkins, Laura M; Bomberger, Jennifer M; Stanton, Bruce A; O'Toole, George A

2014-10-01

Pseudomonas aeruginosa produces outer membrane vesicles (OMVs) that contain a number of secreted bacterial proteins, including phospholipases, alkaline phosphatase, and the CFTR inhibitory factor (Cif). Previously, Cif, an epoxide hydrolase, was shown to be regulated at the transcriptional level by epoxides, which serve as ligands of the repressor, CifR. Here, we tested whether epoxides have an effect on Cif levels in OMVs. We showed that growth of P. aeruginosa in the presence of specific epoxides but not a hydrolysis product increased Cif packaging into OMVs in a CifR-independent fashion. The outer membrane protein, OprF, was also increased under these conditions, but alkaline phosphatase activity was not significantly altered. Additionally, we demonstrated that OMV shape and density were affected by epoxide treatment, with two distinct vesicle fractions present when cells were treated with epibromohydrin (EBH), a model epoxide. Vesicles isolated from the two density fractions exhibited different protein profiles in Western blotting and silver staining. We have shown that a variety of clinically or host-relevant treatments, including antibiotics, also alter the proteins packaged in OMVs. Proteomic analysis of purified OMVs followed by an analysis of transposon mutant OMVs yielded mutants with altered vesicle packaging. Finally, epithelial cell cytotoxicity was reduced in the vesicles formed in the presence of EBH, suggesting that this epoxide alters the function of the OMVs. Our data support a model whereby clinically or host-relevant signals mediate differential packaging of virulence factors in OMVs, which results in functional consequences for host-pathogen interactions. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Methyltrioxorhenium-catalyzed epoxidation of homoallylic alcohols with hydrogen peroxide.

PubMed

Yamazaki, Shigekazu

2012-11-02

Homoallylic alcohols were efficiently converted to the corresponding 3,4-epoxy alcohols in excellent yields by methyltrioxorhenium (MTO)-catalyzed epoxidation with aqueous hydrogen peroxide as the terminal oxidant and 3-methylpyrazole (10 mol %) as an additive. The epoxidations of homoallylic alcohols proceeded under organic solvent-free conditions faster than those in dichloromethane.

COMPARATIVE STUDIES OF THE EFFECT OF POLYCYCLIC AROMATIC HYDROCARBON GEOMETRY ON THE HYDROLYSIS OF DIOL EPOXIDES

EPA Science Inventory

Comparative studies of the effect of polycyclic aromatic hydrocarbon geometry on the hydrolysis of diol epoxides

The interaction of the diol epoxides (DEs) of both planar and non-planar PAHs with water have been examined using quantum mechanical and molecular dynamics. Th...

Recent trends in ring opening of epoxides with sulfur nucleophiles.

PubMed

Ahmad, Sajjad; Zahoor, Ameer Fawad; Naqvi, Syed Ali Raza; Akash, Muhammad

2018-02-01

Thiolysis of epoxides offers an efficient and simple synthetic approach to access [Formula: see text]-hydroxy sulfides which are valuable scaffold in the synthesis of various important molecules in medicinal chemistry. This review article presents a recent compilation of the synthetic approaches developed after 2000 for the thiolysis of epoxides.

Exploring the origins of selectivity in soluble epoxide hydrolase from Bacillus megaterium† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7ob01847a

PubMed Central

Serrano-Hervás, Eila

2017-01-01

Epoxide hydrolase (EH) enzymes catalyze the hydration of racemic epoxides to yield their corresponding vicinal diols. These enzymes present different enantio- and regioselectivity depending upon either the substrate structure or the substitution pattern of the epoxide ring. In this study, we computationally investigate the Bacillus megaterium epoxide hydrolase (BmEH)-mediated hydrolysis of racemic styrene oxide (rac-SO) and its para-nitro styrene oxide (rac-p-NSO) derivative using density functional theory (DFT) and an active site cluster model consisting of 195 and 197 atoms, respectively. Full reaction mechanisms for epoxide ring opening were evaluated considering the attack at both oxirane carbons and considering two possible orientations of the substrate at the BmEH active site. Our results indicate that for both SO and p-NSO substrates the BmEH enantio- and regioselectivity is opposite to the inherent (R)-BmEH selectivity, the attack at the benzylic position (C1) of the (S)-enantiomer being the most favoured chemical outcome. PMID:29026902

Transition-metal-free catalysts for the sustainable epoxidation of alkenes: from discovery to optimisation by means of high throughput experimentation.

PubMed

Lueangchaichaweng, Warunee; Geukens, Inge; Peeters, Annelies; Jarry, Benjamin; Launay, Franck; Bonardet, Jean-Luc; Jacobs, Pierre A; Pescarmona, Paolo P

2012-02-01

Transition-metal-free oxides were studied as heterogeneous catalysts for the sustainable epoxidation of alkenes with aqueous H₂O₂ by means of high throughput experimentation (HTE) techniques. A full-factorial HTE approach was applied in the various stages of the development of the catalysts: the synthesis of the materials, their screening as heterogeneous catalysts in liquid-phase epoxidation and the optimisation of the reaction conditions. Initially, the chemical composition of transition-metal-free oxides was screened, leading to the discovery of gallium oxide as a novel, active and selective epoxidation catalyst. On the basis of these results, the research line was continued with the study of structured porous aluminosilicates, gallosilicates and silica-gallia composites. In general, the gallium-based materials showed the best catalytic performances. This family of materials represents a promising class of heterogeneous catalysts for the sustainable epoxidation of alkenes and offers a valid alternative to the transition-metal heterogeneous catalysts commonly used in epoxidation. High throughput experimentation played an important role in promoting the development of these catalytic systems.

Secondary Organic Aerosol Formation from 2-Methyl-3-Buten-2-ol Photooxidation: Evidence of Acid-Catalyzed Reactive Uptake of Epoxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Haofei; Zhang, Zhenfa; Cui, Tianqu

2014-04-08

Secondary organic aerosol (SOA) formation from 2-methyl-3-buten-2-ol (MBO) photooxidation has recently been observed in both field and laboratory studies. Similar to isoprene, MBO-derived SOA increases with elevated aerosol acidity in the absence of nitric oxide; therefore, an epoxide intermediate, (3,3-dimethyloxiran-2-yl)methanol (MBO epoxide) was synthesized and tentatively proposed here to explain this enhancement. In the present study, the potential of the synthetic MBO epoxide to form SOA via reactive uptake was systematically examined. SOA was observed only in the presence of acidic aerosols. Major SOA constituents, 2,3-dihydroxyisopentanol (DHIP) and MBO-derived organosulfate isomers, were chemically characterized in both laboratory-generated SOA and inmore » ambient fine aerosols collected from the BEACHON-RoMBAS field campaign during summer 2011, where MBO emissions are substantial. Our results support epoxides as potential products of MBO photooxidation leading to formation of atmospheric SOA and suggest that reactive uptake of epoxides may generally explain acid enhancement of SOA observed from other biogenic hydrocarbons.« less

Enantioselective syntheses of cryptocarya triacetate, cryptocaryolone, and cryptocaryolone diacetate.

PubMed

Smith, Catherine M; O'Doherty, George A

2003-05-29

[reaction: see text] The enantioselective syntheses of three natural products from Cryptocarya latifolia have been achieved in 13-15 steps from ethyl sorbate. The route relies upon an enantio- and regioselective Sharpless dihydroxylation and a palladium-catalyzed reduction to establish the absolute stereochemistry. The route also relies upon a highly (E)-selective olefin cross-metathesis reaction to form trans-delta-hydroxy-1-enoates. The resulting delta-hydroxy-1-enoates were subsequently converted into cryptocarya triacetate, cryptocaryolone, and cryptocaryolone diacetate.

Capsanthone 3,6-epoxide, a new carotenoid from the fruits of the red paprika Capsicum annuum L.

PubMed

Maoka, T; Fujiwara, Y; Hashimoto, K; Akimoto, N

2001-08-01

The structure of a new carotenoid, isolated from the fruits of the red tomato-shaped paprika Capsicum annuum L., was elucidated to be (3S,5R,6S,5'R)-3,6-epoxy-5,6-dihydro-5-hydroxy-beta,kappa-carotene-3',6'-dione by spectroscopic analyses, including fast atom bombardment collision-induced dissociation-mass spectrometry/mass spectrometry (FAB CID-MS/MS) and was designated capsanthone 3,6-epoxide. Capsanthone 3,6-epoxide is assumed to be an oxidative metabolite of capsanthin 3,6-epoxide in paprika.

40 CFR 63.1427 - Process vent requirements for processes using extended cookout as an epoxide emission reduction...

Code of Federal Regulations, 2012 CFR

2012-07-01

... reactor liquid at the beginning of the time period, weight percent. k = Reaction rate constant, 1/hr. t = Time, hours. Note: This equation assumes a first order reaction with respect to epoxide concentration... measuring the concentration of the unreacted epoxide, or by using process knowledge, reaction kinetics, and...

Patulin biosynthesis: Epoxidation of toluquinol and gentisyl alcohol by particulate preparations from Penicillium patulum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Priest, J.W.; Light, R.J.

1989-11-14

A crude extract that catalyzes the epoxidation of toluquinol and gentisyl alcohol was isolated from cultures of Penicillium patulum. About 60% of the activity sedimented from crude extract upon centrifugation at 105000g for 2 h, and at 30000g for 30 min after precipitation with 30% ammonium sulfate and resuspension in buffer. The quinone epoxide phyllostine, a product of gentisyl alcohol epoxidation, has previously been shown to be an intermediate in the biosynthesis of patulin and was shown to be further converted to neopatulin by the extract. The epoxide product of toluquinol, desoxyphyllostine (2-methyl-5,6-epoxy-1,4-benzoquinone), has not been reported previously from fungalmore » cultures. Its structure was confirmed by GC-mass spectrometry and proton and {sup 13}C NMR. Its CD spectrum showed the same shape and signs as that of phyllostine, indicating that it too is an enzymatic product with a similar absolute configuration. Whereas chemical epoxidation of toluquinone and gentisly quinone occurs with hydrogen peroxide, the enzymatic epoxidation utilized oxygen and the hydroquinone. The epoxidation was inhibited by 1,10-phenanthroline, EDTA, and {rho}-(chloromercuri)benzenesulfonic acid and by degassing with nitrogen, but no inhibition was observed with KCN, catalase, or CO. The apparent K{sub m}'s were similar for the two substrates with both substrates showing inhibition at 1.0 mM. The rate of desoxyphyllostine formation was more than 10 times that of phyllostine formation at equivalent substrate concentrations. Gentisaldehyde was not a substrate for the enzyme. The epoxidase was induced in late fermentor cultures of P. patulum with the same kinetics as m-hydroxybenzyl alcohol dehydrogenase, another enzyme associated with the induction of patulin biosynthesis.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Askari, Ara A.; Thomson, Scott; Edin, Matthew L.

Highlights: • We examined epoxygenase product formation and regulation in endothelial cells. • The epoxygenase CYP2J2 is an LPS (TLR-4) inducible enzyme in endothelial cells. • The endothelial cell line EA.Hy926 synthesises epoxygenase products. • Inhibition of endothelial epoxygenases increases TNFα secretion. • Soluble epoxide hydrolase inhibitors reduce inflammation-induced TNFα and NFκB. - Abstract: The roles of CYP lipid-metabolizing pathways in endothelial cells are poorly understood. Human endothelial cells expressed CYP2J2 and soluble epoxide hydrolase (sEH) mRNA and protein. The TLR-4 agonist LPS (1 μg/ml; 24 h) induced CYP2J2 but not sEH mRNA and protein. LC–MS/MS analysis of the stablemore » commonly used human endothelial cell line EA.Hy926 showed active epoxygenase and epoxide hydrolase activity: with arachidonic acid (stable epoxide products 5,6-DHET, and 14,15-DHET), linoleic acid (9,10-EPOME and 12,13-EPOME and their stable epoxide hydrolase products 9,10-DHOME and 12,13-DHOME), docosahexaenoic acid (stable epoxide hydrolase product 19,20-DiHDPA) and eicosapentaenoic acid (stable epoxide hydrolase product 17,18-DHET) being formed. Inhibition of epoxygenases using either SKF525A or MS-PPOH induced TNFα release, but did not affect LPS, IL-1β, or phorbol-12-myristate-13-acetate (PMA)-induced TNFα release. In contrast, inhibition of soluble epoxide hydrolase by AUDA or TPPU inhibited basal, LPS, IL-1β and PMA induced TNFα release, and LPS-induced NFκB p65 nuclear translocation. In conclusion, human endothelial cells contain a TLR-4 regulated epoxygenase CYP2J2 and metabolize linoleic acid > eicosapentaenoic acid > arachidonic acid > docosahexaenoic acid to products with anti-inflammatory activity.« less

The de-epoxidase and epoxidase reactions of Mantoniella squamata (Prasinophyceae) exhibit different substrate-specific reaction kinetics compared to spinach.

PubMed

Frommolt, R; Goss, R; Wilhelm, C

2001-07-01

In vivo the prasinophyceaen alga Mantoniella squamata Manton et Parke uses an incomplete violaxanthin (Vx) cycle, leading to a strong accumulation of antheraxanthin (Ax) under conditions of high light. Here, we show that this zeaxanthin (Zx)-depleted Vx/Ax cycle is caused by an extremely slow second de-epoxidation step from Ax to Zx, and a fast epoxidation from Ax back to Vx in the light. The rate constant of Ax epoxidation is 5 to 6 times higher than the rate constant of Zx formation, implying that Ax is efficiently converted back to Vx before it can be de-epoxidated to Zx. It is, however, only half the rate constant of the first de-epoxidation step from Vx to Ax, thus explaining the observed net accumulation of Ax during periods of strong illumination. When comparing the rate constant of the second de-epoxidation step in M. squamata with Zx formation in spinach (Spinacia oleracea L.) thylakoids, we find a 20-fold reduction in the reaction kinetics of the former. This extremely slow Ax de-epoxidation, which is also exhibited by the isolated Mantoniella violaxanthin de-epoxidase (VDE), is due to a reduced substrate affinity of M. squamata VDE for Ax compared with the VDE of higher plants. Mantoniella VDE, which has a similar Km value for Vx, shows a substantially increased Km for the substrate Ax in comparison with spinach VDE. Our results furthermore explain why Zx formation in Mantoniella cells can only be found at low pH values that represent the pH optimum of VDE. A pH of 5 blocks the epoxidation reaction and, consequently, leads to a slow but appreciable accumulation of Zx.

Synthesis of water-soluble multidentate aminoalcohol β-cyclodextrin derivatives via epoxide opening.

PubMed

Martina, K; Caporaso, M; Tagliapietra, S; Heropoulos, G; Rosati, O; Cravotto, G

2011-12-13

New highly soluble β-aminoalcohol β-cyclodextrin (β-CD) derivatives have been synthesized via nucleophilic epoxide opening reactions with mono-6-amino mono-6-deoxy-permethyl-β-CD and mono-6-amino mono-6-deoxy-β-CD. The binding properties of the β-CD were enhanced by linking aminoalcohol subunits which caused its solubility to improve markedly. The reaction conditions were optimised using microwave irradiation giving moderate-to-good yields with a series of epoxides. A regioselective epoxide opening reaction was observed in the reaction with styrene oxide while the stereoselectivity was strictly dependent on substrate structure. Copyright © 2011 Elsevier Ltd. All rights reserved.

Methods of producing epoxides from alkenes using a two-component catalyst system

DOEpatents

Kung, Mayfair C.; Kung, Harold H.; Jiang, Jian

2013-07-09

Methods for the epoxidation of alkenes are provided. The methods include the steps of exposing the alkene to a two-component catalyst system in an aqueous solution in the presence of carbon monoxide and molecular oxygen under conditions in which the alkene is epoxidized. The two-component catalyst system comprises a first catalyst that generates peroxides or peroxy intermediates during oxidation of CO with molecular oxygen and a second catalyst that catalyzes the epoxidation of the alkene using the peroxides or peroxy intermediates. A catalyst system composed of particles of suspended gold and titanium silicalite is one example of a suitable two-component catalyst system.

Effect of epoxidation level on thermal properties and ionic conductivity of epoxidized natural rubber solid polymer nanocomposite electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harun, Fatin; Chan, Chin Han; Winie, Tan

Effect of epoxide content on the thermal and conductivity properties of epoxidized natural rubber (ENR) solid polymer nanocomposite electrolytes was investigated. Commercial available epoxidized natural rubber having 25 (ENR25) and 50 mole% (ENR50) epoxide, respectively were incorporated with lithium perchlorate (LiClO{sub 4}) salt and titanium dioxide (TiO{sub 2}) nanofiller via solution casting method. The solid polymer nanocomposite electrolytes were characterized by differential scanning calorimetry (DSC) and impedance spectroscopy (IS) for their thermal properties and conductivity, respectively. It was evident that introduction of LiClO{sub 4} causes a greater increase in glass transition temperature (T{sub g}) and ionic conductivity of ENR50 asmore » compared to ENR25. Upon addition of TiO{sub 2} in ENR/LiClO{sub 4} system, a remarkable T{sub g} elevation was observed for both ENRs where ENR50 reveals a more pronounced changes. It is interesting to note that they exhibit different phenomenon in ionic conductivity with TiO{sub 2} loading where ENR25 shows enhancement of conductivity while ENR50 shows declination.« less

Occurrence of neoxanthin and lutein epoxide cycle in parasitic Cuscuta species.

PubMed

Kruk, Jerzy; Szymańska, Renata

2008-01-01

In the present study, xanthophyll composition of eight parasitic Cuscuta species under different light conditions was investigated. Neoxanthin was not detected in four of the eight species examined, while in others it occurred at the level of several percent of total xanthophylls. In C. gronovii and C. lupuliformis it was additionally found that the neoxanthin content was considerably stimulated by strong light. In dark-adapted plants, lutein epoxide level amounted to 10-22% of total xanthophylls in only three species, the highest being for C. lupuliformis, while in others it was below 3%, indicating that the lutein epoxide cycle is limited to only certain Cuscuta species. The obtained data also indicate that the presence of the lutein epoxide cycle and of neoxanthin is independent and variable among the Cuscuta species. The xanthophyll cycle carotenoids violaxanthin, antheraxanthin and zeaxanthin were identified in all the examined species and occurred at the level found in other higher plants. The xanthophyll and lutein epoxide cycle pigments showed typical response to high light stress. The obtained results also suggest that the ability of higher plants to synthesize lutein epoxide probably does not depend on the substrate specificity of zeaxanthin epoxidase but on the availability of lutein for the enzyme.

Covalent Heterogenization of a Discrete Mn(II) Bis-Phen Complex by a Metal-Template/Metal-Exchange Method: An Epoxidation Catalyst with Enhanced Reactivity

PubMed Central

Terry, Tracy J.; Stack, T. Daniel P.

2009-01-01

Considerable attention has been devoted to the immobilization of discrete epoxidation catalysts onto solid supports due to the possible benefits of site isolation such as increased catalyst stability, catalyst recycling, and product separation. A synthetic metal-template/metal-exchange method to imprint a covalently attached bis-1,10-phenanthroline coordination environment onto high-surface area, mesoporous SBA-15 silica is reported herein along with the epoxidation reactivity once reloaded with manganese. Comparisons of this imprinted material with material synthesized by random grafting of the ligand show that the template method creates more reproducible, solution-like bis-1,10-phenanthroline coordination at a variety of ligand loadings. Olefin epoxidation with peracetic acid shows the imprinted manganese catalysts have improved product selectivity for epoxides, greater substrate scope, more efficient use of oxidant, and higher reactivity than their homogeneous or grafted analogues independent of ligand loading. The randomly grafted manganese catalysts, however, show reactivity that varies with ligand loading while the homogeneous analogue degrades trisubstituted olefins and produces trans-epoxide products from cis-olefins. Efficient recycling behavior of the templated catalysts is also possible. PMID:18351763

Anti-inflammatory Effects of Omega-3 Polyunsaturated Fatty Acids and Soluble Epoxide Hydrolase Inhibitors in Angiotensin-II Dependent Hypertension

PubMed Central

Ulu, Arzu; Harris, Todd R; Morisseau, Christophe; Miyabe, Christina; Inoue, Hiromi; Schuster, Gertrud; Dong, Hua; Iosif, Ana-Maria; Liu, Jun-Yan; Weiss, Robert H; Chiamvimonvat, Nipavan; Imig, John D; Hammock, Bruce D

2013-01-01

The mechanisms underlying the anti-inflammatory and anti-hypertensive effects of long chain ω-3 polyunsaturated fatty acids (PUFAs) are still unclear. The epoxides of an ω-6 fatty acid, arachidonic acid (epoxyeicosatrienoic acids; EETs) also exhibit anti-hypertensive and anti-inflammatory effects. Thus, we hypothesized that the major ω-3 PUFAs including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may lower blood pressure and attenuate renal markers of inflammation through their epoxide metabolites. Here, we supplemented mice with an ω-3 rich diet for three weeks in a murine model of angiotensin-II dependent hypertension. Also, since EPA and DHA epoxides are metabolized by soluble epoxide hydrolase (sEH), we tested the combination of a sEH inhibitor and the ω-3 rich diet. Our results show that ω-3 rich diet in combination with the sEH inhibitor lowered Ang-II increased blood pressure, further increased renal levels of EPA and DHA epoxides, reduced renal markers of inflammation (i.e. prostaglandins and MCP-1), down-regulated an epithelial sodium channel and up-regulated Angiotensin converting enzyme-2 message (ACE-2) and significantly modulated cyclooxygenase and lipoxygenase metabolic pathways. Overall, our findings suggest that epoxides of the ω-3 PUFAs contribute to lowering SBP and attenuating inflammation in part by reduced prostaglandins and MCP-1 and by up-regulation of ACE-2 in angiotensin-II dependent hypertension. PMID:23676336

The oxidation of copper catalysts during ethylene epoxidation.

PubMed

Greiner, M T; Jones, T E; Johnson, B E; Rocha, T C R; Wang, Z J; Armbrüster, M; Willinger, M; Knop-Gericke, A; Schlögl, R

2015-10-14

The oxidation of copper catalysts during ethylene epoxidation was characterized using in situ photoemission spectroscopy and electron microscopy. Gas chromatography, proton-transfer reaction mass spectrometry and electron-ionization mass spectrometry were used to characterize the catalytic properties of the oxidized copper. We find that copper corrodes during epoxidation in a 1 : 1 mixture of oxygen and ethylene. The catalyst corrosion passes through several stages, beginning with the formation of an O-terminated surface, followed by the formation of Cu2O scale and eventually a CuO scale. The oxidized catalyst exhibits measurable activity for ethylene epoxidation, but with a low selectivity of <3%. Tests on pure Cu2O and CuO powders confirm that the oxides intrinsically exhibit partial-oxidation activity. Cu2O was found to form acetaldehyde and ethylene epoxide in roughly equal amounts (1.0% and 1.2% respectively), while CuO was found to form much less ethyl aldehyde than ethylene epoxide (0.1% and 1.0%, respectively). Metallic copper catalysts were examined in extreme dilute-O2 epoxidation conditions to try and keep the catalyst from oxidizing during the reaction. It was found that in feed of 1 part O2 to 2500 parts C2H4 (PO2 = 1.2 × 10(-4) mbar) the copper surface becomes O-terminated. The O-terminated surface was found to exhibit partial-oxidation selectivity similar to that of Cu2O. With increasing O2 concentration (>8/2500) Cu2O forms and eventually covers the surface.

40 CFR 63.1427 - Process vent requirements for processes using extended cookout as an epoxide emission reduction...

Code of Federal Regulations, 2011 CFR

2011-07-01

... epoxides, and that are using ECO as a control technique to reduce epoxide emissions in order to comply with... provisions of this section. The owner or operator that is using ECO in order to comply with the emission... used to further reduce the HAP emissions from a process vent already controlled by ECO, then the owner...

40 CFR 63.1427 - Process vent requirements for processes using extended cookout as an epoxide emission reduction...

Code of Federal Regulations, 2010 CFR

2010-07-01

... obtaining the liquid sample, along with the test method used to determine the epoxide concentration. This... pressures, the owner or operator shall determine the time when the pressure has fallen to half its total pressure by using Equation 13: ER08MY00.008 Where: Phalf1 = Half the total pressure of the epoxide for...

Cyclohexene oxide/CO2 copolymerization catalyzed by chromium(III) salen complexes and N-methylimidazole: effects of varying salen ligand substituents and relative cocatalyst loading.

PubMed

Darensbourg, Donald J; Mackiewicz, Ryan M; Rodgers, Jody L; Fang, Cindy C; Billodeaux, Damon R; Reibenspies, Joseph H

2004-09-20

A detailed mechanistic study into the copolymerization of CO2 and cyclohexene oxide utilizing CrIII(salen)X complexes and N-methylimidazole, where H2salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediimine and other salen derivatives and X = Cl or N3, has been conducted. By studying salen ligands with various groups on the diimine backbone, we have observed that bulky groups oriented perpendicular to the salen plane reduce the activity of the catalyst significantly, while such groups oriented parallel to the salen plane do not retard copolymer formation. This is not surprising in that the mechanism for asymmetric ring opening of epoxides was found to occur in a bimetallic fashion, whereas these perpendicularly oriented groups along with the tert-butyl groups on the phenolate rings produce considerable steric requirements for the two metal centers to communicate and thus initiate the copolymerization process. It was also observed that altering the substituents on the phenolate rings of the salen ligand had a 2-fold effect, controlling both catalyst solubility as well as electron density around the metal center, producing significant effects on the rate of copolymer formation. This and other data discussed herein have led us to propose a more detailed mechanistic delineation, wherein the rate of copolymerization is dictated by two separate equilibria. The first equilibrium involves the initial second-order epoxide ring opening and is inhibited by excess amounts of cocatalyst. The second equilibrium involves the propagation step and is enhanced by excess cocatalyst. This gives the [cocatalyst] both a positive and negative effect on the overall rate of copolymerization. Copyright 2004 American Chemical Society

Heterogeneous epoxide carbonylation by cooperative ion-pair catalysis in Co(CO) 4 –-incorporated Cr-MIL-101

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Hoyoung D.; Dinca, Mircea; Roman-Leshkov, Yuriy

Here, despite the commercial desirability of epoxide carbonylation to β-lactones, the reliance of this process on homogeneous catalysts makes its industrial application challenging. Here we report the preparation and use of a Co(CO) 4 –-incorporated Cr-MIL-101 (Co(CO) 4cCr-MIL-101, Cr-MIL-101 = Cr 3O(BDC) 3F, H2BDC = 1,4-benzenedicarboxylic acid) heterogeneous catalyst for the ring-expansion carbonylation of epoxides, whose activity, selectivity, and substrate scope are on par with those of the reported homogeneous catalysts. We ascribe the observed performance to the unique cooperativity between the postsynthetically introduced Co(CO) 4 – and the site-isolated Lewis acidic Cr(III) centers in the metal–organic framework (MOF). Themore » heterogeneous nature of Co(CO) 4cCr-MIL-101 allows the first demonstration of gas-phase continuous-flow production of β-lactones from epoxides, attesting to the potential applicability of the heterogeneous epoxide carbonylation strategy.« less

Heterogeneous epoxide carbonylation by cooperative ion-pair catalysis in Co(CO) 4 –-incorporated Cr-MIL-101

DOE PAGES

Park, Hoyoung D.; Dinca, Mircea; Roman-Leshkov, Yuriy

2017-03-21

Here, despite the commercial desirability of epoxide carbonylation to β-lactones, the reliance of this process on homogeneous catalysts makes its industrial application challenging. Here we report the preparation and use of a Co(CO) 4 –-incorporated Cr-MIL-101 (Co(CO) 4cCr-MIL-101, Cr-MIL-101 = Cr 3O(BDC) 3F, H2BDC = 1,4-benzenedicarboxylic acid) heterogeneous catalyst for the ring-expansion carbonylation of epoxides, whose activity, selectivity, and substrate scope are on par with those of the reported homogeneous catalysts. We ascribe the observed performance to the unique cooperativity between the postsynthetically introduced Co(CO) 4 – and the site-isolated Lewis acidic Cr(III) centers in the metal–organic framework (MOF). Themore » heterogeneous nature of Co(CO) 4cCr-MIL-101 allows the first demonstration of gas-phase continuous-flow production of β-lactones from epoxides, attesting to the potential applicability of the heterogeneous epoxide carbonylation strategy.« less

Mechanistic Basis for High Reactivity of (salen)Co–OTs in the Hydrolytic Kinetic Resolution of Terminal Epoxides

PubMed Central

Nielsen, Lars P. C.; Zuend, Stephan J.; Ford, David D.; Jacobsen, Eric N.

2012-01-01

The (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides is a bimetallic process with a rate controlled by partitioning between a nucleophilic (salen)Co–OH catalyst and a Lewis acidic (salen)Co–X catalyst. The commonly used (salen)Co–OAc and (salen)Co–Cl precatalysts undergo complete and irreversible counterion addition to epoxide during the course of the epoxide hydrolysis reaction, resulting in quantitative formation of weakly Lewis acidic (salen)Co–OH, and severely diminished reaction rates in the late stages of HKR reactions. In contrast, (salen)Co–OTs maintains high reactivity over the entire course of HKR reactions. We describe here an investigation of catalyst partitioning with different (salen)Co–X precatalysts, and demonstrate that counterion addition to epoxide is reversible in the case of the (salen)Co–OTs. This reversible counterion addition results in stable partitioning between nucleophilic and Lewis acidic catalyst species, allowing highly efficient catalysis throughout the course of the HKR reaction. PMID:22292515

Mechanistic basis for high reactivity of (salen)Co-OTs in the hydrolytic kinetic resolution of terminal epoxides.

PubMed

Nielsen, Lars P C; Zuend, Stephan J; Ford, David D; Jacobsen, Eric N

2012-03-02

The (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides is a bimetallic process with a rate controlled by partitioning between a nucleophilic (salen)Co-OH catalyst and a Lewis acidic (salen)Co-X catalyst. The commonly used (salen)Co-OAc and (salen)Co-Cl precatalysts undergo complete and irreversible counterion addition to epoxide during the course of the epoxide hydrolysis reaction, resulting in quantitative formation of weakly Lewis acidic (salen)Co-OH and severely diminished reaction rates in the late stages of HKR reactions. In contrast, (salen)Co-OTs maintains high reactivity over the entire course of HKR reactions. We describe here an investigation of catalyst partitioning with different (salen)Co-X precatalysts and demonstrate that counterion addition to epoxide is reversible in the case of the (salen)Co-OTs. This reversible counterion addition results in stable partitioning between nucleophilic and Lewis acidic catalyst species, allowing highly efficient catalysis throughout the course of the HKR reaction.

Succinic anhydrides from epoxides

DOEpatents

Coates, Geoffrey W.; Rowley, John M.

2013-07-09

Catalysts and methods for the double carbonylation of epoxides are disclosed. Each epoxide molecule reacts with two molecules of carbon monoxide to produce a succinic anhydride. The reaction is facilitated by catalysts combining a Lewis acidic species with a transition metal carbonyl complex. The double carbonylation is achieved in single process by using reaction conditions under which both carbonylation reactions occur without the necessity of isolating or purifying the product of the first carbonylation.

Succinic anhydrides from epoxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coates, Geoffrey W.; Rowley, John M.

2016-06-28

Catalysts and methods for the double carbonylation of epoxides are disclosed. Each epoxide molecule reacts with two molecules of carbon monoxide to produce a succinic anhydride. The reaction is facilitated by catalysts combining a Lewis acidic species with a transition metal carbonyl complex. The double carbonylation is achieved in single process by using reaction conditions under which both carbonylation reactions occur without the necessity of isolating or purifying the product of the first carbonylation.

cis-Stilbene and (1 alpha,2 beta,3 alpha)-(2-ethenyl-3-methoxycyclopropyl)benzene as mechanistic probes in the Mn(III)(salen)-catalyzed epoxidation: influence of the oxygen source and the counterion on the diastereoselectivity of the competitive concerted and radical-type oxygen transfer.

PubMed

Adam, Waldemar; Roschmann, Konrad J; Saha-Möller, Chantu R; Seebach, Dieter

2002-05-08

cis-Stilbene (1) has been epoxidized by a set of diverse oxygen donors [OxD], catalyzed by the Mn(III)(salen)X complexes 3 (X = Cl, PF(6)), to afford a mixture of cis- and trans-epoxides 2. The cis/trans ratios range from 29:71 (extensive isomerization) to 92:8, which depends both on the oxygen source [OxD] and on the counterion X of the catalyst. When (1 alpha,2 beta,3 alpha)-(2-ethenyl-3-methoxycyclopropyl)-benzene (4) is used as substrate, a mechanistic probe which differentiates between radical and cationic intermediates, no cationic ring-opening products are found in this epoxidation reaction; thus, isomerized epoxide product arises from intermediary radicals. The dependence of the diastereoselectivity on the oxygen source is rationalized in terms of a bifurcation step in the catalytic cycle, in which concerted Lewis-acid-activated oxygen transfer competes with stepwise epoxidation by the established Mn(V)(oxo) species. The experimental counterion effect is attributed to the computationally assessed ligand-dependent reaction profiles and stereoselectivities of the singlet, triplet, and quintet spin states available to the manganese species.

Anti-Leishmania and cytotoxic activities of perillaldehyde epoxide synthetic positional isomers.

PubMed

Keesen, Tatjana Souza Lima; da Silva, Larisse Virgolino; da Câmara Rocha, Juliana; Andrade, Luciana Nalone; Lima, Tamires Cardoso; de Sousa, Damião Pergentino

2018-03-13

Leishmaniasis belongs to a complex of zoonotic disease caused by protozoa of the genus Leishmania and is considered a major public health problem. Several essential oil chemical components have inhibitory effect against protozoa, including Leishmania donovani. Thus, the aim of this study was to evaluate for the first time the anti-Leishmania activity of two p-menthane monoterpene isomers (EPER-1: perillaldehyde 1,2-epoxide and EPER-2: perillaldehyde 8,9-epoxide) against L. donovani promastigotes as well as evaluating cytotoxic effect on mononuclear peripheral blood cells. Results of anti-Leishmania assay revealed that EPER-2 (IC 50  = 3.8 μg.mL -1 ) was 16-fold more potent than its isomer EPER-1 (IC 50  = 64.6 μg.mL -1 ). In contrast to PBMC cells, EPER-2 was not cytotoxic (IC 50  > 400 μg.mL -1 ) when compared to positive control. These data suggest that the disposition of epoxide group into the p-menthane skeleton affects the anti-Leishmania activity, being that the presence of the exocyclic epoxide group considerably increased potency. Thus, it was possible to observe that the location of the epoxide group into the p-menthane skeleton resulted in different potencies.

Stilbene epoxidation and detoxification in a Photorhabdus luminescens-nematode symbiosis

PubMed Central

Park, Hyun Bong; Sampathkumar, Parthasarathy; Perez, Corey E.; Lee, Joon Ha; Tran, Jeannie; Bonanno, Jeffrey B.; Hallem, Elissa A.; Almo, Steven C.; Crawford, Jason M.

2017-01-01

Members of the gammaproteobacterial Photorhabdus genus share mutualistic relationships with Heterorhabditis nematodes, and the pairs infect a wide swath of insect larvae. Photorhabdus species produce a family of stilbenes, with two major components being 3,5-dihydroxy-4-isopropyl-trans-stilbene (compound 1) and its stilbene epoxide (compound 2). This family of molecules harbors antimicrobial and immunosuppressive activities, and its pathway is responsible for producing a nematode “food signal” involved in nematode development. However, stilbene epoxidation biosynthesis and its biological roles remain unknown. Here, we identified an orphan protein (Plu2236) from Photorhabdus luminescens that catalyzes stilbene epoxidation. Structural, mutational, and biochemical analyses confirmed the enzyme adopts a fold common to FAD-dependent monooxygenases, contains a tightly bound FAD prosthetic group, and is required for the stereoselective epoxidation of compounds 1 and 2. The epoxidase gene was dispensable in a nematode-infective juvenile recovery assay, indicating the oxidized compound is not required for the food signal. The epoxide exhibited reduced cytotoxicity toward its producer, suggesting this may be a natural route for intracellular detoxification. In an insect infection model, we also observed two stilbene-derived metabolites that were dependent on the epoxidase. NMR, computational, and chemical degradation studies established their structures as new stilbene-l-proline conjugates, prolbenes A (compound 3) and B (compound 4). The prolbenes lacked immunosuppressive and antimicrobial activities compared with their stilbene substrates, suggesting a metabolite attenuation mechanism in the animal model. Collectively, our studies provide a structural view for stereoselective stilbene epoxidation and functionalization in an invertebrate animal infection model and provide new insights into stilbene cellular detoxification. PMID:28246174

Tumor initiating activities of various derivatives of benz(a)anthracene and 7, 12-dimethyl-benz(a)anthracene in mouse skin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slaga, T.J.; Gleason, G.L.; DiGiovanni, J.

Current information indicates that polycyclic aromatic hydrocarbons (PAH) exert their toxic, mutagenic, and carcinogenic activities after they have been metabolically activated by target cells to reactive epoxides. The results obtained from IN VIVO and IN VITRO binding, mutagenicity, metabolism, and carcinogenicity studies have led to the conclusion that BP-7, 8-diol is a proximate carcinogenic metabolite of BP, and the BP-diol-epoxide is an ultimate carcinogenic metabolite of BP. Recent results concerning the strong carcinogenicity of BP-7..beta.., 8..cap alpha..-diol-9..cap alpha..,10..cap alpha..-epoxide in newborn mice and in mouse skin strongly indicate that it is the ultimate carcinogenic metabolite of BP. Since diol-epoxides maymore » be responsible for the carcinogenicity of PAH other than BP, diols and diol-epoxides as well as other derivatives of PAH were tested for skin tumor-initiation in a two-stage system of tumorigenesis. In addition, since activation of methylated PAH may involve the side-chain methyl group, the skin tumor-initiating activity of various side-chain derivatives of methylated PA were determined. In this report, the skin tumor initiation of various derivatives of a nonmethylated PAH, BA as well as a methylated PAH, DMBA are compared. The data suggest that bay region diol-epoxides may be important in BA and DMBA carcinogenicity in mice which is supportive of the theory proposed by Jerina and co-workers which predicts that diol-epoxides in the bay region are the major determinants of PAH carcinogenicity.« less

Zeaxanthin epoxidation - an in vitro approach.

PubMed

Kuczyńska, Paulina; Latowski, Dariusz; Niczyporuk, Sylvia; Olchawa-Pajor, Monika; Jahns, Peter; Gruszecki, Wiesław I; Strzałka, Kazimierz

2012-01-01

Zeaxanthin epoxidase (ZE) is an enzyme operating in the violaxanthin cycle, which is involved in photoprotective mechanisms. In this work model systems to study zeaxanthin (Zx) epoxidation were developed. Two assay systems are presented in which epoxidation of Zx was observed. In these assays two mutants of Arabidopsis thaliana which have active only one of the two xanthophyll cycle enzymes were used. The npq1 mutant possesses an active ZE and is thus able to convert Zx to violaxanthin (Vx) but the violaxanthin de-epoxidase (VDE) is inactive, so that Vx cannot be converted to Zx. The other mutant, npq2, possesses an active VDE and can convert exogenous Vx to Zx under strong light conditions but reverse reaction is not possible. The first assay containing thylakoids from npq1 and npq2 mutants of A. thaliana gave positive results and high efficiency of epoxidation reaction was observed. The amount of Zx was reduced by 25%. To optimize high efficiency of epoxidation reaction additional factors facilitating both fusion of the two types of thylakoids and incorporation of Zx to their membranes were also studied. The second kind of assay contained npq1 mutant thylakoids of A. thaliana supplemented with exogenous Zx and monogalactosyldiacylglycerol (MGDG). Experiments with different proportions of Zx and MGDG showed that their optimal ratio is 1:60. In such system, due to epoxidation, the amount of Zx was reduced by 38% of its initial level. The in vitro systems of Zx epoxidation described in this paper enable analysis some properties of the ZE without necessity of its isolation.

Annual Gaseous Electronics Conference (38th) Held at Monterey, California on 15-18 October 1985. Program and Abstracts.

DTIC Science & Technology

1985-10-18

al and CB- 8 PLASMA-SHEATH STRUCTURE FOR AN t GM ELECTRODE CONTACTING AN ISOTHERMAL CA-17 SYNCHROTRON STUDIES OF COLLISION PLASMA: I. FORMULATION AND...77, 817 (1982). 25 S.2’ CA CA-17 Synchrotron Studies of Collision Induced Absorp- tion and Emission in 12 and IC. D. C. LORENTS, AND R. L. SHARPLESS...Aiken June 1954 Gardner, Milton Eugene June 1937 Huber, Elsa Louise June 1954 Bowls, Noodford Eugene Nov. 1937 Maunsell. Charles Dudley Jan. 1955 Chapman

New synthetic routes toward enantiopure nitrogen donor ligands.

PubMed

Sala, Xavier; Rodríguez, Anna M; Rodríguez, Montserrat; Romero, Isabel; Parella, Teodor; von Zelewsky, Alexander; Llobet, Antoni; Benet-Buchholz, Jordi

2006-12-08

New polypyridylic chiral ligands, having either C3 or lower symmetry, have been prepared via a de novo construction of the pyridine nucleus by means of Kröhnke methodology in the key step. The chiral moieties of these ligands originate from the monoterpen chiral pool, namely (-)-alpha-pinene ((-)-14, (-)-15) and (-)-myrtenal ((-)-9, (-)-10). Extension of the above-mentioned asymmetric synthesis procedure to the preparation of enantiopure derivatives of some commonly used polypyridylic ligands has been achieved through a new aldehyde building block ((-)-16). As an example, the synthesis of a chiral derivative of N,N-bis(2-pyridylmethyl)ethylamine (bpea) ligand, (-)-19, has been performed to illustrate the viability of the method. The coordinative ability of the ligands has been tested through the synthesis and characterization of complexes [Mn((-)-19)Br2], (-)-20, and [RuCl((-)-10)(bpy)](BF4), (-)-21. Some preliminary results related to the enantioselective catalytic epoxidation of styrene with the ruthenium complex are also presented.

Direct synthesis of ESBO derivatives-¹⁸O labelled with dioxirane.

PubMed

La Tegola, Stefano; Annese, Cosimo; Suman, Michele; Tommasi, Immacolata; Fusco, Caterina; D'Accolti, Lucia

2013-01-01

This work addresses a new approach developed in our laboratory, consisting in the application of isolated dimethyldioxirane (DDO, 1a) labelled with ¹⁸O for synthesis of epoxidized glyceryl linoleate (Gly-LLL, 2). We expect that this work could contribute in improving analytical methods for the determination of epoxidized soybean oil (ESBO) in complex food matrices by adopting an ¹⁸O-labelled-epoxidized triacylglycerol as an internal standard.

A Bimetallic Aluminium(Salphen) Complex for the Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide.

PubMed

Wu, Xiao; North, Michael

2017-01-10

A bimetallic aluminium(salphen) complex is reported as a sustainable, efficient and inexpensive catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide. In the presence of this complex and tetrabutylammonium bromide, terminal and internal epoxides reacted at 50 °C and 10 bar carbon dioxide pressure to afford their corresponding cyclic carbonates in yields of 50-94 % and 30-71 % for terminal and internal cyclic carbonates, respectively. Mechanistic studies using deuterated epoxides and an analogous monometallic aluminium(salphen) chloride complex support a mechanism for catalysis by the bimetallic complex, which involves intramolecular cooperative catalysis between the two aluminium centres. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

First-principles chemical kinetic modeling of methyl trans-3-hexenoate epoxidation by HO 2

DOE PAGES

Cagnina, S.; Nicolle, Andre; de Bruin, T.; ...

2017-02-16

The design of innovative combustion processes relies on a comprehensive understanding of biodiesel oxidation kinetics. The present study aims at unraveling the reaction mechanism involved in the epoxidation of a realistic biodiesel surrogate, methyl trans-3-hexenoate, by hydroperoxy radicals using a bottom-up theoretical kinetics methodology. The obtained rate constants are in good agreement with experimental data for alkene epoxidation by HO 2. The impact of temperature and pressure on epoxidation pathways involving H-bonded and non-H-bonded conformers was assessed. As a result, the obtained rate constant was finally implemented into a state-of-the-art detailed combustion mechanism, resulting in fairly good agreement with enginemore » experiments.« less

Hydrogen-Bonding Catalysis and Inhibition by Simple Solvents in the Stereoselective Kinetic Epoxide-Opening Spirocyclization of Glycal Epoxides to Form Spiroketals

PubMed Central

Wurst, Jacqueline M.; Liu, Guodong; Tan, Derek S.

2011-01-01

Mechanistic investigations of a MeOH-induced kinetic epoxide-opening spirocyclization of glycal epoxides have revealed dramatic, specific roles for simple solvents in hydrogen-bonding catalysis of this reaction to form spiroketal products stereoselectively with inversion of configuration at the anomeric carbon. A series of electronically-tuned C1-aryl glycal epoxides was used to study the mechanism of this reaction based on differential reaction rates and inherent preferences for SN2 versus SN1 reaction manifolds. Hammett analysis of reaction kinetics with these substrates is consistent with an SN2 or SN2-like mechanism (ρ = −1.3 vs. ρ = −5.1 for corresponding SN1 reactions of these substrates). Notably, the spirocyclization reaction is second-order dependent on MeOH and the glycal ring oxygen is required for second-order MeOH catalysis. However, acetone cosolvent is a first-order inhibitor of the reaction. A transition state consistent with the experimental data is proposed in which one equivalent of MeOH activates the epoxide electrophile via a hydrogen bond while a second equivalent of MeOH chelates the sidechain nucleophile and glycal ring oxygen. A paradoxical previous observation that decreased MeOH concentration leads to increased competing intermolecular methyl glycoside formation is resolved by the finding that this side reaction is only first-order dependent on MeOH. This study highlights the unusual abilities of simple solvents to act as hydrogen-bonding catalysts and inhibitors in epoxide-opening reactions, providing both stereoselectivity and discrimination between competing reaction manifolds. This spirocyclization reaction provides efficient, stereocontrolled access to spiroketals that are key structural motifs in natural products. PMID:21539313

Towards the Synthesis of Dihydrooxepino[4,3-b]pyrrole-Containing Natural Products via Cope Rearrangement of Vinyl Pyrrole Epoxides.

PubMed

Cameron, Alex; Fisher, Brendan; Fisk, Nicholas; Hummel, Jessica; White, Jonathan M; Krenske, Elizabeth H; Rizzacasa, Mark A

2015-12-18

An approach to the dihydrooxepino[4,3-b]pyrrole core of diketopiperazine natural products which utilizes a vinyl pyrrole epoxide Cope rearrangement was investigated. It was found that an ester substituent on the epoxide was essential for the [3,3]-rearrangement to occur. Density functional calculations with M06-2X provided explanations for the effects of the pyrrole and ester groups on these rearrangements.

Selective and metal-free epoxidation of terminal alkenes by heterogeneous polydioxirane in mild conditions

NASA Astrophysics Data System (ADS)

Kazemnejadi, M.; Shakeri, A.; Nikookar, M.; Shademani, R.; Mohammadi, M.

2018-05-01

Polydioxirane (PDOX) was prepared by the treatment of polysalicylaldehyde with Oxone and was found as a selective, highly efficient and heterogeneous reagent for epoxidation of alkenes which can be successfully isolated. This work also introduced a simpler, safer and milder way for epoxidation of alkenes with dioxirane groups than before. PDOX can be simply recovered from the reaction mixture by plain filtration and reused for eight runs without significant reactivity loss.

Autonomic self-healing in epoxidized natural rubber.

PubMed

Rahman, Arifur; Sartore, Luciana; Bignotti, Fabio; Di Landro, Luca

2013-02-01

The development of polymers that can repair damage autonomously would be useful to improve the lifetime of polymeric materials. To date, limited attention has been dedicated to developing elastomers with autonomic self-healing ability, which can recover damages without need for an external or internal source of healing agents. This work investigates the self-healing behavior of epoxidized natural rubber (ENR) with two different epoxidation levels (25 and 50 mol % epoxidation) and of the corresponding unfunctionalized rubber, cis-1,4-polyisoprene (PISP). A self-adhesion assisted self-healing behavior was revealed by T-peel tests on slightly vulcanized rubbers. A higher epoxidation level was found to enhance self-healing. Self-healing of rubbers following ballistic damages was also investigated. A pressurized air flow test setup was used to evaluate the self-healing of ballistic damages in rubbers. Microscope (OM, SEM, and TEM) analyses were carried out to provide further evidence of healing in the impact zones. Self-healing of ballistic damages was observed only in ENR with 50 mol % epoxidation and it was found to be influenced significantly by the cross-link density. Finally, self-healing of ballistic damages was also observed in ENR50/PISP blends only when the content of the healing component (i.e., ENR50) was at least 25 wt %. From an analysis of the results, it was concluded that a synergistic effect between interdiffusion and interaction among polar groups leads to self-healing in ENR.

In-Situ Generated Graphene as the Catalytic Site for Visible-Light Mediated Ethylene Epoxidation on AG Nanocatalysts

NASA Astrophysics Data System (ADS)

Zhang, Xueqiang Alex; Jain, Prashant

2017-06-01

Despite the harsh conditions for chemical conversion, ethylene oxide produced from ethylene epoxidation on Ag-based heterogeneous catalyst constitutes one of the largest volume chemicals in chemical industry. Recently, photocatalytic epoxidation of ethylene over plasmonic Ag nanoparticles enables the chemical conversion under significantly decreased temperature and ambient pressure conditions. Yet a detailed understanding of the photocatalytic process at the reactant/catalyst interface is under debate. Surface enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique that enables the localized detection of rare and/or transient chemical species with high sensitivity under in situ and ambient conditions. Using SERS, we are able to monitor at individual sites of an Ag nanocatalyst the visible-light-mediated adsorption and epoxidation of ethylene. From detected intermediates, we find that the primary step in the photoepoxidation is the transient formation of graphene catalyzed by the Ag surface. Density functional theory (DFT) simulations that model the observed SERS spectra suggest that the defective edge sites of the graphene formed on Ag constitute the active site for C2H4 adsorption and epoxidation. Further studies with pre-formed graphene/Ag catalyst composites confirm the indispensable role of graphene in visible-light-mediated ethylene epoxidation. Carbon is often thought to be either an innocent support or a poison for metallic catalysts; however our studies reveal a surprising role for crystalline carbon layers as potential co-catalysts.

Effect of Monomer Structure on Curing Behavior, CO2 Solubility, and Gas Permeability of Ionic Liquid-Based Epoxy-Amine Resins and Ion-Gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDanel, WM; Cowan, MG; Barton, JA

2015-04-29

New imidazolium- and pyrrolidinium-based bis(epoxide)-functionalized ionic liquid (IL) monorners were synthesized: and reacted with multifunctional amine monomers to produce cross-linked, epoxy-amine poly(ionic liquid) (PIL) resins and PIL/IL ion-gel membranes. The length and chemical nature (i.e., alkyl versus ether) between the irrildazolium group and epokitie groups were studied to determine their effects on CO2 affinity. The CO2 uptake (millimoles per gram) of the epoxy amine resins (between 0.1 and 1 mmol/g) was found to depend predominately on the epoxide-to-amine ratio and the bis(epoxide) IL molecular weight. The effect of using a primary versus a secondary amine-containing multifunctional monoiner was also assessedmore » for the resin-synthesis. Secondary amines can increase CO2 permeability but also increase the iime required for biS(epoxide) coriversion. When either the epoxide or athine monomer structure is changed, the CO2 solubility and permeability of the resulting PIL resins and ion-sel membranes can be tuned.« less

Changes in antioxidant capacity and colour associated with the formation of β-carotene epoxides and oxidative cleavage derivatives.

PubMed

Gurak, Poliana D; Mercadante, Adriana Z; González-Miret, M L; Heredia, Francisco J; Meléndez-Martínez, Antonio J

2014-03-15

In this study HPLC-DAD-MS/MS was applied for the identification of compounds derived from (all-E)-β-carotene following epoxidation and oxidative cleavage. The consequences on the CIELAB colour parameters and antioxidant capacity (AC) were also evaluated. Five apocarotenoids, three secocarotenoids, seven Z isomers and two epoxides were detected as a result of the oxidative cleavage. Four epoxides and three Z isomers were detected as a consequence of the epoxidation reaction. Some compounds were detected for the first time as a result of oxidation reactions. Both treatments led to a marked decrease in b(∗) and Cab(∗) values, indicating that these colour parameters can be used for the rapid assessment of β-carotene oxidation. The oxidative cleavage of β-carotene resulted in increased capacity to both scavenge ABTS(+) and quench singlet oxygen. These results suggest that the study of the AC of these oxidative derivatives and their possible usefulness as food ingredients deserves further attention. Copyright © 2013 Elsevier Ltd. All rights reserved.

Rate and Selectivity Control in Thioether and Alkene Oxidation with H 2 O 2 over Phosphonate-Modified Niobium(V)-Silica Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornburg, Nicholas E.; Notestein, Justin M.

Supported metal oxide catalysts are versatile materials for liquid-phase oxidations, including alkene epoxidation and thioether sulfoxidation with H2O2. Periodic trends in H2O2 activation was recently demonstrated for alkene epoxidation, highlighting Nb-SiO2 as a more active and selective catalyst than Ti-SiO2. Three representative catalysts are studied consisting of NbV, TiIV, and ZrIV on silica, each made through a molecular precursor approach that yields highly dispersed oxide sites, for thioanisole oxidation by H2O2. Initial rates trend Nb>Ti>>Zr, as for epoxidation, and Nb outperforms Ti for a number of other thioethers. In contrast, selectivity to sulfoxide vs. sulfone trends Ti>Nb>>Zr at all conversions.more » Modifying the Nb-SiO2 catalyst with phenylphosphonic acid does not completely remove sulfoxidation reactivity, as it did for photooxidation and epoxidation, and results in an unusual material active for sulfoxidation but neither epoxidation nor overoxidation to the sulfone.« less

Signature Motifs Identify an Acinetobacter Cif Virulence Factor with Epoxide Hydrolase Activity*

PubMed Central

Bahl, Christopher D.; Hvorecny, Kelli L.; Bridges, Andrew A.; Ballok, Alicia E.; Bomberger, Jennifer M.; Cady, Kyle C.; O'Toole, George A.; Madden, Dean R.

2014-01-01

Endocytic recycling of the cystic fibrosis transmembrane conductance regulator (CFTR) is blocked by the CFTR inhibitory factor (Cif). Originally discovered in Pseudomonas aeruginosa, Cif is a secreted epoxide hydrolase that is transcriptionally regulated by CifR, an epoxide-sensitive repressor. In this report, we investigate a homologous protein found in strains of the emerging nosocomial pathogens Acinetobacter nosocomialis and Acinetobacter baumannii (“aCif”). Like Cif, aCif is an epoxide hydrolase that carries an N-terminal secretion signal and can be purified from culture supernatants. When applied directly to polarized airway epithelial cells, mature aCif triggers a reduction in CFTR abundance at the apical membrane. Biochemical and crystallographic studies reveal a dimeric assembly with a stereochemically conserved active site, confirming our motif-based identification of candidate Cif-like pathogenic EH sequences. Furthermore, cif expression is transcriptionally repressed by a CifR homolog (“aCifR”) and is induced in the presence of epoxides. Overall, this Acinetobacter protein recapitulates the essential attributes of the Pseudomonas Cif system and thus may facilitate airway colonization in nosocomial lung infections. PMID:24474692

Simple Epoxide Formation for the Organic Laboratory Using Oxone

ERIC Educational Resources Information Center

Broshears, Williams C.; Esteb, John J.; Richter, Jeremy; Wilson, Anne M.

2004-01-01

Epoxide chemistry is widely used in organic synthesis and regularly discussed in organic chemistry textbooks. An experiment to generate dimethyldioxirane in situ from acetone using Oxone is explained.

Gold(I)-Catalyzed Cascade Cyclization of Allenyl Epoxides

PubMed Central

Tarselli, Michael A.; Lucas Zuccarello, J

2009-01-01

Cationic gold(I) phosphite catalysts activate allenes for epoxide cascade reactions. The system is tolerant of numerous functional groups (sulfones, esters, ethers, sulfonamides) and proceeds at room temperature in dichloromethane. The cyclization pathway is sensitive to the substitution pattern of the epoxide, and the backbone structure of the A-ring. It is capable of producing medium-ring ethers, fused 6-5 bicyclic, and linked pyran-furan structures. The resulting cycloisomers are reminiscent of structures found in numerous polyether natural products. PMID:19588972

A strategy for position-selective epoxidation of polyprenols.

PubMed

Gnanadesikan, Vijay; Corey, E J

2008-06-25

An effective strategy has been developed for the efficient site-selective epoxidation of poylolefinic isoprenoid alcohols, based on the use of an internal control element for intramolecular reaction. The approach is illustrated by application to a series of polyisoprenoid alcohols (polyprenols) at substrate concentration of 0.5 mM. With polyprenol substrates having the hydroxyl function at one terminus, the internal epoxidation can be directed at the double bond of the polyprenol, which is either four or five away from the terminal hydroxyprenyl subunit.

Epoxidized natural rubber toughened aqueous resole type liquefied EFB resin: Physical and chemical characterization

NASA Astrophysics Data System (ADS)

Amran, Umar Adli; Zakaria, Sarani; Chia, Chin Hua

2013-11-01

A preliminary study on the reaction between aqueous resole type resinified liquefied palm oil empty fruit bunches fibres (RLEFB) with epoxidized natural rubber (ENR). Liquefaction of empty fruit bunches (EFB) is carried out at different ratio of phenol to EFB (P:EFB). Resole type phenolic resin is prepared using sodium hydroxide (NaOH) as the catalyst with the ratio of liquefied EFB (LEFB) to formaldehyde (LEFB:F) of 1:1.8. 50% epoxidation of epoxidized natural rubber (ENR-50) is used to react with resole resin by mixing with ENR with aqueous resole resin. The cured resin is characterized with FT-IR and SEM. Aqueous system have been found to be unsuitable medium in the reaction between resin and ENR. This system produced a highly porous product when RLEFB/ENR resin is cured.

Benzil, a potent activator of microsomal epoxide hydrolase in vitro.

PubMed

Seidegård, J; DePierre, J W

1980-12-01

Benzil was found to be a very potent activator of microsomal epoxide hydrolase activity (measured with styrene oxide as substrate) in vitro. The activating effect was uncompetitive and benzil causes approximately ninefold increases in both the apparent V and the apparent Km of the enzyme(s). The half-maximal effect on activity was obtained as a 0.3 mM concentration of benzil. The activating effect obtained with benzil was found to be very specific, since a variety of structurally related compounds had little or no effect on microsomal epoxide hydrolase activity. In order to obtain indications for the existence of more than one microsomal epoxide hydrolase the effect of benzil on this activity from rats induced with phenobarbital, 3-methylcholanthrene, 2-acetylaminofluorene, trans-stilbene oxide, and benzil was tested. The differences observed were minor.

Synthesis and physicochemical properties of epoxidized Tmp trioleate by in situ method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samidin, Salma; Salimon, Jumat

2014-09-03

Tmp trioleate was initially synthesized via esterification of trimetilolprapane and oleic acid (90%) using 1.5% of H{sub 2}SO{sub 4} as a catalyst. The production of Tmp trioleate was observed at 98% (w/w). The iodine value of Tmp trioleate was analyzed for further reaction of epoxidation. Epoxide was important reaction as an intermediate for preparation of chemical modified lubricants from vegetable oils. Finding the best way of epoxidation process will give high quality for further modification of oil instead of reduce the cost and time for the preparation process during reaction of epoxidation. In this study, the epoxidation of unsaturation Tmpmore » trioleate with peroxyformic acid generated in-situ from hydrogen peroxide 30% in H{sub 2}O{sub 2} with formic acid was studied. 95% conversion to oxygen oxirane content (OOC) ring was obtained. The derivatization showed an improvement of the compound's oxidative stability evidenced from pressurized differential scanning calorimetry (PDSC) data which are 177°C to 200°C. Physicochemical properties showed increasing of temperature of flash point from 280°C to 300°C and viscosity index (VI) from 146 to 154. However, the pour point showed increasing temperature which was −58.81°C to −17.32°C. From the data obtained, these derivatives have shown better performance of lubricity properties. Overall, the data indicates that these performances are compatible to the commercial lubricants.« less

Development of epoxide compound from kapok oil for enhanced oil recovery

NASA Astrophysics Data System (ADS)

Anam, M. K.; Supranto; Murachman, B.; Purwono, S.

2017-06-01

Epoxide compound is made by reacting Kapok Oil with acetic acid and hydrogen peroxide with in situ method. The epoxidation reaction was varied at temperatures of 60 °C, 70 °C and 80 °C, while the time of reaction time was varied at 15 minutes, 30 minutes, 60 minutes and 90 minutes. The reaction rate coefficient for the epoxide was obtained as {\\boldsymbol{k}}{\\boldsymbol{=}}{{124}}{\\boldsymbol{,}}{{82}} {{\\exp }} {\\boldsymbol{\\bigg(}}\\frac{{\\boldsymbol-}{{24}}{\\boldsymbol{,}}{{14}}}{{\\boldsymbol{R}}{\\boldsymbol{T}}}{\\boldsymbol{\\bigg)}}. The addition of the epoxide compound 0.5 w/w in the formulation of SLS was able to reduce the IFT value up to 9.95 x 10-2 m N/m. The addition of co-surfactant (1-octanol) was varied between 0.1 and 0.4 of the total mass of the main formulation (SLS + epoxide + water formation). The smallest interfacial tension value is obtained on the addition of co-surfactants as much as 0.2 w/w, with the IFT value is 2.43 x 10-3 m N/m. The effectiveness of the chemicals was tested through micro displacement using artificial porous medium. The experimental results show that some chemicals developed in the laboratory can be used as EOR chemicals. The oil displacement experiments show that as much as 20 to 80 of remaining oil can be recovered by flooding it with the chemicals. The results also show that the oil recovery depends on type of chemicals and chemical concentration.

Iron-catalyzed olefin epoxidation in the presence of acetic acid: insights into the nature of the metal-based oxidant.

PubMed

Mas-Ballesté, Rubén; Que, Lawrence

2007-12-26

The iron complexes [(BPMEN)Fe(OTf)2] (1) and [(TPA)Fe(OTf)2] (2) [BPMEN = N,N'-bis-(2-pyridylmethyl)-N,N'-dimethyl-1,2-ethylenediamine; TPA = tris-(2-pyridylmethyl)amine] catalyze the oxidation of olefins by H2O2 to yield epoxides and cis-diols. The addition of acetic acid inhibits olefin cis-dihydroxylation and enhances epoxidation for both 1 and 2. Reactions carried out at 0 degrees C with 0.5 mol % catalyst and a 1:1.5 olefin/H2O2 ratio in a 1:2 CH3CN/CH3COOH solvent mixture result in nearly quantitative conversions of cyclooctene to epoxide within 1 min. The nature of the active species formed in the presence of acetic acid has been probed at low temperature. For 2, in the absence of substrate, [(TPA)FeIII(OOH)(CH3COOH)]2+ and [(TPA)FeIVO(NCCH3)]2+ intermediates can be observed. However, neither is the active epoxidizing species. In fact, [(TPA)FeIVO(NCCH3)]2+ is shown to form in competition with substrate oxidation. Consequently, it is proposed that epoxidation is mediated by [(TPA)FeV(O)(OOCCH3)]2+, generated from O-O bond heterolysis of the [(TPA)FeIII(OOH)(CH3COOH)]2+ intermediate, which is promoted by the protonation of the terminal oxygen atom of the hydroperoxide by the coordinated carboxylic acid.

INTERACTION OF BENZO(A)PYRENE DIOL EPOXIDE WITH SVAO MINICHROMOSOMES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamper, Howard B.; Yokota, Hisao A.; Bartholomew, James C.

SV40 minichromosomes were reacted with (+)7{beta},8{alpha}-dihydroxy-9{alpha},10{alpha}-epoxy- 7,8,9,10-tetrahydrobenzo[a]pyrene (BaP diol epoxide). Low levels of modification (< 5 DNA adducts/minichromosome) did not detectably alter the structure of the minichromosomes but high levels (> 200 DNA adducts/minichromosome) led to extensive fragmentation. Relative to naked SV40 DNA BaP diol epoxide induced alkylation and strand scission of minichromosomal DNA was reduced or enhanced by factors of 1.5 and 2.0, respectively. The reduction in covalent binding was attributed to the presence of histones, which competed with DNA for the hydrocarbon and reduced the probability of BaP diol epoxide intercalation by tightening the helix. The enhancement ofmore » strand scission was probably due to the catalytic effect of histones on the rate of S-elimination at apurinic sites, although an altered adduct profile or the presence of a repair endonuclease were not excluded. Staphylococcal nuclease digestion indicated that BaP dial epoxide randomly alkylated the minichromosomal DNA. This is in contrast to studies with cellular chromatin where internucleosomal DNA was preferentially modified. Differences in the minichromosomal protein complement were responsible for this altered susceptibility.« less

Theoretical study on the mechanism of a ring-opening reaction of oxirane by the active-site aspartic dyad of HIV-1 protease.

PubMed

Kóna, Juraj

2008-01-21

Two possible mechanisms of the irreversible inhibition of HIV-1 protease by epoxide inhibitors are investigated on an enzymatic model using ab initio (MP2) and density functional theory (DFT) methods (B3LYP, MPW1K and M05-2X). The calculations predict the inhibition as a general acid-catalyzed nucleophilic substitution reaction proceeding by a concerted SN2 mechanism with a reaction barrier of ca. 15-21 kcal mol(-1). The irreversible nature of the inhibition is characterized by a large negative reaction energy of ca. -17-(-24) kcal mol(-1). A mechanism with a direct proton transfer from an aspartic acid residue of the active site onto the epoxide ring has been shown to be preferred compared to one with the proton transfer from the acid catalyst facilitated by a bridging catalytic water molecule. Based on the geometry of the transition state, structural data important for the design of irreversible epoxide inhibitors of HIV-1 protease were defined. Here we also briefly discuss differences between the epoxide ring-opening reaction in HIV-1 protease and epoxide hydrolase, and the accuracy of the DFT method used.

Functionalization of multi-walled carbon nanotubes by epoxide ring-opening polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin Fanlong; Rhee, Kyong Yop; Park, Soo-Jin, E-mail: sjpark@inha.ac.kr

2011-12-15

In this study, covalent functionalization of carbon nanotubes (CNTs) was accomplished by surface-initiated epoxide ring-opening polymerization. FT-IR spectra showed that polyether and epoxide group covalently attached to the sidewalls of CNTs. TGA results indicated that the polyether was successfully grown from the CNT surface, with the final products having a polymer weight percentage of ca. 14-74 wt%. The O/C ratio of CNTs increased significantly from 5.1% to 29.8% after surface functionalization of CNTs. SEM and TEM images of functionalized CNTs exhibited that the tubes were enwrapped by polymer chains with thickness of several nanometers, forming core-shell structures with CNTs atmore » the center. - Graphical abstract: Functionalized CNTs were enwrapped by polymer chains with thickness of several nanometers, forming core-shell structures with CNTs at the center. Highlights: Black-Right-Pointing-Pointer CNTs were functionalized by epoxide ring-opening polymerization. Black-Right-Pointing-Pointer Polyether and epoxide group covalently attached to the sidewalls of CNTs. Black-Right-Pointing-Pointer Functionalized CNTs have a polymer weight percentage of ca. 14-74 wt%. Black-Right-Pointing-Pointer Functionalized CNTs were enwrapped by polymer chains with thickness of several nanometers.« less

VizieR Online Data Catalog: H-α emission regions in Southern Milky Way (Rodgers+ 1960)

NASA Astrophysics Data System (ADS)

Rodgers, A. W.; Campbell, C. T.; Whiteoak, J. B.

2000-05-01

The Catalogue of Rodgers, Cambell, and Whiteoak (RCW), was the result of a survey of emission nebulae carried out at Mt. Stromlo Observatory from December 1957 to April 1959. The entire region of the Milky Way southward of the Palomar sky survey with a latitude of plus or minus 15 degrees of the galactic equator was photographed in the light of hydrogen alpha with comparison plates obtained in yellow light. This work roughly complements the Sharpless (Sh2, see Cat. ) survey published in 1959. (2 data files).

Synthesis and structure-activity relationship of piperidine-derived non-urea soluble epoxide hydrolase inhibitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pecic, Stevan; Pakhomova, Svetlana; Newcomer, Marcia E.

2013-09-27

A series of potent amide non-urea inhibitors of soluble epoxide hydrolase (sEH) is disclosed. The inhibition of soluble epoxide hydrolase leads to elevated levels of epoxyeicosatrienoic acids (EETs), and thus inhibitors of sEH represent one of a novel approach to the development of vasodilatory and anti-inflammatory drugs. Structure–activities studies guided optimization of a lead compound, identified through high-throughput screening, gave rise to sub-nanomolar inhibitors of human sEH with stability in human liver microsomal assay suitable for preclinical development.

Heptachlor epoxide

Integrated Risk Information System (IRIS)

Heptachlor epoxide ; CASRN 1024 - 57 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogen

21 CFR 177.1650 - Polysulfide polymer-polyepoxy resins.

Code of Federal Regulations, 2011 CFR

2011-04-01

...(2-chloroethyl) formal Bis(dichloropropyl) formal Cross-linking agent. Butyl alcohol Solvent. Carbon black (channel process) Chlorinated paraffins Cross-linking agent. Epoxidized linseed oil Epoxidized... monobutyl ether Solvent. Magnesium chloride Methyl isobutyl ketone Solvent. Naphthalene sulfonic acid...

Epoxy resin

DOEpatents

Wilson, Glenn R.; Salyer, Ival O.; Ball, III, George L.

1976-07-13

By mixing one part of a prepolymer containing a polyamine partially polymerized with an organic epoxide and subsequently reacted with a fatty acid containing from 8 to 32 carbon atoms, and then reacting this prepolymer mixture with 3 parts of an organic epoxide, a composition was obtained which made a gas frothable, shear-stable, room temperature curing, low density foam. A particularly advantageous prepolymer was prepared using a polyamine selected from the group consisting of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, partially polymerized with an organic epoxide having an average molecular weight of about 350 and having an epoxide equivalent of 185 to 192, and reacted with 2-10 weight percent linoleic acid. When one part of this prepolymer was reacted with about three parts of epoxy, and frothed by whipping in air or nitrogen an epoxy foam was produced which could be troweled onto surfaces and into corners or crevices, and subsequently cured, at near ambient temperature, to a strong dimensionally stable foam product.

Persistence and changes in bioavailability of dieldrin, DDE and heptachlor epoxide in earthworms over 45 years

USGS Publications Warehouse

Beyer, W. Nelson; Gale, Robert W.

2013-01-01

The finding of dieldrin (88 ng/g), DDE (52 ng/g), and heptachlor epoxide (19 ng/g) in earthworms from experimental plots after a single moderate application (9 kg/ha) 45 years earlier attests to the remarkable persistence of these compounds in soil and their continued uptake by soil organisms. Half-lives (with 95 % confidence intervals) in earthworms, estimated from exponential decay equations, were as follows: dieldrin 4.9 (4.3-5.7) years, DDE 5.3 (4.7-6.1) years, and heptachlor epoxide 4.3 (3.8-4.9) years. These half-lives were not significantly different from those estimated after 20 years. Concentration factors (dry weight earthworm tissue/dry weight soil) were initially high and decreased mainly during the first 11 years after application. By the end of the study, average concentration factors were 1.5 (dieldrin), 4.0 (DDE), and 1.8 (heptachlor epoxide), respectively.

Stereoselective Epoxidation of 4-Deoxypentenosides: A Polarized-πModel

PubMed Central

Cheng, Gang; Boulineau, Fabien P.; Liew, Siong-Tern; Shi, Qicun; Wenthold, Paul G.; Wei, Alexander

2008-01-01

The high facioselectivity in the epoxidation of 4-deoxypentenosides (4-DPs) by dimethyldioxirane (DMDO) correlates with a stereoelectronic bias in the 4-DPs’ ground-state conformations, as elucidated by polarized-π frontier molecular orbital (PPFMO) analysis. PMID:16986946

An artificial molecular machine that builds an asymmetric catalyst

NASA Astrophysics Data System (ADS)

De Bo, Guillaume; Gall, Malcolm A. Y.; Kuschel, Sonja; De Winter, Julien; Gerbaux, Pascal; Leigh, David A.

2018-05-01

Biomolecular machines perform types of complex molecular-level tasks that artificial molecular machines can aspire to. The ribosome, for example, translates information from the polymer track it traverses (messenger RNA) to the new polymer it constructs (a polypeptide)1. The sequence and number of codons read determines the sequence and number of building blocks incorporated into the biomachine-synthesized polymer. However, neither control of sequence2,3 nor the transfer of length information from one polymer to another (which to date has only been accomplished in man-made systems through template synthesis)4 is easily achieved in the synthesis of artificial macromolecules. Rotaxane-based molecular machines5-7 have been developed that successively add amino acids8-10 (including β-amino acids10) to a growing peptide chain by the action of a macrocycle moving along a mono-dispersed oligomeric track derivatized with amino-acid phenol esters. The threaded macrocycle picks up groups that block its path and links them through successive native chemical ligation reactions11 to form a peptide sequence corresponding to the order of the building blocks on the track. Here, we show that as an alternative to translating sequence information, a rotaxane molecular machine can transfer the narrow polydispersity of a leucine-ester-derivatized polystyrene chain synthesized by atom transfer radical polymerization12 to a molecular-machine-made homo-leucine oligomer. The resulting narrow-molecular-weight oligomer folds to an α-helical secondary structure13 that acts as an asymmetric catalyst for the Juliá-Colonna epoxidation14,15 of chalcones.

A Natal Microcosm

NASA Technical Reports Server (NTRS)

2004-01-01

In the quest to better understand the birth of stars and the formation of new worlds, astronomers have used NASA's Spitzer Space Telescope to examine the massive stars contained in a cloudy region called Sharpless 140. This cloud is a fascinating microcosm of a star-forming region since it exhibits, within a relatively small area, all of the classic manifestations of stellar birth.

Sharpless 140 lies almost 3000 light-years from Earth in the constellation Cepheus. At its heart is a cluster of three deeply embedded young stars, which are each several thousand times brighter than the Sun. Though they are strikingly visible in this image from Spitzer's infrared array camera, they are completely obscured in visible light, buried within the core of the surrounding dust cloud.

The extreme youth of at least one of these stars is indicated by the presence of a stream of gas moving at high velocities. Such outflows are signatures of the processes surrounding a star that is still gobbling up material as part of its formation.

The bright red bowl, or arc, seen in this image traces the outer surface of the dense dust cloud encasing the young stars. This arc is made up primarily of organic compounds called polycyclic aromatic hydrocarbons, which glow on the surface of the cloud. Ultraviolet light from a nearby bright star outside of the image is 'eating away' at these molecules. Eventually, this light will destroy the dust envelope and the masked young stars will emerge.

This false-color image was taken on Oct. 11, 2003 and is composed of photographs obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

A Natal Microcosm

NASA Image and Video Library

2004-05-11

In the quest to better understand the birth of stars and the formation of new worlds, astronomers have used NASA's Spitzer Space Telescope to examine the massive stars contained in a cloudy region called Sharpless 140. This cloud is a fascinating microcosm of a star-forming region since it exhibits, within a relatively small area, all of the classic manifestations of stellar birth. Sharpless 140 lies almost 3000 light-years from Earth in the constellation Cepheus. At its heart is a cluster of three deeply embedded young stars, which are each several thousand times brighter than the Sun. Though they are strikingly visible in this image from Spitzer's infrared array camera, they are completely obscured in visible light, buried within the core of the surrounding dust cloud. The extreme youth of at least one of these stars is indicated by the presence of a stream of gas moving at high velocities. Such outflows are signatures of the processes surrounding a star that is still gobbling up material as part of its formation. The bright red bowl, or arc, seen in this image traces the outer surface of the dense dust cloud encasing the young stars. This arc is made up primarily of organic compounds called polycyclic aromatic hydrocarbons, which glow on the surface of the cloud. Ultraviolet light from a nearby bright star outside of the image is "eating away" at these molecules. Eventually, this light will destroy the dust envelope and the masked young stars will emerge. This false-color image was taken on Oct. 11, 2003 and is composed of photographs obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). http://photojournal.jpl.nasa.gov/catalog/PIA05878

Teaching Green Chemistry with Epoxidized Soybean Oil

ERIC Educational Resources Information Center

Barcena, Homar; Tuachi, Abraham; Zhang, Yuanzhuo

2017-01-01

The synthesis of epoxidized soybean oil (ESO) provides students a vantage point on the application of green chemistry principles in a series of experiments. Qualitative tests review the reactions of alkenes, whereas spectroscopic analyses provide insight in monitoring functional group transformations.

40 CFR 721.2685 - Polyisobutene epoxide (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

....2685 Section 721.2685 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.2685 Polyisobutene epoxide (generic). (a) Chemical substances and significant new uses...

Ring-Opening Copolymerization of Epoxides and Cyclic Anhydrides with Discrete Metal Complexes: Structure-Property Relationships.

PubMed

Longo, Julie M; Sanford, Maria J; Coates, Geoffrey W

2016-12-28

Polyesters synthesized through the alternating copolymerization of epoxides and cyclic anhydrides compose a growing class of polymers that exhibit an impressive array of chemical and physical properties. Because they are synthesized through the chain-growth polymerization of two variable monomers, their syntheses can be controlled by discrete metal complexes, and the resulting materials vary widely in their functionality and physical properties. This polymer-focused review gives a perspective on the current state of the field of epoxide/anhydride copolymerization mediated by discrete catalysts and the relationships between the structures and properties of these polyesters.

Biosynthetic machinery of ionophore polyether lasalocid: enzymatic construction of polyether skeleton.

PubMed

Minami, Atsushi; Oguri, Hiroki; Watanabe, Kenji; Oikawa, Hideaki

2013-08-01

Diversity of natural polycyclic polyethers originated from very simple yet versatile strategy consisting of epoxidation of linear polyene followed by epoxide opening cascade. To understand two-step enzymatic transformations at molecular basis, a flavin containing monooxygenase (EPX) Lsd18 and an epoxide hydrolase (EH) Lsd19 were selected as model enzymes for extensive investigation on substrate specificity, catalytic mechanism, cofactor requirement and crystal structure. This pioneering study on prototypical lasalocid EPX and EH provides insight into detailed mechanism of ionophore polyether assembly machinery and clarified remaining issues for polyether biosynthesis. Copyright © 2013 Elsevier Ltd. All rights reserved.

Evaluation of in vitro anticancer activity of Ocimum basilicum, Alhagi maurorum, Calendula officinalis and their parasite Cuscuta campestris.

PubMed

Behbahani, Mandana

2014-01-01

The present investigation was carried out to study the relationship between presence of cytotoxic compounds in Ocimum basilicum, Alhagi maurorum, Calendula officinalis and their parasite Cuscuta campestris. The cytotoxic activity of the pure compounds was performed by MTT assay against breast cancer cell lines (MCF-7 and MDA-MB-231) and normal breast cell line (MCF 10A). The induction of apoptosis was measured by the expression levels of p53, bcl-2, bax and caspase-3 genes using quantitative Real Time PCR. Three active fractions were detected by nuclear magnetic resonance as lutein, lupeol and eugenol, respectively, in C. officinalis, A. maurorum and O. basilicum. These compounds and their epoxidized forms were also detected in their parasite C. campestris. The cytotoxic activity of lutein epoxide, lupeol epoxide and eugenol epoxide was significantly more than lutein, lupeol and eugenol. The mRNA expression level of p53, caspase-3 and bax genes were increased in both cancer cells treated with all pure compounds. However, bcl-2 gene expression decreased in treated breast cancer cells. In conclusion, all the data indicated that the epoxide forms of lupeol, lutein and eugenol are potential drug candidates for inducing apoptosis in human breast cancer cells.

Evaluation of In Vitro Anticancer Activity of Ocimum Basilicum, Alhagi Maurorum, Calendula Officinalis and Their Parasite Cuscuta Campestris

PubMed Central

Behbahani, Mandana

2014-01-01

The present investigation was carried out to study the relationship between presence of cytotoxic compounds in Ocimum basilicum, Alhagi maurorum, Calendula officinalis and their parasite Cuscuta campestris. The cytotoxic activity of the pure compounds was performed by MTT assay against breast cancer cell lines (MCF-7 and MDA-MB-231) and normal breast cell line (MCF 10A). The induction of apoptosis was measured by the expression levels of p53, bcl-2, bax and caspase-3 genes using quantitative Real Time PCR. Three active fractions were detected by nuclear magnetic resonance as lutein, lupeol and eugenol, respectively, in C. officinalis, A. maurorum and O. basilicum. These compounds and their epoxidized forms were also detected in their parasite C. campestris. The cytotoxic activity of lutein epoxide, lupeol epoxide and eugenol epoxide was significantly more than lutein, lupeol and eugenol. The mRNA expression level of p53, caspase-3 and bax genes were increased in both cancer cells treated with all pure compounds. However, bcl-2 gene expression decreased in treated breast cancer cells. In conclusion, all the data indicated that the epoxide forms of lupeol, lutein and eugenol are potential drug candidates for inducing apoptosis in human breast cancer cells. PMID:25548920

Interaction of water, alkyl hydroperoxide, and allylic alcohol with a single-site homogeneous Ti-Si epoxidation catalyst: A spectroscopic and computational study.

PubMed

Urakawa, Atsushi; Bürgi, Thomas; Skrabal, Peter; Bangerter, Felix; Baiker, Alfons

2005-02-17

Tetrakis(trimethylsiloxy)titanium (TTMST, Ti(OSiMe3)4) possesses an isolated Ti center and is a highly active homogeneous catalyst in epoxidation of various olefins. The structure of TTMST resembles that of the active sites in some heterogeneous Ti-Si epoxidation catalysts, especially silylated titania-silica mixed oxides. Water cleaves the Ti-O-Si bond and deactivates the catalyst. An alkyl hydroperoxide, TBHP (tert-butyl hydroperoxide), does not cleave the Ti-O-Si bond, but interacts via weak hydrogen-bonding as supported by NMR, DOSY, IR, and computational studies. ATR-IR spectroscopy combined with computational investigations shows that more than one, that is, up to four, TBHP can undergo hydrogen-bonding with TTMST, leading to the activation of the O-O bond of TBHP. The greater the number of TBHP molecules that form hydrogen bonds to TTMST, the more electrophilic the O-O bond becomes, and the more active the complex is for epoxidation. An allylic alcohol, 2-cyclohexen-1-ol, does not interact strongly with TTMST, but the interaction is prominent when it interacts with the TTMST-TBHP complex. On the basis of the experimental and theoretical findings, a hydrogen-bond-assisted epoxidation mechanism of TTMST is suggested.

Can the epoxides of cinnamyl alcohol and cinnamal show new cases of contact allergy?

PubMed

Hagvall, Lina; Niklasson, Ida B; Luthman, Kristina; Karlberg, Ann-Therese

2018-06-01

Cinnamyl alcohol is considered to be a prohapten and prehapten with cinnamal as the main metabolite. However, many individuals who are allergic to cinnamyl alcohol do not react to cinnamal. Sensitizing epoxides of cinnamyl alcohol and cinnamal have been identified as metabolites and autoxidation products of cinnamyl alcohol. To investigate the clinical relevance of contact allergy to epoxycinnamyl alcohol and epoxycinnamal. Irritative effects of the epoxides were investigated in 12 dermatitis patients. Epoxycinnamyl alcohol and epoxycinnamal were patch tested in 393 and 390 consecutive patients, respectively. In parallel, cinnamyl alcohol and cinnamal were patch tested in 607 and 616 patients, respectively. Both epoxides were irritants, but no more positive reactions were detected than when testing was performed with cinnamyl alcohol and cinnamal. Late allergic reactions to epoxycinnamyl alcohol were observed. In general, patients with late reactions showed doubtful or positive reactions to cinnamal and fragrance mix I at regular patch testing. The investigated epoxides are not important haptens in contact allergy to cinnamon fragrance. The high frequency of fragrance allergy among patients included in the irritancy study showed the difficulty of suspecting fragrance allergy on the basis of history; patch testing broadly with fragrance compounds is therefore important. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

A Computational Study of Acid Catalyzed Aerosol Reactions of Atmospherically Relevant Epoxides

EPA Science Inventory

Epoxides are important intermediates of atmospheric isoprene oxidation. Their subsequent reactions in the particle phase lead to the production of organic compounds detected in ambient aerosols. We apply density functional theory to determine the important kinetic factors that ...

Ring-opening Polymerization of Epoxidized Soybean Oil

USDA-ARS?s Scientific Manuscript database

Ring opening polymerization of epoxidized soybean oil (ESO) initiated by boron trifluoride diethyl etherate, (BF3•OEt2), in methylene chloride was conducted in an effort to develop useful biodegradable polymers. The resulting polymers (PESO) were characterized using Infrared (IR), differential scan...

Biobased composites from thermoplastic polyurethane elastomer and cross-linked acrylated-epoxidized soybean oil

USDA-ARS?s Scientific Manuscript database

Soybean oil is an important sustainable material. Crosslinked acrylated epoxidized soybean oil (AESO) is brittle without flexibility and the incorporation of thermoplastic polyurethane improves its toughness for industrial applications. The hydrophilic functional groups from both oil and polyurethan...

ULTRASOUND-ASSISTED ORGANIC SYNTHESIS: ALCOHOL OXIDATION AND OLEFIN EPOXIDATION

EPA Science Inventory

Ultrasound-assisted Organic Synthesis: Alcohol Oxidation and Olefin Epoxidation

Unnikrishnan R Pillai, Endalkachew Sahle-Demessie , Vasudevan Namboodiri, Quiming Zhao, Juluis Enriquez
U.S. EPA , 26 W. Martin Luther King Dr. , Cincinnati, OH 45268
Phone: 513-569-773...

Toughening mechanism in elastomer-modified epoxy resins, part 2

NASA Technical Reports Server (NTRS)

Yee, A. F.; Pearson, R. A.

1984-01-01

The role of matrix ductility on the toughenability and toughening mechanism of elastomer-modified DGEBRA epoxies was investigated. Matrix ductility was varied by using epoxide resins of varying epoxide monomer molecular weights. These epoxide resins were cured using 4,4' diaminodiphenyl sulfone (DDS) and, in some cases, modified with 10% HYCAR(r)CTBN 1300X8. Fracture roughness values for the neat epoxies were found to be almost independent on the monomer molecular weight of the epoxide resin used. However, it was found that the fracture toughness of the elastomer-modified epoxies was very dependent upon the epoxide monomer molecular weight. Tensile dilatometry indicated that the toughening mechanism, when present, is similar to the mechanisms found for the piperidine cured epoxies in Part 1. SEM and OM corroborate this finding. Dynamic mechanical studies were conducted to shed light on the toughenability of the epoxies. The time-dependent small strain behavior of these epoxies were separated into their bulk and shear components. The bulk component is related to brittle fracture, whereas the shear component is related to yielding. It can be shown that the rates of shear and bulk strain energy buildup for a given stress are uniquely determined by the values of Poisson's ratio, nu. It was found that nu increases as the monomer molecular weight of the epoxide resin used increases. This increase in nu can be associated with the low temperature beta relaxation. The effect of increasing cross-link density is to shift the beta relaxation to higher temperatures and to decrease the magnitude of the beta relaxation. Thus, increasing cross-link density decreases nu and increases the tendency towards brittle fracture.

In Silico Prediction of Cytochrome P450-Mediated Biotransformations of Xenobiotics: A Case Study of Epoxidation.

PubMed

Zhang, Jing; Ji, Li; Liu, Weiping

2015-08-17

Predicting the biotransformation of xenobiotics is important in toxicology; however, as more compounds are synthesized than can be investigated experimentally, powerful computational methods are urgently needed to prescreen potentially useful candidates. Cytochrome P450 enzymes (P450s) are the major enzymes involved in xenobiotic metabolism, and many substances are bioactivated by P450s to form active compounds. An example is the conversion of olefinic substrates to epoxides, which are intermediates in the metabolic activation of many known or suspected carcinogens. We have calculated the activation energies for epoxidation by the active species of P450 enzymes (an iron-oxo porphyrin cation radical oxidant, compound I) for a diverse set of 36 olefinic substrates with state-of-the-art density functional theory (DFT) methods. Activation energies can be estimated by the computationally less demanding method of calculating the ionization potentials of the substrates, which provides a useful and simple predictive model based on the reaction mechanism; however, the preclassification of these diverse substrates into weakly polar and strongly polar groups is a prerequisite for the construction of specific predictive models with good predictability for P450 epoxidation. This approach has been supported by both internal and external validations. Furthermore, the relation between the activation energies for the regioselective epoxidation and hydroxylation reactions of P450s and experimental data has been investigated. The results show that the computational method used in this work, single-point energy calculations with the B3LYP functional including zero-point energy and solvation and dispersion corrections based on B3LYP-optimized geometries, performs well in reproducing the experimental trends of the epoxidation and hydroxylation reactions.

Microsomal oxidation of tribromoethylene and reactions of tribromoethylene oxide.

PubMed

Yoshioka, Tadao; Krauser, Joel A; Guengerich, F Peter

2002-11-01

Halogenated olefins are of interest because of their widespread use in industry and their potential toxicity to humans. Epoxides are among the enzymatic oxidation products and have been studied in regard to their toxicity. Most of the attention has been given to chlorinated epoxides, and we have previously studied the reactions of the mono-, di-, tri-, and tetrachloroethylene oxides. To further test some hypotheses concerning the reactivity of these compounds, we prepared tribromoethylene (TBE) oxide and compared it to trichloroethylene (TCE) oxide and other chlorinated epoxides. TBE oxide reacted with H(2)O about 3 times faster than did TCE oxide. Several hydrolysis products of TBE oxide were the same as formed from TCE oxide, i.e., glyoxylic acid, CO, and HCO(2)H. Br(2)CHCO(2)H was formed from TBE oxide; the yield was higher than for Cl(2)CHCO(2)H formed in the hydrolysis of TCE oxide. The yield of tribromoacetaldehyde was < 0.4% in aqueous buffer (pH 7.4). In rat liver microsomal incubations containing TBE and NADPH, Br(2)CHCO(2)H was a major product, and tribromoacetaldehyde was a minor product. These results are consistent with schemes previously developed for halogenated epoxides, with migration of bromine being more favorable than for chlorine. Reaction of TBE oxide with lysine yielded relatively more N-dihaloacetyllysine and less N-formyllysine than in the case of TCE oxide. This same pattern was observed in the products of the reaction of TBE oxide with the lysine residues in bovine serum albumin. We conclude that the proposed scheme of hydrolysis of halogenated epoxides follows the expected halide order and that this can be used to rationalize patterns of hydrolysis and reactivity of other halogenated epoxides.

Species differences in the hydrolysis of 2-cyanoethylene oxide, the epoxide metabolite of acrylonitrile.

PubMed

Kedderis, G L; Batra, R

1993-04-01

The carcinogenic effects of acrylonitrile in rats are believed to be mediated by its DNA-reactive epoxide metabolite, 2-cyanoethylene oxide (CEO). Previous studies have shown that conjugation with glutathione is the major detoxication pathway for both acrylonitrile and CEO. This study investigated the role of epoxide hydrolase in the hydrolysis of CEO by HPLC analysis of the products from [2,3-14C]CEO. CEO is a relatively stable epoxide with a half-life of 99 min at 37 degrees C in sodium phosphate buffer (0.1 M), pH 7.3. Incubation with hepatic microsomes or cytosols from male F-344 rats or B6C3F1 mice did not enhance the rate of hydrolysis of CEO (0.69 nmol/min). Human hepatic microsomes significantly increased the rate of hydrolysis of CEO, whereas human hepatic cytosols did not. Human hepatic microsomal hydrolysis activity was heat-sensitive and potently inhibited by 1,1,1-trichloropropene oxide (IC50 of 23 microM), indicating that epoxide hydrolase was the catalyst. The hydrolysis of CEO catalyzed by hepatic microsomes from six individuals exhibited normal saturation kinetics with KM ranging from 0.6 to 3.2 mM and Vmax from 8.3 to 18.8 nmol hydrolysis products/min/mg protein. Pretreatment of rodents with phenobarbital or acetone induced hepatic microsomal hydrolysis activity toward CEO, whereas treatment with beta-naphthoflavone, dexamethasone or acrylonitrile itself was without effect. These data show that humans possess an additional detoxication pathway for CEO that is not active in rodents (but is inducible). The presence of an active epoxide hydrolase hydrolysis activity toward CEO in humans should be considered in assessments of cancer risk from acrylonitrile exposure.

Synthesis of Vitamin K Expoxide: An Undergraduate Biochemistry Experiment.

ERIC Educational Resources Information Center

Thierry-Palmer, M.

1984-01-01

Provides procedures for synthesizing and purifying a vitamin K metabolite (2,3-epoxide) to introduce many of the techniques used in lipid biochemistry. Includes typical results obtained as well as an optional experiment designed to test the purity of the epoxide obtained. (JM)

A new efficient iron catalyst for olefin epoxidation with hydrogen peroxide.

PubMed

Mikhalyova, Elena A; Makhlynets, Olga V; Palluccio, Taryn D; Filatov, Alexander S; Rybak-Akimova, Elena V

2012-01-18

A new aminopyridine ligand derived from bipiperidine (the product of full reduction of bipyridine, bipy) coordinates to iron(II) in a cis-α fashion, yielding a new selective catalyst for olefin epoxidation with H(2)O(2) under limiting substrate conditions.

Enhanced metal loading in SBA-15-type catalysts facilitated by salt addition. Synthesis, characterization and catalytic epoxide alcoholysis activity of molybdenum incorporated porous silica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budhi, Sridhar; Peeraphatdit, Chorthip; Pylypenko, Svitlana

2014-02-07

We report a novel method to increase the metal loading in SBA-15 silica matrix via direct synthesis. It was demonstrated through the synthesis and characterization of a series of molybdenum containing SBA-15 mesoporous silica catalysts prepared with and without diammonium hydrogen phosphate (DHP) as an additive. Catalysts prepared with DHP show a 2–3 times increase in incorporation of molybdenum in the silica matrix and pore size enlargement. The synthesized catalysts were characterized using nitrogen sorption, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma–optical emission spectroscopy (ICP–OES). Themore » catalytic activity of catalysts prepared with DHP for alcoholysis of epoxides was superior than the catalyst prepared without DHP. Alcoholysis of epoxides was demonstrated for a range of alcohols and epoxides under ambient conditions in as little as 30 min with high selectivity.« less

Alphatic 3,4-epoxyalcohols. Metabolism by epoxide hydrase and mutagenic activity.

PubMed

Ortiz de Montellano, P R; Boparai, A S

1978-12-18

Rabbit hepatic microsomal epoxide hydrase catalyzes the rapid hydrolysis of 1,2-epoxy-4-heptanol to 1,2,4-heptanetriol. Both diastereomers of the substrate are hydrolyzed, and both product diastereomers are formed. Similarly both cis- and trans-3,4-epoxy-1-hexanol are hydrolyzed, albeit more slowly, to give 1,3,4-hexanetriol. The trans isomer gives exclusively one diastereomer (erythro) of the triol, while the cis isomer gives the other diastereomer (threo). The product expected if a primary cationic intermediate were to be formed and trapped intramolecularly during the hydrolysis of 1,2-epoxy-4-heptanol, 2-propyl-4-tetrahydrofuranol, was not observed. A comparison of the mutagenic activity in the Ames test of 1-heptane, 1-hepten-4-ol, 1,2-epoxyheptane, and 1,2-epoxy-4-heptanol revealed that only the latter is a detectable mutagen. A vicinal hydroxyl therefore does not interfere significantly with enzymatic epoxide hydrolysis, but it does enhance the bioalkylating potential of even an aliphatic epoxide.

Characterization of an epoxide hydrolase from the Florida red tide dinoflagellate, Karenia brevis.

PubMed

Sun, Pengfei; Leeson, Cristian; Zhi, Xiaoduo; Leng, Fenfei; Pierce, Richard H; Henry, Michael S; Rein, Kathleen S

2016-02-01

Epoxide hydrolases (EH, EC 3.3.2.3) have been proposed to be key enzymes in the biosynthesis of polyether (PE) ladder compounds such as the brevetoxins which are produced by the dinoflagellate Karenia brevis. These enzymes have the potential to catalyze kinetically disfavored endo-tet cyclization reactions. Data mining of K. brevis transcriptome libraries revealed two classes of epoxide hydrolases: microsomal and leukotriene A4 (LTA4) hydrolases. A microsomal EH was cloned and expressed for characterization. The enzyme is a monomeric protein with molecular weight 44kDa. Kinetic parameters were evaluated using a variety of epoxide substrates to assess substrate selectivity and enantioselectivity, as well as its potential to catalyze the critical endo-tet cyclization of epoxy alcohols. Monitoring of EH activity in high and low toxin producing cultures of K. brevis over a three week period showed consistently higher activity in the high toxin producing culture implicating the involvement of one or more EH in brevetoxin biosynthesis. Copyright © 2015 Elsevier Ltd. All rights reserved.

Epoxidation of cottonseed oil by aqueous hydrogen peroxide catalysed by liquid inorganic acids.

PubMed

Dinda, Srikanta; Patwardhan, Anand V; Goud, Vaibhav V; Pradhan, Narayan C

2008-06-01

The kinetics of epoxidation of cottonseed oil by peroxyacetic acid generated in situ from hydrogen peroxide and glacial acetic acid in the presence of liquid inorganic acid catalysts were studied. It was possible to obtain up to 78% relative conversion to oxirane with very less oxirane cleavage by in situ technique. The rate constants for sulphuric acid catalysed epoxidation of cottonseed oil were in the range 0.39-5.4 x 10(-6)L mol(-1)s(-1) and the activation energy was found to be 11.7 kcal mol(-1). Some thermodynamic parameters such as enthalpy, entropy, and free energy of activation were determined to be of 11.0 kcal mol(-1), -51.4 cal mol(-1)K(-1) and 28.1 kcal mol(-1), respectively. The order of effectiveness of catalysts was found to be sulphuric acid>phosphoric acid>nitric acid>hydrochloric acid. Acetic acid was found to be superior to formic acid for the in situ cottonseed oil epoxidation.

Metabolism of halogenated ethylenes.

PubMed Central

Leibman, K C; Ortiz, E

1977-01-01

The metabolism of the chlorinated ethylenes may be explained by the formation of chloroethylene epoxides as the first intermediate products. The evidence indicates that these epoxides rearrange with migration of chlorine to form chloroacetaldehydes and chloroacetyl chlorides. Thus, monochloroacetic acid, chloral hydrate, and trichloroacetic acid have been found in reaction mixtures of 1,1-dichloroethylene, trichloroethylene, and tetrachloroethylene, respectively, with rat liver microsomal systems. Rearrangements of the chloroethylene, and glycols formed from the epoxides by hydration may also take place, but would appear, at least in the case of 1,1-dichloroethylene, to be quantitatively less important. The literature on the metabolism of chlorinated ethylenes and its relationship to their toxicity is reviewed. PMID:612463

Diastereoselective Synthesis of a Strawberry Flavoring Agent by Epoxidation of Ethyl trans-b-Methylcinnamate

NASA Astrophysics Data System (ADS)

Pageau, Gayle J.; Mabaera, Rodwell; Kosuda, Kathryn M.; Sebelius, Tamara A.; Ghaffari, Ali H.; Kearns, Kenneth A.; McIntyre, Jean P.; Beachy, Tina M.; Thamattoor, Dasan M.

2002-01-01

The diastereoselective synthesis of ethyl (E)-3-methyl-3-phenylglycidate, a strawberry flavoring agent, is carried out by epoxidizing ethyl trans-b-methylcinnamate with m-chloroperbenzoic acid. This epoxidation is appropriate for the introductory organic laboratory and augments the small number of such experiments currently available for undergraduate education. In the course of performing this exercise, students are exposed to many important facets of organic chemistry such as synthesis, reaction mechanism, stereochemistry, chromatography, quantitative analysis, spectroscopy, and computational chemistry. The 1H NMR spectrum of this compound is especially interesting and presents instructive examples of diastereotopic protons and shielding effects of the aromatic ring current.

Oxidative Reactions with Nonaqueous Enzymes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jonathan S. Dordick; Douglas Clark; Brian H Davison

2001-12-30

The objective of this work is to demonstrate a proof-of-concept of enzymatic oxidative processing in nonaqueous media using alkene epoxidation and phenolic polymerization as relevant targets. This project will provide both the fundamental and applied investigations necessary to initiate the implementation of oxidative biocatalysts as commercially relevant alternatives to chemical processing in general, and to phenolic polymerizations and alkene epoxidation specifically. Thus, this work will address the Bioprocessing Solicitation Area to: (1) makes major improvements to phenolic polymerization and alkene epoxidation technologies; (2) is expected to be cost competitive with competing conventional processes; and (3) produces higher yields with lessmore » waste.« less

Residential Segregation, Housing Status, and Prostate Cancer in African American and White Men

DTIC Science & Technology

2008-04-01

and Leu432Val, microsomal epoxide hydrolase (mEH) Tyr113His and His139Arg, CYP3A4 A(−392)G] and conjugation [glutathione S-transferase (GST) M1 null...CYP1B1, or CYP3A4 (16) can then transform the dihydrodiol to a highly reactive diol-epoxide [benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide, BPDE] that can...Although mEH (18) and CYP1B1 (19) are expressed in the prostate, CYP1A1 may only be induced under androgen dependency (20) and CYP3A4 may require

Synthesis and characterization of estolides containing epoxy and cyclic carbonate groups

USDA-ARS?s Scientific Manuscript database

The unsaturated sites in 2-ethylhexyl estolides were converted into 5-membered cyclic carbonate groups utilizing a two-step process. First, epoxidation of the alkene bonds was accomplished using formic acid and hydrogen peroxide. The epoxidized estolide material was then reacted with supercritical c...

Polymercaptanized soybean oil – properties and tribological characterization

USDA-ARS?s Scientific Manuscript database

Polymercaptanized vegetable oils are produced in industrial scale by the addition of hydrogen sulfide across double bonds or epoxides of vegetable oils, in the presence of UV-light. To date, soybean oil, epoxidized soybean oil, and castor oil has been mercaptanized using such a procedure. Depending ...

Polymerization of epoxidized triglycerides with fluorosulfonic acid

USDA-ARS?s Scientific Manuscript database

The use of triglycerides as agri-based renewable raw materials for the development of new products is highly desirable in view of uncertain future petroleum prices. A new method of polymerizing epoxidized soybean oil has been devised with the use of fluorosulfonic acid. Depending on the reaction con...

Epoxide pathways improve model predictions of isoprene markers and reveal key role of acidity in aerosol formation

EPA Science Inventory

Isoprene significantly contributes to organic aerosol in the southeastern United States where biogenic hydrocarbons mix with anthropogenic emissions. In this work, the Community Multiscale Air Quality model is updated to predict isoprene aerosol from epoxides produced under both ...

Lipid Sulfates and Sulfonates Are Allosteric Competitive Inhibitors of the N-Terminal Phosphatase Activity of the Mammalian Soluble Epoxide Hydrolase†

PubMed Central

Tran, Katherine L.; Aronov, Pavel A.; Tanaka, Hiromasa; Newman, John W.; Hammock, Bruce D.; Morisseau, Christophe

2006-01-01

The EPXH2 gene encodes for the soluble epoxide hydrolase (sEH), a homodimeric enzyme with each monomer containing two domains with distinct activities. The C-terminal domain, containing the epoxide hydrolase activity (Cterm-EH), is involved in the metabolism of arachidonic acid epoxides, endogenous chemical mediators that play important roles in blood pressure regulation, cell growth, and inflammation. We recently demonstrated that the N-terminal domain contains a Mg2+-dependent lipid phosphate phosphatase activity (Nterm-phos). However, the biological role of this activity is unknown. The inability of known phosphatase inhibitors to inhibit the Nterm-phos constitutes a significant barrier to the elucidation of its function. We describe herein sulfate, sulfonate, and phosphonate lipids as novel potent inhibitors of Nterm-phos. These compounds are allosteric competitive inhibitors with KI in the hundred nanomolar range. These inhibitors may provide a valuable tool to investigate the biological role of the Nterm-phos. We found that polyisoprenyl phosphates are substrates of Nterm-phos, suggesting a possible role in sterol synthesis or inflammation. Furthermore, some of these compounds inhibit the C-terminal sEH activity through a noncompetitive inhibition mechanism involving a new binding site on the C-terminal domain. This novel site may play a role in the natural in vivo regulation of epoxide hydrolysis by sEH. PMID:16142916

Significance of the lipid phase in the dynamics and functions of the xanthophyll cycle as revealed by PsbS overexpression in tobacco and in-vitro de-epoxidation in monogalactosyldiacylglycerol micelles.

PubMed

Hieber, A David; Kawabata, Osamu; Yamamoto, Harry Y

2004-01-01

The dynamics of the xanthophyll cycle relative to non-photochemical quenching (NPQ) were examined in tobacco plants overexpressing violaxanthin de-epoxidase (VDE), PsbS and PsbS+VDE for effects on NPQ and violaxanthin (V) de-epoxidation over a range of light intensities. Induction of de-epoxidation and NPQ increased in overexpressed VDE and PsbS plants, respectively. Surprisingly, under low light, overexpressing PsbS enhanced de-epoxidation in addition to NPQ. The effect was hypothesized as due to PsbS binding zeaxanthin (Z) or inducing the binding of Z within the quenching complex, thus shifting the equilibrium toward higher de-epoxidation states. Studies in model systems show that Z can stereospecifically inhibit VDE activity against violaxanthin. This effect, observed under conditions of limiting lipid concentration, was interpreted as product feedback inhibition. These results support the hypothesis that the capacity of the thylakoid lipid phase for xanthophylls is limited and modulates xanthophyll-cycle activity, in conjunction with the release of V and binding of Z by pigment-binding proteins. These modulating factors are incorporated into a lipid-matrix model that has elements of a signal transduction system wherein the light-generated protons are the signal, VDE the signal receptor, Z the secondary messenger, the lipid phase the transduction network, and Z-binding proteins the targets.

3-D QSAR ANALYSIS OF INHIBITION OF MURINE SOLUBLE EPOXIDE HYDROLASE (MSEH) BY BENZOYLUREAS, ARYLUREAS, AND THEIR ANALOGUES. (R825433)

EPA Science Inventory

Two hundred and seventy-one compounds including benzoylureas, arylureas and related compounds were assayed using recombinant murine soluble epoxide hydrolase (MsEH) produced from a baculovirus expression system. Among all the insect growth regulators assayed, 18 benzoylphenylu...

40 CFR 63.1431 - Process vent annual epoxides emission factor plan requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., recovery, or recapture device, along with the expected percent efficiency. (iii) Annual emissions after the... section, kg/yr. R = Expected control efficiency of the combustion, recovery, or recapture device, percent....1426(c) to determine the epoxide control efficiency of the combustion, recovery, or recapture device...

40 CFR 63.1431 - Process vent annual epoxides emission factor plan requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., recovery, or recapture device, along with the expected percent efficiency. (iii) Annual emissions after the... section, kg/yr. R = Expected control efficiency of the combustion, recovery, or recapture device, percent....1426(c) to determine the epoxide control efficiency of the combustion, recovery, or recapture device...

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane, substituted...

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane, substituted...

40 CFR 63.1425 - Process vent control requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Standards for Hazardous Air Pollutant Emissions for Polyether Polyols Production § 63.1425 Process vent... operators of all affected sources using epoxides in the production of polyether polyols are subject to the... (c) of this section only if epoxides are used in the production of polyether polyols and nonepoxide...

Synthesis of epoxidized cardanol and its antioxidative properties for vegetable oils and biodiesel

USDA-ARS?s Scientific Manuscript database

A novel antioxidant epoxidized cardanol (ECD), derived from cardanol, was synthesized and characterized by FT-IR, 1H-NMR and 13C-NMR. Oxidative stability of ECD used in vegetable oils and biodiesel was evaluated by pressurized differential scanning calorimetry (PDSC) and the Rancimat method, respect...

Catalytic epoxidation activity of keplerate polyoxomolybdate nanoball toward aqueous suspension of olefins under mild aerobic conditions.

PubMed

Rezaeifard, Abdolreza; Haddad, Reza; Jafarpour, Maasoumeh; Hakimi, Mohammad

2013-07-10

Catalytic efficiency of a sphere-shaped nanosized polyoxomolybdate {Mo132} in the aerobic epoxidation of olefins in water at ambient temperature and pressure in the absence of reducing agent is exploited which resulted good-to-high yields and desired selectivity.

EXPOXIDATION OF OLEFINS AND α,β-UNSATURATED KEYTONES OVER SONOCHEMICALLY PREPARED HYDROXYAPATITES USING HYDROGEN PEROXIDE

EPA Science Inventory

An effective and environmentally friendly protocol for the epoxidation of olefins and α,β-unsaturated ketones in the presence of hydroxyapatite as catalyst using hydrogen peroxide is described. The catalyst is active and reusable for the selective epoxidation of a variety...

ULTRASOUND-ASSISTED EPOXIDATION OF OLEFINS AND A,B-UNSATURATED KETONES OVER HYDROTALCITES USING HYDROGEN PEROXIDE

EPA Science Inventory

An efficient ultrasound-assisted epoxidation of olefins and a,B-unsaturated ketones over hydrotacite catalysts in the presence of hydrogen peroxide and acetonitrile is described. This general and selective protocol is relatively fast and is applicable to a wide variety of substra...

Formation of furan fatty alkyl esters from their bis-epoxide fatty esters

USDA-ARS?s Scientific Manuscript database

Reactions of epoxidized alkyl soyate with four different alcohols: ethanol, isopropyl alcohol, 2-ethylhexanol, and benzyl alcohol were investigated in the presence of Bronsted acid catalyst. Products not reported in prior studies of similar reactions were found. These were furan fatty acid alkyl est...

Formation of furan fatty alkyl esters from their bis-epoxide fatty esters

USDA-ARS?s Scientific Manuscript database

Reactions of epoxidized alkyl soyate with four different alcohols: ethanol, isopropyl alcohol, 2-ethylhexanol, benzyl alcohol, in the presence of Bronsted acid catalyst, were investigated. Products that were not reported in prior studies of similar reactions were found. These were furan fatty acid a...

21 CFR 172.723 - Epoxidized soybean oil.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Epoxidized soybean oil. 172.723 Section 172.723 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN...

21 CFR 172.723 - Epoxidized soybean oil.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Epoxidized soybean oil. 172.723 Section 172.723 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN...

Epoxidation of 1-Octene with hydrogen peroxide aqueous catalyzed by titania supported sulfonated coal

NASA Astrophysics Data System (ADS)

Nurhadi, Mukhamad

2017-02-01

Titania supported sulfonated coal was created as heterogeneous catalyst for epoxidation of 1-octene with aqueous hydrogen peroxide as oxidant at room temperature. The catalysts were prepared from coal that was sulfonated with H2SO4 (97%) and impregnated 7.2%wt with titanium(IV) isopropoxide (Ti(PrO)4). All catalysts coal (C), CS, Ti(7.2)-CS and Ti(7.2)-CSC were characterized by FTIR. The catalytic performance was tested for epoxidation of 1-octene with H2O2 aqueous as oxidant. It is found that Ti(7.2)-CS possessed the best catalytic performance and it gave the highest 1,2 epoxyoctene 322 µmol.

Ladder Polyether Synthesis via Epoxide-Opening Cascades Directed by a Disappearing Trimethylsilyl Group

PubMed Central

Heffron, Timothy P.; Simpson, Graham L.; Merino, Estibaliz; Jamison, Timothy F.

2010-01-01

Epoxide-opening cascades offer the potential to construct complex polyether natural products expeditiously and in a manner that emulates the biogenesis proposed for these compounds. Herein we provide a full account of our development of a strategy that addresses several important challenges of such cascades. The centerpiece of the method is a trimethylsilyl (SiMe3) group that serves several purposes and leaves no trace of itself by the time the cascade has come to an end. The main function of the SiMe3 group is to dictate the regioselectivity of epoxide opening. This strategy is the only general method of effecting endo-selective cascades under basic conditions. PMID:20302314

Layered transition metal carboxylates: efficient reusable heterogeneous catalyst for epoxidation of olefins.

PubMed

Sen, Rupam; Bhunia, Susmita; Mal, Dasarath; Koner, Subratanath; Miyashita, Yoshitaro; Okamoto, Ken-Ichi

2009-12-01

Layered metal carboxylates [M(malonato)(H(2)O)(2)](n) (M = Ni(II) and Mn(II)) that have a claylike structure have been synthesized hydrothermally and characterized. The interlayer separation in these layered carboxylates is comparable to that of the intercalation distance of the naturally occurring clay materials or layered double hydroxides (LDHs). In this study, we have demonstrated that, instead of intercalating the metal complex into layers of the clay or LDH, layered transition metal carboxylates, [M(malonato)(H(2)O)(2)](n), as such can be used as a recyclable heterogeneous catalyst in olefin epoxidation reaction. Metal carboxylates [M(malonato)(H(2)O)(2)](n) exhibit excellent catalytic performance in olefin epoxidation reaction.

Measurement of the degree of cure in epoxies with ultrasonic velocity

NASA Technical Reports Server (NTRS)

Winfree, W. P.; Parker, F. R.

1986-01-01

The use of ultrasonic longitudinal velocity values to measure the degree of cure (defined for an epoxide system as the concentration of epoxide/amine bonds divided by the initial epoxide concentration) in epoxy resins is investigated. The experimental setup used to measure the changes in longitudinal velocity with time is described, together with the technique used to calculate the degree of cure from the acoustic data, using the principle of additive module. Measurements were done with diglycidyl ether of bisphenol A epoxy resin cured with an amine adduct agent. Good qualitative agreement was shown between the time dependence of the acoustically measured degree of cure and the predicted rate of reaction.

Thermochemical Studies of Epoxides and Related Compounds

PubMed Central

Morgan, Kathleen M.; Ellis, Jamie A.; Lee, Joseph; Fulton, Ashley; Wilson, Shavonda L.; Dupart, Patrick S.; Dastoori, Rosanna

2013-01-01

Gas phase heats of formation for the our butene oxide isomers are reported. They were obtained by measuring the condensed-phase heat of reduction to the corresponding alcohol using reaction calorimetry. Heats of vaporization were determined, and allow gas-phase heats of formation to be obtained. The experimental measurements are compared to calculations obtained using a variety of computational methods. Overall, the G3 and CBS-APNO methods agree quite well with the experimental data. The influence of alkyl substituents on epoxide stability is discussed. Comparisons to alkenes, cyclopropanes, aziridines, thiiranes and phosphiranes are also made. Isodesmic-type reactions were used to determine strain energies of the epoxides and related compounds with various substituents. PMID:23551240

Bismuth(III) trifluoromethanesulfonate catalyzed ring opening reaction of mono epoxy oleochemicals to form keto and diketo derivatives

USDA-ARS?s Scientific Manuscript database

Using a catalytic system, methyl oleate is transformed into long chain keto and diketo derivatives via an epoxide route. Methyl 9(10)-oxooctadecanoate and methyl 9,10-dioxooctadecanoate were made by a ring opening reaction of epoxidized methyl oleate using bismuth triflate catalyst. Lower reaction t...

Synthesis of an Epoxide Carbonylation Catalyst: Exploration of Contemporary Chemistry for Advanced Undergraduates

ERIC Educational Resources Information Center

Getzler, Yutan D. Y. L.; Schmidt, Joseph A. R.; Coates, Geoffrey W.

2005-01-01

A class of highly active, well-defined compounds for the catalytic carbonylation of epoxides and aziridines to beta-lactones and beta-lactams are introduced. The synthesis of one of the catalysts involves a simple imine condensation to form the ligand followed by air-sensitive metalation and salt metathesis steps.

EXPRESSION AND CHARACTERIZATION OF THE RECOMBINANT JUVENILE HORMONE EPOXIDE HYDROLASE (JHEH) FROM MANDUCA SEXTA. (R825433)

EPA Science Inventory

The cDNA of the microsomal Juvenile Hormone Epoxide Hydrolase (JHEH) from Manduca sexta was expressed in vitro in the baculovirus system. In insect cell culture, the recombinant enzyme (Ms-JHEH) was produced at a high level (100 fold over background EH catalytic activit...

Thermal behavior of epoxidized cardanol diethyl phosphate as novel renewable plasticizer for poly(vinyl chloride)

USDA-ARS?s Scientific Manuscript database

A novel plasticizer, epoxidized cardanol diethyl phosphate (ECEP), based on cardanol was synthesized. Chemical structure of ECEP was characterized by fourier transform infrared (FTIR), 1H-nuclear magnetic resonance(1H NMR) and 13C-nuclear magnetic resonance(13C NMR) spectroscopy. Effects of ECEP sub...

Nanobody based immunoassay for human soluble epoxide hydrolase detection using polyHRP for signal enhancement—the rediscovery of polyHRP

USDA-ARS?s Scientific Manuscript database

Soluble epoxide hydrolase (sEH) is a potential pharmacological target for treating hypertension, vascular inflammation, cancer, pain and multiple cardiovascular related diseases. A variable domain of a heavy chain only antibody (termed sdAb, nanobody or VHH) possesses advantages of small size, high ...

Epoxidation with Possibilities: Discovering Stereochemistry in Organic Chemistry via Coupling Constants

ERIC Educational Resources Information Center

Treadwell, Edward M.; Yan, Zhiqing; Xiao, Xiao

2017-01-01

A one-day laboratory epoxidation experiment, requiring no purification, is described, wherein the students are given an "unknown" stereoisomer of 3-hexen-1-ol, and use [superscript 1]H NMR coupling constants to determine the stereochemistry of their product. From this they work backward to determine the stereochemistry of their starting…

Lipase catalyzed epoxidation of fatty acid methyl esters derived from unsaturated vegetable oils in absence of carboxylic acid.

PubMed

Sustaita-Rodríguez, Alejandro; Ramos-Sánchez, Víctor H; Camacho-Dávila, Alejandro A; Zaragoza-Galán, Gerardo; Espinoza-Hicks, José C; Chávez-Flores, David

2018-04-11

Nowadays the industrial chemistry reactions rely on green technologies. Enzymes as lipases are increasing its use in diverse chemical processes. Epoxidized fatty acid methyl esters obtained from transesterification of vegetable oils have recently found applications as polymer plasticizer, agrochemical, cosmetics, pharmaceuticals and food additives. In this research article, grapeseed, avocado and olive oils naturally containing high percents of mono and poly unsaturations were used as starting materials for the production of unsaturated fatty acid methyl esters. The effect of lauric acid as an active oxygen carrier was studied on epoxidation reactions where unsaturated fatty acid methyl esters were converted to epoxy fatty acid methyl esters using immobilized Candida antarctica Lipase type B as catalyst and hydrogen peroxide as oxygen donor at mild temperature and pressure conditions. After this study it was confirmed by 1 H NMR, 13 C NMR and GC-MS that the addition of lauric acid to the enzymatic reaction is unnecessary to transform the alkenes in to epoxides. It was found that quantitative conversions were possible in despite of a carboxylic acid absence.

Chemo-Enzymatic Synthesis of Chiral Epoxides Ethyl and Methyl (S)-3-(Oxiran-2-yl)propanoates from Renewable Levoglucosenone: An Access to Enantiopure (S)-Dairy Lactone.

PubMed

Peru, Aurélien A M; Flourat, Amandine L; Gunawan, Christian; Raverty, Warwick; Jevric, Martyn; Greatrex, Ben W; Allais, Florent

2016-07-29

Chiral epoxides-such as ethyl and methyl (S)-3-(oxiran-2-yl)propanoates ((S)-1a/1b)-are valuable precursors in many chemical syntheses. Until recently, these compounds were synthesized from glutamic acid in four steps (deamination, reduction, tosylation and epoxide formation) in low to moderate overall yield (20%-50%). Moreover, this procedure requires some harmful reagents such as sodium nitrite ((eco)toxic) and borane (carcinogen). Herein, starting from levoglucosenone (LGO), a biobased chiral compound obtained through the flash pyrolysis of acidified cellulose, we propose a safer and more sustainable chemo-enzymatic synthetic pathway involving lipase-mediated Baeyer-Villiger oxidation, palladium-catalyzed hydrogenation, tosylation and treatment with sodium ethoxide/methoxide as key steps. This route afforded ethyl and methyl (S)-3-(oxiran-2-yl)propanoates in 57% overall yield, respectively. To demonstrate the potentiality of this new synthetic pathway from LGO, the synthesis of high value-added (S)-dairy lactone was undertaken from these epoxides and provided the target in 37% overall yield from LGO.

Efficient epoxidation of a terminal alkene containing allylic hydrogen atoms: trans-methylstyrene on Cu{111}.

PubMed

Cropley, Rachael L; Williams, Federico J; Urquhart, Andrew J; Vaughan, Owain P H; Tikhov, Mintcho S; Lambert, Richard M

2005-04-27

The selective oxidation of trans-methylstyrene, a phenyl-substituted propene that contains labile allylic hydrogen atoms, has been studied on Cu{111}. Mass spectrometry and synchrotron fast XPS were used to detect, respectively, desorbing gaseous products and the evolution of surface species as a function of temperature and time. Efficient partial oxidation occurs yielding principally the epoxide, and the behavior of the system is sensitive to the order in which reactants are adsorbed. The latter is understandable in terms of differences in the spatial distribution of oxygen adatoms; isolated adatoms lead to epoxidation, while islands of "oxidic" oxygen do not. NEXAFS data taken over a range of coverages and in the presence and absence of coadsorbed oxygen indicate that the adsorbed alkene lies essentially flat with the allylic hydrogen atoms close to the surface. The photoemission results and comparison with the corresponding behavior of styrene on Cu{111} strongly suggest that allylic hydrogen abstraction is indeed a critical factor that limits epoxidation selectivity. An overall mechanism consistent with the structural and reactive properties is proposed.

A Lewis acid β-diiminato-zinc-complex as all-rounder for co- and terpolymerisation of various epoxides with carbon dioxide.

PubMed

Reiter, M; Vagin, S; Kronast, A; Jandl, C; Rieger, B

2017-03-01

A β-diiminato-zinc-N(SiMe 3 ) 2 complex ( 1 ) was synthesised and fully characterised, including an X-ray diffraction study. The activity of catalyst 1 towards the coupling reaction of CO 2 and various epoxides, including propylene oxide (PO), cyclohexene oxide (CHO), styrene oxide (SO), limonene oxide (LO), octene oxide (OO) and epichlorohydrin (ECH), was investigated. Terpolymerisation of CO 2 , PO and LO, as well as CO 2 , CHO and PO, was successfully realised, resulting in polymers with adjustable glass transition temperatures and transparencies. Reaction conditions such as temperature, pressure and catalyst concentration were varied to find the optimal reaction values, especially regarding LO/CO 2 . In situ IR experiments hinted that at 60 °C and a critical LO concentration, polymerisation and depolymerisation are in an equilibrium (ceiling effect). Pressurising catalyst 1 with carbon dioxide resulted in a dimeric catalyst ( 2 ) with a OSiMe 3 group as a new initiator. Homopolymerisation of different epoxides was carried out in order to explain the reactivity concerning copolymerisation reaction of CO 2 and epoxides.

Assignment of the relative and absolute stereochemistry of two novel epoxides using NMR and DFT-GIAO calculations

NASA Astrophysics Data System (ADS)

Moraes, F. C.; Alvarenga, E. S.; Demuner, A. J.; Viana, V. M.

2018-07-01

Considering the potential biological application of isobenzofuranones, especially as agrochemical defensives, two novel epoxides, (1aR,2R,2aR,5S,5aS,6S,6aS)-5-(hydroxymethyl)hexahydro-2,6-methanooxireno[2,3-f]isobenzofuran-3(1aH)-one (9), and (1aS,2S,2aR,5S,5aS,6R,6aR)-5-(hydroxymethyl)hexahydro-2,6-methanooxireno[2,3-f]isobenzofuran-3(1aH)-one (10), were synthesized from the readily available D-mannitol in six steps. The multiplicities of the hydrogens located at the bridge of the bicycle are distinct for epoxides 9 and 10 due to W coupling, and this feature was employed to confirm the assignment of these nuclei. Besides analyses of the 2D NMR spectra, the assignments of the nuclei at the epoxide ring were also inferred from information obtained by theoretical calculations. The calculated 1H and 13C NMR chemical shifts for eight candidate structures were compared with the experimental chemical shifts of 9 and 10 by measuring the mean absolute errors (MAE) and by the DP4 statistical analysis. The structures and relative configurations of 9, and 10 were determined via NMR spectroscopy assisted with theoretical calculations. As consequence of the enantioselective syntheses starting from a natural polyol, the absolute configurations of the epoxides 9 and 10 were also defined.

Arabidopsis thaliana EPOXIDE HYDROLASE1 (AtEH1) is a cytosolic epoxide hydrolase involved in the synthesis of poly-hydroxylated cutin monomers.

PubMed

Pineau, Emmanuelle; Xu, Lin; Renault, Hugues; Trolet, Adrien; Navrot, Nicolas; Ullmann, Pascaline; Légeret, Bertrand; Verdier, Gaëtan; Beisson, Fred; Pinot, Franck

2017-07-01

Epoxide hydrolases (EHs) are present in all living organisms. They have been extensively characterized in mammals; however, their biological functions in plants have not been demonstrated. Based on in silico analysis, we identified AtEH1 (At3g05600), a putative Arabidopsis thaliana epoxide hydrolase possibly involved in cutin monomer synthesis. We expressed AtEH1 in yeast and studied its localization in vivo. We also analyzed the composition of cutin from A. thaliana lines in which this gene was knocked out. Incubation of recombinant AtEH1 with epoxy fatty acids confirmed its capacity to hydrolyze epoxides of C18 fatty acids into vicinal diols. Transfection of Nicotiana benthamiana leaves with constructs expressing AtEH1 fused to enhanced green fluorescent protein (EGFP) indicated that AtEH1 is localized in the cytosol. Analysis of cutin monomers in loss-of-function Ateh1-1 and Ateh1-2 mutants showed an accumulation of 18-hydroxy-9,10-epoxyoctadecenoic acid and a concomitant decrease in corresponding vicinal diols in leaf and seed cutin. Compared with wild-type seeds, Ateh1 seeds showed delayed germination under osmotic stress conditions and increased seed coat permeability to tetrazolium red. This work reports a physiological role for a plant EH and identifies AtEH1 as a new member of the complex machinery involved in cutin synthesis. © 2017 CNRS New Phytologist © 2017 New Phytologist Trust.

An efficient hybrid, nanostructured, epoxidation catalyst: titanium silsesquioxane-polystyrene copolymer supported on SBA-15.

PubMed

Zhang, Lei; Abbenhuis, Hendrikus C L; Gerritsen, Gijsbert; Bhriain, Nollaig Ní; Magusin, Pieter C M M; Mezari, Brahim; Han, Wei; van Santen, Rutger A; Yang, Qihua; Li, Can

2007-01-01

A novel interfacial hybrid epoxidation catalyst was designed with a new immobilization method for homogeneous catalysts by coating an inorganic support with an organic polymer film containing active sites. The titanium silsesquioxane (TiPOSS) complex, which contains a single-site titanium active center, was immobilized successfully by in-situ copolymerization on a mesoporous SBA-15-supported polystyrene polymer. The resulting hybrid materials exhibit attractive textural properties (highly ordered mesostructure, large specific surface area (>380 m2 g-1) and pore volume (>or==0.46 cm3 g-1)), and high activity in the epoxidation of alkenes. In the epoxidation of cyclooctene with tert-butyl hydrogen peroxide (TBHP), the hybrid catalysts have rate constants comparable with that of their homogeneous counterpart, and can be recycled at least seven times. They can also catalyze the epoxidation of cyclooctene with aqueous H2O2 as the oxidant. In two-phase reaction media, the catalysts show much higher activity than their homogeneous counterpart due to the hydrophobic environment around the active centers. They behave as interfacial catalysts due to their multifunctionality, that is, the hydrophobicity of polystyrene and the polyhedral oligomeric silsesquioxanes (POSS), and the hydrophilicity of the silica and the mesoporous structure. Combination of the immobilization of homogeneous catalysts on two conventional supports, inorganic solid and organic polymer, is demonstrated to achieve novel heterogeneous catalytic ensembles with the merits of attractive textural properties, tunable surface properties, and optimized environments around the active sites.

Kinetics and mechanism of styrene epoxidation by chlorite: role of chlorine dioxide.

PubMed

Leigh, Jessica K; Rajput, Jonathan; Richardson, David E

2014-07-07

An investigation of the kinetics and mechanism for epoxidation of styrene and para-substituted styrenes by chlorite at 25 °C in the pH range of 5-6 is described. The proposed mechanism in water and water/acetonitrile includes seven oxidation states of chlorine (-I, 0, I, II, III, IV, and V) to account for the observed kinetics and product distributions. The model provides an unusually detailed quantitative mechanism for the complex reactions that occur in mixtures of chlorine species and organic substrates, particularly when the strong oxidant chlorite is employed. Kinetic control of the reaction is achieved by the addition of chlorine dioxide to the reaction mixture, thereby eliminating a substantial induction period observed when chlorite is used alone. The epoxidation agent is identified as chlorine dioxide, which is continually formed by the reaction of chlorite with hypochlorous acid that results from ClO produced by the epoxidation reaction. The overall stoichiometry is the result of two competing chain reactions in which the reactive intermediate ClO reacts with either chlorine dioxide or chlorite ion to produce hypochlorous acid and chlorate or chloride, respectively. At high chlorite ion concentrations, HOCl is rapidly eliminated by reaction with chlorite, minimizing side reactions between HOCl and Cl2 with the starting material. Epoxide selectivity (>90% under optimal conditions) is accurately predicted by the kinetic model. The model rate constant for direct reaction of styrene with ClO2(aq) to produce epoxide is (1.16 ± 0.07) × 10(-2) M(-1) s(-1) for 60:40 water/acetonitrile with 0.20 M acetate buffer. Rate constants for para substituted styrenes (R = -SO3(-), -OMe, -Me, -Cl, -H, and -NO2) with ClO2 were determined. The results support the radical addition/elimination mechanism originally proposed by Kolar and Lindgren to account for the formation of styrene oxide in the reaction of styrene with chlorine dioxide.

Reaction Mechanism for Direct Propylene Epoxidation by Alumina-Supported Silver Aggregates. The Role of the Particle / Support Interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Lei; Yin, Chunrong; Mehmood, Faisal

2013-11-21

Sub-nanometer Ag aggregates on alumina supports have been found to be active toward direct propylene epoxidation to propylene oxide by molecular oxygen at low temperatures, with a negligible amount of carbon dioxide formation (Science 328, p. 224, 2010). In this work, we computationally and experimentally investigate the origin of the high reactivity of the sub-nanometer Ag aggregates. Computationally, we study O 2 dissociation and propylene epoxidation on unsupported Ag 19 and Ag 20 clusters, as well as alumina-supported Ag 19. The O 2 dissociation and propylene epoxidation apparent barriers at the interface between the Ag aggregate and the alumina supportmore » are calculated to be 0.2 and 0.2~0.4 eV, respectively. These barriers are somewhat lower than those on sites away from the interface. The mechanism at the interface is similar to what was previously found for the silver trimer on alumina and can account for the high activity observed for the direct oxidation of propylene on the Ag aggregates. The barriers for oxygen dissociation on these model systems both at the interface and on the surfaces are small compared to crystalline surfaces, indicating that availability of oxygen will not be a rate limiting step for the aggregates, as in the case of the crystalline surfaces. Experimentally, we investigate Ultrananocrystalline Diamond (UNCD)-supported silver aggregates under reactive conditions of propylene partial oxidation. The UNCD-supported Ag clusters are found to be not measurably active toward propylene oxidation, in contrast to the alumina supported Ag clusters. This suggests that the lack of metal-oxide interfacial sites of the Ag-UNCD catalyst, limits the epoxidation catalytic activity. This combined computational and experimental study shows the importance of the metal-oxide interface as well as the non-crystalline nature of the alumina-supported sub-nanometer Ag aggregate catalysts for propylene epoxidation.« less

An integrated computational approach of molecular dynamics simulations, receptor binding studies and pharmacophore mapping analysis in search of potent inhibitors against tuberculosis.

PubMed

Agarwal, Shivangi; Verma, Ekta; Kumar, Vivek; Lall, Namrita; Sau, Samaresh; Iyer, Arun K; Kashaw, Sushil K

2018-05-03

Tuberculosis is an infectious chronic disease caused by obligate pathogen Mycobacterium tuberculosis that affects millions of people worldwide. Although many first and second line drugs are available for its treatment, but their irrational use has adversely lead to the emerging cases of multiple drug resistant and extensively drug-resistant tuberculosis. Therefore, there is an intense need to develop novel potent analogues for its treatment. This has prompted us to develop potent analogues against TB. The Mycobacterium tuberculosis genome provides us with number of validated targets to combat against TB. Study of Mtb genome disclosed six epoxide hydrolases (A to F) which convert harmful epoxide into diols and act as a potential drug target for rational drug design. Our current strategy is to develop such analogues which inhibits epoxide hydrolase enzyme present in Mtb genome. To achieve this, we adopted an integrated computational approach involving QSAR, pharmacophore mapping, molecular docking and molecular dynamics simulation studies. The approach envisaged vital information about the role of molecular descriptors, essential pharmacophoric features and binding energy for compounds to bind into the active site of epoxide hydrolase. Molecular docking analysis revealed that analogues exhibited significant binding to Mtb epoxide hydrolase. Further, three docked complexes 2s, 37s and 15s with high, moderate and low docking scores respectively were selected for molecular dynamics simulation studies. RMSD analysis revealed that all complexes are stable with average RMSD below 2 Å throughout the 10 ns simulations. The B-factor analysis showed that the active site residues of epoxide hydrolase are flexible enough to interact with inhibitor. Moreover, to confirm the binding of these urea derivatives, MM-GBSA binding energy analysis were performed. The calculations showed that 37s has more binding affinity (ΔGtotal = -52.24 kcal/mol) towards epoxide hydrolase compared to 2s (ΔGtotal = -51.70 kcal/mol) and 15s (ΔGtotal = -49.97 kcal/mol). The structural features inferred in our study may provide the future directions to the scientists towards the discovery of new chemical entity exhibiting anti-TB property. Copyright © 2018 Elsevier Inc. All rights reserved.

40 CFR 63.1427 - Process vent requirements for processes using extended cookout as an epoxide emission reduction...

Code of Federal Regulations, 2014 CFR

2014-07-01

... = Concentration of epoxide in the reactor liquid at the beginning of the time period, weight percent. k = Reaction rate constant, 1/hr. t = Time, hours. Note: This equation assumes a first order reaction with respect... process knowledge, reaction kinetics, and engineering knowledge, in accordance with paragraph (a)(2)(i) of...

40 CFR 63.1427 - Process vent requirements for processes using extended cookout as an epoxide emission reduction...

Code of Federal Regulations, 2013 CFR

2013-07-01

... = Concentration of epoxide in the reactor liquid at the beginning of the time period, weight percent. k = Reaction rate constant, 1/hr. t = Time, hours. Note: This equation assumes a first order reaction with respect... process knowledge, reaction kinetics, and engineering knowledge, in accordance with paragraph (a)(2)(i) of...

Alkene epoxidation employing metal nitro complexes

DOEpatents

Andrews, M.A.; Cheng, C.W.; Kelley, K.P.

1982-07-15

Process for converting alkenes to form epoxides utilizes transition metal nitro complexes of the formula: M(RCN)/sub 2/XNO/sub 2/ wherein M is palladium or platinum, R is an alkyl or aryl group containing up to 12 carbon atoms, and X is a monoanionic, monodentate ligand such as chlorine, optionally in the presence of molecular oxygen.

The Epoxidation of 2,5-Di-tert-butyl-1,4-benzoquinone: A Consecutive Reaction for the Physical Chemistry Laboratory.

ERIC Educational Resources Information Center

Hairfield, E. M.; And Others

1985-01-01

Reports a consecutive first-order reaction for which the concentrations of reactant, intermediate, and products can be determined simulataneously. This reaction is the epoxidation of 2,5-di-tert-butyl-1,4-benzoquinone (I) by alkaline hydroperoxidation using tert-butyl hydroperoxide and benzyltrimethylammonium hydroxide (Triton B) catalyst.…

Gold nanoparticle-catalyzed environmentally benign deoxygenation of epoxides to alkenes.

PubMed

Noujima, Akifumi; Mitsudome, Takato; Mizugaki, Tomoo; Jitsukawa, Koichiro; Kaneda, Kiyotomi

2011-09-28

We have developed a highly efficient and green catalytic deoxygenation of epoxides to alkenes using gold nanoparticles (NPs) supported on hydrotalcite [HT: Mg(6)Al(2)CO(3)(OH)(16)] (Au/HT) with alcohols, CO/H(2)O or H(2) as the reducing reagent. Various epoxides were selectively converted to the corresponding alkenes. Among the novel metal NPs on HT, Au/HT was found to exhibit outstanding catalytic activity for the deoxygenation reaction. Moreover, Au/HT can be separated from the reaction mixture and reused with retention of its catalytic activity and selectivity. The high catalytic performance of Au/HT was attributed to the selective formation of Au-hydride species by the cooperative effect between Au NPs and HT.

FAD C(4a)-hydroxide stabilized in a naturally fused styrene monooxygenase

PubMed Central

Schlömann, Michael; van Berkel, Willem J.H.; Gassner, George T.

2013-01-01

StyA2B represents a new class of styrene monooxygenases that integrates flavin-reductase and styrene-epoxidase activities into a single polypeptide. This naturally-occurring fusion protein offers new avenues for studying and engineering biotechnologically relevant enantioselective biochemical epoxidation reactions. Stopped-flow kinetic studies of StyA2B reported here identify reaction intermediates similar to those reported for the separate reductase and epoxidase components of related two-component systems. Our studies identify substrate epoxidation and elimination of water from the FAD C(4a)-hydroxide as rate-limiting steps in the styrene epoxidation reaction. Efforts directed at accelerating these reaction steps are expected to greatly increase catalytic efficiency and the value of StyA2B as biocatalyst. PMID:24157359

Lithium Diisopropylamide-Mediated Reactions of Imines, Unsaturated Esters, Epoxides, and Aryl Carbamates: Influence of Hexamethylphosphoramide and Ethereal Cosolvents on Reaction Mechanisms

PubMed Central

Ma, Yun

2010-01-01

Several reactions mediated by lithium diisopropylamide (LDA) with added hex-amethylphosphoramide (HMPA) are described. The N-isopropylimine of cyclohex-anone lithiates via an ensemble of monomer-based pathways. Conjugate addition of LDA/HMPA to an unsaturated ester proceeds via di- and tetra-HMPA-solvated dimers. Deprotonation of norbornene epoxide by LDA/HMPA proceeds via an intermediate metalated epoxide as a mixed dimer with LDA. Ortholithiation of an aryl carbamate proceeds via a mono-HMPA-solvated monomer-based pathway. Dependencies on THF and other ethereal cosolvents suggest that secondary-shell solvation effects are important in some instances. The origins of the inordinate mechanistic complexity are discussed. PMID:17985891

Use of dimethyldioxirane in the epoxidation of the main constituents of the essential oils obtained from Tagetes lucida, Cymbopogon citratus, Lippia alba and Eucalyptus citriodora.

PubMed

Veloza, Luz A; Orozco, Lina M; Sepúlveda-Arias, Juan C

2011-07-01

Dimethyldioxirane (DMDO), a widely used oxidant in organic synthesis is considered an environmentally friendly oxygen transfer reagent because acetone is the only byproduct formed in its oxidation reactions. This work describes the isolation of the main constituents (terpenes) in the essential oils obtained from Tagetes lucida, Cymbopogon citratus, Lippia alba and Eucalyptus citriodora, their epoxidation with DMDO in acetone solution and the characterization of the resulting epoxides by GC-MS (EI) and NMR. This is one of the first reports involving the application of dioxirane chemistry to essential oils in order to generate modified compounds with potential uses in several areas of medicine and industry.

Ozonides and epoxides from ozonization of pyrethroids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruzo, L.O.; Kimmel, E.C.; Casida, J.E.

Ozonization of pyrethroids as solutions or thin films yields products proposed to be epoxides from the 2,2-dihalovinyl substituents of deltamethrin and permethrin and transitory ozonides from these compounds and more stable ozonides from the 2-methyl-1-propenyl and 2-chloro-3,3,3-trifluoropropenyl substituents of phenothrin and descyanocyhalothrin, respectively. The unstable epoxydeltamethrin from ozonization is identified by /sup 1/H nuclear magnetic resonance spectroscopy and chemical ionization-mass spectroscopy and by reversion to deltamethrin on treatment of reaction mixtures with triphenylphosphine. Degradation of the ozonides yields the corresponding caronaldehyde in each case and trifluoroacetyl chloride from the chlorotrifluoropropenyl analogues. The ozonolysis mixtures are direct acting but weak bacterialmore » mutagens presumable due to their epoxide and ozonide components.« less

Unprecedented Carbonato Intermediates in Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium(Salen) Complexes.

PubMed

Castro-Osma, José A; North, Michael; Offermans, Willem K; Leitner, Walter; Müller, Thomas E

2016-04-21

The mechanism by which [Al(salen)]2 O complexes catalyse the synthesis of cyclic carbonates from epoxides and carbon dioxide in the absence of a halide cocatalyst has been investigated. Density functional theory (DFT) studies, mass spectrometry and (1) H NMR, (13) C NMR and infrared spectroscopies provide evidence for the formation of an unprecedented carbonato bridged bimetallic aluminium complex which is shown to be a key intermediate for the halide-free synthesis of cyclic carbonates from epoxides and carbon dioxide. Deuterated and enantiomerically-pure epoxides were used to study the reaction pathway. Based on the experimental and theoretical results, a catalytic cycle is proposed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

40 CFR 63.1426 - Process vent requirements for determining organic HAP concentration, control efficiency, and...

Code of Federal Regulations, 2010 CFR

2010-07-01

... percent reduction may be measured as total epoxide, total organic HAP, or as TOC minus methane and ethane... TOC (minus methane and ethane) concentrations in all process vent streams and primary and secondary... million by volume total epoxide or TOC limit in § 63.1425(b)(1)(ii) or (b)(2)(iii), the sampling site...

BENZO[A]PYRENE AND BENZO[C]PHENANTHRENE: THE EFFECT OF STRUCTURE ON THE BINDING OF WATER MOLECULES TO THE DIOL EPOXIDES

EPA Science Inventory

ABSTRACT
The interaction with water of the diol epoxides (DEs) of both a planar and a non-planar PAH have been examined using molecular dynamics. To determine probable water locations around the DE for later use in the study of DE protonation, molecular dynamics simulations u...

Transformations of Carotenoids in the Oceanic Water Column.

DTIC Science & Technology

1982-11-01

suggests that dehydration and epoxide rearrangement occur over considerably longer time scales than ester hydrolysis . Isofucoxanthin was not isolated...transformations: 1) ester hydrolysis via zooplanktonic metabolism, 2) dehydration via bacterial metabolism, and 3) epoxide opening via slow chemical...be restricted to zooplankton and not common to other higher heLerotrophs, as is ester hydrolysis . The high concentration of fuco- dehydrates and short

Lipid-modifying enzymes in oat and faba bean.

PubMed

Yang, Zhen; Piironen, Vieno; Lampi, Anna-Maija

2017-10-01

The aim was to study lipase, lipoxygenase (LOX) and peroxygenase (POX) activities in oat and faba bean samples to be able to evaluate their potential in formation of lipid-derived off-flavours. Lipase and LOX activities were measured by spectroscopy, and POX activities via the formation of epoxides. An ultra-high performance liquid chromatography method was developed to study the formation of fatty acid epoxides. The epoxides of esters were measured by gas chromatography. Mass spectroscopy was used to verify the identity of the epoxides. Both oat and faba bean possessed high lipase activities. In faba bean, LOX catalysed the formation of hydroperoxides, whose break-down products are the likely cause of off-flavours. Since oat had low LOX activity, autoxidation is needed to initiate lipid oxidation. Oat had high POX activity, which is able to convert hydroperoxides to epoxy and hydroxy fatty acids that could contribute significantly to off-flavours. POX activity in the faba bean was low. Thus, in faba bean volatile lipid oxidation products could rapidly be formed by LOX, whereas in oat reactions are slower due to the need of autoxidation prior to further reactions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Microsomal epoxide hydrolase of rat liver. Purification and characterization of enzyme fractions with different chromatographic characteristics.

PubMed Central

Bulleid, N J; Graham, A B; Craft, J A

1986-01-01

Microsomal epoxide hydrolase was purified from rat liver, and different fractions of the purified enzyme, which varied in their contents of phospholipid, were obtained by ion-exchange chromatography. One fraction (A), which did not bind to CM-cellulose, had a high phospholipid content, and a second fraction (B), which was eluted from CM-cellulose at high ionic strength, had a low phospholipid content. Removal of most of the phospholipid from fraction A altered its chromatographic behaviour. When the delipidated material was re-applied to CM-cellulose, most of the enzyme bound to the cation-exchanger. The specific activities of all the fractions described (with styrene epoxide [(1,2-epoxyethyl)benzene] as substrate) were altered by adding the non-ionic detergent Lubrol PX or phospholipid. Lubrol PX inhibited enzyme activity, and phospholipid reversed this inhibition. The various enzyme fractions isolated appeared to be different forms of the same protein, as judged by their minimum Mr values and immunochemical properties. These results indicate that different fractions of epoxide hydrolase isolated by ion-exchange chromatography probably are not different isoenzyme forms. Images Fig. 2. Fig. 3. PMID:3082328

Peroxotantalate-Based Ionic Liquid Catalyzed Epoxidation of Allylic Alcohols with Hydrogen Peroxide.

PubMed

Ma, Wenbao; Chen, Chen; Kong, Kang; Dong, Qifeng; Li, Kun; Yuan, Mingming; Li, Difan; Hou, Zhenshan

2017-05-29

The efficient and environmentally benign epoxidation of allylic alcohols has been attained by using new kinds of monomeric peroxotantalate anion-functionalized ionic liquids (ILs=[P 4,4,4,n ] 3 [Ta(O) 3 (η-O 2 )], P 4,4,4,n =quaternary phosphonium cation, n=4, 8, and 14), which have been developed and their structures determined accordingly. This work revealed the parent anions of the ILs underwent structural transformation in the presence of H 2 O 2 . The formed active species exhibited excellent catalytic activity, with a turnover frequency for [P 4,4,4,4 ] 3 [Ta(O) 3 (η-O 2 )] of up to 285 h -1 , and satisfactory recyclability in the epoxidation of various allylic alcohols under very mild conditions by using only one equivalent of hydrogen peroxide as an oxidant. NMR studies showed the reaction was facilitated through a hydrogen-bonding mechanism, in which the peroxo group (O-O) of the peroxotantalate anion served as the hydrogen-bond acceptor and hydroxyl group in the allylic alcohols served as the hydrogen-bond donor. This work demonstrates that simple monomeric peroxotantalates can catalyze epoxidation of allylic alcohols efficiently. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lysophosphatidic acids are new substrates for the phosphatase domain of soluble epoxide hydrolase[S

PubMed Central

Oguro, Ami; Imaoka, Susumu

2012-01-01

Soluble epoxide hydrolase (sEH) is a bifunctional enzyme that has a C-terminus epoxide hydrolase domain and an N-terminus phosphatase domain. The endogenous substrates of epoxide hydrolase are known to be epoxyeicosatrienoic acids, but the endogenous substrates of the phosphatase activity are not well understood. In this study, to explore the substrates of sEH, we investigated the inhibition of the phosphatase activity of sEH toward 4-methylumbelliferyl phosphate by using lecithin and its hydrolyzed products. Although lecithin itself did not inhibit the phosphatase activity, the hydrolyzed lecithin significantly inhibited it, suggesting that lysophospholipid or fatty acid can inhibit it. Next, we investigated the inhibition of phosphatase activity by lysophosphatidyl choline, palmitoyl lysophosphatidic acid, monopalmitoyl glycerol, and palmitic acid. Palmitoyl lysophosphatidic acid and fatty acid efficiently inhibited phosphatase activity, suggesting that lysophosphatidic acids (LPAs) are substrates for the phosphatase activity of sEH. As expected, palmitoyl, stearoyl, oleoyl, and arachidonoyl LPAs were efficiently dephosphorylated by sEH (Km, 3–7 μM; Vmax, 150–193 nmol/min/mg). These results suggest that LPAs are substrates of sEH, which may regulate physiological functions of cells via their metabolism. PMID:22217705

Lysophosphatidic acids are new substrates for the phosphatase domain of soluble epoxide hydrolase.

PubMed

Oguro, Ami; Imaoka, Susumu

2012-03-01

Soluble epoxide hydrolase (sEH) is a bifunctional enzyme that has a C-terminus epoxide hydrolase domain and an N-terminus phosphatase domain. The endogenous substrates of epoxide hydrolase are known to be epoxyeicosatrienoic acids, but the endogenous substrates of the phosphatase activity are not well understood. In this study, to explore the substrates of sEH, we investigated the inhibition of the phosphatase activity of sEH toward 4-methylumbelliferyl phosphate by using lecithin and its hydrolyzed products. Although lecithin itself did not inhibit the phosphatase activity, the hydrolyzed lecithin significantly inhibited it, suggesting that lysophospholipid or fatty acid can inhibit it. Next, we investigated the inhibition of phosphatase activity by lysophosphatidyl choline, palmitoyl lysophosphatidic acid, monopalmitoyl glycerol, and palmitic acid. Palmitoyl lysophosphatidic acid and fatty acid efficiently inhibited phosphatase activity, suggesting that lysophosphatidic acids (LPAs) are substrates for the phosphatase activity of sEH. As expected, palmitoyl, stearoyl, oleoyl, and arachidonoyl LPAs were efficiently dephosphorylated by sEH (Km, 3-7 μM; Vmax, 150-193 nmol/min/mg). These results suggest that LPAs are substrates of sEH, which may regulate physiological functions of cells via their metabolism.

Morphology and phase control of iron oxide polymorph nanoparticles

NASA Astrophysics Data System (ADS)

Cui, Hongtao; Wang, Li; Shi, Min; Li, Yanhong

2017-04-01

In this work, lepidocrocite (γ-FeOOH) nanobundles were prepared by a facile NH4F assisted epoxide precipitation route. The reactions between epoxide and [Fe(H2O)6]2+ promoted the hydrolysis and condensation of [Fe(H2O)6]2+, resulting in the formation of iron oxyhydroxide. After calcination of γ-FeOOH nanobundles at 400 °C, the produced α-Fe2O3 still kept the bundle morphology. Due to the unique chemistry of epoxide, the morphology and phase of iron oxide polymorph nanoparticles (goethite, akaganeite, lepidocrocite, magnetite) were well-controlled through controlling reaction conditions such as Fe2+ concentration, NH4F additive and reaction temperature. It is particularly interesting that NH4F working as phase controlling agent is able to control the phase development of iron oxyhydroxides. This phase control effect of NH4F is attributed to the promoted reaction rate of epoxide originating from the higher electronegativity of fluoride ions than chloride ions. Based on the results in this work and our other preliminary works, it is considered that this route can be used as a general strategy for controlling the morphology and phase of transition element compounds.

Structural requirements for bioactivation of anticonvulsants to cytotoxic metabolites in vitro.

PubMed Central

Riley, R J; Kitteringham, N R; Park, B K

1989-01-01

The formation of cytotoxic metabolites from the anticonvulsants phenytoin and carbamazepine was investigated in vitro using a hepatic microsomal enzyme system and human mononuclear leucocytes as target cells. Both drugs were metabolised to cytotoxic products. In order to assess the structural requirements for this bioactivation, a series of structurally related compounds was investigated. It was found that molecules which contain either an amide function or an aryl ring may undergo activation in vitro, but only the metabolism-dependent toxicity of the latter is potentiated by pre-treatment of the target cells with an epoxide hydrolase inhibitor. Taken collectively, these data are consistent with the concept that reactive epoxide metabolites of both phenytoin and carbamazepine may produce toxicity in individuals with an inherited deficiency in epoxide hydrolase. PMID:2590607

Epoxy thermoset networks derived from vegetable oils and their blends

NASA Astrophysics Data System (ADS)

Ryu, Chang; Ravalli, Matthew

2015-03-01

Epoxidized vegetable oils (EVOs), such as epoxidized soybean oil and linseed oils were prepared by the partial oxidation of the unsaturated double bonds in vegetable oils and used as monomers for preparing epoxy thermoset materials based on the cationic polymerization. These EVOs have been used to prepare epoxy thermosets of different network densities by cationic polymerization using onium salt catalyst. The crosslinked epoxy thermosets provide an ideal platform to study the structure-property-relationships of networked polymers. In particular, rheological studies on the epoxidized vegetable oil thermosets have been performed to measure the molecular weights between crosslinks (Mx) in the epoxy thermosets and to ultimately elucidate the role of functionality of epoxy groups in EVO on the mechanical and thermophysical properties of the epoxy thermoset materials. NSF DMR POLYMERS 1308617.

Ionic Liquid Epoxy Resin Monomers

NASA Technical Reports Server (NTRS)

Paley, Mark S. (Inventor)

2013-01-01

Ionic liquid epoxide monomers capable of reacting with cross-linking agents to form polymers with high tensile and adhesive strengths. Ionic liquid epoxide monomers comprising at least one bis(glycidyl) N-substituted nitrogen heterocyclic cation are made from nitrogen heterocycles corresponding to the bis(glycidyl) N-substituted nitrogen heterocyclic cations by a method involving a non-nucleophilic anion, an alkali metal cation, epichlorohydrin, and a strong base.

Microbial production of epoxides

DOEpatents

Clark, Thomas R.; Roberto, Francisco F.

2003-06-10

A method for microbial production of epoxides and other oxygenated products is disclosed. The method uses a biocatalyst of methanotrophic bacteria cultured in a biphasic medium containing a major amount of a non-aqueous polar solvent. Regeneration of reducing equivalents is carried out by using endogenous hydrogenase activity together with supplied hydrogen gas. This method is especially effective with gaseous substrates and cofactors that result in liquid products.

Lutein from Deepoxidation of Lutein Epoxide Replaces Zeaxanthin to Sustain an Enhanced Capacity for Nonphotochemical Chlorophyll Fluorescence Quenching in Avocado Shade Leaves in the Dark1

PubMed Central

Förster, Britta; Pogson, Barry James; Osmond, Charles Barry

2011-01-01

Leaves of avocado (Persea americana) that develop and persist in deep shade canopies have very low rates of photosynthesis but contain high concentrations of lutein epoxide (Lx) that are partially deepoxidized to lutein (L) after 1 h of exposure to 120 to 350 μmol photons m−2 s−1, increasing the total L pool by 5% to 10% (ΔL). Deepoxidation of Lx to L was near stoichiometric and similar in kinetics to deepoxidation of violaxanthin (V) to antheraxanthin (A) and zeaxanthin (Z). Although the V pool was restored by epoxidation of A and Z overnight, the Lx pool was not. Depending on leaf age and pretreatment, the pool of ΔL persisted for up to 72 h in the dark. Metabolism of ΔL did not involve epoxidation to Lx. These contrasting kinetics enabled us to differentiate three states of the capacity for nonphotochemical chlorophyll fluorescence quenching (NPQ) in attached and detached leaves: ΔpH dependent (NPQΔpH) before deepoxidation; after deepoxidation in the presence of ΔL, A, and Z (NPQΔLAZ); and after epoxidation of A+Z but with residual ΔL (NPQΔL). The capacity of both NPQΔLAZ and NPQΔL was similar and 45% larger than NPQΔpH, but dark relaxation of NPQΔLAZ was slower. The enhanced capacity for NPQ was lost after metabolism of ΔL. The near equivalence of NPQΔLAZ and NPQΔL provides compelling evidence that the small dynamic pool ΔL replaces A+Z in avocado to “lock in” enhanced NPQ. The results are discussed in relation to data obtained with other Lx-rich species and in mutants of Arabidopsis (Arabidopsis thaliana) with increased L pools. PMID:21427278

Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

PubMed

Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

2015-05-21

Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.

Epoxide metabolism in the liver of mice treated with clofibrate (ethyl-alpha-(p-chlorophenoxyisobutyrate)), a peroxisome proliferator.

PubMed

Moody, D E; Loury, D N; Hammock, B D

1985-05-01

An increase in cytosolic epoxide hydrolase (cEH) activity occurs in the livers of mice treated with peroxisome proliferating-hypolipidemic-nongenotoxic carcinogens. As increases in activity of epoxide metabolizing enzymes may reflect the carcinogenic mechanism, a detailed comparison of the response of cEH, microsomal epoxide hydrolase (mEH), and cytosolic glutathione S-transferase (cGST) activities using the geometrical isomers trans- and cis-stilbene oxide as substrates has been performed in livers from mice treated with clofibrate (ethyl-alpha-(p-chlorophenoxyisobutyrate]. The maximal increase of cEH activity occurred at lower dietary doses of clofibrate (0.5%) and within a shorter time (5 days) than mEH and cGST (2%, 14 days) activity. After 14 days at 0.5% clofibrate, cEH, mEH, and cGST activities were 250, 175, and 165% and 290, 220, and 75% of control values in male and female mice, respectively. Withdrawal of clofibrate from the diet resulted in a reversion of activities to control values within 7 days. Clofibrate treatment shifted the apparent subcellular compartmentation of all three enzymatic activities with an increase in the ratio of soluble to particulate activity. In particular, the relative specific activity of all three enzymes decreased in the light mitochondrial (peroxisomal) cell fraction, and an increase of a mEH-like activity (benzo[a]pyrene-4,5-oxide and cis-stilbene oxide hydrolysis) in the cytosol occurred. Both the increase of cEH activity and the appearance of mEH-like activity in the cytosol are novel responses of epoxide metabolizing enzymes, which may be related to the novel cellular responses that follow clofibrate treatment, peroxisome proliferation, hypolipidemia, and nongenotoxic carcinogenesis.

Violaxanthin de-epoxidase is rate-limiting for non-photochemical quenching under subsaturating light or during chilling in Arabidopsis.

PubMed

Chen, Zhong; Gallie, Daniel R

2012-09-01

In response to conditions of excess light energy, plants induce non-photochemical quenching (NPQ) as a protective mechanism to prevent over reduction of photosystem II and the generation of reactive oxygen species (ROS). The xanthophyll cycle, which contributes significantly to reversible NPQ to thermally dissipate excess absorbed light energy, involves de-epoxidation of violaxanthin and antheraxanthin to zeaxanthin in response to excess light energy. The activation of violaxanthin de-epoxidase (VDE), which catalyzes the de-epoxidation reaction, requires the generation of a light-induced, transthylakoid pH gradient. In this work, we overexpressed or repressed the expression of VDE in Arabidopsis (Arabidopsis thaliana) to examine whether VDE is rate-limiting for the induction of NPQ. Increasing VDE expression increased the de-epoxidation state of xanthophyll pigments, the rate of NPQ induction, and the level of NPQ achieved under subsaturating light. In saturating light, however, overexpression of VDE did not increase the xanthophyll pigment de-epoxidation state, the level of NPQ achieved following its initial induction, or substantially improve tolerance to high light. Only under chilling, which reduces VDE activity, did an increase in VDE expression provide slightly greater phototolerance. Repression of VDE expression impaired violaxanthin de-epoxidation, reduced the generation of NPQ, and lowered the level of NPQ achieved while increasing photosensitivity. These results demonstrate that the endogenous level of VDE is rate-limiting for NPQ in Arabidopsis under subsaturating but not saturating light and can become rate-limiting under chilling conditions. These results also show that increasing VDE expression confers greater phototolerance mainly under conditions which limit endogenous VDE activity. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Silica-supported, single-site titanium catalysts for olefin epoxidation. A molecular precursor strategy for control of catalyst structure.

PubMed

Jarupatrakorn, Jonggol; Don Tilley, T

2002-07-17

A molecular precursor approach involving simple grafting procedures was used to produce site-isolated titanium-supported epoxidation catalysts of high activity and selectivity. The tris(tert-butoxy)siloxy titanium complexes Ti[OSi(O(t)Bu)(3)](4) (TiSi4), ((i)PrO)Ti[OSi(O(t)Bu)(3)](3) (TiSi3), and ((t)BuO)(3)TiOSi(O(t)Bu)(3) (TiSi) react with the hydroxyl groups of amorphous Aerosil, mesoporous MCM-41, and SBA-15 via loss of HO(t)Bu and/or HOSi(O(t)Bu)(3) and introduction of titanium species onto the silica surface. Powder X-ray diffraction, nitrogen adsorption/desorption, infrared, and diffuse reflectance ultraviolet spectroscopies were used to investigate the structures and chemical natures of the surface-bound titanium species. The titanium species exist mainly in isolated, tetrahedral coordination environments. Increasing the number of siloxide ligands in the molecular precursor decreases the amount of titanium that can be introduced this way, but also enhances the catalytic activity and selectivity for the epoxidation of cyclohexene with cumene hydroperoxide as oxidant. In addition, the high surface area mesoporous silicas (MCM-41 and SBA-15) are more effective than amorphous silica as supports for these catalysts. Supporting TiSi3 on the SBA-15 affords highly active cyclohexene epoxidation catalysts (0.25-1.77 wt % Ti loading) that provide turnover frequencies (TOFs) of 500-1500 h(-1) after 1 h (TOFs are reduced by about half after calcination). These results demonstrate that oxygen-rich siloxide complexes of titanium are useful as precursors to supported epoxidation catalysts.

Monolithic Nickel (II) Oxide Aerogels Using an Organic Epoxide: The Importance of the Counter Ion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gash, A E; Satcher, J H; Simpson, R L

2004-01-13

The synthesis and characterization of nickel (II) oxide aerogel materials prepared using the epoxide addition method is described. The addition of the organic epoxide propylene oxide to an ethanolic solution of NiCl{sub 2} 6H{sub 2}O resulted in the formation of an opaque light green monolithic gel and subsequent drying with supercritical CO{sub 2} gave a monolithic aerogel material of the same color. This material has been characterized using powder X-ray diffraction, electron microscopy, elemental analysis, and nitrogen adsorption/desorption analysis. The results indicate that the nickel (II) oxide aerogel has very low bulk density (98 kg/m{sup 3} ({approx}98 %porous)), high surfacemore » area (413 m{sup 2}/g), and has a particulate-type aerogel microstructure made up of very fine spherical particles with an open porous network. By comparison, a precipitate of Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} is obtained when the same preparation is attempted with the common Ni(NO{sub 3}){sub 2} 6H{sub 2}O salt as the precursor. The implications of the difference of reactivity of the two different precursors are discussed in the context of the mechanism of gel formation via the epoxide addition method. The synthesis of nickel (II) oxide aerogel, using the epoxide addition method, is especially unique in our experience. It is our first example of the successful preparation of a metal oxide aerogel using a metal divalent metal ion and may have implications for the application of this method to the preparation of aerogels or nanoparticles of other divalent metal oxides. To our knowledge this is the first report of a monolithic pure nickel (II) oxide aerogel materials.« less

Gender differences in the metabolism of 1,3-butadiene to butadiene diepoxide in Sprague-Dawley rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornton-Manning, J.R.; Dahl, A.R.; Bechtold, W.E.

1995-12-01

1,3-Butadiene (BD), a gaseous compound used in the production of rubber, is a potent carcinogen in mice and a weak carcinogen in rats. The mechanism of BD-induced carcinogenicity is thought to involve genotoxic effects of its reactive epoxide metabolites butadiene monoepoxide (BDO) and butadiene diepoxide (BDO{sub 2}). Studies in our laboratory have shown that levels of the epoxides, particularly BDO{sub 2}, are greater in mice-the more sensitive species-than rats. While both epoxides are genotoxic in a number of assays, BDO{sub 2} is mutagenic in TK6 human lymphoblastoid cells at concentrations approximately 100-fold lower than BDO. Species differences in carcinogenicity ofmore » BD have posed a dilemma to investigators deciding which animal model is most appropriate for BD risk assessment.« less

The determination and quantification of photosynthetic pigments by reverse phase high-performance liquid chromatography, thin-layer chromatography, and spectrophotometry.

PubMed

Pocock, Tessa; Król, Marianna; Huner, Norman P A

2004-01-01

Chorophylls and carotenoids are functionally important pigment molecules in photosynthetic organisms. Methods for the determination of chlorophylls a and b, beta-carotene, neoxanthin, and the pigments that are involved in photoprotective cycles such as the xanthophylls are discussed. These cycles involve the reversible de-epoxidation of violaxanthin into antheraxanthin and zeaxanthin, as well as the reversible de-epoxidation of lutein-5,6-epoxide into lutein. This chapter describes pigment extraction procedures from higher plants and green algae. Methods for the determination and quantification using high-performance liquid chromatograpy (HPLC) are described as well as methods for the separation and purification of pigments for use as standards using thin-layer chromatography (TLC). In addition, several spectrophotometric methods for the quantification of chlorophylls a and b are described.

Propylene epoxidation over biogenic Au/TS-1 catalysts by Cinnamomum camphora extract in the presence of H2 and O2

NASA Astrophysics Data System (ADS)

Du, Mingming; Huang, Jiale; Sun, Daohua; Li, Qingbiao

2016-03-01

The Au/TS-1 catalysts with different Au nanoparticles (NPs) sizes ranging from 3.1 to 8.4 nm but the same Au loading of 0.5 wt% were prepared by Cinnamomum camphora (CC) extract, and were used for propylene epoxidation. The results showed that the interaction between Au and TS-1 support surface is important for propylene epoxidation and much smaller Au NPs (<3 nm) are the dominant active sites. After reaction of 100 h, there is no decreasing in both the activity and the PO selectivity for the Au/TS-1 catalysts, and only 1.8 wt% of the carbonaceous deposits on the surface of the catalyst after reaction, suggesting that the desorption of the product from the modified catalysts surface by residual biomolecules is much easier.

Epoxidation of alkenes and oxidation of alcohols with hydrogen peroxide catalyzed by a manganese(V) nitrido complex.

PubMed

Kwong, Hoi-Ki; Lo, Po-Kam; Lau, Kai-Chung; Lau, Tai-Chu

2011-04-14

The manganese(V) nitrido complex (PPh(4))(2)[Mn(N)(CN)(4)] is an active catalyst for alkene epoxidation and alcohol oxidation using H(2)O(2) as an oxidant. The catalytic oxidation is greatly enhanced by the addition of just one equivalent of acetic acid. The oxidation of ethene by this system has been studied computationally by the DFT method.

Optical properties and indentation hardness of thin-film acrylated epoxidized oil

NASA Astrophysics Data System (ADS)

Rahman, Mohammad Syuhaimi Ab.; Shaktur, Khaled Mohamed; Mohammad, Rahmah; Zalikha, Wan Aimi; Nawi, Norwimie; Mohd, Ahmad Faiza

2012-02-01

Epoxy acrylate has been widely used as optical resin for applications such as cladding, the core of a waveguide, and other photonic devices. In this study, sustainable resin from edible oil was used as an alternative to epoxy acrylate. Structural features and the transmission of planar thin-film resin from an ultraviolet-visible spectroscopy (UV-VIS) spectrometer were investigated upon UV exposure. It was found that high transmission still persists for all samples with and without an UV absorber for exposed and unexposed samples. The film was found to absorb strongly below 400 nm. A change in the cut-off wavelength was observed upon exposure. Thin-film hardness and its dynamic indentation in the load-unload mode with different test forces were evaluated. Vickers hardness and the elastic modulus were determined for unacrylated epoxidized soybean oil (ESO) and acrylated epoxidized soybean oil (AESO). It was found that the AESO has a higher Vickers hardness and elastic modulus than those of unacrylated thin film. The Vickers hardness and elastic modulus were found to increase as the applied test force increased. The refractive index, thickness, and modes present were characterized from a spin-coated planar thin film. The refractive index in the transverse electric mode (TE) and transverse magnetic mode (TM) were determined and compared for unacrylated and acrylated epoxidized oil.

Artificial sunlight and ultraviolet light induced photo-epoxidation of propylene over V-Ti/MCM-41 photocatalyst

PubMed Central

Nguyen, Van-Huy; Bai, Hsunling

2014-01-01

Summary The light irradiation parameters, including the wavelength spectrum and intensity of light source, can significantly influence a photocatalytic reaction. This study examines the propylene photo-epoxidation over V-Ti/MCM-41 photocatalyst by using artificial sunlight (Xe lamp with/without an Air Mass 1.5 Global Filter at 1.6/18.5 mW·cm−2) and ultraviolet light (Mercury Arc lamp with different filters in the range of 0.1–0.8 mW·cm−2). This is the first report of using artificial sunlight to drive the photo-epoxidation of propylene. Over V-Ti/MCM-41 photocatalyst, the propylene oxide (PO) formation rate is 193.0 and 112.1 µmol·gcat −1·h−1 with a PO selectivity of 35.0 and 53.7% under UV light and artificial sunlight, respectively. A normalized light utilization (NLU) index is defined and found to correlate well with the rate of both PO formation and C3H6 consumption in log–log scale. The light utilization with a mercury arc lamp is better than with a xenon lamp. The selectivity to PO remains practically unchanged with respect to NLU, suggesting that the photo-epoxidation occurs through the same mechanism under the conditions tested in this study. PMID:24991493

Assessment of epoxidized soy bean oil (ESBO) migrating into foods: comparison with ESBO-like epoxy fatty acids in our normal diet.

PubMed

Fankhauser-Noti, Anja; Fiselier, Katell; Biedermann-Brem, Sandra; Grob, Koni

2006-08-01

Epoxidized soy bean oil (ESBO) was found to be toxic for rats, but the toxic constituent is unknown. It became an issue as the migration from the gaskets in the lids for jars into oily foods regularly far exceeds the European legal limit (overall migration limit and specific migration limit derived from the tolerable daily intake (TDI)). In the context of risk management it was of interest to determine the epoxidized fatty acids of ESBO in those foods of our normal diet which are expected to contain the highest concentrations, i.e., oxidized edible oils (including degraded frying oils), fried foods, bakery ware and roasted meat. The contribution of epoxy oleic acid from ESBO to our diet turned out to be negligible. If this acid were the toxic component in ESBO, the toxicological assessment would primarily be a warning regarding oxidized fats and oils. The contribution of diepoxy linoleic acid from ESBO might be similar to the exposure from oxidized fats and oils of our diet, whereas the intake of triepoxy linolenic acid from ESBO exceeds that from normal food by around two orders of magnitude. Hence use of an epoxidized edible oil virtually free of linolenic acid would be inconspicuous in our diet.

New biobased high functionality polyols and their use in polyurethane coatings.

PubMed

Pan, Xiao; Webster, Dean C

2012-02-13

High-functionality polyols for application in polyurethanes (PUs) were prepared by epoxide ring-opening reactions from epoxidized sucrose esters of soybean oil-epoxidized sucrose soyates-in which secondary hydroxyl groups were generated from epoxides on fatty acid chains. Ester polyols were prepared by using a base-catalyzed acid-epoxy reaction with carboxylic acids (e.g., acetic acid); ether polyols were prepared by using an acid-catalyzed alcohol-epoxy reaction with monoalcohols (e.g., methanol). The polyols were characterized by using gel permeation chromatography, FTIR spectroscopy, (1)H NMR spectroscopy, differential scanning calorimetry (DSC), and viscosity measurements. PU thermosets were prepared by using aliphatic polyisocyanates based on isophorone diisocyanate and hexamethylene diisocyanate. The properties of the PUs were studied by performing tensile testing, dynamic mechanical analysis, DSC, and thermogravimetric analysis. The properties of PU coatings on steel substrates were evaluated by using ASTM methods to determine coating hardness, adhesion, solvent resistance, and ductility. Compared to a soy triglyceride polyol, sucrose soyate polyols provide greater hardness and range of cross-link density to PU thermosets because of the unique structure of these macromolecules: well-defined compact structures with a rigid sucrose core coupled with high hydroxyl group functionality. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Production of epoxide hydrolases in batch fermentations of Botryosphaeria rhodina.

PubMed

Melzer, Guido; Junne, Stefan; Wohlgemuth, Roland; Hempel, Dietmar C; Götz, Peter

2008-06-01

The filamentous fungus Botryosphaeria rhodina (ATCC 9055) was investigated related to its ability for epoxide hydrolase (EH) production. Epoxide hydrolase activity is located at two different sites of the cells. The larger part is present in the cytosol (70%), while the smaller part is associated to membranes (30%). In media optimization experiments, an activity of 3.5 U/gDW for aromatic epoxide hydrolysis of para-nitro-styrene oxide (pNSO) could be obtained. Activity increased by 30% when pNSO was added to the culture during exponential growth. An increase of enzyme activity up to 6 U/gDW was achieved during batch-fermentations in a bioreactor with 2.7 l working volume. Evaluation of fermentations with 30 l working volume revealed a relation of oxygen uptake rate to EH expression. Oxygen limitation resulted in a decreased EH activity. Parameter estimation by the linearization method of Hanes yielded Km values of 2.54 and 1.00 mM for the substrates S-pNSO and R-pNSO, respectively. vmax was 3.4 times higher when using R-pNSO. A protein purification strategy leading to a 47-fold increase in specific activity (940 U/mgProtein) was developed as a first step to investigate molecular and structural characteristics of the EH.

Enzymatic catalysis of anti-Baldwin ring closure in polyether biosynthesis.

PubMed

Hotta, Kinya; Chen, Xi; Paton, Robert S; Minami, Atsushi; Li, Hao; Swaminathan, Kunchithapadam; Mathews, Irimpan I; Watanabe, Kenji; Oikawa, Hideaki; Houk, Kendall N; Kim, Chu-Young

2012-03-04

Polycyclic polyether natural products have fascinated chemists and biologists alike owing to their useful biological activity, highly complex structure and intriguing biosynthetic mechanisms. Following the original proposal for the polyepoxide origin of lasalocid and isolasalocid and the experimental determination of the origins of the oxygen and carbon atoms of both lasalocid and monensin, a unified stereochemical model for the biosynthesis of polyether ionophore antibiotics was proposed. The model was based on a cascade of nucleophilic ring closures of postulated polyepoxide substrates generated by stereospecific oxidation of all-trans polyene polyketide intermediates. Shortly thereafter, a related model was proposed for the biogenesis of marine ladder toxins, involving a series of nominally disfavoured anti-Baldwin, endo-tet epoxide-ring-opening reactions. Recently, we identified Lsd19 from the Streptomyces lasaliensis gene cluster as the epoxide hydrolase responsible for the epoxide-opening cyclization of bisepoxyprelasalocid A to form lasalocid A. Here we report the X-ray crystal structure of Lsd19 in complex with its substrate and product analogue to provide the first atomic structure-to our knowledge-of a natural enzyme capable of catalysing the disfavoured epoxide-opening cyclic ether formation. On the basis of our structural and computational studies, we propose a general mechanism for the enzymatic catalysis of polyether natural product biosynthesis. © 2012 Macmillan Publishers Limited. All rights reserved

Molecular Mechanisms and New Treatment Paradigm for Atrial Fibrillation.

PubMed

Sirish, Padmini; Li, Ning; Timofeyev, Valeriy; Zhang, Xiao-Dong; Wang, Lianguo; Yang, Jun; Lee, Kin Sing Stephen; Bettaieb, Ahmed; Ma, Sin Mei; Lee, Jeong Han; Su, Demetria; Lau, Victor C; Myers, Richard E; Lieu, Deborah K; López, Javier E; Young, J Nilas; Yamoah, Ebenezer N; Haj, Fawaz; Ripplinger, Crystal M; Hammock, Bruce D; Chiamvimonvat, Nipavan

2016-05-01

Atrial fibrillation represents the most common arrhythmia leading to increased morbidity and mortality, yet, current treatment strategies have proven inadequate. Conventional treatment with antiarrhythmic drugs carries a high risk for proarrhythmias. The soluble epoxide hydrolase enzyme catalyzes the hydrolysis of anti-inflammatory epoxy fatty acids, including epoxyeicosatrienoic acids from arachidonic acid to the corresponding proinflammatory diols. Therefore, the goal of the study is to directly test the hypotheses that inhibition of the soluble epoxide hydrolase enzyme can result in an increase in the levels of epoxyeicosatrienoic acids, leading to the attenuation of atrial structural and electric remodeling and the prevention of atrial fibrillation. For the first time, we report findings that inhibition of soluble epoxide hydrolase reduces inflammation, oxidative stress, atrial structural, and electric remodeling. Treatment with soluble epoxide hydrolase inhibitor significantly reduces the activation of key inflammatory signaling molecules, including the transcription factor nuclear factor κ-light-chain-enhancer, mitogen-activated protein kinase, and transforming growth factor-β. This study provides insights into the underlying molecular mechanisms leading to atrial fibrillation by inflammation and represents a paradigm shift from conventional antiarrhythmic drugs, which block downstream events to a novel upstream therapeutic target by counteracting the inflammatory processes in atrial fibrillation. © 2016 American Heart Association, Inc.

Stiffness and strength of oxygen-functionalized graphene with vacancies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zandiatashbar, A.; Ban, E.; Picu, R. C., E-mail: picuc@rpi.edu

2014-11-14

The 2D elastic modulus (E{sup 2D}) and strength (σ{sup 2D}) of defective graphene sheets containing vacancies, epoxide, and hydroxyl functional groups are evaluated at 300 K by atomistic simulations. The fraction of vacancies is controlled in the range 0% to 5%, while the density of functional groups corresponds to O:C ratios in the range 0% to 25%. In-plane modulus and strength diagrams as functions of vacancy and functional group densities are generated using models with a single type of defect and with combinations of two types of defects (vacancies and functional groups). It is observed that in models containing only vacancies,more » the rate at which strength decreases with increasing the concentration of defects is largest, followed by models containing only epoxide groups and those with only hydroxyl groups. The effect on modulus of vacancies and epoxides present alone in the model is similar, and much stronger than that of hydroxyl groups. When the concentration of defects is large, the combined effect of the functional groups and vacancies cannot be obtained as the superposition of individual effects of the two types of defects. The elastic modulus deteriorates faster (slower) than predicted by superposition in systems containing vacancies and hydroxyl groups (vacancies and epoxide groups)« less

In situ epoxide generation by dimethyldioxirane oxidation and the use of epichlorohydrin in the flow synthesis of a library of β-amino alcohols.

PubMed

Cossar, Peter J; Baker, Jennifer R; Cain, Nicholas; McCluskey, Adam

2018-04-01

The flow coupling of epichlorohydrin with substituted phenols, while efficient, limits the nature of the epoxide available for the development of focused libraries of β-amino alcohols. This limitation was encountered in the production of analogues of 1-(4-nitrophenoxy)-3-((2-((4-(trifluoromethyl)pyrimidin-2-yl)amino)ethyl)amino)propan-2-ol 1 , a potential antibiotic lead. The in situ (flow) generation of dimethyldoxirane (DMDO) and subsequent flow olefin epoxidation abrogates this limitation and afforded facile access to structurally diverse β-amino alcohols. Analogues of 1 were readily accessed either via (i) a flow/microwave hybrid approach, or (ii) a sequential flow approach. Key steps were the in situ generation of DMDO, with olefin epoxidation in typically good yields and a flow-mediated ring opening aminolysis to form an expanded library of β-amino alcohols 1 and 10a - 18g , resulting in modest ( 11a , 21%) to excellent ( 12g , 80%) yields. Alternatively flow coupling of epichlorohydrin with phenols 4a - 4m (22%-89%) and a Bi(OTf) 3 catalysed microwave ring opening with amines afforded a select range of β-amino alcohols, but with lower levels of aminolysis regiocontrol than the sequential flow approach.

In situ epoxide generation by dimethyldioxirane oxidation and the use of epichlorohydrin in the flow synthesis of a library of β-amino alcohols

PubMed Central

Cossar, Peter J.; Baker, Jennifer R.; Cain, Nicholas

2018-01-01

The flow coupling of epichlorohydrin with substituted phenols, while efficient, limits the nature of the epoxide available for the development of focused libraries of β-amino alcohols. This limitation was encountered in the production of analogues of 1-(4-nitrophenoxy)-3-((2-((4-(trifluoromethyl)pyrimidin-2-yl)amino)ethyl)amino)propan-2-ol 1, a potential antibiotic lead. The in situ (flow) generation of dimethyldoxirane (DMDO) and subsequent flow olefin epoxidation abrogates this limitation and afforded facile access to structurally diverse β-amino alcohols. Analogues of 1 were readily accessed either via (i) a flow/microwave hybrid approach, or (ii) a sequential flow approach. Key steps were the in situ generation of DMDO, with olefin epoxidation in typically good yields and a flow-mediated ring opening aminolysis to form an expanded library of β-amino alcohols 1 and 10a–18g, resulting in modest (11a, 21%) to excellent (12g, 80%) yields. Alternatively flow coupling of epichlorohydrin with phenols 4a–4m (22%–89%) and a Bi(OTf)3 catalysed microwave ring opening with amines afforded a select range of β-amino alcohols, but with lower levels of aminolysis regiocontrol than the sequential flow approach. PMID:29765627

Crosslinking of Perfluorocarbon Polymers

DTIC Science & Technology

1977-04-01

absorption in the 8.0-8.7 M region, the presence of oxide can be excluded and thus the higher than to date reported melting point is most likely due...did not produce any epoxide. Apparently the stabilizer present in the Mallinckrodt hydrogen peroxide ( acetanilide ) promoted degradation of the epoxide...DTA curve (see Figure 3) Freon E-7 has a boiling point above 2500C. The broadness of the endotherm indicates that it is a multi-component mixture

General Approach to the Synthesis of the Chlorosulfolipids Danicalipin A, Mytilipin A, and Malhamensilipin A in Enantioenriched Form

PubMed Central

2015-01-01

A second-generation synthesis of three structurally related chlorosulfolipids has been developed. Key advances include highly stereocontrolled additions to α,β-dichloroaldehydes, kinetic resolutions of complex chlorinated vinyl epoxide intermediates, and Z-selective alkene cross metatheses of cis-vinyl epoxides. This strategy facilitated the synthesis of enantioenriched danicalipin A, mytilipin A, and malhamensilipin A in nine, eight, and 11 steps, respectively. PMID:24494597

Crystal structures and catalytic performance of three new methoxy substituted salen type nickel(II) Schiff base complexes derived from meso-1,2-diphenyl-1,2-ethylenediamine

NASA Astrophysics Data System (ADS)

Ghaffari, Abolfazl; Behzad, Mahdi; Pooyan, Mahsa; Amiri Rudbari, Hadi; Bruno, Giuseppe

2014-04-01

Three new nickel(II) complexes of a series of methoxy substituted salen type Schiff base ligands were synthesized and characterized by IR, UV-Vis and 1H NMR spectroscopy and elemental analysis. The ligands were synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with n-methoxysalicylaldehyde (n = 3, 4 and 5). Crystal structures of these complexes were determined. Electrochemical behavior of the complexes was studied by means of cyclic voltammetry in DMSO solutions. Catalytic performance of the complexes was studied in the epoxidation of cyclooctene using tert-butylhydroperoxide (TBHP) as oxidant under various conditions to find the optimum operating parameters. Low catalytic activity with moderate epoxide selectivity was observed in in-solvent conditions but in the solvent-free conditions, enhanced catalytic activity with high epoxide selectivity was achieved.

Exploiting epoxidized natural rubber latex (ENRL) as a starting raw material for latex-based products

NASA Astrophysics Data System (ADS)

Siti Nor Qamarina, M.; Fatimah Rubaizah, M. R.; Nurul Suhaira, A.; Norhanifah, M. Y.

2017-12-01

Epoxidized natural rubber latex (ENRL) is a chemically modified natural rubber latex produced from epoxidation process that involves usage of organic peracids. Conversion of the ENRL into dry rubber products has been known to exhibit many beneficial properties, however limited published works were found on diversifiying the ENRL latex-based products applications. In this preliminary work, different source of raw materials and neutralization systems were investigated. The objective was to explore possibilities in producing distinctive ENRL. Findings have demonstrated that different source of raw materials and neutralization systems influenced the typical ENRL specifications, stability behavior and particle size distribution. Morphological observations performed on these ENRL systems appeared to agree with the ENRL characteristics achieved. Since experimenting these two main factors resulted in encouraging ENRL findings, detailed work shall be further scrutinized to search for an optimum condition in producing marketable ENRL specifically for latex-based products applications.

Na@SiO2-Mediated Addition of Organohalides to Carbonyl Compounds for the Formation of Alcohols and Epoxides

NASA Astrophysics Data System (ADS)

Kapoor, Mohit; Hwu, Jih Ru

2016-11-01

Alcohols and epoxides were generated by the addition of organohalides to carbonyl compounds in the presence of sodium metal impregnated with silica gel (Na@SiO2) in THF at 25 °C through a radical pathway. Under the same conditions, Schiff bases were also successfully converted to the corresponding amines. Furthermore, the reaction of aldehydes with α-haloesters or 4-(chloromethyl)-coumarin with the aid of Na@SiO2 generated trans epoxides. An unprecedented mechanism is proposed for their formation. The advantages associated with these new reactions include: (1) products are obtained in good-to-excellent yields, (2) reactions are completed at room temperatures in a short period of time (<2.0 h), (3) it is unnecessary to perform the reactions under anhydrous conditions, and (4) the entire process requires only simple manipulations.

Exciton characteristics in graphene epoxide.

PubMed

Zhu, Xi; Su, Haibin

2014-02-25

Exciton characteristics in graphene epoxide (GE) are investigated by density functional theory with quasi-particle corrections and many-body interactions. The nature of the exciton is influenced by epoxide content and detailed geometric configurations. Two kinds of excitons are identified in GE: Frenkel-like exciton originated from the sp(2) carbon cluster and charge-transfer exciton formed by localized states involving both oxygen and carbon atoms. The unusual blue shift associated with the Frenkel-like exciton leaking is highlighted. One scaling relationship is proposed to address the power-law dependence of Frenkel-like exciton binding strength on its size. The charge-transfer exciton appears in GE samples with the high oxygen coverage. Particularly, the exciton in GE structures exhibits long lifetime by analyzing both radiative and nonradiative decay processes. This study sheds light on the potential applications of GE-based structures with attractive high quantum yield in light emission and optoelectronic technology.

Efficient alkene epoxidation catalyzed by molybdenyl acetylacetonate supported on aminated UiO-66 metal-organic framework

NASA Astrophysics Data System (ADS)

Kardanpour, Reihaneh; Tangestaninejad, Shahram; Mirkhani, Valiollah; Moghadam, Majid; Mohammadpoor-Baltork, Iraj; Zadehahmadi, Farnaz

2015-03-01

Metal-organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH2 (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV-vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic and linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity.

Structural insights into human microsomal epoxide hydrolase by combined homology modeling, molecular dynamics simulations, and molecular docking calculations.

PubMed

Saenz-Méndez, Patricia; Katz, Aline; Pérez-Kempner, María Lucía; Ventura, Oscar N; Vázquez, Marta

2017-04-01

A new homology model of human microsomal epoxide hydrolase was derived based on multiple templates. The model obtained was fully evaluated, including MD simulations and ensemble-based docking, showing that the quality of the structure is better than that of only previously known model. Particularly, a catalytic triad was clearly identified, in agreement with the experimental information available. Analysis of intermediates in the enzymatic mechanism led to the identification of key residues for substrate binding, stereoselectivity, and intermediate stabilization during the reaction. In particular, we have confirmed the role of the oxyanion hole and the conserved motif (HGXP) in epoxide hydrolases, in excellent agreement with known experimental and computational data on similar systems. The model obtained is the first one that fully agrees with all the experimental observations on the system. Proteins 2017; 85:720-730. © 2016 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Experimental verification, and domain definition, of structural alerts for protein binding: epoxides, lactones, nitroso, nitros, aldehydes and ketones.

PubMed

Nelms, M D; Cronin, M T D; Schultz, T W; Enoch, S J

2013-01-01

This study outlines how a combination of in chemico and Tetrahymena pyriformis data can be used to define the applicability domain of selected structural alerts within the profilers of the OECD QSAR Toolbox. Thirty-three chemicals were profiled using the OECD and OASIS profilers, enabling the applicability domain of six structural alerts to be defined, the alerts being: epoxides, lactones, nitrosos, nitros, aldehydes and ketones. Analysis of the experimental data showed the applicability domains for the epoxide, nitroso, aldehyde and ketone structural alerts to be well defined. In contrast, the data showed the applicability domains for the lactone and nitro structural alerts needed modifying. The accurate definition of the applicability domain for structural alerts within in silico profilers is important due to their use in the chemical category in predictive and regulatory toxicology. This study highlights the importance of utilizing multiple profilers in category formation.

Rhodococcus erythropolis DCL14 Contains a Novel Degradation Pathway for Limonene

PubMed Central

van der Werf, Mariët J.; Swarts, Henk J.; de Bont, Jan A. M.

1999-01-01

Strain DCL14, which is able to grow on limonene as a sole source of carbon and energy, was isolated from a freshwater sediment sample. This organism was identified as a strain of Rhodococcus erythropolis by chemotaxonomic and genetic studies. R. erythropolis DCL14 also assimilated the terpenes limonene-1,2-epoxide, limonene-1,2-diol, carveol, carvone, and (−)-menthol, while perillyl alcohol was not utilized as a carbon and energy source. Induction tests with cells grown on limonene revealed that the oxygen consumption rates with limonene-1,2-epoxide, limonene-1,2-diol, 1-hydroxy-2-oxolimonene, and carveol were high. Limonene-induced cells of R. erythropolis DCL14 contained the following four novel enzymatic activities involved in the limonene degradation pathway of this microorganism: a flavin adenine dinucleotide- and NADH-dependent limonene 1,2-monooxygenase activity, a cofactor-independent limonene-1,2-epoxide hydrolase activity, a dichlorophenolindophenol-dependent limonene-1,2-diol dehydrogenase activity, and an NADPH-dependent 1-hydroxy-2-oxolimonene 1,2-monooxygenase activity. Product accumulation studies showed that (1S,2S,4R)-limonene-1,2-diol, (1S,4R)-1-hydroxy-2-oxolimonene, and (3R)-3-isopropenyl-6-oxoheptanoate were intermediates in the (4R)-limonene degradation pathway. The opposite enantiomers [(1R,2R,4S)-limonene-1,2-diol, (1R,4S)-1-hydroxy-2-oxolimonene, and (3S)-3-isopropenyl-6-oxoheptanoate] were found in the (4S)-limonene degradation pathway, while accumulation of (1R,2S,4S)-limonene-1,2-diol from (4S)-limonene was also observed. These results show that R. erythropolis DCL14 metabolizes both enantiomers of limonene via a novel degradation pathway that starts with epoxidation at the 1,2 double bond forming limonene-1,2-epoxide. This epoxide is subsequently converted to limonene-1,2-diol, 1-hydroxy-2-oxolimonene, and 7-hydroxy-4-isopropenyl-7-methyl-2-oxo-oxepanone. This lactone spontaneously rearranges to form 3-isopropenyl-6-oxoheptanoate. In the presence of coenzyme A and ATP this acid is converted further, and this finding, together with the high levels of isocitrate lyase activity in extracts of limonene-grown cells, suggests that further degradation takes place via the β-oxidation pathway. PMID:10224006

Mechanism of epoxide hydrolysis in microsolvated nucleotide bases adenine, guanine and cytosine: a DFT study.

PubMed

Vijayalakshmi, Kunduchi P; Mohan, Neetha; Ajitha, Manjaly J; Suresh, Cherumuttathu H

2011-07-21

Six water molecules have been used for microsolvation to outline a hydrogen bonded network around complexes of ethylene epoxide with nucleotide bases adenine (EAw), guanine (EGw) and cytosine (ECw). These models have been developed with the MPWB1K-PCM/6-311++G(3df,2p)//MPWB1K/6-31+G(d,p) level of DFT method and calculated S(N)2 type ring opening of the epoxide due to amino group of the nucleotide bases, viz. the N6 position of adenine, N2 position of guanine and N4 position of cytosine. Activation energy (E(act)) for the ring opening was found to be 28.06, 28.64, and 28.37 kcal mol(-1) respectively for EAw, EGw and ECw. If water molecules were not used, the reactions occurred at considerably high value of E(act), viz. 53.51 kcal mol(-1) for EA, 55.76 kcal mol(-1) for EG and 56.93 kcal mol(-1) for EC. The ring opening led to accumulation of negative charge on the developing alkoxide moiety and the water molecules around the charge localized regions showed strong hydrogen bond interactions to provide stability to the intermediate systems EAw-1, EGw-1 and ECw-1. This led to an easy migration of a proton from an activated water molecule to the alkoxide moiety to generate a hydroxide. Almost simultaneously, a proton transfer chain reaction occurred through the hydrogen bonded network of water molecules and resulted in the rupture of one of the N-H bonds of the quaternized amino group. The highest value of E(act) for the proton transfer step of the reaction was 2.17 kcal mol(-1) for EAw, 2.93 kcal mol(-1) for EGw and 0.02 kcal mol(-1) for ECw. Further, the overall reaction was exothermic by 17.99, 22.49 and 13.18 kcal mol(-1) for EAw, EGw and ECw, respectively, suggesting that the reaction is irreversible. Based on geometric features of the epoxide-nucleotide base complexes and the energetics, the highest reactivity is assigned for adenine followed by cytosine and guanine. Epoxide-mediated damage of DNA is reported in the literature and the present results suggest that hydrated DNA bases become highly S(N)2 active on epoxide systems and the occurrence of such reactions can inflict permanent damage to the DNA.

Benzo(a)pyrene diol epoxides as intermediates in nucleic acid binding in vitro and in vivo.

PubMed

Weinstein, I B; Jeffrey, A M; Jennette, K W; Blobstein, S H; Harvey, R G; Harris, C; Autrup, H; Kasai, H; Nakanishi, K

1976-08-13

Evidence has been obtained that a specific isomer of a diol epoxide derivative of benzo(a)pyrene, (+/-)-7 beta,8alpha-dihydroxy-9alpha, 10alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene, is an intermediate in the binding of benzo(a)pyrene to RNA in cultured bovine bronchial mucosa. An adduct is formed between position 10 of this derivative and the 2-amino group of guanine.

Photooxidation of mixed aryl and biarylphosphines.

PubMed

Zhang, Dong; Celaje, Jeff A; Agua, Alon; Doan, Chad; Stewart, Timothy; Bau, Robert; Selke, Matthias

2010-07-02

Arylphosphines and dialkylbiarylphosphines react with singlet oxygen to form phosphine oxides and phosphinate esters. For mixed arylphosphines, the most electron-rich aryl group migrates to form the phosphinate, while for dialkylbiarylphosphines migration of the alkyl group occurs. Dialkylbiarylphosphines also yield arene epoxides, especially in electron-rich systems. Phosphinate ester formation is increased at high temperature, while protic solvents increase the yield of epoxide. The product distribution provides evidence for Buchwald's recent conformational model for the aerobic oxidation of dialkylbiarylphosphines.

Förster resonance energy transfer competitive displacement assay for human soluble epoxide hydrolase

PubMed Central

Lee, Kin Sing Stephen; Morisseau, Christophe; Yang, Jun; Wang, Peng; Hwang, Sung Hee; Hammock, Bruce D.

2013-01-01

The soluble epoxide hydrolase (sEH), responsible for the hydrolysis of various fatty acid epoxides to their corresponding 1,2-diols, is becoming an attractive pharmaceutical target. These fatty acid epoxides, particularly epoxyeicosatrienoic acids (EETs), play an important role in human homeostatic and inflammation processes. Therefore, inhibition of human sEH, which stabilizes EETs in vivo, brings several beneficial effects to human health. Although there are several catalytic assays available to determine the potency of sEH inhibitors, measuring the in vitro inhibition constant (Ki) for these inhibitors using catalytic assay is laborious. In addition, koff, which has been recently suggested to correlate better with the in vivo potency of inhibitors, has never been measured for sEH inhibitors. To better measure the potency of sEH inhibitors, a reporting ligand, 1-(adamantan-1-yl)-3-(1-(2-(7-hydroxy-2-oxo-2H-chromen-4-yl)acetyl) piperidin-4-yl)urea (ACPU), was designed and synthesized. With ACPU, we have developed a Förster resonance energy transfer (FRET)-based competitive displacement assay using intrinsic tryptophan fluorescence from sEH. In addition, the resulting assay allows us to measure the Ki values of very potent compounds to the picomolar level and to obtain relative koff values of the inhibitors. This assay provides additional data to evaluate the potency of sEH inhibitors. PMID:23219719

Development and characterization of soy-based epoxy resins and pultruded FRP composites

NASA Astrophysics Data System (ADS)

Zhu, Jiang

This dissertation focuses on the development, manufacture and characterization of novel soy-based epoxy FRP composites. Use of alternative epoxy resin systems derived from a renewable resource holds potential for low cost raw materials for the polymer and composite industries. Epoxidized Allyl Soyate (EAS) and Epoxidized Methyl Soyate (EMS) were developed from soybean oil with two chemical modification procedures: transesterification and epoxidation. This research investigates the curing characteristics and thermal and mechanical properties of the neat soyate resin systems. The derived soyate resins have higher reactivity and superior performance compared to commercially available epoxidized soybean oil. An efficient two-step curing method was developed in order to utilize these soyate resins to their full potential. The epoxy co-resin systems with varied soyate resin content were successfully used to fabricate composite material through pultrusion. The pultrusion resin systems with 30 wt% soyate resins yielded improved, or comparable mechanical properties with neat commercial resins. A finite element analysis of the heat transfer and curing process was performed to study the processing characterization on glass/epoxy composite pultrusion. This model can be used to establish baseline process variables and will benefit subsequent optimization. This research demonstrates that soy-based resins, especially EAS, show considerable promise as an epoxy resin supplement for use in polymer and composite structural applications. The new products derived from soybean oil can provide competitive performance, low cost and environmental advantages.

A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative using NMR spectroscopy techniques.

PubMed

Hamzah, Rosniza; Bakar, Mohamad Abu; Khairuddean, Melati; Mohammed, Issam Ahmed; Adnan, Rohana

2012-09-12

A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative was carried out using NMR spectroscopy techniques. The overlapping (1)H-NMR signals of ENR-50 at δ 1.56, 1.68-1.70, 2.06, 2.15-2.17 ppm were successfully assigned. In this work, the <(13)C-NMR chemical shift assignments of ENR-50 were consistent to the previously reported work. A cyclic dithiocarbonate derivative of ENR-50 was synthesized from the reaction of purified ENR-50 with carbon disulfide (CS(2)), in the presence of 4-dimethylaminopyridine (DMAP) as catalyst at reflux temperature. The cyclic dithiocarbonate formation involved the epoxide ring opening of the ENR-50. This was followed by insertion of the C-S moiety of CS(2) at the oxygen attached to the quaternary carbon and methine carbon of epoxidized isoprene unit, respectively. The bands due to the C=S and C-O were clearly observed in the FTIR spectrum while the (1)H-NMR spectrum of the derivative revealed the peak attributed to the methylene protons had split. The (13)C-NMR spectrum of the derivative further indicates two new carbon peaks arising from the >C=S and quaternary carbon of cyclic dithiocarbonate. All other (1)H- and (13)C-NMR chemical shifts of the derivative remain unchanged with respect to the ENR-50.

Engineering Styrene Monooxygenase for Biocatalysis: Reductase-Epoxidase Fusion Proteins.

PubMed

Heine, Thomas; Tucker, Kathryn; Okonkwo, Nonye; Assefa, Berhanegebriel; Conrad, Catleen; Scholtissek, Anika; Schlömann, Michael; Gassner, George; Tischler, Dirk

2017-04-01

The enantioselective epoxidation of styrene and related compounds by two-component styrene monooxygenases (SMOs) has targeted these enzymes for development as biocatalysts. In the present work, we prepare genetically engineered fusion proteins that join the C-terminus of the epoxidase (StyA) to the N-terminus of the reductase (StyB) through a linker peptide and demonstrate their utility as biocatalysts in the synthesis of Tyrain purple and other indigoid dyes. A single-vector expression system offers a simplified platform for transformation and expansion of the catalytic function of styrene monooxygenases, and the resulting fusion proteins are self-regulated and couple efficiently NADH oxidation to styrene epoxidation. We find that the reductase domain proceeds through a sequential ternary-complex mechanism at low FAD concentration and a double-displacement mechanism at higher concentrations of FAD. Single-turnover studies indicate an observed rate constant for FAD-to-FAD hydride transfer of ~8 s -1 . This step is rate limiting in the styrene epoxidation reaction and helps to ensure that flavin reduction and styrene epoxidation reactions proceed without wasteful side reactions. Comparison of the reductase activity of the fusion proteins with the naturally occurring reductase, SMOB, and N-terminally histidine-tagged reductase, NSMOB, suggests that the observed changes in catalytic mechanism are due in part to an increase in flavin-binding affinity associated with the N-terminal extension of the reductase.

Enzymatic catalysis of anti-Baldwin ring closure in polyether biosynthesis

PubMed Central

Hotta, Kinya; Chen, Xi; Paton, Robert S.; Minami, Atsushi; Li, Hao; Swaminathan, Kunchithapadam; Mathews, Irimpan I.; Watanabe, Kenji; Oikawa, Hideaki; Houk, Kendall N.; Kim, Chu-Young

2012-01-01

Polycyclic polyether natural products have fascinated chemists and biologists alike owing to their useful biological activity, highly complex structure and intriguing biosynthetic mechanisms. Following the original proposal for the polyepoxide origin of lasalocid and isolasalocid1 and the experimental determination of the origins of the oxygen and carbon atoms of both lasalocid and monensin, a unified stereochemical model for the biosynthesis of polyether ionophore antibiotics was proposed2. The model was based on a cascade of nucleophilic ring closures of postulated polyepoxide substrates generated by stereospecific oxidation of all-trans polyene polyketide intermediates2. Shortly thereafter, a related model was proposed for the biogenesis of marine ladder toxins, involving a series of nominally disfavoured anti-Baldwin, endo-tet epoxide-ring-opening reactions3–5. Recently, we identified Lsd19 from the Streptomyces lasaliensis gene cluster as the epoxide hydrolase responsible for the epoxide-opening cyclization of bisepoxyprelasalocid A6 to form lasalocid A7,8. Here we report the X-ray crystal structure of Lsd19 in complex with its substrate and product analogue9 to provide the first atomic structure—to our knowledge—of a natural enzyme capable of catalysing the disfavoured epoxide-opening cyclic ether formation. On the basis of our structural and computational studies, we propose a general mechanism for the enzymatic catalysis of polyether natural product biosynthesis. PMID:22388816

Antisense suppression of violaxanthin de-epoxidase in tobacco does not affect plant performance in controlled growth conditions.

PubMed

Chang, S H; Bugos, R C; Sun, W H; Yamamoto, H Y

2000-01-01

Violaxanthin de-epoxidase (VDE) catalyzes the de-epoxidation of violaxanthin to antheraxanthin and zeaxanthin in the xanthophyll cycle. Tobacco was transformed with an antisense VDE construct under control of the cauliflower mosaic virus 35S promoter to determine the effect of reduced levels of VDE on plant growth. Screening of 40 independent transformants revealed 18 antisense lines with reduced levels of VDE activity with two in particular (TAS32 and TAS39) having greater than 95% reduction in VDE activity. Northern analysis demonstrated that these transformants had greatly suppressed levels of VDE mRNA. De-epoxidation of violaxanthin was inhibited to such an extent that no zeaxanthin and only very low levels of antheraxanthin could be detected after exposure of leaves to high light (2000 mumol m(-2) s(-1) for 20 min) with no observable effect on levels of other carotenoids and chlorophyll. Non-photochemical quenching was greatly reduced in the antisense VDE tobacco, demonstrating that a significant level of the non-photochemical quenching in tobacco requires de-epoxidation of violaxanthin. Although the antisense plants demonstrated a greatly impaired de-epoxidation of violaxanthin, no effect on plant growth or photosynthetic rate was found when plants were grown at a photon flux density of 500 or 1000 mumol m(-2) s(-1) under controlled growth conditions as compared to wild-type tobacco.

Heteropolytungstate nanoparticles: Microemulsion-mediated preparation and investigation of their catalytic activity in the epoxidation of olefins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masteri-Farahani, M., E-mail: mfarahany@yahoo.com; Ghorbani, M.

2016-04-15

Highlights: • Keggin type Q{sub 3}PW{sub 12}O{sub 40} nanoparticles were synthesized by using microemulsion system. • The nanoparticles have uniform size of about 25 nm and spherical morphologies. • The prepared nanoparticles act as reusable catalyst in the epoxidation of olefins with H{sub 2}O{sub 2}. - Abstract: Keggin type Q{sub 3}PW{sub 12}O{sub 40} nanoparticles (Q = cetyltrimethylammonium cation) were synthesized in water-in-oil (w/o) microemulsion consisted of water/cetyltrimethylammonium bromide/n-butanol/isooctane. Reaction of Na{sub 2}WO{sub 4}, Na{sub 2}HPO{sub 4} and hydrochloric acid within water containing nanoreactors of reverse micelles resulted in the preparation of Q{sub 3}PW{sub 12}O{sub 40} nanoparticles. The resultant nanoparticles weremore » analyzed by physicochemical methods such as FT-IR spectroscopy, X-ray diffraction, energy-dispersive X-ray analysis, thermogravimetric analyses (TGA-DTA), scanning and transmission electron microscopy and atomic force microscopy which show nearly uniform spherical nanoparticles with size of about 15 nm. Finally, catalytic activity of the Q{sub 3}PW{sub 12}O{sub 40} nanoparticles was examined in the epoxidation of olefins with H{sub 2}O{sub 2}. The prepared nanoparticles acted as recoverable and reusable catalyst in the epoxidation of olefins with H{sub 2}O{sub 2}.« less

Lutein from deepoxidation of lutein epoxide replaces zeaxanthin to sustain an enhanced capacity for nonphotochemical chlorophyll fluorescence quenching in avocado shade leaves in the dark.

PubMed

Förster, Britta; Pogson, Barry James; Osmond, Charles Barry

2011-05-01

Leaves of avocado (Persea americana) that develop and persist in deep shade canopies have very low rates of photosynthesis but contain high concentrations of lutein epoxide (Lx) that are partially deepoxidized to lutein (L) after 1 h of exposure to 120 to 350 μmol photons m(-2) s(-1), increasing the total L pool by 5% to 10% (ΔL). Deepoxidation of Lx to L was near stoichiometric and similar in kinetics to deepoxidation of violaxanthin (V) to antheraxanthin (A) and zeaxanthin (Z). Although the V pool was restored by epoxidation of A and Z overnight, the Lx pool was not. Depending on leaf age and pretreatment, the pool of ΔL persisted for up to 72 h in the dark. Metabolism of ΔL did not involve epoxidation to Lx. These contrasting kinetics enabled us to differentiate three states of the capacity for nonphotochemical chlorophyll fluorescence quenching (NPQ) in attached and detached leaves: ΔpH dependent (NPQ(ΔpH)) before deepoxidation; after deepoxidation in the presence of ΔL, A, and Z (NPQ(ΔLAZ)); and after epoxidation of A+Z but with residual ΔL (NPQ(ΔL)). The capacity of both NPQ(ΔLAZ) and NPQ(ΔL) was similar and 45% larger than NPQ(ΔpH), but dark relaxation of NPQ(ΔLAZ) was slower. The enhanced capacity for NPQ was lost after metabolism of ΔL. The near equivalence of NPQ(ΔLAZ) and NPQ(ΔL) provides compelling evidence that the small dynamic pool ΔL replaces A+Z in avocado to "lock in" enhanced NPQ. The results are discussed in relation to data obtained with other Lx-rich species and in mutants of Arabidopsis (Arabidopsis thaliana) with increased L pools.

Cholesterol-5,6-epoxides: chemistry, biochemistry, metabolic fate and cancer.

PubMed

Poirot, Marc; Silvente-Poirot, Sandrine

2013-03-01

In the nineteen sixties it was proposed that cholesterol might be involved in the etiology of cancers and cholesterol oxidation products were suspected of being causative agents. Researchers had focused their attention on cholesterol-5,6-epoxides (5,6-ECs) based on several lines of evidence: 1) 5,6-ECs contained an oxirane group that was supposed to confer alkylating properties such as those observed for aliphatic and aromatic epoxides. 2) cholesterol-5,6-epoxide hydrolase (ChEH) was induced in pre-neoplastic lesions of skin from rats exposed to ultraviolet irradiations and ChEH was proposed to be involved in detoxification processes like other epoxide hydrolases. However, 5,6-ECs failed to induce carcinogenicity in rodents which ruled out a potent carcinogenic potential for 5,6-ECs. Meanwhile, clinical studies revealed an anomalous increase in the concentrations of 5,6β-EC in the nipple fluids of patients with pre-neoplastic breast lesions and in the blood of patients with endometrious cancers, suggesting that 5,6-ECs metabolism could be linked with cancer. Paradoxically, ChEH has been recently shown to be totally inhibited by therapeutic concentrations of tamoxifen (Tam), which is one of the main drugs used in the hormonotherapy and the chemoprevention of breast cancers. These data would suggest that the accumulation of 5,6-ECs could represent a risk factor, but we found that 5,6-ECs were involved in the induction of breast cancer cell differentiation and death induced by Tam suggesting a positive role of 5,6-ECs. These observations meant that the biochemistry and the metabolism of 5,6-ECs needed to be extensively studied. We will review the current knowledge and the future direction of 5,6-ECs chemistry, biochemistry, metabolism, and relationship with cancer. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Formation of a Cyclopropyl Epoxide via a Leukotriene A Synthase-related Pathway in an Anaerobic Reaction of Soybean Lipoxygenase-1 with 15S-Hydroperoxyeicosatetraenoic Acid

PubMed Central

Zheng, Yuxiang; Brash, Alan R.

2010-01-01

The further conversion of an arachidonic acid hydroperoxide to a leukotriene A (LTA) type epoxide by specific lipoxygenase (LOX) enzymes constitutes a key step in inflammatory mediator biosynthesis. Whereas mammalian 5-LOX transforms its primary product (5S-hydroperoxyeicosatetraenoic acid; 5S-HPETE) almost exclusively to LTA4, the model enzyme, soybean LOX-1, normally produces no detectable leukotrienes and instead further oxygenates its primary product 15S-HPETE to 5,15- and 8,15-dihydroperoxides. Mammalian 15-LOX-1 displays both types of activity. We reasoned that availability of molecular oxygen within the LOX active site favors oxygenation, whereas lack of O2 promotes LTA epoxide synthesis. To test this, we reacted 15S-HPETE with soybean LOX-1 under anaerobic conditions and identified the products by high pressure liquid chromatography, UV, mass spectrometry, and NMR. Among the products, we identified a pair of 8,15-dihydroxy diastereomers with all-trans-conjugated trienes that incorporated 18O from H218O at C-8, indicative of the formation of 14,15-LTA4. A pair of 5,15-dihydroxy diastereomers containing two trans,trans-conjugated dienes (6E,8E,11E,13E) and that incorporated 18O from H218O at C-5 was deduced to arise from hydrolysis of a novel epoxide containing a cyclopropyl ring, 14,15-epoxy-[9,10,11-cyclopropyl]-eicosa-5Z,7E,13E-trienoic acid. Also identified was the δ-lactone of the 5,15-diol, a derivative that exhibited no 18O incorporation due to its formation by intramolecular reaction of the carboxyl anion with the proposed epoxide intermediate. Our results support a model in which access to molecular oxygen within the active site directs the outcome from competing pathways in the secondary reactions of lipoxygenases. PMID:20194505

Gaucher disease types 1, 2, and 3: differential mutations of the acid beta-glucosidase active site identified with conduritol B epoxide derivatives and sphingosine.

PubMed Central

Grabowski, G A; Dinur, T; Osiecki, K M; Kruse, J R; Legler, G; Gatt, S

1985-01-01

To elucidate the genetic heterogeneity in Gaucher disease, the residual beta-glucosidase in cultured fibroblasts from affected patients with each of the major phenotypes was investigated in vitro and/or in viable cells by inhibitor studies using the covalent catalytic site inhibitors, conduritol B epoxide or its bromo derivative, and the reversible cationic inhibitor, sphingosine. These studies delineated three distinct groups (designated A, B, and C) of residual activities with characteristic responses to these inhibitors. Group A residual enzymes had normal I50 values (i.e., the concentration of inhibitor that results in 50% inhibition) for the inhibitors and normal or nearly normal t1/2 values for conduritol B epoxide. All neuronopathic (types 2 and 3) and most non-Jewish nonneuronopathic (type 1) patients had group A residual activities and, thus, could not be distinguished by these inhibitor studies. Group B residual enzymes had about four- to fivefold increased I50 values for the inhibitors and similarly increased t1/2 values for conduritol B epoxide. All Ashkenazi Jewish type 1 and only two non-Jewish type 1 patients had group B residual activities. The differences in I50 values between groups A and B also were confirmed by determining the uninhibited enzyme activity after culturing the cells in the presence of bromo-conduritol B epoxide. Group C residual activity had intermediate I50 values for the inhibitors and represented a single Afrikaner type 1 patient: this patient was a genetic compound for the group A (type 2) and group B (type 1) mutations. These inhibition studies indicated that: Gaucher disease type 1 is biochemically heterogeneous, neuronopathic and non-Jewish nonneuronopathic phenotypes cannot be reliably distinguished by these inhibitor studies, and the Ashkenazi Jewish form of Gaucher disease type 1 results from a unique mutation in a specific active site domain of acid beta-glucosidase that leads to a defective enzyme with a decreased Vmax. PMID:4003396

Original Synthesis of Fluorenyl Alcohol Derivatives by Reductive Dehalogenation Initiated by TDAE.

PubMed

Giuglio-Tonolo, Alain Gamal; Terme, Thierry; Vanelle, Patrice

2016-10-24

We report here a novel and easy-to-handle reductive dehalogenation of 9-bromofluorene in the presence of arylaldehydes and dicarbonyl derivatives to give the corresponding fluorenyl alcohol derivatives and Darzens epoxides as by-products in tetrakis(dimethylamino)ethylene (TDAE) reaction conditions. The reaction is believed to proceed via two successive single electron transfers to generate the fluorenyl anion which was able to react with different electrophiles. A mechanistic study was conducted to understand the formation of the epoxide derivatives.

Synthesis of Potential Metaboliters in the 1,2,3,4, and 5,6,7,8 Benzo Ring Positions of the Polycyclic Aromatic Hydrocarbon Benzo(G)Chrysene.

DTIC Science & Technology

1986-01-01

biological activity. Pullman, in 1945 , noted that active compounds contained angular benzo rings. She introduced the terminology "K- region" to refer to...Figure 1.6) give .... ~~~~~. .. .. .. . ........ . _............ . _.-.•.-•.. . ..... ... ,. 12 .xcellent correlation when measured reactivity ( hydrolysis ...molecular plane, the diol epoxide is trans or series 2. Early studies indicated that isomer 1 is the more reactive diol epoxide in hydrolysis reactions

Gas-phase and solution-phase polymerization of epoxides by Cr(salen) complexes: evidence for a dinuclear cationic mechanism.

PubMed

Schön, Eva; Zhang, Xiangyang; Zhou, Zhiping; Chisholm, Malcolm H; Chen, Peter

2004-11-15

The gas-phase reactions of a series of mass-selected mononuclear and dinuclear Cr(salen) complexes with propylene oxide suggest that the enhanced reactivity of the dinuclear complexes in gas-phase and in solution may derive from a dicationic mechanism in which the alkoxide chain is mu(2)-coordinated to two Lewis acidic metal centers. The double coordination is proposed to suppress backbiting, and hence chain-transfer in the gas-phase homopolymerization of epoxides.

Photooxidation of Mixed Aryl and Biarylphosphines

PubMed Central

Zhang, Dong; Celaje, Jeff A.; Agua, Alon; Doan, Chad; Stewart, Timothy; Bau, Robert; Selke, Matthias

2010-01-01

Aryl phosphines and dialkylbiaryl phosphines react with singlet oxygen to form phosphinate esters. For mixed arylphosphines, the most electron-rich aryl group migrates to form the phosphinate, while for dialkylbiaryl phosphines migration of the alkyl group occurs. Dialkylbiaryl phosphines also yield arene epoxides, especially in electron rich systems. Phosphinate ester formation is increased at high temperature while protic solvents increase the yield of epoxide. The product distribution provides evidence for Buchwald’s recent conformational model for the aerobic oxidation of dialkylbiaryl phosphines. PMID:20527907

The stability of the three transmembrane and the four transmembrane human vitamin K epoxide reductase models

NASA Astrophysics Data System (ADS)

Wu, Sangwook

2016-04-01

The three transmembrane and the four transmembrane helix models are suggested for human vitamin K epoxide reductase (VKOR). In this study, we investigate the stability of the human three transmembrane/four transmembrane VKOR models by employing a coarse-grained normal mode analysis and molecular dynamics simulation. Based on the analysis of the mobility of each transmembrane domain, we suggest that the three transmembrane human VKOR model is more stable than the four transmembrane human VKOR model.

Alkyl halide-free heteroatom alkylation and epoxidation facilitated by a recyclable polymer-supported oxidant for the in-flow preparation of diazo compounds.

PubMed

Nicolle, Simon M; Hayes, Christopher J; Moody, Christopher J

2015-03-16

Highly reactive metal carbenes, generated from simple ketones via diazo compounds, including diazo-amides and -phosphonates, using a recyclable reagent in-flow, are transient but versatile electrophiles for heteroatom alkylation reactions and for epoxide formation. The method produces no organic waste, with the only by-products being water, KI and nitrogen, without the attendant hazards of isolation of intermediate diazo compounds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enantioselective Ring Opening of Epoxides with 4-Methoxyphenol Catalyzed by Gallium Heterobimetallic Complexes: An Efficient Method for the Synthesis of Optically Active 1,2-Diol Monoethers.

PubMed

Iida, Takehiko; Yamamoto, Noriyoshi; Matsunaga, Shigeki; Woo, Hee-Gweon; Shibasaki, Masakatsu

1998-09-04

Useful chiral building blocks such as 1,2-diols can be obtained by the enantioselective ring opening of achiral epoxides with oxygen nucleophiles. The ring opening is carried out effectively (up to 94 % ee) with 4-methoxyphenol and catalytic amounts of gallium complexes. The novel complex GaSO 1 displays a particularly high catalytic activity. © 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

Integrated process and dual-function catalyst for olefin epoxidation

DOEpatents

Zhou, Bing; Rueter, Michael

2003-01-01

The invention discloses a dual-functional catalyst composition and an integrated process for production of olefin epoxides including propylene oxide by catalytic reaction of hydrogen peroxide from hydrogen and oxygen with olefin feeds such as propylene. The epoxides and hydrogen peroxide are preferably produced simultaneously in situ. The dual-functional catalyst comprises noble metal crystallites with dimensions on the nanometer scale (on the order of <1 nm to 10 nm), specially dispersed on titanium silicalite substrate particles. The dual functional catalyst catalyzes both the direct reaction of hydrogen and oxygen to generate hydrogen peroxide intermediate on the noble metal catalyst surface and the reaction of the hydrogen peroxide intermediate with the propylene feed to generate propylene oxide product. Combining both these functions in a single catalyst provides a very efficient integrated process operable below the flammability limits of hydrogen and highly selective for the production of hydrogen peroxide to produce olefin oxides such as propylene oxide without formation of undesired co-products.

Enhanced mechanical properties of low-surface energy thin films by simultaneous plasma polymerization of fluorine and epoxy containing polymers

NASA Astrophysics Data System (ADS)

Karaman, Mustafa; Uçar, Tuba

2016-01-01

Thin films of poly(2,2,3,4,4,4 hexafluorobutyl acrylate-glycidyl methacrylate) (P(HFBA-GMA) were deposited on different surfaces using an inductively coupled RF plasma reactor. Fluorinated polymer was used to impart hydrophobicity, whereas epoxy polymer was used for improved durability. The deposition at a low plasma power and temperature was suitable for the functionalization of fragile surfaces such as textile fabrics. The coated rough textile surfaces were found to be superhydrophobic with water contact angles greater than 150° due to the high retention of long fluorinated side chains. The hydrophobicity of the surfaces was observed to be stable after many exposures to ultrasonification tests, which is attributed to the mechanical durability of the films due to their epoxide functionality. FTIR and XPS analyses of the deposited films confirmed that the epoxide functionality of the polymers increased with increasing glycidyl methacrylate fraction in the reactor inlet. The modulus and hardness values of the films also increase with increasing epoxide functionality.

Carbocation/Polyol Systems as Efficient Organic Catalysts for the Preparation of Cyclic Carbonates.

PubMed

Rulev, Yuri A; Gugkaeva, Zalina T; Lokutova, Anastasia V; Maleev, Victor I; Peregudov, Alexander S; Wu, Xiao; North, Michael; Belokon, Yuri N

2017-03-22

Carbocation/polyol systems are shown to be highly efficient catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide at 50 °C and 5 MPa CO 2 pressure. The best activity was shown by the combination of crystal violet and 1,1'-bi-2-naphthol (BINOL), which could be recycled five times with no loss of activity. The presence of specific interactions between the amino groups of the carbocation and the hydroxyl protons was confirmed by NMR experiments. The Job plots for the crystal violet iodide/BINOL and brilliant green iodide/BINOL systems showed that the catalytic systems consist of one molecule of the carbocation and one molecule of BINOL. Mechanistic studies using a deuterated epoxide indicate that there was some loss of epoxide stereochemistry during the reaction, but predominant retention of stereochemistry is observed. On this basis, a catalytic cycle is proposed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detection and characterization of human serum antibodies to polycyclic aromatic hydrocarbon diol-epoxide DNA adducts.

PubMed Central

Newman, M J; Light, B A; Weston, A; Tollurud, D; Clark, J L; Mann, D L; Blackmon, J P; Harris, C C

1988-01-01

The presence of serum antibodies to the diol-epoxide DNA adducts of representative polycyclic aromatic hydrocarbons (PAH), chrysene, benz[a]anthracene and benzo[a]pyrene, was determined by ELISA using serum samples obtained from normal healthy individuals. Antibodies that reacted against PAH adducted-DNA, but not against PAH-adducted protein, were found in the serum of approximately 40% of the test individuals. Specificity analysis of the antibodies demonstrated that serological cross-reactions between the benzo[a]pyrene and the chrysene diol-epoxide adducts were present. Similar cross-reactivity between the benz[a]anthracene and the chrysene adducts was observed. Sera containing antibodies that were apparently specific for each of the three PAH-DNA adducts were also identified. The presence of antibodies to PAH-DNA adducts indicates both past exposure to these carcinogenic PAH and their metabolic activation to the DNA damaging metabolites. These antibodies may prove to be useful in both retrospective and prospective epidemiological studies of various diseases associated with PAH exposure. PMID:3392204

Stable and solubilized active Au atom clusters for selective epoxidation of cis-cyclooctene with molecular oxygen

DOE PAGES

Qian, Linping; Wang, Zhen; Beletskiy, Evgeny V.; ...

2017-03-28

Here, the ability of Au catalysts to effect the challenging task of utilizing molecular oxygen for the selective epoxidation of cyclooctene is fascinating. Although supported nanometre-size Au particles are poorly active, here we show that solubilized atomic Au clusters, present in ng ml –1 concentrations and stabilized by ligands derived from the oxidized hydrocarbon products, are active. They can be formed from various Au sources. They generate initiators and propagators to trigger the onset of the auto-oxidation reaction with an apparent turnover frequency of 440 s –1, and continue to generate additional initiators throughout the auto-oxidation cycle without direct participationmore » in the cycle. Spectroscopic characterization suggests that 7–8 atom clusters are effective catalytically. Extension of work based on these understandings leads to the demonstration that these Au clusters are also effective in selective oxidation of cyclohexene, and that solubilized Pt clusters are also capable of generating initiators for cyclooctene epoxidation.« less

Effect of Organo-Modified Nanoclay on the Thermal and Bulk Structural Properties of Poly(3-hydroxybutyrate)-Epoxidized Natural Rubber Blends: Formation of Multi-Components Biobased Nanohybrids.

PubMed

Salehabadi, Ali; Bakar, Mohamad Abu; Bakar, Noor Hana Hanif Abu

2014-06-13

Multi-component nanohybrids comprising of organo-modified montmorillonite (MMT) and immiscible biopolymer blends of poly(3-hydroxybutyrate) (PHB) and epoxidized natural rubber (ENR-50) were prepared by solvent casting technique. The one and three dimensional morphology of PHB/ENR-50/MMT systems were studied using Polarizing Optical Microscopy (POM) and Scanning Electron Microscopy (SEM). Differential scanning calorimetry (DSC) technique was used to evaluate the thermal properties of the nanohybrids. The melting temperature ( T m ) and enthalpy of melting (Δ H m ) of PHB decrease with respect to the increase in ENR-50 as well as MMT content. The non-isothermal decomposition of the nanohybrids was studied using thermogravimetric (TG-DTG) analysis. FTIR-ATR spectra supported ring opening of the epoxide group via reaction with carboxyl group of PHB and amines of organic modifier. The reaction mechanism towards the formation of the nanohybrids is proposed.

Electronic Structure Calculations of Ammonia Adsorption on Graphene and Graphene Oxide with Epoxide and Hydroxyl Groups

NASA Astrophysics Data System (ADS)

Nancy Anna Anasthasiya, A.; Khaneja, Mamta; Jeyaprakash, B. G.

2017-10-01

Ammonia adsorption on graphene (G) and graphene oxide (GO) was investigated through density functional theory calculations. In the GO system, the obtained binding energy, band gap, charge transfer and electronic structure revealed that the epoxide (GO-O) and hydroxyl groups (GO-OH) in GO enhance the NH3 adsorption, which leads to the chemisorption of NH3 on GO. The dissociation of NH3 to NH2 and formation of OH was also observed when the O and H atoms were separated at 0.985 Å, 1.019 Å, 1.035 Å, and 1.044 Å for various GO systems. The maximum charge transfer value was found to be 0.054 |e| with the binding energy of 1.143 eV for GO with a single epoxide (GO-1O) group. The charge transfer from NH3 to G or GO and the bond formation in this study agree with the reported experimental results.

Stable and solubilized active Au atom clusters for selective epoxidation of cis-cyclooctene with molecular oxygen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Linping; Wang, Zhen; Beletskiy, Evgeny V.

Here, the ability of Au catalysts to effect the challenging task of utilizing molecular oxygen for the selective epoxidation of cyclooctene is fascinating. Although supported nanometre-size Au particles are poorly active, here we show that solubilized atomic Au clusters, present in ng ml –1 concentrations and stabilized by ligands derived from the oxidized hydrocarbon products, are active. They can be formed from various Au sources. They generate initiators and propagators to trigger the onset of the auto-oxidation reaction with an apparent turnover frequency of 440 s –1, and continue to generate additional initiators throughout the auto-oxidation cycle without direct participationmore » in the cycle. Spectroscopic characterization suggests that 7–8 atom clusters are effective catalytically. Extension of work based on these understandings leads to the demonstration that these Au clusters are also effective in selective oxidation of cyclohexene, and that solubilized Pt clusters are also capable of generating initiators for cyclooctene epoxidation.« less

Biochemical and molecular aspects of mammalian susceptibility to aflatoxin B{sub 1} carcinogenicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massey, T.E.; Stewart, R.K.; Daniels, J.M.

Aflatoxin B{sub 1} (AFB{sub 1}) is a fungal toxin that has been implicated as a causative agent in human hepatic and extrahepatic carcinogenesis. In this review, the mechanisms involved in AFB{sub 1} toxicity are delineated, in order to describe the features that make a specific cell, tissue, or species susceptible to the mycotoxin. Important considerations include: (i) different mechanisms for bioactivation of AFB{sub 1} to its ultimate carcinogenic epoxide metabolite; (ii) the balance between bioactivation to and detoxification of the epoxide; (iii) the interaction of AFB{sub 1} epoxide with DNA and the mutational events leading to neoplastic transformation; (iv) themore » role of cytotoxicity in AFB{sub 1} carcinogenesis; (v) the significance of nonepoxide metabolites in toxicity; and (vi) the contribution of mycotoxin-unrelated disease processes. Although considerable controversy remains about the importance of specific events, a great deal has been learned about biochemical and molecular actions of AFB{sub 1}. 157 refs., 4 figs., 1 tab.« less

Optimization of Lipase-Mediated Synthesis of 1-Nonene Oxide Using Phenylacetic Acid and Hydrogen Peroxide

PubMed Central

Abdulmalek, Emilia; Arumugam, Mahashanon; Basri, Mahiran; Rahman, Mohd Basyaruddin Abdul

2012-01-01

Herein, an efficient epoxidation of 1-nonene is described. In a simple epoxidation system, commercially available Novozym 435, an immobilized Candida antarctica lipase B, and hydrogen peroxide (H2O2) were utilized to facilitate the in situ oxidation of phenylacetic acid to the corresponding peroxy acid which then reacted with 1-nonene to give 1-nonene oxide with high yield and selectivity. The aliphatic terminal alkene was epoxidised efficiently in chloroform to give an excellent yield (97%–99%) under the optimum reaction conditions, including temperature (35 °C), initial H2O2 concentration (30%), H2O2 amount (4.4 mmol), H2O2 addition rate (one step), acid amount (8.8 mmol), and stirring speed (250 rpm). Interestingly, the enzyme was stable under the single-step addition of H2O2 with a catalytic activity of 190.0 Ug−1. The entire epoxidation process was carried out within 12 h using a conventional water bath shaker. PMID:23202943

Studies on the structural changes during curing of epoxy and its blend with CTBN

NASA Astrophysics Data System (ADS)

Srivastava, Kavita; Rathore, Ashwani Kumar; Srivastava, Deepak

2018-01-01

Cashew nut shell liquid (CNSL), an agricultural renewable resource material, produces natural phenolic distillates such as cardanol. Cardanol condenses with formaldehyde at the ortho- and para-position of the phenolic ring under acidic or alkaline condition to yield a series of polymers of novolac- or resol-type phenolic resins. These phenolic resins may further be modified by epoxidation with epichlorohydrin to duplicate the performance of such phenolic-type novolacs (CFN). The structural changes during curing of blend samples of epoxy and carboxyl terminated poly (butadiene-co-acrylonitrile) (CTBN) were studies by Fourier-transform infrared (FTIR) spectrophotometer. The epoxy samples were synthesized by biomass material, cardanol. Blend sample was prepared by physical mixing of CTBN ranging between 0 and 20 weight percent CTBN liquid rubber into cardanol-based epoxidized novolac (CEN) resin. The FTIR spectrum of uncured blend sample clearly indicated that there appeared a band in the region of 3200-3500 cm- 1 which might be due to the presence of phenolic hydroxyl group and sbnd OH group of the opened epoxide. Pure epoxy resin showed peaks near 856 cm- 1 which might be due to oxirane functionality of the epoxidized novolac resin. Both epoxy and its blend sample was cured with polyamine. The cure temperature of CEN resin was found to be decreased by the incorporation of CTBN. The decomposition behavior was also studied by thermogravimetric analyzer (TGA). Two-step decomposition behavior was observed in both epoxy and its blend samples.

Synthesis of Transesterified Palm Olein-Based Polyol and Rigid Polyurethanes from this Polyol.

PubMed

Arniza, Mohd Zan; Hoong, Seng Soi; Idris, Zainab; Yeong, Shoot Kian; Hassan, Hazimah Abu; Din, Ahmad Kushairi; Choo, Yuen May

Transesterification of palm olein with glycerol can increase the functionality by introducing additional hydroxyl groups to the triglyceride structure, an advantage compared to using palm olein directly as feedstock for producing palm-based polyol. The objective of this study was to synthesize transesterified palm olein-based polyol via a three-step reaction: (1) transesterification of palm olein, (2) epoxidation and (3) epoxide ring opening. Transesterification of palm olein yielded approximately 78 % monoglyceride and has an hydroxyl value of approximately 164 mg KOH g -1 . The effect of formic acid and hydrogen peroxide concentrations on the epoxidation reaction was studied. The relationships between epoxide ring-opening reaction time and residual oxirane oxygen content and hydroxyl value were monitored. The synthesized transesterified palm olein-based polyol has hydroxyl value between 300 and 330 mg KOH g -1 and average molecular weight between 1,000 and 1,100 Da. On the basis of the hydroxyl value and average molecular weight of the polyol, the transesterified palm olein-based polyol is suitable for producing rigid polyurethane foam, which can be designed to exhibit desirable properties. Rigid polyurethane foams were synthesized by substituting a portion of petroleum-based polyol with the transesterified palm olein-based polyol. It was observed that by increasing the amount of transesterified palm olein-based polyol, the core density and compressive strength were reduced but at the same time the insulation properties of the rigid polyurethane foam were improved.

Studies on the structural changes during curing of epoxy and its blend with CTBN.

PubMed

Srivastava, Kavita; Rathore, Ashwani Kumar; Srivastava, Deepak

2018-01-05

Cashew nut shell liquid (CNSL), an agricultural renewable resource material, produces natural phenolic distillates such as cardanol. Cardanol condenses with formaldehyde at the ortho- and para-position of the phenolic ring under acidic or alkaline condition to yield a series of polymers of novolac- or resol-type phenolic resins. These phenolic resins may further be modified by epoxidation with epichlorohydrin to duplicate the performance of such phenolic-type novolacs (CFN). The structural changes during curing of blend samples of epoxy and carboxyl terminated poly (butadiene-co-acrylonitrile) (CTBN) were studies by Fourier-transform infrared (FTIR) spectrophotometer. The epoxy samples were synthesized by biomass material, cardanol. Blend sample was prepared by physical mixing of CTBN ranging between 0 and 20weightpercent CTBN liquid rubber into cardanol-based epoxidized novolac (CEN) resin. The FTIR spectrum of uncured blend sample clearly indicated that there appeared a band in the region of 3200-3500cm -1 which might be due to the presence of phenolic hydroxyl group and OH group of the opened epoxide. Pure epoxy resin showed peaks near 856cm -1 which might be due to oxirane functionality of the epoxidized novolac resin. Both epoxy and its blend sample was cured with polyamine. The cure temperature of CEN resin was found to be decreased by the incorporation of CTBN. The decomposition behavior was also studied by thermogravimetric analyzer (TGA). Two-step decomposition behavior was observed in both epoxy and its blend samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Physicochemical characterization and toxicity of decursin and their derivatives from Angelica gigas.

PubMed

Mahat, Bimit; Chae, Jung-Woo; Baek, In-Hwan; Song, Gyu-Yong; Song, Jin-Sook; Cho, Seong-Kwon; Kwon, Kwang-Il

2012-01-01

Angelica gigas NAKAI is used to treat dysmenorrhea, amenorrhea, menopause, abdominal pain, injuries, migraine, and arthritis. The present study provided a physicochemical and toxicological characterization of compounds in A. gigas NAKAI (decursin, decursinol angelate, diketone decursin, ether decursin, epoxide decursin and oxim decursin). Diketone decursin (173.16 μg/mL) and epoxide decursin (122.12 μg/mL) exhibited >100 μg/mL kinetic solubility after applying nephelometry, suggesting a highly soluble compound. The Student’s t-test revealed significant differences in the pKa ranges of the compounds by automatic titration from capillary electrophoresis (p<0.05). Diketone decursin, epoxide decursin and oxim decursin might be formulated into an oral dosage form (log P: 0-3) by an automatic titration analysis. A parallel artificial membrane permeability assay demonstrated permeability coefficients of <10 x 10⁻⁶ cm/s for all of the compounds, suggesting poor permeability. Ether decursin exhibited a toxic effect after being applied to mouse (NIH 3T3, EC₅₀: 57.9 μM) and human (HT-29, EC₅₀: 36.1 μM; Hep-G2, EC₅₀: 4.92 μM) cells. Additionally, epoxide and oxim decursin were toxic through acute oral toxicity (four and three deaths of Institute of Cancer Research (ICR) mice) and mutation toxicity testing by applying Salmonella typhimurium cells with and without S9. Although diketone decursin exhibited less permeability, it is potentially valuable pharmacological compound that should be investigated.

Effect of coexposure to asbestos and kerosene soot on pulmonary drug-metabolizing enzyme system.

PubMed Central

Arif, J M; Khan, S G; Mahmood, N; Aslam, M; Rahman, Q

1994-01-01

This article reports the effect of coexposure to Indian chrysotile asbestos (5 mg/rat) and kerosene soot (5 mg/rat) on the pulmonary phase I and phase II drug-metabolizing enzymes 1, 4, 8, 16, 30, 90, and 150 days after a single intratracheal inoculation. Exposure to soot resulted in a significant induction of the pulmonary microsomal cytochrome P450 and the activity of dependent monooxygenase, benzo(a)pyrene (B[a]P) hydroxylase, and epoxide hydrase at all time intervals. On the other hand, the cytosolic glutathione S-transferase (GST) activity was induced at days 1, 4, 8, 16, and 30 after exposure, followed by inhibition in the enzyme activity. In contrast, chrysotile exposure depleted cytochrome P450, B[a]P hydroxylase, epoxide hydrase, and GST at initial stages, while all these parameters except GST were induced at later stages. However, coexposure to chrysotile and soot led to a significant inhibition in the cytochrome P450 levels, activities of B[a]P hydroxylase, epoxide hydrase, and GST at initial stages of exposure. At advanced stages, however, an additional increase in cytochrome P450, B[a]P hydroxylase, and epoxide hydrase but a decrease in GST was observed. These results clearly show that the intratracheal coexposure to high levels of asbestos and kerosene soot alters the metabolic activity of the lung, which is turn may retain toxins in the system for a longer period, resulting in adverse pathological disorders. PMID:7882926

Metabolic Profile of Skimmianine in Rats Determined by Ultra-Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Tandem Mass Spectrometry.

PubMed

Huang, Aihua; Xu, Hui; Zhan, Ruoting; Chen, Weiwen; Liu, Jiawei; Chi, Yuguang; Chen, Daidi; Ji, Xiaoyu; Luo, Chaoquan

2017-03-23

Skimmianine is a furoquinoline alkaloid present mainly in the Rutaceae family. It has been reported to have analgesic, antispastic, sedative, anti-inflammatory, and other pharmacologic activities. Despite its critical pharmacological function, its metabolite profiling is still unclear. In this study, the in vivo metabolite profiling of skimmianine in rats was investigated using ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF-MS). The metabolites were predicted using MetabolitePilot TM software. These predicted metabolites were further analyzed by MS² spectra, and compared with the detailed fragmentation pathway of the skimmianine standard and literature data. A total of 16 metabolites were identified for the first time in rat plasma, urine, and feces samples after oral administration of skimmianine. Skimmianine underwent extensive Phase I and Phase II metabolism in rats. The Phase I biotransformations of skimmianine consist of epoxidation of olefin on its furan ring (M1) followed by the hydrolysis of the epoxide ring (M4), hydroxylation (M2, M3), O -demethylation (M5-M7), didemethylation (M14-M16). The Phase II biotransformations include glucuronide conjugation (M8-M10) and sulfate conjugation (M11-M13). The epoxidation of 2,3-olefinic bond followed by the hydrolysis of the epoxide ring and O -demethylation were the major metabolic pathways of skimmianine. The results provide key information for understanding the biotransformation processes of skimmianine and the related furoquinoline alkaloids.

The novel 13S,14S-epoxy-maresin is converted by human macrophages to maresin 1 (MaR1), inhibits leukotriene A4 hydrolase (LTA4H), and shifts macrophage phenotype

PubMed Central

Dalli, Jesmond; Zhu, Min; Vlasenko, Nikita A.; Deng, Bin; Haeggström, Jesper Z.; Petasis, Nicos A.; Serhan, Charles N.

2013-01-01

Maresins are produced by macrophages from docosahexaenoic acid (DHA) and exert potent proresolving and tissue homeostatic actions. Maresin 1 (MaR1; 7R,14S-dihydroxy-docosa-4Z,8E,10E,12Z,16Z,19Z-hexaenoic acid) is the first identified maresin. Here, we investigate formation, stereochemistry, and precursor role of 13,14-epoxy-docosahexaenoic acid, an intermediate in MaR1 biosynthesis. The 14-lipoxygenation of DHA by human macrophage 12-lipoxygenase (hm12-LOX) gave 14-hydro(peroxy)-docosahexaenoic acid (14-HpDHA), as well as several dihydroxy-docosahexaenoic acids, implicating an epoxide intermediate formation by this enzyme. Using a stereo-controlled synthesis, enantiomerically pure 13S,14S-epoxy-docosa-4Z,7Z,9E,11E,16Z,19Z-hexaenoic acid (13S,14S-epoxy-DHA) was prepared, and its stereochemistry was confirmed by NMR spectroscopy. When this 13S,14S-epoxide was incubated with human macrophages, it was converted to MaR1. The synthetic 13S,14S-epoxide inhibited leukotriene B4 (LTB4) formation by human leukotriene A4 hydrolase (LTA4H) ∼40% (P<0.05) to a similar extent as LTA4 (∼50%, P<0.05) but was not converted to MaR1 by this enzyme. 13S,14S-epoxy-DHA also reduced (∼60%; P<0.05) arachidonic acid conversion by hm12-LOX and promoted conversion of M1 macrophages to M2 phenotype, which produced more MaR1 from the epoxide than M1. Together, these findings establish the biosynthesis of the 13S,14S-epoxide, its absolute stereochemistry, its precursor role in MaR1 biosynthesis, and its own intrinsic bioactivity. Given its actions and role in MaR1 biosynthesis, this epoxide is now termed 13,14-epoxy-maresin (13,14-eMaR) and exhibits new mechanisms in resolution of inflammation in its ability to inhibit proinflammatory mediator production by LTA4 hydrolase and to block arachidonate conversion by human 12-LOX rather than merely terminating phagocyte involvement.—Dalli, J., Zhu, M., Vlasenko, N. A., Deng, B., Haeggström, J. Z., Petasis, N. A., Serhan, C. N. The novel 13S,14S-epoxy-maresin is converted by human macrophages to maresin 1 (MaR1), inhibits leukotriene A4 hydrolase (LTA4H) and shifts macrophage phenotype. PMID:23504711

Catalysts for CO2/epoxide ring-opening copolymerization

PubMed Central

Trott, G.; Saini, P. K.; Williams, C. K.

2016-01-01

This article summarizes and reviews recent progress in the development of catalysts for the ring-opening copolymerization of carbon dioxide and epoxides. The copolymerization is an interesting method to add value to carbon dioxide, including from waste sources, and to reduce pollution associated with commodity polymer manufacture. The selection of the catalyst is of critical importance to control the composition, properties and applications of the resultant polymers. This review highlights and exemplifies some key recent findings and hypotheses, in particular using examples drawn from our own research. PMID:26755758

Co(III)(salen)-catalyzed phenolic kinetic resolution of two stereocentered benzyloxy and azido epoxides: its application in the synthesis of ICI-118,551, an anti-hypertensive agent.

PubMed

Karabal, Pratibha U; Kamble, Dayanand A; Sudalai, Arumugam

2014-04-21

The salen Co(III)-catalyzed phenolic kinetic resolution of racemic anti- or syn-azido and benzyloxy epoxides provides a practical route to a range of enantioenriched anti- or syn-1-aryloxy-3-azido or benzyloxy-2-alcohols in excellent yields and ees. The synthetic potential of this protocol is illustrated with an enantioselective synthesis of ICI-118,551, a β-blocker, in a highly optically pure form (99% ee).

One-Pot Conversion of Epoxidized Soybean Oil (ESO) into Soy-Based Polyurethanes by MoCl₂O₂ Catalysis.

PubMed

Pantone, Vincenzo; Annese, Cosimo; Fusco, Caterina; Fini, Paola; Nacci, Angelo; Russo, Antonella; D'Accolti, Lucia

2017-02-21

An innovative and eco-friendly one-pot synthesis of bio-based polyurethanes is proposed via the epoxy-ring opening of epoxidized soybean oil (ESO) with methanol, followed by the reaction of methoxy bio-polyols intermediates with 2,6-tolyl-diisocyanate (TDI). Both synthetic steps, methanolysis and polyurethane linkage formation, are promoted by a unique catalyst, molybdenum(VI) dichloride dioxide (MoCl₂O₂), which makes this procedure an efficient, cost-effective, and environmentally safer method amenable to industrial scale-up.

Quantum chemical study of the mechanism of action of vitamin K epoxide reductase (VKOR)

NASA Astrophysics Data System (ADS)

Deerfield, David, II; Davis, Charles H.; Wymore, Troy; Stafford, Darrel W.; Pedersen, Lee G.

Possible model, but simplistic, mechanisms for the action of vitamin K epoxide reductase (VKOR) are investigated with quantum mechanical methods (B3LYP/6-311G**). The geometries of proposed model intermediates in the mechanisms are energy optimized. Finally, the energetics of the proposed (pseudo-enzymatic) pathways are compared. We find that the several pathways are all energetically feasible. These results will be useful for designing quantum mechanical/molecular mechanical method (QM/MM) studies of the enzymatic pathway once three-dimensional structural data are determined and available for VKOR.

Olefin Epoxidation by Methyltrioxorhenium: A Density Functional Study on Energetics and Mechanisms.

PubMed

Gisdakis, Philip; Antonczak, Serge; Köstlmeier, Sibylle; Herrmann, Wolfgang A; Rösch, Notker

1998-09-04

A spiro attack on a peroxo group is calculated to be the preferred reaction pathway for olefin epoxidation with the catalytic system CH 3 ReO 3 /H 2 O 2 (see picture). This finding is supported by density functional calculations on more than ten transition states for the most probable mechanisms. Hydration has significant effects on various reaction species: it stabilizes the intermediates and destabilizes, with one exception, the transition states. © 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

A combined experimental and theoretical study of the supramolecular self-assembly of the natural benzopyran 2,2-dimethyl-3-hydroxy-6-acetyl-chromane and its isomeric benzofuran 10,11-dihydro-10-hydroxytremetone

NASA Astrophysics Data System (ADS)

Gil, Diego M.; Lizarraga, E.; Echeverría, G. A.; Piro, O. E.; Catalán, C. A. N.; Ben Altabef, A.

2017-10-01

Epoxidation of 4HMBA, the main metabolite of the medicinal plant Sencecionutans, produces an unstable epoxide eventually giving rise to a mixture of four derivatives, three of them previously reported as natural products. The epoxide product easily undergoes an intra-molecular attack of the phenolic hydroxyl against the epoxide group carbons to produce either a benzofuran or a chromane derivative. When dissolved in methanol-water mixture at room temperature the epoxide is completely solvolyzed to give the corresponding diol (hydrolysis) or vicinal hydroxyl-methoxy (methanolysis) derivative. All the compounds involved in the above reactions were characterized by IR, Raman, H NMR and UV-vis spectroscopies, and by mass spectrometry. Density functional theory (DFT) computations were used to optimize the structure conformations. The optimized structures were further subjected to a Natural Bond Orbital (NBO) and electrostatic potentials analysis. The crystal structures of the title compounds (for short, 3 and 4 respectively) were determined by X-ray diffraction methods. Compound 3 crystallizes in the triclinic P-1 space group with a = 6.4289 (6) Å, b = 8.7120 (6) Å, c = 10.952 (1) Å, α = 92.280 (7)°, β = 95.738 (7)°, γ = 103.973 (7)°, and Z = 2 molecules per unit cell and 4 in the monoclinic P21/c space group with a = 11.2891 (6) Å, b = 9.1902 (4) Å, c = 12.4272 (7) Å. Β = 113.689 (7)°, and Z = 4. In 3 neighboring molecules are linked to each other by OH⋯O (keto) bonds giving rise to a polymeric structure. In 4 the OH group is a bifurcate H-bond donor. It forms a weak intra-molecular OH⋯O (furan) bond and also a much stronger inter-molecular Osbnd H⋯O (keto) bond giving rise to a zig-zag polymeric structure. A detailed analysis of the solid state molecular interactions of compounds 3 and 4 has been performed using Hirshfeld surface analysis and their associated 2D fingerprint plots.

Design and preparation of plant oil-based polymers and their applications

NASA Astrophysics Data System (ADS)

Ahn, Byung-Jun Kollbe

Renewable materials are desirable for many applications due to the finite fossil resources and environmental issues. Plant oil is one of the most promising renewable feedstocks. Plant oils and functionalized oleo-chemicals including functionalized soybean oils have become attractive sustainable chemicals for industrial applications. Especially, epoxidized oleo-chemicals such as epoxidized soybean oil (ESO) are one of the most well-known readily available inexpensive functionalized plant oils. In this study, novel polymers and nanocomposites for sustainable materials applications were designed and prepared via ring-opening of epoxide in plant oils, and their chemical and physical properties were characterized. The novel transparent elastomers derived from functionalized plant oils have a great potential as flexible electronic and biological applications with their inherent low toxicity. Especially, their rheological properties showed a potential for pressure sensitive adhesives (PSAs). The dominant thermal stability and transparency were obtained via green processing: one pot, single step, fast reactions in moderate conditions, or solvent-free UV curing conditions. These oleo-based elastomers presented excellent end-use properties for PSAs application comparable to commercial PSA tapes. Based on the principal chemical studies, the roles of the each component have been identified: polymer derived from the ring-opening of epoxides as an elastomer, and dihydroxylated triglycerides as a tackifier. Their interaction was also elucidated with an element label analysis. The mechanical and rheological properties of the oleo-polymer as PSAs were able to be improved with a rosin ester tackifier. In addition, biogreases and bio-thermoplastics were developed via the environmentally benign process, which will contribute to further application on the production of new bio-based materials. Further, this study essays a novel acid functionalized iron/iron oxide nanoparticles catalyst with excellent product yields for epoxide ring opening of oleochemicals for a greener synthetic method of biopolyols, and excellent environmental benefits with life cycle assessment of syntheses. Those functionalized iron/iron oxide core shell nanoparticles catalysts has great potential for biomedical engineering process with the highest magnetization of Fe(0) core among all metals.

Attenuation of Cisplatin-Induced Renal Injury by Inhibition of Soluble Epoxide Hydrolase Involves Nuclear Factor κB Signaling

PubMed Central

Liu, Yingmei; Webb, Heather K.; Fukushima, Hisayo; Micheli, Janine; Markova, Svetlana; Olson, Jean L.

2012-01-01

Acute kidney injury is associated with a significant inflammatory response that has been the target of renoprotection strategies. Epoxyeicosatrienoic acids (EETs) are anti-inflammatory cytochrome P450-derived eicosanoids that are abundantly produced in the kidney and metabolized by soluble epoxide hydrolase (sEH; Ephx2) to less active dihydroxyeicosatrienoic acids. Genetic disruption of Ephx2 and chemical inhibition of sEH were used to test whether the anti-inflammatory effects of EETs, and other lipid epoxide substrates of sEH, afford protection against cisplatin-induced nephrotoxicity. EET hydrolysis was significantly reduced in Ephx2(−/−) mice and was associated with an attenuation of cisplatin-induced increases in serum urea nitrogen and creatinine levels. Histological evidence of renal tubular damage and neutrophil infiltration was also reduced in the Ephx2(−/−) mice. Likewise, cisplatin had no effect on renal function, neutrophil infiltration, or tubular structure and integrity in mice treated with the potent sEH inhibitor 1-adamantan-1-yl-3-(1-methylsulfonyl-piperidin-4-yl-urea) (AR9273). Consistent with the ability of EETs to interfere with nuclear factor-κB (NF-κB) signaling, the observed renoprotection was associated with attenuation of renal NF-κB activity and corresponding decreases in the expression of tumor necrosis factor (TNF) α, TNF receptor (TNFR) 1, TNFR2, and intercellular adhesive molecule-1 before the detection of tubular injury. These data suggest that EETs or other fatty acid epoxides can attenuate cisplatin-induced kidney injury and sEH inhibition is a novel renoprotective strategy. PMID:22414856

The mechanism of epoxide carbonylation by [Lewis Acid]+[Co(CO)4]- catalysts.

PubMed

Church, Tamara L; Getzler, Yutan D Y L; Coates, Geoffrey W

2006-08-09

A detailed mechanistic investigation of epoxide carbonylation by the catalyst [(salph)Al(THF)2]+ [Co(CO)4]- (1, salph = N,N'-o-phenylenebis(3,5-di-tert-butylsalicylideneimine), THF = tetrahydrofuran) is reported. When the carbonylation of 1,2-epoxybutane (EB) to beta-valerolactone is performed in 1,2-dimethoxyethane solution, the reaction rate is independent of the epoxide concentration and the carbon monoxide pressure but first order in 1. The rate of lactone formation varies considerably in different solvents and depends primarily on the coordinating ability of the solvent. In mixtures of THF and cis/trans-2,5-dimethyltetrahydrofuran, the reaction is first order in THF. From spectroscopic and kinetic data, the catalyst resting state was assigned to be the neutral (beta-aluminoxy)acylcobalt species (salph)AlOCH(Et)CH2COCo(CO)4 (3a), which was successfully trapped with isocyanates. As the formation of 3a from EB, CO, and 1 is rapid, lactone ring closing is rate-determining. The favorable impact of donating solvents was attributed to the necessity of stabilizing the aluminum cation formed upon generation of the lactone.

Induction of hepatic aryl hydrocarbon hydroxylase and epoxide hydrase in Wistar rats pretreated with oral methadone hydrochloride.

PubMed

Bellward, G D; Gontovnick, L S; Otten, M

1977-01-01

Methadone-HCl added to the drinking water of adult female Wistar rats for 4 weeks produced an increase in the aryl hydrocarbon hydroxylase activity of the hepatic microsomal fraction to 222% of control levels. No change was seen in epoxide hydrase activity. In contrast, when male rats were treated similarly, there was an increase in epoxide hydrase activity to 212% of controls with no change in aryl hydrocarbon hydroxylase activity. No such changes were observed when the subcutaneous route of administration or chronic, low-dose, intraperitoneal injections were used. There were no differences in hepatic cytochrome P-450 or protein concentrations in treated animals as compared to their respective control groups. Control studies were carried out with quinine sulfate in the drinking water to decrease water intake to the level of the methadone-treated group. No elevation in either enzyme activity occurred in this control group. Similarly, paired-feeding studies showed the elevation of enzyme activity to be due to the methadone, not food deprivation. The effects of concurrent therapy of methadone with phenobarbital sodium or 3-methylcholanthrene were compared.

A PLS-based extractive spectrophotometric method for simultaneous determination of carbamazepine and carbamazepine-10,11-epoxide in plasma and comparison with HPLC

NASA Astrophysics Data System (ADS)

Hemmateenejad, Bahram; Rezaei, Zahra; Khabnadideh, Soghra; Saffari, Maryam

2007-11-01

Carbamazepine (CBZ) undergoes enzyme biotransformation through epoxidation with the formation of its metabolite, carbamazepine-10,11-epoxide (CBZE). A simple chemometrics-assisted spectrophotometric method has been proposed for simultaneous determination of CBZ and CBZE in plasma. A liquid extraction procedure was operated to separate the analytes from plasma, and the UV absorbance spectra of the resultant solutions were subjected to partial least squares (PLS) regression. The optimum number of PLS latent variables was selected according to the PRESS values of leave-one-out cross-validation. A HPLC method was also employed for comparison. The respective mean recoveries for analysis of CBZ and CBZE in synthetic mixtures were 102.57 (±0.25)% and 103.00 (±0.09)% for PLS and 99.40 (±0.15)% and 102.20 (±0.02)%. The concentrations of CBZ and CBZE were also determined in five patients using the PLS and HPLC methods. The results showed that the data obtained by PLS were comparable with those obtained by HPLC method.

Synthesis and properties of a novel bio-based polymer from modified soybean oil

NASA Astrophysics Data System (ADS)

Li, Y. T.; Yang, L. T.; Zhang, H.; Tang, Z. J.

2017-02-01

Maleated acrylated epoxidized soybean oil (MAESO) was prepared by acrylated epoxidized soybean oil (AESO) and maleic anhydride. AESO were obtained by the reaction of epoxidized soybean oil (ESO) with acrylic acid as the ring-opening reagent. The polymer was prepared by MAESO react with styrene. The structures of the products were studied by Fourier transformation infrared spectrometer (FT-IR), and were consistent with the theoretical structures. Swelling experiment indicated that the crosslinking degree increased with increasing epoxy value of ESO. Thermal properties was tested by thermo-gravimetric analysis (TG) and differential scanning calorimetry analysis (DSC), indicating that glass transition temperature (Tg) of the polymer increased with increasing epoxy value of ESO, and thermal stability of polymer have a good correlation with the crosslinking degree. Mechanical properties analysis presented that tensile strength and impact strength affected by epoxy value of ESO. With the increase of epoxy value, the tensile strength increase, while the impact strength decrease. The property of the polymer ranged from elastomer to plastic character depended on the functionality of the ESO.

Epoxide hydrolase Lsd19 for polyether formation in the biosynthesis of lasalocid A: direct experimental evidence on polyene-polyepoxide hypothesis in polyether biosynthesis.

PubMed

Shichijo, Yoshihiro; Migita, Akira; Oguri, Hiroki; Watanabe, Mami; Tokiwano, Tetsuo; Watanabe, Kenji; Oikawa, Hideaki

2008-09-17

Polyether metabolites are an important class of natural products. Although their biosynthesis, especially construction of polyether skeletons, attracted organic chemists for many years, no experimental data on the enzymatic polyether formation has been obtained. In this study, a putative epoxide hydrolase gene lsd19 found on the biosynthetic gene cluster of an ionophore polyether lasalocid was cloned and successfully overexpressed in Escherichia coli. Using the purified Lsd19, a proposed substrate, bisepoxyprelasalocid, and its synthesized analogue were successfully converted into lasalocid A and its derivative via a 6-endo-tet cyclization mode. On the other hand, treatment of the bisepoxide with trichloroacetic acid gave isolasalocid A via a 5-exo-tet cyclization mode. Therefore, the enzymatic conversion observed in this study unambiguously showed that the bisepoxyprelasalocid is an intermediate of the lasalocid biosynthesis and that Lsd19 catalyzes the sequential cyclic ether formations involving an energetically disfavored 6-endo-tet cyclization. This is the first example of the enzymatic epoxide-opening reactions leading to a polyether natural product.

Rapid, Microwave-Assisted Synthesis of Cubic, Three-Dimensional, Highly Porous MOF-205 for Room Temperature CO2 Fixation via Cyclic Carbonate Synthesis.

PubMed

Babu, Robin; Roshan, Roshith; Kathalikkattil, Amal Cherian; Kim, Dong Woo; Park, Dae-Won

2016-12-14

A dual-porous, three-dimensional, metal-organic framework [Zn 4 O(2,6-NDC)(BTB) 4/3 ] (MOF-205, BET = 4200 m 2 /g) has been synthesized using microwave power as an alternative energy source for the first time, and its catalytic activity has been exploited for CO 2 -epoxide coupling reactions to produce five-membered cyclic carbonates under solvent-free conditions. Microwave synthesis was performed at different time intervals to reveal the formation of the crystals. Significant conversion of various epoxides was obtained at room temperature, with excellent selectivity toward the desired five-membered cyclic carbonates. The importance of the dual porosity and the synergistic effect of quaternary ammonium salts on efficiently catalyzed CO 2 conversion were investigated using various experimental and physicochemical characterization techniques, and the results were compared with those of the solvothermally synthesized MOF-205 sample. On the basis of literature and experimental inferences, a rationalized mechanism mediated by the zinc center of MOF-205 for the CO 2 -epoxide cycloaddition reaction has been proposed.

Irreversible covalent modification of type I dehydroquinase with a stable Schiff base.

PubMed

Tizón, Lorena; Maneiro, María; Peón, Antonio; Otero, José M; Lence, Emilio; Poza, Sergio; van Raaij, Mark J; Thompson, Paul; Hawkins, Alastair R; González-Bello, Concepción

2015-01-21

The irreversible inhibition of type I dehydroquinase (DHQ1), the third enzyme of the shikimic acid pathway, is investigated by structural, biochemical and computational studies. Two epoxides, which are mimetics of the natural substrate, were designed as irreversible inhibitors of the DHQ1 enzyme and to study the binding requirements of the linkage to the enzyme. The epoxide with the S configuration caused the covalent modification of the protein whereas no reaction was obtained with its epimer. The first crystal structure of DHQ1 from Salmonella typhi covalently modified by the S epoxide, which is reported at 1.4 Å, revealed that the modified ligand is surprisingly covalently attached to the essential Lys170 by the formation of a stable Schiff base. The experimental and molecular dynamics simulation studies reported here highlight the huge importance of the conformation of the C3 carbon of the ligand for covalent linkage to this type of aldolase I enzyme, revealed the key role played by the essential His143 as a Lewis acid in this process and show the need for a neatly closed active site for catalysis.

4D printing smart biomedical scaffolds with novel soybean oil epoxidized acrylate

PubMed Central

Miao, Shida; Zhu, Wei; Castro, Nathan J.; Nowicki, Margaret; Zhou, Xuan; Cui, Haitao; Fisher, John P.; Zhang, Lijie Grace

2016-01-01

Photocurable, biocompatible liquid resins are highly desired for 3D stereolithography based bioprinting. Here we solidified a novel renewable soybean oil epoxidized acrylate, using a 3D laser printing technique, into smart and highly biocompatible scaffolds capable of supporting growth of multipotent human bone marrow mesenchymal stem cells (hMSCs). Porous scaffolds were readily fabricated by simply adjusting the printer infill density; superficial structures of the polymerized soybean oil epoxidized acrylate were significantly affected by laser frequency and printing speed. Shape memory tests confirmed that the scaffold fixed a temporary shape at −18 °C and fully recovered its original shape at human body temperature (37 °C), which indicated the great potential for 4D printing applications. Cytotoxicity analysis proved that the printed scaffolds had significant higher hMSC adhesion and proliferation than traditional polyethylene glycol diacrylate (PEGDA), and had no statistical difference from poly lactic acid (PLA) and polycaprolactone (PCL). This research is believed to significantly advance the development of biomedical scaffolds with renewable plant oils and advanced 3D fabrication techniques. PMID:27251982

Bioluminescence as the Basis for the Detection of Trichothecenes

DTIC Science & Technology

1986-03-17

screened for their ability to quench bioluminescence were obtained through the courtesy of Dr. Lou Carson, of the Toxicology Division of the Food and...34 Recent Adv. Phytochem . 9, 167 (1974). 13. Lyman, J. and Fleming, R.H., "Composition of Seawater," J. Mar. Res. 3, 134 (1940). 14. Mayer, C.F., "Endemic...DIELDRIN Cl CI Cl~c C 1 2I• HEPTACHLOR EPOXIDE OCTACHLOR EPOXIDE "Fig. 11 - Pesticides screened for ability to quench bioluminescence Ir £ d, PF K.I IR 10 R 125 - I ’S * N 586 9 -q

Pesticide contamination of endangered gray bats and their food base in Boone County, Missouri, 1982

USGS Publications Warehouse

Clawson, R.L.; Clark, D.R.

1989-01-01

Gray bat guano from Devil's Icebox and Hunters Caves contained dieldrin at levels previously associated with gray bat mortality. Two of four gray bats found dead in Holton Cave had lethal brain concentrations of dieldrin. Twenty-five of 28 (86%) insect samples from bat foraging areas contained measurable dieldrin, heptachlor epoxide or both. Beetle samples were most heavily contaminated containing up to 2.2 ppm and 1.1 ppm heptachlor epoxide. The addition of Holton Cave brings to five the number of Missouri caves where gray bats have died of food chain pesticide poisoning.

Curing agent for polyepoxides and epoxy resins and composites cured therewith. [preventing carbon fiber release

NASA Technical Reports Server (NTRS)

Serafini, T. T.; Delvigs, P.; Vannucci, R. D. (Inventor)

1981-01-01

A curing for a polyepoxide is described which contains a divalent aryl radical such as phenylene a tetravalent aryl radical such as a tetravalent benzene radical. An epoxide is cured by admixture with the curing agent. The cured epoxy product retains the usual properties of cured epoxides and, in addition, has a higher char residue after burning, on the order of 45% by weight. The higher char residue is of value in preventing release to the atmosphere of carbon fibers from carbon fiber-epoxy resin composites in the event of burning of the composite.

Titanocene(III) chloride mediated radical-induced addition to Baylis-Hillman adducts: synthesis of (E)- and (Z)-trisubstituted alkenes and alpha-methylene/arylidene delta-lactones.

PubMed

Mandal, Samir K; Paira, Moumita; Roy, Subhas C

2008-05-16

Baylis-Hillman adduct underwent smooth radical-induced condensation with activated bromo compounds and epoxides using titanocene(III) chloride (Cp2TiCl) as the radical generator. The reactions of activated bromo compounds with 3-acetoxy-2-methylene alkanoates provided (E)-alkenes exclusively, whereas similar reactions with 3-acetoxy-2-methylenealkanenitriles led to (Z)-alkenes as the major product. The reactions of epoxides with Baylis-Hillman adduct furnished alpha-methylene/arylidene-delta-lactones in good yield via addition followed by in situ lactonization.

N-Methylpyrrolidone Hydroperoxide/Cs2 CO3 as an Excellent Reagent System for the Hydroxy-Directed Diastereoselective Epoxidation of Electron-Deficient Olefins.

PubMed

Victor, Napoleon John; Gana, Janardhanan; Muraleedharan, Kannoth Manheri

2015-10-12

This report introduces N-methylpyrrolidone hydroperoxide (NMPOOH)/base as an excellent reagent system for hydroxy-directed syn selective epoxidation of electron-deficient olefins, characterized by high diastereoselectivity, short reaction times and remarkable chemoselectivity, especially in presence of oxidatively labile nitrogen or sulfur atoms. NMPOOH also proves efficient in the oxidation of electron-deficient aromatic aldehydes, in the removal of oxazolidinone chiral auxiliary, and in the functionalization of alkenes and alkynes, showing wide application potential. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Epoxide acrylate maleic resin and hydroxyapatite composite material as a bone graft substitute in surgical correction of orbital reconstruction].

PubMed

Mu, X; Dong, J; Wang, W

1995-11-01

This paper illustrates the results of surgical correction in 11 cases with orbital deformities such as periorbital deficiency after orbitotomy for retinoblastoma and orbital malposition after facial trauma. EH composite material, mixture of hydroxyapatite and epoxide acrylate maleic resin in constant proportion, was used as a good bone graft substitute in all 11 cases. This material was easier to be molded during surgery, safe to human body, had no toxic effects, no irritation and no implant-related complications. The early results obtained in these patients are encouraging.

Prilezhaev dihydroxylation of olefins in a continuous flow process.

PubMed

van den Broek, Bas A M W; Becker, René; Kössl, Florian; Delville, Mariëlle M E; Nieuwland, Pieter J; Koch, Kaspar; Rutjes, Floris P J T

2012-02-13

Epoxidation of both terminal and non-terminal olefins with peroxy acids is a well-established and powerful tool in a wide variety of chemical processes. In an additional step, the epoxide can be readily converted into the corresponding trans-diol. Batch-wise scale-up, however, is often troublesome because of the thermal instability and explosive character of the peroxy acids involved. This article describes the design and semi-automated optimization of a continuous flow process and subsequent scale-up to preparative production volumes in an intrinsically safe manner. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface Science and the Advancement of Direct Olefin Epoxidation A Perspective on the Article, ‘‘Partial Oxidation of Higher Olefins on Ag(111) and Ag(110): Conversion of Styrene to Styrene Oxide, Benzene, and Benzoic Acid’’, by Andreas Klust and Robert J. Madix.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barteau, Mark A.

2006-10-04

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Few reactions are as conceptually simple or as devilishly difficult as the epoxidation of ethylene to form ethylene oxide:

Calcium oxide supported gold nanoparticles as catalysts for the selective epoxidation of styrene by t-butyl hydroperoxide.

PubMed

Dumbre, Deepa K; Choudhary, Vasant R; Patil, Nilesh S; Uphade, Balu S; Bhargava, Suresh K

2014-02-01

Gold nanoparticles are deposited on basic CaO supports as catalysts for the selective conversion of styrene into styrene oxide. Synthetic methods, gold loading and calcination temperatures are varied to permit an understanding of their influence on gold nanoparticle size, the presence of cationic gold species and the nature of interaction between the gold nanoparticles and the CaO support. Based on these studies, optimal conditions are designed to make the Au/CaO catalyst efficient for the selective epoxidation of styrene. Copyright © 2013 Elsevier Inc. All rights reserved.

Studies toward brevisulcenal F via convergent strategies for marine ladder polyether synthesis.

PubMed

Katcher, Matthew; Jamison, Timothy F

2018-03-15

Shortly after the initial isolation of marine ladder polyether natural products, biomimetic epoxide-opening cascade reactions were proposed as an efficient strategy for the synthesis of these compounds. However, difficulties in assembling the cascade precursors have limited the realization of these cascades. In this report, we describe strategies that provide convergent access to cascade precursors via regioselective allylation and efficient fragment coupling. We then investigate epoxide-opening cascades promoted by strong bases for the formation of fused tetrahydropyrans. These strategies are evaluated in the context of the synthesis of rings CDEFG of brevisulcenal F.

Analysis of trichothecene mycotoxins in contaminated grains by gas chromatography/matrix isolation/Fourier transform infrared spectroscopy and gas chromatography/mass spectrometry.

PubMed

Mossoba, M M; Adams, S; Roach, J A; Trucksess, M W

1996-01-01

Gas chromatography/matrix isolation/Fourier transform infrared (GC/MI/FTIR) spectroscopy and GC/mass spectrometry (MS) were used to confirm the identities of trimethylsilyl (TMS) derivatives of trichothecene mycotoxins in naturally contaminated grains. Infrared spectral bands observed in the fingerprint region were unique for 10 trichothecene standards. Characteristic absorption bands were observed for the ester (near 1750 cm-1) and ketone (near 1700 cm-1) carbonyl stretching vibrations, the acetate CH3 symmetric bend (1370 cm-1), the epoxide ring (1262 cm-1), the trimethylsilyl CH3 in-plane deformation (1253 cm-1), the ester (O)C-O asymmetric stretching vibration (near 1244 cm-1), and several other bands including intense features due to the TMS function. Infrared bands observed under cryogenic matrix isolation conditions were compared with those found at room temperature in a potassium bromide matrix for 5 of these standards. Identities of deoxynivalenol (DON) from barley and mixed feed, nivalenol from wheat and barley, and DON and fusarenon-x from sweet corn were confirmed by comparison of their infrared spectral bands with those of standards. The identity of DON in the same test samples of sweet corn was confirmed further by GC/MS. GC/MS was also used to quantitate the levels of DON (67-455 ppm) in sweet corn test samples.

Determination of mineral oil aromatic hydrocarbons in edible oils and fats by online liquid chromatography-gas chromatography-flame ionization detection - Evaluation of automated removal strategies for biogenic olefins.

PubMed

Nestola, Marco; Schmidt, Torsten C

2017-07-07

The determination of mineral oil aromatic hydrocarbons (MOAH) in foodstuffs gained in importance over the last years as carcinogenicity cannot be excluded for certain MOAH. The existence of olefins in foodstuffs, such as edible oils and fats, can be problematic for the determination of MOAH by LC-GC-FID. Removal of these interfering substances by HPLC based on polarity differences is not possible. During gas chromatographic separation heavily overloaded peaks are observed rendering the detection of small mineral oil contaminations almost impossible. Therefore, removal of these olefins is necessary before subjection of the sample to LC-GC-FID. Epoxidation of olefins to increase their polarity proved to be a valuable tool in the past. Precision and trueness of the results as shown in a collaborative trial, however, are relying on exact reaction conditions. Additionally, it is known that certain MOAH are oxidized during epoxidation and therefore get lost. In the scope of this work, hydroboration, bromohydrin reaction, and epoxidation were examined for their potential for derivatization of unsaturated hydrocarbons with increased robustness and higher recovery of MOAH. Epoxidation by meta-chloroperoxybenzoic acid (mCPBA) delivered the best removal of olefins. Factors influencing this reaction were enlightened. Adaption of the reaction conditions and time-controlled automation increased the recovery of polycyclic MOAH. Good precision (RSD r <1.5%) and recovery (95-102%) for MOAH were also observed for sunflower and olive oils spiked with a lubricating mineral oil (at 24.5mg/kg of MOAH). The trueness of the method was verified by analyzing collaborative trial samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Reduced sensitizing capacity of epoxy resin systems: a structure-activity relationship study.

PubMed

Niklasson, Ida B; Broo, Kerstin; Jonsson, Charlotte; Luthman, Kristina; Karlberg, Ann-Therese

2009-11-01

Epoxy resins can be prepared from numerous chemical compositions. Until recently, alternatives to epoxy resins based on diglycidyl ethers of bisphenol A (DGEBA) or bisphenol F (DGEBF) monomers have not received commercial interest, but are presently doing so, as epoxy resins with various properties are desired. Epoxy resin systems are known to cause allergic contact dermatitis because of contents of uncured monomers, reactive diluents, and hardeners. Reactive diluents, for example, glycidyl ethers, which also contain epoxide moieties, are added to reduce viscosity and improve polymerization. We have investigated the contact allergenic properties of a series of six analogues to phenyl glycidyl ether (PGE), all with similar basic structures but with varying carbon chain lengths and degrees of saturation. The chemical reactivity of the compounds in the test series toward the hexapeptide H-Pro-His-Cys-Lys-Arg-Met-OH was investigated. All epoxides were shown to bind covalently to both cysteine and proline residues. The percent depletion of nonreacted peptide was also studied resulting in 88% depletion when using PGE and 46% when using butyl glycidyl ether (5) at the same time point, thus revealing a large difference between the fastest and the slowest reacting epoxide. The skin sensitization potencies of the epoxides using the murine local lymph node assay (LLNA) were evaluated in relation to the observed physicochemical and reactivity properties. To enable determination of statistical significance between structurally closely related compounds, a nonpooled LLNA was performed. It was found that the compounds investigated ranged from strong to weak sensitizers, congruent with the reactivity data, indicating that even small changes in chemical structure result in significant differences in sensitizing capacity.

Impact of a heteroatom in a structure-activity relationship study on analogues of phenyl glycidyl ether (PGE) from epoxy resin systems.

PubMed

Niklasson, Ida B; Delaine, Tamara; Luthman, Kristina; Karlberg, Ann-Therese

2011-04-18

Epoxy resins are among the most common causes of occupational contact dermatitis. They are normally used in so-called epoxy resin systems (ERS). These commercial products are combinations of epoxy resins, curing agents, modifiers, and reactive diluents. The most frequently used resins are diglycidyl ethers based on bisphenol A (DGEBA) and bisphenol F (DGEBF). In this study, we have investigated the contact allergenic properties of a series of analogues to the reactive diluent phenyl glycidyl ether (PGE), all with similar basic structures but with varying heteroatoms or with no heteroatom present. The chemical reactivity of the compounds in the test series toward the hexapeptide H-Pro-His-Cys-Lys-Arg-Met-OH was investigated. All epoxides were shown to bind covalently to both cysteine and proline residues. The percent depletion of nonreacted peptide was also studied resulting in ca. 60% depletion when using either PGE, phenyl 2,3-epoxypropyl sulfide (2), or N-(2,3-epoxypropyl)aniline (3), and only 15% when using 1,2-epoxy-4-phenylbutane (4) at the same time point. The skin sensitization potencies of the epoxides using the murine local lymph node assay (LLNA) were evaluated in relation to the observed physicochemical and reactivity properties. To enable determination of statistical significance between structurally closely related compounds, a nonpooled LLNA was performed. It was found that all investigated compounds containing a heteroatom in the α-position to the epoxide were strong sensitizers, congruent with the reactivity data, indicating that the impact of a heteroatom is crucial for the sensitizing capacity for this type of epoxides.

Determinants of reactivity and selectivity in soluble epoxide hydrolase from quantum mechanics/molecular mechanics modeling.

PubMed

Lonsdale, Richard; Hoyle, Simon; Grey, Daniel T; Ridder, Lars; Mulholland, Adrian J

2012-02-28

Soluble epoxide hydrolase (sEH) is an enzyme involved in drug metabolism that catalyzes the hydrolysis of epoxides to form their corresponding diols. sEH has a broad substrate range and shows high regio- and enantioselectivity for nucleophilic ring opening by Asp333. Epoxide hydrolases therefore have potential synthetic applications. We have used combined quantum mechanics/molecular mechanics (QM/MM) umbrella sampling molecular dynamics (MD) simulations (at the AM1/CHARMM22 level) and high-level ab initio (SCS-MP2) QM/MM calculations to analyze the reactions, and determinants of selectivity, for two substrates: trans-stilbene oxide (t-SO) and trans-diphenylpropene oxide (t-DPPO). The calculated free energy barriers from the QM/MM (AM1/CHARMM22) umbrella sampling MD simulations show a lower barrier for phenyl attack in t-DPPO, compared with that for benzylic attack, in agreement with experiment. Activation barriers in agreement with experimental rate constants are obtained only with the highest level of QM theory (SCS-MP2) used. Our results show that the selectivity of the ring-opening reaction is influenced by several factors, including proximity to the nucleophile, electronic stabilization of the transition state, and hydrogen bonding to two active site tyrosine residues. The protonation state of His523 during nucleophilic attack has also been investigated, and our results show that the protonated form is most consistent with experimental findings. The work presented here illustrates how determinants of selectivity can be identified from QM/MM simulations. These insights may also provide useful information for the design of novel catalysts for use in the synthesis of enantiopure compounds.

3,3′,4,4′,5-Pentachlorobiphenyl (PCB 126) Decreases Hepatic and Systemic Ratios of Epoxide to Diol Metabolites of Unsaturated Fatty Acids in Male Rats

PubMed Central

Wu, Xianai; Yang, Jun; Morisseau, Christophe; Robertson, Larry W.; Hammock, Bruce; Lehmler, Hans-Joachim

2016-01-01

Disruption of the homeostasis of oxygenated regulatory lipid mediators (oxylipins), potential markers of exposure to aryl hydrocarbon receptor (AhR) agonists, such as 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126), is associated with a range of diseases, including nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Here we test the hypothesis that PCB 126 exposure alters the levels of oxylipins in rats. Male Sprague-Dawley rats (5-weeks old) were treated over a 3-month period every 2 weeks with intraperitoneal injections of PCB 126 in corn oil (cumulative doses of 0, 19.8, 97.8, and 390 µg/kg b.w.; 6 injections total). PCB 126 treatment caused a reduction in growth rates at the highest dose investigated, a dose-dependent decrease in thymus weights, and a dose-dependent increase in liver weights. Liver PCB 126 levels increased in a dose-dependent manner, while levels in plasma were below or close to the detection limit. The ratios of several epoxides to diol metabolites formed via the cytochrome P450 (P450) monooxygenase/soluble epoxide hydrolase (sEH) pathway from polyunsaturated fatty acids displayed a dose-dependent decrease in the liver and plasma, whereas levels of oxylipins formed by other metabolic pathways were generally not altered by PCB 126 treatment. The effects of PCB 126 on epoxide-to-diol ratios were associated with an increased CYP1A activity in liver microsomes and an increased sEH activity in liver cytosol and peroxisomes. These results suggest that oxylipins are potential biomarkers of exposure to PCB 126 and that the P450/sEH pathway is a therapeutic target for PCB 126-mediated hepatotoxicity that warrants further attention. PMID:27208083

The main thylakoid membrane lipid monogalactosyldiacylglycerol (MGDG) promotes the de-epoxidation of violaxanthin associated with the light-harvesting complex of photosystem II (LHCII).

PubMed

Schaller, Susann; Latowski, Dariusz; Jemioła-Rzemińska, Małgorzata; Wilhelm, Christian; Strzałka, Kazimierz; Goss, Reimund

2010-03-01

In higher plants, the major part of the xanthophyll cycle pigment violaxanthin (Vx) is non-covalently bound to the main light-harvesting complex of PSII (LHCII). Under saturating light conditions Vx has to be released from its binding site into the surrounding lipid phase, where it is converted to zeaxanthin (Zx) by the enzyme Vx de-epoxidase (VDE). In the present study we investigated the influence of thylakoid lipids on the de-epoxidation of Vx, which was still associated with the LHCII. We isolated LHCII with different concentrations of native, endogenous lipids and Vx by sucrose gradient centrifugation or successive cation precipitation. Analysis of the different LHCII preparations showed that the concentration of LHCII-associated Vx was correlated with the concentration of the main thylakoid lipid monogalactosyldiacylglycerol (MGDG) associated with the complexes. Decreases in the MGDG content of the LHCII led to a diminished Vx concentration, indicating that a part of the total Vx pool was located in an MGDG phase surrounding the LHCII, whereas another part was bound to the LHCII apoproteins. We further studied the convertibility of LHCII-associated Vx in in-vitro enzyme assays by addition of isolated VDE. We observed an efficient and almost complete Vx conversion in the LHCII fractions containing high amounts of endogenous MGDG. LHCII preparations with low concentrations of MGDG exhibited a strongly reduced Vx de-epoxidation, which could be increased by addition of exogenous, pure MGDG. The de-epoxidation of LHCII-associated Vx was saturated at a much lower concentration of native, endogenous MGDG compared with the concentration of isolated, exogenous MGDG, which is needed for optimal VDE activity in in-vitro assays employing pure isolated Vx. Copyright 2009 Elsevier B.V. All rights reserved.

Functional roles of the major chloroplast lipids in the violaxanthin cycle.

PubMed

Yamamoto, Harry Y

2006-08-01

Monogalactosyldiacylglyceride (MGDG) and digalactosyldiacylglyceride (DGDG) are the major membrane lipids of chloroplasts. The question of the specialized functions of these unique lipids has received limited attention. One function is to support violaxanthin de-epoxidase (VDE) activity, an enzyme of the violaxanthin cycle. To understand better the properties of this system, the effects of galactolipids and phosphatidylcholines on VDE activity were examined by two independent methods. The results show that the micelle-forming lipid (MGDG) and bilayer forming lipids (DGDG and phosphatidylcholines) support VDE activity differently. MGDG supported rapid and complete de-epoxidation starting at a threshold lipid concentration (10 microM) coincident with complete solubilization of violaxanthin. In contrast, DGDG supported slow but nevertheless complete to nearly complete de-epoxidation at a lower lipid concentration (6.7 microM) that did not completely solubilize violaxanthin. Phosphotidylcholines showed similar effects as DGDG except that de-epoxidation was incomplete. Since VDE requires solubilized violaxanthin, aggregated violaxanthin in DGDG at low concentration must become solubilized as de-epoxidation proceeds. High lipid concentrations had lower activity possibly due to formation of multilayered structures (liposomes) that restrict accessibility of violaxanthin to VDE. MGDG micelles do not present such restrictions. The results indicate VDE operates throughout the lipid phase of the single bilayer thylakoid membrane and is not limited to putative MGDG micelle domains. Additionally, the results also explain the differential partitioning of violaxanthin between the envelope and thylakoid as due to the relative solubilities of violaxanthin and zeaxanthin in MGDG, DGDG and phospholipids. The violaxanthin cycle is hypothesized to be a linked system of the thylakoid and envelope for signal transduction of light stress.

Activation of violaxanthin cycle in darkness is a common response to different abiotic stresses: a case study in Pelvetia canaliculata

PubMed Central

2011-01-01

Background In the violaxanthin (V) cycle, V is de-epoxidized to zeaxanthin (Z) when strong light or light combined with other stressors lead to an overexcitation of photosystems. However, plants can also suffer stress in darkness and recent reports have shown that dehydration triggers V-de-epoxidation in the absence of light. In this study, we used the highly stress-tolerant brown alga Pelvetia canaliculata as a model organism, due to its lack of lutein and its non-photochemical quenching independent of the transthylakoidal-ΔpH, to study the triggering of the V-cycle in darkness induced by abiotic stressors. Results We have shown that besides desiccation, other factors such as immersion, anoxia and high temperature also induced V-de-epoxidation in darkness. This process was reversible once the treatments had ceased (with the exception of heat, which caused lethal damage). Irrespective of the stressor applied, the resulting de-epoxidised xanthophylls correlated with a decrease in Fv/Fm, suggesting a common function in the down-regulation of photosynthetical efficiency. The implication of the redox-state of the plastoquinone-pool and of the differential activity of V-cycle enzymes on V-de-epoxidation in darkness was also examined. Current results suggest that both violaxanthin de-epoxidase (VDE) and zeaxanthin-epoxidase (ZE) have a basal constitutive activity even in darkness, being ZE inhibited under stress. This inhibition leads to Z accumulation. Conclusion This study demonstrates that V-cycle activity is triggered by several abiotic stressors even when they occur in an absolute absence of light, leading to a decrease in Fv/Fm. This finding provides new insights into an understanding of the regulation mechanism of the V-cycle and of its ecophysiological roles. PMID:22269024

A Search for Structure in PAH Emission in Extended Sources at 3.3 and 3.4 Microns

NASA Technical Reports Server (NTRS)

Bregman, Jesse; Temi, P.; Rank, D. M.; Sloan, G. C.; Schultz, A. S. B.; Witteborn, Fred C. (Technical Monitor)

1994-01-01

We have observed three extended sources of the infrared emission features associated with polycyclic aromatic hydrocarbons (PAHs), using a 128x128 InSb array mounted on the 1.5 m NASA/Steward telescope on Mt. Lemmon. We used a CVF (1.5% bandpass) to isolate the emission from the 3.29 and 3.40 microns PAH features in NGC 1333 #3, Sharpless 106, and the Orion Bar. In all three sources, the 3.29 and 3.40 microns emission features arise from the same regions, but show decidedly different structure. We are analyzing the images to determine the relationship of the 3.40 microns feature to the main feature at 3.29 microns. The 3.40 microns feature may be a vibrational overtone of the 3.29 microns feature, or it may arise from attached molecular sidegroups.

Construction and photophysical properties of organic-inorganic nanonetworks based on oligo(phenylenevinylene) and functionalized gold nanoparticles.

PubMed

Yang, Jien; Liu, Xiaofeng; Huang, Changshui; Zhou, Chunjie; Li, Yuliang; Zhu, Daoben

2010-02-22

Novel organic-inorganic nanonetworks of oligo(phenylenevinylene) (OPV) and gold nanoparticles (GNPs) have been synthesized by the amine-based epoxide ring-opening reaction. The resulting OPV-GNPs nanocomposites exhibit homogeneous and well-defined interfaces between the organic ligands and the inorganic nanoparticles, thereby promoting efficient electronic interfacial interaction between the two constituents. The functionalized gold nanoparticles serve as chemical reagents for the construction of nanohybrids, while the epoxide-terminated OPV acts as linkage between gold nanoparticles. The new architecture provides a facile methodology for fabrication of novel organic-inorganic nanohybrids under relatively mild conditions, which facilitates further applications of hybrid materials.

Sustainable epoxy and oxetane thermosets from photo-initiated cationic polymerization

NASA Astrophysics Data System (ADS)

Ryu, Chang

A group of sustainable materials are proposed and produced from multifunctional epoxides and oxetanes obtained from renewable sources. Monomers are photopolymerized using diaryliodonium salts designed and synthesized by our group as initiator. A detailed investigation of the network formation of epoxidized linseed oil revealed that crosslinks is markedly dependent to the thickness and viscosity of substrate. Copolymerization studies of difunctional oxetane showed that limonene dioxide was effective in increasing the reaction rates and shorten the inherent induction period, also known as kick-starting effect. Such oxetane thermoset can achieve desirable curing rates and Tg compared to petroleum based epoxy used in applications such as large scale surface coatings.

Plant Oil-Derived Epoxy Polymers toward Sustainable Biobased Thermosets.

PubMed

Wang, Zhongkai; Yuan, Liang; Ganewatta, Mitra S; Lamm, Meghan E; Rahman, Md Anisur; Wang, Jifu; Liu, Shengquan; Tang, Chuanbing

2017-06-01

Epoxy polymers (EPs) derived from soybean oil with varied chemical structures are synthesized. These polymers are then cured with anhydrides to yield soybean-oil-derived epoxy thermosets. The curing kinetic, thermal, and mechanical properties are well characterized. Due to the high epoxide functionality per epoxy polymer chain, these thermosets exhibit tensile strength over an order of magnitude higher than a control formulation with epoxidized soybean oil. More importantly, thermosetting materials ranging from soft elastomers to tough thermosets can be obtained simply by using different EPs and/or by controlling feed ratios of EPs to anhydrides. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

H2O-Polyaluminium chloride-TBAB as synergistic catalysts for the synthesis of cyclic carbonate

NASA Astrophysics Data System (ADS)

Liu, X. J.; Yan, P.; Han, Y.

2018-01-01

An efficient catalytic system consisting of H2O, Polyaluminium chloride (PAC) and Tetrabutylammonium bromide (TBAB) was applied to the cycloaddition of carbon dioxide (CO2) to epoxides under mild conditions. Their catalytic cycloaddition activities were found to be well correlated with H2O and polyaluminium chloride, which had a synergetic effect with the halide anion of TBAB. The presence of H2O and PAC could remarkably improve the yield of propylene carbonate (PC) by which the reaction yield is about 4-5 times higher than TBAB. alone.The catalytic system also exhibited excellent cycloaddition activities for various epoxide substrates.

1H and 13C NMR Chemical Shift Assignments and Conformational Analysis for the Two Diastereomers of the Vitamin K Epoxide Reductase Inhibitor Brodifacoum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cort, John R.; Cho, Herman M.

2009-10-01

Proton and 13C NMR chemical shift assignments and 1H-1H scalar couplings for the two diastereomers of the vitamin K epoxide reductase (VKOR) inhibitor brodifacoum have been determined from acetone solutions containing both diastereomers. Data were obtained from homo- and heteronuclear correlation spectra acquired at 1H frequencies of 750 and 900 MHz over a 268-303 K temperature range. Conformations inferred from scalar coupling and 1-D NOE measurements exhibit large differences between the diastereomers. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Enantiomeric Recognition of Organic Ammonium Salts by Chiral Dialkyl-, Dialkenyl-, and Tetramethyl-Substituted Pyridino-18-Crown-6 and Tetramethyl- Substituted Bis-Pyridino-18-Crown-6 Ligands: Comparison of Temperature-Dependent 1H NMR and Empirical Force Field Techniques

DTIC Science & Technology

1990-04-18

COVERED 14, DATE OF REPORT (Year. Month, Day) 15. PAGE COUNT Interim FROM _ _ TO April 18, 1990 16. SUPPLEMENTARY NOTATION 17 , COSATI CODES 18. SUBJECT...to epoxide 17 was carried out ,o by using the method of Koppenhoefer and Schurig.241-2 Our epoxides 17 where R was isopropyl, isobutyl, and Scheme i... 17 with diethylene glycol and a catalytic amount of sodium was carried out as reported for the preparation of the chiral dimethyl- tetraethylene glycol

Decomposition reactions of (hydroxyalkyl) nitrosoureas and related compounds: possible relationship to carcinogenicity.

PubMed

Singer, S S

1985-08-01

(Hydroxyalkyl)nitrosoureas and the related cyclic carbamates N-nitrosooxazolidones are potent carcinogens. The decompositions of four such compounds, 1-nitroso-1-(2-hydroxyethyl)urea (I), 3-nitrosooxazolid-2-one (II), 1-nitroso-1-(2-hydroxypropyl)urea (III), and 5-methyl-3-nitrosooxazolid-2-one (IV), in aqueous buffers at physiological pH were studied to determine if any obvious differences in decomposition pathways could account for the variety of tumors obtained from these four compounds. The products predicted by the literature mechanisms for nitrosourea and nitrosooxazolidone decompositions (which were derived from experiments at pH 10-12) were indeed the products formed, including glycols, active carbonyl compounds, epoxides, and, from the oxazolidones, cyclic carbonates. Furthermore, it was shown that in pH 6.4-7.4 buffer epoxides were stable reaction products. However, in the presence of hepatocytes, most of the epoxide was converted to glycol. The analytical methods developed were then applied to the analysis of the decomposition products of some related dialkylnitrosoureas, and similar results were obtained. The formation of chemically reactive secondary products and the possible relevance of these results to carcinogenesis studies are discussed.

Hydroxyl-Exchanged Nanoporous Ionic Copolymer toward Low-Temperature Cycloaddition of Atmospheric Carbon Dioxide into Carbonates.

PubMed

Guo, Zengjing; Cai, Xiaochun; Xie, Jingyan; Wang, Xiaochen; Zhou, Yu; Wang, Jun

2016-05-25

An ionic copolymer catalyst with nanopores, large surface area, high ionic density, and superior basicity was prepared via the radical copolymerization of amino-functionalized ionic liquid bromide and divinylbenzene, followed with a hydroxyl exchange for removing bromonium. Evaluated in chemical fixation of CO2 with epoxides into cyclic carbonates in the absence of any solvent and basic additive, the nanoporous copolymer catalyst showed high and stable activity, superior to various control catalysts including the halogen-containing analogue. Further, high yields were obtained over a wide scope of substrates including aliphatic long carbon-chain alkyl epoxides and internal epoxide, even under atmospheric pressure and less than 100 °C for the majority of the substrates. On the basis of in situ Fourier transform infrared (FT-IR) investigation and density functional theory (DFT) calculation for the reaction intermediates, we proposed a possible reaction mechanism accounting for the superior catalytic activity of the ionic copolymer. The specifically prepared ionic copolymer material of this work features highly stable, noncorrosive, and sustainable catalysis and, thus, may be a new possibility for efficient chemical fixation of CO2 since it is an environmentally friendly, metal-free solid catalyst.

Direct characterization of cotton fabrics treated with di-epoxide by nuclear magnetic resonance.

PubMed

Xiao, Min; Chéry, Joronia; Keresztes, Ivan; Zax, David B; Frey, Margaret W

2017-10-15

A non-acid-based, di-functional epoxide, neopentyl glycol diglycidyl ether (NPGDGE), was used to modify cotton fabrics. Direct characterization of the modified cotton was conducted by Nuclear Magnetic Resonance (NMR) without grinding the fabric into a fine powder. NaOH and MgBr 2 were compared in catalyzing the reaction between the epoxide groups of NPGDGE and the hydroxyl groups of cellulose. Possible reaction routes were discussed. Scanning electron microscopy (SEM) images showed that while the MgBr 2 -catalyzed reaction resulted in self-polymerization of NPGDGE, the NaOH-catalyzed reaction did not. Fourier transform infrared spectroscopy (FTIR) showed that at high NaOH concentration cellulose restructures from allomorph I to II. NMR studies verified the incorporation of NPGDGE into cotton fabrics with a clear NMR signal, and confirmed that at higher NaOH concentration the efficiency of grafting of NPGDGE was increased. This demonstrates that use of solid state NMR directly on woven fabric samples can simultaneously characterize chemical modification and crystalline polymorph of cotton. No loss of tensile strength was observed for cotton fabrics modified with NPGDGE. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ethyl 2-(4-meth-oxy-phen-yl)-6-oxa-3-aza-bicyclo[3.1.0]hexane-3-carboxyl-ate: crystal structure and Hirshfeld analysis.

PubMed

Zukerman-Schpector, Julio; Sugiyama, Fabricia H; Garcia, Ariel L L; Correia, Carlos Roque D; Jotani, Mukesh M; Tiekink, Edward R T

2017-07-01

The title compound, C 14 H 17 NO 4 , features an epoxide-O atom fused to a pyrrolidyl ring, the latter having an envelope conformation with the N atom being the flap. The 4-meth-oxy-phenyl group is orthogonal to [dihedral angle = 85.02 (6)°] and lies to the opposite side of the five-membered ring to the epoxide O atom, while the N-bound ethyl ester group (r.m.s. deviation of the five fitted atoms = 0.0187 Å) is twisted with respect to the ring [dihedral angle = 17.23 (9)°]. The most prominent inter-actions in the crystal are of the type methine-C-H⋯O(carbon-yl) and these lead to the formation of linear supra-molecular chains along the c axis; weak benzene-C-H⋯O(epoxide) and methine-C-H⋯O(meth-oxy) inter-actions connect these into a three-dimensional architecture. The analysis of the Hirshfeld surface confirms the presence of C-H⋯O inter-actions in the crystal, but also the dominance of H⋯H dispersion contacts.

Crosslinking Amine-Modified Silica Aerogels with Epoxies: Mechanically Strong Lightweight Porous Materials

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Fabrizio, Eve F.; Ilhan, Faysal; Dass, Amala; Zhang, Guo-Hui; Vassilaras, Plousia; Johnston, J. Chris; Leventis, Nicholas

2005-01-01

The mesoporous surfaces of TMOS-derived silica aerogels have been modified with amines by co-polymerization of TMOS with APTES. The amine sites have become anchors for crosslinking the nanoparticles of the skeletal backbone of the aerogel by attachment of di-, tri and tetra-functional epoxies. The resulting conformal coatings increase the density of the native aerogels by a factor of 2-3 but the strength of the resulting materials may increase by more than two orders of magnitude. Processing variables such as amount of APTES used to make the gels, the epoxy type and concentration used for crosslinking, as well as the crosslinking temperature and time were varied according to a multivariable design-of-experiments (DOE) model. It was found that while elastic modulus follows a similar trend with density, maximum strength is attained neither at the maximum density nor at the highest concentration of -NH2 groups, suggesting surface saturation effects. Aerogels crosslinked with the tri-functional epoxide always show improved strength compared with aerogels crosslinked with the other two epoxides under identical conditions. Solid C-13 NMR studies show residual unreacted epoxides, which condense with ne another by heating crosslinked aerogels at 150 C.

Synthesis of a highly dispersed CuO catalyst on CoAl-HT for the epoxidation of styrene.

PubMed

Hu, Rui; Yang, Pengfei; Pan, Yongning; Li, Yunpeng; He, Yufei; Feng, Junting; Li, Dianqing

2017-10-10

A highly dispersed CuO catalyst was prepared by the deposition-precipitation method and evaluated for the catalytic epoxidation of styrene with tert-butyl hydroperoxide (TBHP) as the oxidant under solvent acetonitrile conditions. Compared with MgAl hydrotalcite (MgAl-HT)-, MgO-, TiO 2 -, C-, and MCM-22-supported catalysts, CuO/CoAl-HT exhibited preferable activity and selectivity towards styrene oxide (72% selectivity at 99.5% styrene conversion) due to its high dispersion of CuO and surface area of Cu. The improved dispersion of CuO/CoAl-HT could be ascribed to the nature of HT support, especially the synergistic effect of acidic and basic sites on the surface, which facilitated the formation of highly dispersed CuO species. A structure-performance relationship study indicated that copper(ii) in CuO was the active site for the epoxidation and oxidation of styrene, and that Cu II of rich electronic density favored the improvement of selectivity of styrene oxide. Based on these results, a reaction mechanism was proposed. Moreover, the preferred catalytic performance of CuO/CoAl-HT could be maintained in five reused cycles.

Precursor effect on the property and catalytic behavior of Fe-TS-1 in butadiene epoxidation

NASA Astrophysics Data System (ADS)

Wu, Mei; Zhao, Huahua; Yang, Jian; Zhao, Jun; Song, Huanling; Chou, Lingjun

2017-11-01

The effect of iron precursor on the property and catalytic behavior of iron modified titanium silicalite molecular sieve (Fe-TS-1) catalysts in butadiene selective epoxidation has been studied. Three Fe-TS-1 catalysts were prepared, using iron nitrate, iron chloride and iron sulfate as precursors, which played an important role in adjusting the textural properties and chemical states of TS-1. Of the prepared Fe-TS-1 catalysts, those modified by iron nitrate (FN-TS-1) exhibited a significant enhanced performance in butadiene selective epoxidation compared to those derived from iron sulfate (FS-TS-1) or iron chloride (FC-TS-1) precursors. To obtain a deep understanding of their structure-performance relationship, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Temperature programmed desorption of NH3 (NH3-TPD), Diffuse reflectance UV-Vis spectra (DR UV-Vis), Fourier transformed infrared spectra (FT-IR) and thermal gravimetric analysis (TGA) were conducted to characterize Fe-TS-1 catalysts. Experimental results indicated that textural structures and acid sites of modified catalysts as well as the type of Fe species influenced by the precursors were all responsible for the activity and product distribution.

Interfacial Strength and Physical Properties of Functionalized Graphene - Epoxy Nanocomposites

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Heimann, Paula; Scheiman, Daniel; Adamson, Douglas H.; Aksay, Iihan A.; Prud'homme, Robert K.

2006-01-01

The toughness and coefficient of thermal expansion of a series of functionalized graphene sheet - epoxy nanocomposites are investigated. Functionalized graphene sheets are produced by splitting graphite oxide into single graphene sheets through a rapid thermal expansion process. These graphene sheets contain approx. 10% oxygen due to the presence of hydroxide, epoxide, and carboxyl functional groups which assist in chemical bond formation with the epoxy matrix. Intrinsic surface functionality is used to graft alkyl amine chains on the graphene sheets, and the addition of excess hardener insures covalent bonding between the epoxide matrix and graphene sheets. Considerable improvement in the epoxy dimensional stability is obtained. An increase in nanocomposite toughness is observed in some cases.

Biosynthesis of (R)-phenyl-1,2-ethanediol from racemic styrene oxide by using bacterial and marine fish epoxide hydrolases.

PubMed

Kim, Hee Sook; Lee, Ok Kyung; Hwang, Seungha; Kim, Beum Jun; Lee, Eun Yeol

2008-01-01

Enantio-convergent hydrolysis of racemic styrene oxides was achieved to prepare enantiopure (R)-phenyl-1,2-ethanediol by using two recombinant epoxide hydrolases (EHs) of a bacterium, Caulobacter crescentus, and a marine fish, Mugil cephalus. The recombinant C. crescentus EH primarily attacked the benzylic carbon of (S)-styrene oxide, while the M. cephalus EH preferentially attacked the terminal carbon of (R)-styrene oxide, thus leading to the formation of (R)-phenyl-1,2-ethanediol as the main product. (R)-Phenyl-1,2-ethanediol was obtained with 90% enantiomeric excess and yield as high as 94% from 50 mM racemic styrene oxides in a one-pot process.

Interaction of benzo[a]pyrene diol epoxide isomers with human serum albumin: Site specific characterisation of adducts and associated kinetics

NASA Astrophysics Data System (ADS)

Motwani, Hitesh V.; Westberg, Emelie; Törnqvist, Margareta

2016-11-01

Carcinogenicity of benzo[a]pyrene {B[a]P, a polycyclic aromatic hydrocarbon (PAH)} involves DNA-modification by B[a]P diol epoxide (BPDE) metabolites. Adducts to serum albumin (SA) are not repaired, unlike DNA adducts, and therefore considered advantageous in assessment of in vivo dose of BPDEs. In the present work, kinetic experiments were performed in relation to the dose (i.e. concentration over time) of different BPDE isomers, where human SA (hSA) was incubated with respective BPDEs under physiological conditions. A liquid chromatography (LC) tandem mass spectrometry methodology was employed for characterising respective BPDE-adducts at histidine and lysine. This strategy allowed to structurally distinguish between the adducts from racemic anti- and syn-BPDE and between (+)- and (-)-anti-BPDE, which has not been attained earlier. The adduct levels quantified by LC-UV and the estimated rate of disappearance of BPDEs in presence of hSA gave an insight into the reactivity of the diol epoxides towards the N-sites on SA. The structure specific method and dosimetry described in this work could be used for accurate estimation of in vivo dose of the BPDEs following exposure to B[a]P, primarily in dose response studies of genotoxicity, e.g. in mice, to aid in quantitative risk assessment of PAHs.

Identification of geometrical isomers and comparison of different isomeric samples of astaxanthin.

PubMed

Qiu, Dan; Wu, Yue-Chan; Zhu, Wen-Li; Yin, Hong; Yi, Long-Tao

2012-09-01

A high-performance liquid chromatographic (HPLC) analysis system for isomeric astaxanthin was developed. The separation system consisted of a C(30) column and an elution system of methanol/MTBE/water/dichloromethane (77:13:8:2, v/v/v/v). Using the combination of HPLC diode array detector and HPLC atmospheric pressure chemical ionization mass spectrometry, 11 geometrical isomers and 4 epoxides of astaxanthin were successfully identified. Referred to crystal, only isomerization with different degrees was found for solvent dissolving and iodine catalysis, while melting of astaxanthin caused isomerization, slight oxidation, and more noticeable polymerization confirmed by gel permeation chromatography. Chemical changes in isomeric samples all caused a decrease in UV content. The vibrational spectra (infrared and Raman) showed that epoxide was the only new functional group generated for melting. Changes of several key bands and formations of new bands were found in iodine catalysis and melting samples because of isomerization. Practical Application:  Eleven geometrical isomers and 4 epoxides, which were normally generated for solvent dissolving, iodine catalysis, and melting of astaxanthin, have been identified by C(30) -HPLC-MS technology. Furthermore, different samples were measured by gel permeation chromatography, UV, infrared, and Raman, based on the analysis of messages, the effect of each processing was well understood. © 2012 Institute of Food Technologists®

A DFT-Based Computational-Experimental Methodology for Synthetic Chemistry: Example of Application to the Catalytic Opening of Epoxides by Titanocene.

PubMed

Jaraíz, Martín; Enríquez, Lourdes; Pinacho, Ruth; Rubio, José E; Lesarri, Alberto; López-Pérez, José L

2017-04-07

A novel DFT-based Reaction Kinetics (DFT-RK) simulation approach, employed in combination with real-time data from reaction monitoring instrumentation (like UV-vis, FTIR, Raman, and 2D NMR benchtop spectrometers), is shown to provide a detailed methodology for the analysis and design of complex synthetic chemistry schemes. As an example, it is applied to the opening of epoxides by titanocene in THF, a catalytic system with abundant experimental data available. Through a DFT-RK analysis of real-time IR data, we have developed a comprehensive mechanistic model that opens new perspectives to understand previous experiments. Although derived specifically from the opening of epoxides, the prediction capabilities of the model, built on elementary reactions, together with its practical side (reaction kinetics simulations of real experimental conditions) make it a useful simulation tool for the design of new experiments, as well as for the conception and development of improved versions of the reagents. From the perspective of the methodology employed, because both the computational (DFT-RK) and the experimental (spectroscopic data) components can follow the time evolution of several species simultaneously, it is expected to provide a helpful tool for the study of complex systems in synthetic chemistry.

Development of an HTS assay for EPHX2 phosphatase activity and screening of nontargeted libraries.

PubMed

Morisseau, Christophe; Sahdeo, Sunil; Cortopassi, Gino; Hammock, Bruce D

2013-03-01

The EPXH2 gene encodes soluble epoxide hydrolase (sEH), which has two distinct enzyme activities: epoxide hydrolase (Cterm-EH) and phosphatase (Nterm-phos). The Cterm-EH is involved in the metabolism of arachidonic acid epoxides that play important roles in blood pressure, cell growth, inflammation, and pain. While recent findings suggested complementary biological roles for Nterm-phos, research is limited by the lack of potent bioavailable inhibitors of this phosphatase activity. Also, a potent bioavailable inhibitor of this activity could be important in the development of therapy for cardiovascular diseases. We report herein the development of an HTS enzyme-based assay for Nterm-phos (Z'>0.9) using AttoPhos as the substrate. This assay was used to screen a wide variety of chemical entities, including a library of known drugs that have reached through clinical evaluation (Pharmakon 1600), as well as a library of pesticides and environmental toxins. We discovered that ebselen inhibits sEH phosphatase activity. Ebselen binds to the N-terminal domain of sEH (K(I)=550 nM) and chemically reacts with the enzyme to quickly and irreversibly inhibit Nterm-phos, and subsequently Cterm-EH, and thus represents a new class of sEH inhibitor. Copyright © 2012 Elsevier Inc. All rights reserved.

Mechanistic Basis for High Stereoselectivity and Broad Substrate Scope in the (salen)Co(III)-Catalyzed Hydrolytic Kinetic Resolution

PubMed Central

Ford, David D.; Nielsen, Lars P. C.; Zuend, Stephan J.; Jacobsen, Eric N.

2013-01-01

In the (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides, the rate- and stereoselectivity-determining epoxide ring-opening step occurs by a cooperative bimetallic mechanism with one Co(III) complex acting as a Lewis acid and another serving to deliver the hydroxide nucleophile. In this paper, we analyze the basis for the extraordinarily high stereoselectivity and broad substrate scope observed in the HKR. We demonstrate that the stereochemistry of each of the two (salen)Co(III) complexes in the rate-determining transition structure is important for productive catalysis: a measurable rate of hydrolysis occurs only if the absolute stereochemistry of each of these (salen)Co(III) complexes is the same. Experimental and computational studies provide strong evidence that stereochemical communication in the HKR is mediated by the stepped conformation of the salen ligand, and not the shape of the chiral diamine backbone of the ligand. A detailed computational analysis reveals that the epoxide binds the Lewis acidic Co(III) complex in a well-defined geometry imposed by stereoelectronic, rather than steric effects. This insight serves as the basis of a complete stereochemical and transition structure model that sheds light on the reasons for the broad substrate generality of the HKR. PMID:24041239

Mechanistic basis for high stereoselectivity and broad substrate scope in the (salen)Co(III)-catalyzed hydrolytic kinetic resolution.

PubMed

Ford, David D; Nielsen, Lars P C; Zuend, Stephan J; Musgrave, Charles B; Jacobsen, Eric N

2013-10-16

In the (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides, the rate- and stereoselectivity-determining epoxide ring-opening step occurs by a cooperative bimetallic mechanism with one Co(III) complex acting as a Lewis acid and another serving to deliver the hydroxide nucleophile. In this paper, we analyze the basis for the extraordinarily high stereoselectivity and broad substrate scope observed in the HKR. We demonstrate that the stereochemistry of each of the two (salen)Co(III) complexes in the rate-determining transition structure is important for productive catalysis: a measurable rate of hydrolysis occurs only if the absolute stereochemistry of each of these (salen)Co(III) complexes is the same. Experimental and computational studies provide strong evidence that stereochemical communication in the HKR is mediated by the stepped conformation of the salen ligand, and not the shape of the chiral diamine backbone of the ligand. A detailed computational analysis reveals that the epoxide binds the Lewis acidic Co(III) complex in a well-defined geometry imposed by stereoelectronic rather than steric effects. This insight serves as the basis of a complete stereochemical and transition structure model that sheds light on the reasons for the broad substrate generality of the HKR.

Inhibition of β-Glucocerebrosidase Activity Preserves Motor Unit Integrity in a Mouse Model of Amyotrophic Lateral Sclerosis.

PubMed

Henriques, Alexandre; Huebecker, Mylene; Blasco, Hélène; Keime, Céline; Andres, Christian R; Corcia, Philippe; Priestman, David A; Platt, Frances M; Spedding, Michael; Loeffler, Jean-Philippe

2017-07-12

Recent metabolomic reports connect dysregulation of glycosphingolipids, particularly ceramide and glucosylceramide, to neurodegeneration and to motor unit dismantling in amyotrophic lateral sclerosis at late disease stage. We report here altered levels of gangliosides in the cerebrospinal fluid of amyotrophic lateral sclerosis patients in early disease stage. Conduritol B epoxide is an inhibitor of acid beta-glucosidase, and lowers glucosylceramide degradation. Glucosylceramide is the precursor for all of the more complex glycosphingolipids. In SOD1 G86R mice, an animal model of amyotrophic lateral sclerosis, conduritol B epoxide preserved ganglioside distribution at the neuromuscular junction, delayed disease onset, improved motor function and preserved motor neurons as well as neuromuscular junctions from degeneration. Conduritol B epoxide mitigated gene dysregulation in the spinal cord and restored the expression of genes involved in signal transduction and axonal elongation. Inhibition of acid beta-glucosidase promoted faster axonal elongation in an in vitro model of neuromuscular junctions and hastened recovery after peripheral nerve injury in wild type mice. Here, we provide evidence that glycosphingolipids play an important role in muscle innervation, which degenerates in amyotrophic lateral sclerosis from the early disease stage. This is a first proof of concept study showing that modulating the catabolism of glucosylceramide may be a therapeutic target for this devastating disease.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bahl, C.; Morisseau, C; Bomberger, J

Cystic fibrosis transmembrane conductance regulator (CFTR) inhibitory factor (Cif) is a virulence factor secreted by Pseudomonas aeruginosa that reduces the quantity of CFTR in the apical membrane of human airway epithelial cells. Initial sequence analysis suggested that Cif is an epoxide hydrolase (EH), but its sequence violates two strictly conserved EH motifs and also is compatible with other {alpha}/{beta} hydrolase family members with diverse substrate specificities. To investigate the mechanistic basis of Cif activity, we have determined its structure at 1.8-{angstrom} resolution by X-ray crystallography. The catalytic triad consists of residues Asp129, His297, and Glu153, which are conserved across themore » family of EHs. At other positions, sequence deviations from canonical EH active-site motifs are stereochemically conservative. Furthermore, detailed enzymatic analysis confirms that Cif catalyzes the hydrolysis of epoxide compounds, with specific activity against both epibromohydrin and cis-stilbene oxide, but with a relatively narrow range of substrate selectivity. Although closely related to two other classes of {alpha}/{beta} hydrolase in both sequence and structure, Cif does not exhibit activity as either a haloacetate dehalogenase or a haloalkane dehalogenase. A reassessment of the structural and functional consequences of the H269A mutation suggests that Cif's effect on host-cell CFTR expression requires the hydrolysis of an extended endogenous epoxide substrate.« less

Conserved Loop Cysteines of Vitamin K Epoxide Reductase Complex Subunit 1-like 1 (VKORC1L1) Are Involved in Its Active Site Regeneration*

PubMed Central

Tie, Jian-Ke; Jin, Da-Yun; Stafford, Darrel W.

2014-01-01

Vitamin K epoxide reductase complex subunit 1 (VKORC1) reduces vitamin K epoxide in the vitamin K cycle for post-translational modification of proteins that are involved in a variety of biological functions. However, the physiological function of VKORC1-like 1 (VKORC1L1), a paralogous enzyme sharing about 50% protein identity with VKORC1, is unknown. Here we determined the structural and functional differences of these two enzymes using fluorescence protease protection (FPP) assay and an in vivo cell-based activity assay. We show that in vivo VKORC1L1 reduces vitamin K epoxide to support vitamin K-dependent carboxylation as efficiently as does VKORC1. However, FPP assays show that unlike VKORC1, VKORC1L1 is a four-transmembrane domain protein with both its termini located in the cytoplasm. Moreover, the conserved loop cysteines, which are not required for VKORC1 activity, are essential for VKORC1L1's active site regeneration. Results from domain exchanges between VKORC1L1 and VKORC1 suggest that it is VKORC1L1's overall structure that uniquely allows for active site regeneration by the conserved loop cysteines. Intermediate disulfide trapping results confirmed an intra-molecular electron transfer pathway for VKORC1L1's active site reduction. Our results allow us to propose a concerted action of the four conserved cysteines of VKORC1L1 for active site regeneration; the second loop cysteine, Cys-58, attacks the active site disulfide, forming an intermediate disulfide with Cys-139; the first loop cysteine, Cys-50, attacks the intermediate disulfide resulting in active site reduction. The different membrane topologies and reaction mechanisms between VKORC1L1 and VKORC1 suggest that these two proteins might have different physiological functions. PMID:24532791

Conserved loop cysteines of vitamin K epoxide reductase complex subunit 1-like 1 (VKORC1L1) are involved in its active site regeneration.

PubMed

Tie, Jian-Ke; Jin, Da-Yun; Stafford, Darrel W

2014-03-28

Vitamin K epoxide reductase complex subunit 1 (VKORC1) reduces vitamin K epoxide in the vitamin K cycle for post-translational modification of proteins that are involved in a variety of biological functions. However, the physiological function of VKORC1-like 1 (VKORC1L1), a paralogous enzyme sharing about 50% protein identity with VKORC1, is unknown. Here we determined the structural and functional differences of these two enzymes using fluorescence protease protection (FPP) assay and an in vivo cell-based activity assay. We show that in vivo VKORC1L1 reduces vitamin K epoxide to support vitamin K-dependent carboxylation as efficiently as does VKORC1. However, FPP assays show that unlike VKORC1, VKORC1L1 is a four-transmembrane domain protein with both its termini located in the cytoplasm. Moreover, the conserved loop cysteines, which are not required for VKORC1 activity, are essential for VKORC1L1's active site regeneration. Results from domain exchanges between VKORC1L1 and VKORC1 suggest that it is VKORC1L1's overall structure that uniquely allows for active site regeneration by the conserved loop cysteines. Intermediate disulfide trapping results confirmed an intra-molecular electron transfer pathway for VKORC1L1's active site reduction. Our results allow us to propose a concerted action of the four conserved cysteines of VKORC1L1 for active site regeneration; the second loop cysteine, Cys-58, attacks the active site disulfide, forming an intermediate disulfide with Cys-139; the first loop cysteine, Cys-50, attacks the intermediate disulfide resulting in active site reduction. The different membrane topologies and reaction mechanisms between VKORC1L1 and VKORC1 suggest that these two proteins might have different physiological functions.

Metabolic inactivation of five glycidyl ethers in lung and liver of humans, rats and mice in vitro.

PubMed

Boogaard, P J; de Kloe, K P; Bierau, J; Kuiken, G; Borkulo, P E; Watson, W P; van Sittert, N J

2000-05-01

1. Some glycidyl ethers (GE) have been shown to be direct mutagens in short-term in vitro tests and consequently GE are considered to be potentially mutagenic in vivo. However, GE may be metabolically inactivated in the body by two different enzymatic routes: conjugation of the epoxide moiety with the endogenous tripeptide glutathione (GSH) catalysed by glutathione S-transferase (GST) or hydrolysis of the epoxide moiety catalysed by epoxide hydrolase (EH). 2. The metabolic inactivation of five different GE, the diglycidyl ethers of bisphenol A (BADGE), 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl (Epikote YX4000) and 1,6-hexanediol (HDDGE) and the GE of 1-dodecanol (C12GE) and o-cresol (o-CGE), has been studied in subcellular fractions of human, C3H mouse and F344 rat liver and lung. 3. All GE were chemically very stable and resistant to aqueous hydrolysis, but were rapidly hydrolysed by EH in cytosolic and microsomal fractions of liver and lung. The aromatic GE were very good substrates for EH. In general, microsomal EH is more efficient than cytosolic EH in hydrolysis of GE, and human microsomes are more efficient than rodent microsomes. 4. The more water-soluble GE, o-CGE and HDDGE, were good substrates for GST whereas the more lipophilic GE, YX4000 and C12GE, were poor substrates for GST. In general, rodents are more efficient in GSH conjugation of GE than humans. 5. In general, the epoxide groups of YX4000 are the most and those of HDDGE the least efficiently inactivated of the five GE under study. For the other three GE no general trend was observed: the relative efficiency of inactivation varied with organ and species. 6. The large variation in metabolism observed with five representative GE indicate that GE have variable individual properties and should not be considered as a single, homogenous class of compounds.

Synthesis and coherent vibrational laser spectroscopy of putative molecular constituents in isoprene-derived secondary organic aerosol particles

NASA Astrophysics Data System (ADS)

Ebben, C. J.; Strick, B. F.; Upshur, M. A.; Chase, H. M.; Achtyl, J. L.; Thomson, R. J.; Geiger, F. M.

2013-11-01

SOA particle formation ranks among the least understood processes in the atmosphere, rooted in part in (a) the limited knowledge about SOA chemical composition; (b) the availability of only little concrete evidence for chemical structures; and (c) little availability of reference compounds needed for benchmarking and chemical identification in pure and homogenous form. Here, we address these challenges by synthesizing and subjecting to physical and chemical analysis putative isoprene-derived SOA particle constituents. Our surface-selective spectroscopic analysis of these compounds is followed by comparison to synthetic SOA particles prepared at the Harvard Environmental Chamber (HEC) and to authentic SOA particles collected in a tropical forest environment, namely the Amazon Basin, where isoprene oxidation by OH radicals has been reported to dominate SOA particle formation (Martin et al., 2010b; Sun et al., 2003; Hudson et al., 2008; Yasmeen et al., 2010). We focus on the epoxides and tetraols that have been proposed to be present in the SOA particles. We characterize the compounds prepared here by a variety of physical measurements and polarization-resolved vibrational sum frequency generation (SFG), paying particular attention to the phase state (condensed vs. vapor) of four epoxides and two tetraols in contact with a fused silica window. We compare the spectral responses from the tetraol and epoxide model compounds with those obtained from the natural and synthetic SOA particle samples that were collected on filter substrates and pressed against a fused silica window and discuss a possible match for the SFG response of one of the epoxides with that of the synthetic SOA particle material. We conclude our work by discussing how the approach described here will allow for the study of the SOA particle formation pathways from first- and second-generation oxidation products by effectively "fast-forwarding" through the initial reaction steps of particle nucleation via a chemically resolved approach aimed at testing the underlying chemical mechanisms of SOA particle formation.

Is the mu-oxo-mu-peroxodiiron intermediate of a ribonucleotide reductase biomimetic a possible oxidant of epoxidation reactions?

PubMed

de Visser, Sam P

2008-01-01

Density functional calculations on a mu-oxo-mu-peroxodiiron complex (1) with a tetrapodal ligand BPP (BPP=N,N-bis(2-pyridylmethyl)-3-aminopropionate) are presented that is a biomimetic of the active site region of ribonucleotide reductase (RNR). We have studied all low-lying electronic states and show that it has close-lying broken-shell singlet and undecaplet (S=0, 5) ground states with essentially two sextet spin iron atoms. In strongly distorted electronic systems in which the two iron atoms have different spin states, the peroxo group moves considerably out of the plane of the mu-oxodiiron group due to orbital rearrangements. The calculated absorption spectra of (1,11)1 are in good agreement with experimental studies on biomimetics and RNR enzyme systems. Moreover, vibrational shifts in the spectrum due to (18)O(2) substitution of the oxygen atoms in the peroxo group follow similar trends as experimental observations. To identify whether the mu-oxo-mu-1,2-peroxodiiron or the mu-oxo-mu-1,1-peroxodiiron complexes are able to epoxidize substrates, we studied the reactivity patterns versus propene. Generally, the reactions are stepwise via radical intermediates and proceed by two-state reactivity patterns on competing singlet and undecaplet spin state surfaces. However, both the mu-oxo-mu-1,2-peroxodiiron and mu-oxo-mu-1,1-peroxodiiron complex are sluggish oxidants with high epoxidation barriers. The epoxidation barriers for the mu-oxo-mu-1,1-peroxodiiron complex are significantly lower than the ones for the mu-oxo-mu-1,2-peroxodiiron complex but still are too high to be considered for catalytic properties. Thus, theory has ruled out two possible peroxodiiron catalysts as oxidants in RNR enzymes and biomimetics and the quest to find the actual oxidant in the enzyme mechanism continues.

3,3',4,4',5-Pentachlorobiphenyl (PCB 126) Decreases Hepatic and Systemic Ratios of Epoxide to Diol Metabolites of Unsaturated Fatty Acids in Male Rats.

PubMed

Wu, Xianai; Yang, Jun; Morisseau, Christophe; Robertson, Larry W; Hammock, Bruce; Lehmler, Hans-Joachim

2016-08-01

Disruption of the homeostasis of oxygenated regulatory lipid mediators (oxylipins), potential markers of exposure to aryl hydrocarbon receptor (AhR) agonists, such as 3,3',4,4',5-pentachlorobiphenyl (PCB 126), is associated with a range of diseases, including nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Here we test the hypothesis that PCB 126 exposure alters the levels of oxylipins in rats. Male Sprague-Dawley rats (5-weeks old) were treated over a 3-month period every 2 weeks with intraperitoneal injections of PCB 126 in corn oil (cumulative doses of 0, 19.8, 97.8, and 390 µg/kg b.w.; 6 injections total). PCB 126 treatment caused a reduction in growth rates at the highest dose investigated, a dose-dependent decrease in thymus weights, and a dose-dependent increase in liver weights. Liver PCB 126 levels increased in a dose-dependent manner, while levels in plasma were below or close to the detection limit. The ratios of several epoxides to diol metabolites formed via the cytochrome P450 (P450) monooxygenase/soluble epoxide hydrolase (sEH) pathway from polyunsaturated fatty acids displayed a dose-dependent decrease in the liver and plasma, whereas levels of oxylipins formed by other metabolic pathways were generally not altered by PCB 126 treatment. The effects of PCB 126 on epoxide-to-diol ratios were associated with an increased CYP1A activity in liver microsomes and an increased sEH activity in liver cytosol and peroxisomes. These results suggest that oxylipins are potential biomarkers of exposure to PCB 126 and that the P450/sEH pathway is a therapeutic target for PCB 126-mediated hepatotoxicity that warrants further attention. © The Author 2016. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. for Permissions, please e-mail: journals.permissions@oup.com.

Theoretical study of photoinduced epoxidation of olefins catalyzed by ruthenium porphyrin.

PubMed

Ishikawa, Atsushi; Sakaki, Shigeyoshi

2011-05-12

Epoxidation of olefin by [Ru(TMP)(CO)(O)](-) (TMP = tetramesitylporphine), which is a key step of the photocatalyzed epoxidation of olefin by [Ru(TMP)(CO)], is studied mainly with the density functional theory (DFT) method, where [Ru(Por)(CO)] is employed as a model complex (Por = unsubstituted porphyrin). The CASSCF method was also used to investigate the electronic structure of important species in the catalytic cycle. In all of the ruthenium porphyrin species involved in the catalytic cycle, the weight of the main configuration of the CASSCF wave function is larger than 85%, suggesting that the static correlation is not very large. Also, unrestricted-DFT-calculated natural orbitals are essentially the same as CASSCF-calculated ones, here. On the basis of these results, we employed the DFT method in this work. Present computational results show characteristic features of this reaction, as follows: (i) The epoxidation reaction occurs via carboradical-type transition state. Neither carbocation-type nor concerted oxene-insertion-type character is observed in the transition state. (ii) Electron and spin populations transfer from the olefin moiety to the porphyrin ring in the step of the C-O bond formation. (iii) Electron and spin populations of the olefin and porphyrin moieties considerably change around the transition state. (iv) The atomic and spin populations of Ru change little in the reaction, indicating that the Ru center keeps the +II oxidation state in the whole catalytic cycle. (v) The stability of the olefin adduct [Ru(Por)(CO)(O)(olefin)](-) considerably depends on the kind of olefin, such as ethylene, n-hexene, and styrene. In particular, styrene forms a stable olefin adduct. And, (vi) interestingly, the difference in the activation barrier among these olefins is small in the quantitative level (within 5 kcal/mol), indicating that this catalyst can be applied to various substrates. This is because the stabilities and electronic structures of both the olefin adduct and the transition state are similarly influenced by the substituent of olefin.

Exogenous Melatonin Mitigates Photoinhibition by Accelerating Non-photochemical Quenching in Tomato Seedlings Exposed to Moderate Light during Chilling

PubMed Central

Ding, Fei; Wang, Meiling; Liu, Bin; Zhang, Shuoxin

2017-01-01

Melatonin plays an important role in tolerance to multiple stresses in plants. Recent studies have shown that melatonin relieves photoinhibition in plants under cold stress; however, the mechanisms are not fully understood. Non-photochemical quenching (NPQ) is a key process thermally dissipating excess light energy that plants employ as a protective mechanism to prevent the over reduction of photosystem II. Here, we report the effects of exogenous melatonin on NPQ and mitigation of photoinhibition in tomato seedlings exposed to moderate light during chilling. In response to moderate light during chilling, the maximum quantum yield (Fv/Fm) and the effective photochemical efficiency (F′v/F′m) of PSII were both substantially reduced, showing severe photoinhibition in tomato seedlings, whereas exogenous application of melatonin effectively alleviated the photoinhibition. Further experiment showed that melatonin accelerated the induction of NPQ in response to moderate light and maintained higher level of NPQ upon longer exposure to light during chilling. Consistent with the increased NPQ was the elevated de-epoxidation state of xanthophyll pigments in melatonin-pretreated seedlings exposed to light during chilling. Enzyme activity assay showed that violaxanthin de-epoxidase (VDE), which catalyzes the de-epoxidation reaction in the xanthophyll cycle, was activated by light and the activity was further enhanced by application of melatonin. Further analysis revealed that melatonin induced the expression of VDE gene in tomato seedlings under moderate light and chilling conditions. Ascorbic acid is an essential cofactor of VDE and the level of it was found to be increased in melatonin-pretreated seedlings. Feeding tomato seedlings with dithiothreitol, an inhibitor of VDE, blocked the effects of melatonin on the de-epoxidation state of xanthophyll pigments and the induction of NPQ. Collectively, these results suggest that exogenous melatonin mitigates photoinhibition by accelerating NPQ through the stimulation of VDE activity and the enhancement of de-epoxidation state of xanthophyll pigments. PMID:28265283

Exogenous Melatonin Mitigates Photoinhibition by Accelerating Non-photochemical Quenching in Tomato Seedlings Exposed to Moderate Light during Chilling.

PubMed

Ding, Fei; Wang, Meiling; Liu, Bin; Zhang, Shuoxin

2017-01-01

Melatonin plays an important role in tolerance to multiple stresses in plants. Recent studies have shown that melatonin relieves photoinhibition in plants under cold stress; however, the mechanisms are not fully understood. Non-photochemical quenching (NPQ) is a key process thermally dissipating excess light energy that plants employ as a protective mechanism to prevent the over reduction of photosystem II. Here, we report the effects of exogenous melatonin on NPQ and mitigation of photoinhibition in tomato seedlings exposed to moderate light during chilling. In response to moderate light during chilling, the maximum quantum yield (Fv/Fm) and the effective photochemical efficiency (F'v/F'm) of PSII were both substantially reduced, showing severe photoinhibition in tomato seedlings, whereas exogenous application of melatonin effectively alleviated the photoinhibition. Further experiment showed that melatonin accelerated the induction of NPQ in response to moderate light and maintained higher level of NPQ upon longer exposure to light during chilling. Consistent with the increased NPQ was the elevated de-epoxidation state of xanthophyll pigments in melatonin-pretreated seedlings exposed to light during chilling. Enzyme activity assay showed that violaxanthin de-epoxidase (VDE), which catalyzes the de-epoxidation reaction in the xanthophyll cycle, was activated by light and the activity was further enhanced by application of melatonin. Further analysis revealed that melatonin induced the expression of VDE gene in tomato seedlings under moderate light and chilling conditions. Ascorbic acid is an essential cofactor of VDE and the level of it was found to be increased in melatonin-pretreated seedlings. Feeding tomato seedlings with dithiothreitol, an inhibitor of VDE, blocked the effects of melatonin on the de-epoxidation state of xanthophyll pigments and the induction of NPQ. Collectively, these results suggest that exogenous melatonin mitigates photoinhibition by accelerating NPQ through the stimulation of VDE activity and the enhancement of de-epoxidation state of xanthophyll pigments.

The Molecular Structure of Epoxide Hydrolase B From And Its Complex With Urea-Based Inhibitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biswal, B.K.; Morisseau, C.; Garen, G.

2009-05-11

Mycobacterium tuberculosis (Mtb), the intracellular pathogen that infects macrophages primarily, is the causative agent of the infectious disease tuberculosis in humans. The Mtb genome encodes at least six epoxide hydrolases (EHs A to F). EHs convert epoxides to trans-dihydrodiols and have roles in drug metabolism as well as in the processing of signaling molecules. Herein, we report the crystal structures of unbound Mtb EHB and Mtb EHB bound to a potent, low-nanomolar (IC(50) approximately 19 nM) urea-based inhibitor at 2.1 and 2.4 A resolution, respectively. The enzyme is a homodimer; each monomer adopts the classical alpha/beta hydrolase fold that composesmore » the catalytic domain; there is a cap domain that regulates access to the active site. The catalytic triad, comprising Asp104, His333 and Asp302, protrudes from the catalytic domain into the substrate binding cavity between the two domains. The urea portion of the inhibitor is bound in the catalytic cavity, mimicking, in part, the substrate binding; the two urea nitrogen atoms donate hydrogen bonds to the nucleophilic carboxylate of Asp104, and the carbonyl oxygen of the urea moiety receives hydrogen bonds from the phenolic oxygen atoms of Tyr164 and Tyr272. The phenolic oxygen groups of these two residues provide electrophilic assistance during the epoxide hydrolytic cleavage. Upon inhibitor binding, the binding-site residues undergo subtle structural rearrangement. In particular, the side chain of Ile137 exhibits a rotation of around 120 degrees about its C(alpha)-C(beta) bond in order to accommodate the inhibitor. These findings have not only shed light on the enzyme mechanism but also have opened a path for the development of potent inhibitors with good pharmacokinetic profiles against all Mtb EHs of the alpha/beta type.« less

Syntheses, Structures, and Binding Constants of Cyclic Ether and Thioether Adducts of Soluble Cadmium(II) Carboxylates. Intermediates in the Homopolymerization of Oxiranes and Thiiranes and in Carbon Dioxide Coupling Processes.

PubMed

Darensbourg, Donald J.; Niezgoda, Sharon A.; Holtcamp, Matthew W.; Draper, Jennifer D.; Reibenspies, Joseph H.

1997-05-21

A synthetic methodology for the preparation of a large variety of eta(3)-HB(3-Phpz)(3)Cd(acetate) adducts is presented which involves replacement of toluene in the eta(3)-HB(3-Phpz)(3)Cd(acetate) solvate complex by the appropriate cyclic ether or cyclic thioether. In this manner, adducts of THF, dioxane, propylene oxide, cyclohexene oxide, and propylene sulfide were isolated. The solid-state structures of several of these complexes were determined by X-ray crystallography, revealing a six-coordinate complex where the acetate ligand is shown to be fairly symmetrically bonded to the cadmium center. In methylene chloride solution, the cyclic ether or thioether readily dissociates to afford the five-coordinate complex, as demonstrated by (113)Cd NMR. A quantitative assessment of the binding of these base adducts of eta(3)-HB(3-Phpz)(3)Cd(acetate) was determined by measuring the temperature dependence of the equilibrium constants for the five- and six-coordinate derivatives. The presence of one sharp (113)Cd resonance in this equilibrium mixture is indicative of rapid intermolecular exchange between the five- and six-coordinate complexes when compared to the chemical shift differences in these two species ( approximately 6600 Hz at 89 MHz). The order established for ether binding is THF > dioxane > propylene sulfide > cyclohexene oxide >/= propylene oxide, with DeltaH degrees and DeltaS degrees spanning the ranges -27.7 to 24.3 kJ/mol and -89.7 to -94.1 J/(mol K). The epoxide and thioepoxide adducts were shown to serve as models for the initiation step in the copolymerization of epoxides with carbon dioxide catalyzed by metal carboxylates. That is, the carboxylate ligand was shown to ring-open the epoxide or thioepoxide, subsequently affording polyethers or polythioethers with ester end groups. By way of contrast, in the presence of CO(2) and epoxides, this system led to cyclic carbonate production.

Combination of natural fiber Boehmeria nivea (ramie) with matrix epoxide for bullet proof vest body armor

NASA Astrophysics Data System (ADS)

Anggoro, Didi Dwi; Kristiana, Nunung

2015-12-01

Ballistic protection equipment, such as a bulletproof vest, is a soldier's most important means of preserving life and survivability in extreme combat conditions. The bulletproof vests are designed to protect the user's chest from injury without disturbing the ability to perform his duties. Aromatic polyamide or aramid fibers known under the trade name Kevlar, Trawon and so is synthetic fiber materials commonly used in the manufacture of bulletproof vests. This synthetic fibers have high tensile strength and ductility. Kevlar is expensive and imported material. In this study, will introduce local natural raw materials, ramie fiber (Boehmeria nivea) which is cheaper and environmentally friendly. It has enough tenacity and tensile strength as a bulletproof vest. This experiment uses two panels, there are Panel A as front surface of Panel B. Panel A is a combination of ramie and epoxide matrix, while panel B is only ramie. From several variations of experimental combinations between Panel A and Panel B, optimal combination obtained with 16 layers of panel A and 31-34 layers of panel B which is able to protect againts cal. 7.65 mm × 17 mm (.32 ACP) bullet fired through pistol .32 Pindad from a distance of 20 meters. Panel with a size of 20 cm × 20 cm has a total thickness between 12,922 to13,745 mm and a total weight between 506,26 to 520,926gram. Scanning electron microscopy (SEM) observations indicated that the porosity and surface area of the ramie fiber is smooth, fiber surfaces showed topography with micropores. SEM also showed well-arranged structure of fibers bonding. Energy Dispersive X-ray (EDX) analysis indicated 100 % carbon contents in ramie fiber. Test result indicates that panel from composite ramie-epoxide can reach the level 1of International Standard of NIJ - 010104. Compared to panel from polyester fiber, the panel from composite ramie-epoxide (0,50-0,52 kg) is lighter weight than panel polyester fiber (1,642 kg).

Omeprazole increases the efficacy of a soluble epoxide hydrolase inhibitor in a PGE{sub 2} induced pain model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goswami, Sumanta Kumar; Inceoglu, Bora; Yang, Jun

Epoxyeicosatrienoic acids (EETs) are potent endogenous analgesic metabolites produced from arachidonic acid by cytochrome P450s (P450s). Metabolism of EETs by soluble epoxide hydrolase (sEH) reduces their activity, while their stabilization by sEH inhibition decreases both inflammatory and neuropathic pain. Here, we tested the complementary hypothesis that increasing the level of EETs through induction of P450s by omeprazole (OME), can influence pain related signaling by itself, and potentiate the anti-hyperalgesic effect of sEH inhibitor. Rats were treated with OME (100 mg/kg/day, p.o., 7 days), sEH inhibitor TPPU (3 mg/kg/day, p.o.) and OME (100 mg/kg/day, p.o., 7 days) + TPPU (3 mg/kg/day,more » p.o., last 3 days of OME dose) dissolved in vehicle PEG400, and their effect on hyperalgesia (increased sensitivity to pain) induced by PGE{sub 2} was monitored. While OME treatment by itself exhibited variable effects on PGE{sub 2} induced hyperalgesia, it strongly potentiated the effect of TPPU in the same assay. The significant decrease in pain with OME + TPPU treatment correlated with the increased levels of EETs in plasma and increased activities of P450 1A1 and P450 1A2 in liver microsomes. The results show that reducing catabolism of EETs with a sEH inhibitor yielded a stronger analgesic effect than increasing generation of EETs by OME, and combination of both yielded the strongest pain reducing effect under the condition of this study. - Highlights: • The soluble epoxide hydrolase (sEH) inhibitor TPPU is anti-hyperalgesic. • Omeprazole potentiates the anti-hyperalgesic actions of TPPU. • This potentiation is associated with increased P450 activity. • The potentiation is associated with an increase in fatty acid epoxide/diol ratio. • Joint use of sEH inhibitors and P450 inducers could result in drug–drug interactions.« less

[Production technology and use of composite materials in the aeronautics industry, risks and pathology in the manufacturing workers].

PubMed

Franco, G; Candura, F

1985-01-01

The type and applications of composite materials have increased greatly during the last forty years, particularly in the aircraft and aerospace industries. The foreseeable increase of the employment of composite materials in future needs an adequate engagement in finding out health risks involved with technological processes. Composite materials - considered as a close union between a continuous glass, aramid or carbon reinforcing fibre and a epoxy matrix - present several advantages over traditional materials. Structural epoxy adhesives are defined as complex formulated systems. By mixing a large number of ingredients a formulated resin is obtained, which represents the start of the production process for adhesive manufacture. The most important ingredients such as catalysts, accelerators, the groups of epoxy monomers and oligomers, additives most used and their role into the epoxy matrices are illustrated. Of the various technologies existing for the fabrication of aircraft structures the one so called "vacuum bag" is described. The knowledge of the chemical composition of the substances used in the production of composite materials and epoxy adhesives allows to verify the possible existence of hazard for workers health. Among the potentially dangerous chemicals, epoxy monomers and oligomers, catalysts, accelerators are to be considered. The metabolism and the mechanisms of toxicity of epoxides are summarized. However the toxic effects of most epoxides are far from being wholly investigated. In man epoxides ingestion, inhalation or absorption through the skin can lead to several toxic effects: irritation and sensitisation, alterations of liver and nervous function. Finally some epoxides are considered to be carcinogenic in animals and in man; however for many compounds, the results are not yet conclusive. From what it is said above come out the necessity of a careful sanitary control of the workers exposed to these hazards, control that is made difficult by the lack of adequate biological indices for the risks found.

Exploring the synthesis and characterization of nanoenergetic materials from sol-gel chemistry

NASA Astrophysics Data System (ADS)

Walker, Jeremy D.

Nanoenergetic composite materials have been synthesized by a sol-gel chemical process where the addition of a weak base molecule induces the gelation of a hydrated metal salt solution. A proposed 'proton scavenging' mechanism, where a weak base molecule extracts a proton from the coordination sphere of the hydrated iron (III) complex in the gelation process to form iron (III) oxide/hydroxide, FeIIIxOyHz, has been confirmed for the weak base propylene oxide (PO), a 1,2 epoxide, as well as for the weak bases tetrahydrofuran (THF), a 1,4 epoxide, and pyridine, a heterocyclic nitrogen-containing compound. Gelation mechanisms for the formation of FeIIIxOyHz from THF and pyridine have been presented and confirmed through pH, XPS, and IR studies. THF follows a similar mechanism as PO, where the epoxide extracts a proton from the coordination sphere of the hydrated iron complex forming a protonated epoxide, which then undergoes irreversible ring-opening after reaction with a nucleophile in solution. Pyridine also extracts a proton from the hydrated metal complex, however, the stable six-membered molecule has low associated ring strain and does not endure ring-opening. Energetic properties for the Fe2O3/Al and RuO 2/Al sol-gel synthesized systems are also presented. Sol-gel chemistry synthesizes x-ray amorphous oxide matrices which contain substantial quantities of residual water and organic species. The iron (III) matrix, formed from the addition of a weak base epoxide molecule to a hydrated iron (III) nitrate solution, consists of stoichiometric Fe2O3, FeO(OH), and Fe(OH)3 and can only definitely be described as of Fe IIIxOyHz. XPS characterization of the metal oxide matrix synthesized from the addition of the weak base propylene oxide to a hydrated ruthenium (III) chloride solution corresponds to that of hydrous ruthenium (IV) oxide. Fe2O3/Al energetic systems were synthesized from the epoxides PO, trimethylene oxide (TMO) and 3,3 dimethyl oxetane (DMO). Energetic systems formed from each epoxide were each synthesized with different components, including: varying concentrations of nano-scale Al, micron Al, and carbon nanotubes. Surface area analysis of the synthesized matrices shows a direct correlation between the surface area of the iron (III) oxide matrix and the quantified exothermic heat of reaction of the energetic material due to the magnitude of the interfacial surface area contact between the iron (III) oxide matrix and the aluminum particles. The Fe2O3(PO)/Al systems possess the highest heat of reaction values due to the oxide surface area available for contact with the aluminum particles. Also, within systems, 1:1 Fe:nano Al samples possess the highest heat of reaction. Samples with nano-scale Al particles start reaction at 430°C, before the melting point of Al, whereas samples containing micron-Al do not react until ˜800°C, after the melting point of Al. The RuO2/Al energetic systems behave differently dependent on the atmosphere the sample is heated. Heating the RuO2/Al samples in an inert atmosphere results in the complete reduction of the ruthenium oxide matrix to Ru(0) before reaction with the aluminum particles. This results in the exothermic formation of RuxAly intermetallics, with the stoichiometry dependent on the initial Ru:Al concentration. However, heating the samples in an oxygen-rich atmosphere results in an exothermic reaction between RuO2 and Al. Post-reaction analysis of these samples reveals the sole existence of ruthenium (IV) oxide as the exothermic reaction vaporizes the aluminum particles.

Catalytic performance of Mn 3O 4 and Co 3O 4 nanocrystals prepared by sonochemical method in epoxidation of styrene and cyclooctene

NASA Astrophysics Data System (ADS)

Askarinejad, Azadeh; Bagherzadeh, Mojtaba; Morsali, Ali

2010-09-01

A simple sonochemical method was developed to synthesis uniform sphere-like Co 3O 4 and Mn 3O 4 nanocrystals. Epoxidation of styrene and cyclooctene by anhydrous tert-butyl hydroperoxide over the prepared Co 3O 4 and Mn 3O 4 nanocatalysts was investigated. The results of conversion activity were compared with bulk Co 3O 4 and Mn 3O 4. Under optimized reaction conditions, the nanocatalysts showed a superior catalytic performance as compared to the bulk catalysts. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface area, were used to characterize and investigate the nanocatalysts.

Chlordane in birds: A study of lethal residues and loss rates

USGS Publications Warehouse

Stickel, L.F.; Stickel, W.H.; McArthur, R.D.; Hughes, D.L.

1979-01-01

Lethal residues of heptachlor epoxide in brains of birds fed heptachlor ranged from 9 to 27 ppm wet weight; residues of oxychlordane in birds fed oxychlordane ranged from 6 to 16 ppm; both were diagnostically distinct from those in equally exposed survivors. In birds fed chlordane, brains of those that died contained less than 30% of these amounts but also contained trans-nonachlor, compound C, and compound E, suggesting additivity or synergism. In birds fed chlordane followed by untreated feed, oxychlordane was most persistent; trans-nonachlor, heptachlor epoxide, and compounds C and E followed, in that order. Loss rates were best expressed on a wet weight basis because lipid-based rates were distorted by seasonal weight gains.

A new approach to the side chain formation of 24-alkyl-22-hydroxy steroids: application to the preparation of early brassinolide biosynthetic precursors.

PubMed

Hurski, Alaksiej L; Zhabinskii, Vladimir N; Khripach, Vladimir A

2012-06-01

A new synthetic route to 22S-hydroxy-24R-methyl steroids has been developed and applied for the preparation of cathasterone, (22S)-hydroxycampesterol, and 6-deoxocathasterone, which are precursors in the early stages of the biosynthesis of brassinolide. The construction of the steroid side chain with the correct stereochemistry at C-24 is based on the use of Claisen rearrangement. The introduction of the 22-hydroxyl group has been achieved by epoxidation of the Δ(22)-double bond, nucleophilic opening of the intermediate mesyl epoxide with sodium sulfide, and desulfurization of the formed tetrahydrothiophenes with Raney nickel. Copyright © 2012 Elsevier Inc. All rights reserved.

Methacrylate gels with epoxide groups as supports for immobilization of enzymes in pH range 3-12.

PubMed

Turková, J; Bláha, K; Malaníková, M; Vancurová, D; Svec, F; Kálal, J

1978-05-11

Glycidyl methacrylate gels are carriers suitable for attachment of enzymes and for use in affinity chromatography. Experiments on the coupling of glycyl-L-leucine and acetyl-L-leucine to these gels have shown a high pH-dependence of the bond formation between the support and the alpha-amino group (pH optimum 9.7); the coupling reaction between the epoxide group and the carboxyl group is practically pH-independent. Serum albumin and trypsin were attached to a greater extent in acidic than in alkaline media. The effects of time and temperature were also studied. The catalytic action of immobilized trypsin, as well as its use for affinity chromatography of trypsin inhibitor, were studied.

Highly efficient sulfated Zr-doped titanoniobate nanoplates for the alcoholysis of styrene epoxide at room temperature

NASA Astrophysics Data System (ADS)

Zhang, Lihong; Hu, Chenhui; Mei, Weigang; Zhang, Junfeng; Cheng, Liyuan; Xue, Nianhua; Ding, Weiping; Chen, Jing; Hou, Wenhua

2015-12-01

Sulfated Zr-doped titanoniobate nanoplates were prepared and evaluated as a solid acid catalyst in the alcoholysis of styrene epoxide at room temperature. Compared with undoped and Zr-doped nanosheets, the resulting sulfated catalyst exhibited an excellent catalytic performance to afford corresponding β-alkoxyalcohols (99% yield with methanol as nucleophile in only 10 min) due to the high dispersion of zirconia species on nanosheets, appropriate Lewis acid strength and amount from the strong interaction between zirconia and sulfate species, and greatly increased surface area arisen from the exfoliation and house-of-cards restacking of nanosheets. The corresponding catalytic mechanism was proposed and discussed. The obtained material may act as a promising catalyst in many acid catalyzed reactions.

Novel radiation-resistant glass fiber/epoxy composite for cryogenic insulation system

NASA Astrophysics Data System (ADS)

Wu, Z. X.; Zhang, H.; Yang, H. H.; Chu, X. X.; Li, L. F.

2010-08-01

A new radiation-resistant epoxy resin system was developed that has low viscosity and long working time at 45 °C. The system consists of triglycidyl-p-aminophenol (TGPAP) epoxide, isopropylidenebisphenol bis[(2-glycidyloxy-3-n-butoxy)-1-propylether] (IPBE) epoxide and diethyl toluene diamine (DETD). Boron-free glass fiber composites of epoxy resin with different ratio of TGPAP/IPBE/DETD were prepared by vacuum press impregnation. The ratio of TGPAP/IPBE affected the working time and the viscosity at the impregnation. The mechanical properties of the composites at 300 K and at 77 K were measured before and after 60Co γ-ray irradiation of 1 MGy at ambient temperature. The γ-ray radiation scarcely affected the properties of the composites.

Zirconium(IV)-Catalyzed Ring Opening of on-DNA Epoxides in Water.

PubMed

Fan, Lijun; Davie, Christopher P

2017-05-04

DNA-encoded library technology (ELT) has spurred wide interest in the pharmaceutical industry as a powerful tool for hit and lead generation. In recent years a number of "DNA-compatible" chemical modifications have been published and used to synthesize vastly diverse screening libraries. Herein we report a newly developed, zirconium tetrakis(dodecyl sulfate) [Zr(DS) 4 ] catalyzed ring-opening of on-DNA epoxides in water with amines, including anilines. Subsequent cyclization of the resulting on-DNA β-amino alcohols leads to a variety of biologically interesting, nonaromatic heterocycles. Under these conditions, a library of 137 million on-DNA β-amino alcohols and their cyclization products was assembled. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of epoxidized soybean oil on mechanical and rheological properties of poly(butylene succinate)/lignin via vane extruder

NASA Astrophysics Data System (ADS)

Liu, Huanyu; Huang, Zhaoxia; Qu, Jinping; Meng, Cong

2016-03-01

Epoxidized Soybean Oil (ESO) have been used as the compatilizer in the Poly (butylene succinate)/lignin (PBS/lignin) composites. Compatibilized composites were fabricated by a novel vane extruder (VE) which can generate global and dynamic elongational flow. The effects of ESO on the mechanical, rheological properties and morphology of PBS/lignin were studied. The results indicated that the use of ESO had plasticizing effect on the matrix PBS while the addition reduced tensile strength. From SEM micrographs it could be clearly observed that there was a better interfacial adhesion between lignin and matrix. Meanwhile, rheological tests showed the incorporation of ESO improved its Newtonian behavior and can enhance PBS's flexibility.

Ionic liquid syntheses via click chemistry: expeditious routes toward versatile functional materials.

PubMed

Mirjafari, Arsalan

2018-03-25

Since the introduction of click chemistry by K. B. Sharpless in 2001, its exploration and exploitation has occurred in countless fields of materials sciences in both academic and industrial spheres. Click chemistry is defined as an efficient, robust, and orthogonal synthetic platform for the facile formation of new carbon-heteroatom bonds, using readily available starting materials. Premier examples of click reactions are copper(i)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC) and the thiol-X (X = ene and yne) coupling reactions to form C-N and C-S bonds, respectively. The emphasis of this review is centered on the rapidly expanding area of click chemistry-mediated synthesis of functional ionic liquids via CuAAC, thiol-X and oxime formation, and selected examples of nucleophilic ring-opening reactions, while offering some thoughts on emerging challenges, opportunities and ultimately the evolution of this field. Click chemistry offers tremendous opportunities, and introduces intriguing perspectives for efficient and robust generation of tailored task-specific ionic liquids - an important class of soft materials.

Rate of Interfacial Electron Transfer through the 1,2,3-Triazole Linkage

PubMed Central

Devaraj, Neal K.; Decreau, Richard A.; Ebina, Wataru; Collman, James P.; Chidsey, Christopher E. D.

2012-01-01

The rate of electron transfer is measured to two ferrocene and one iron tetraphenylporphyrin redox species coupled through terminal acetylenes to azide-terminated thiol monolayers by the Cu(I)-catalyzed azide–alkyne cycloaddition (a Sharpless “click” reaction) to form the 1,2,3-triazole linkage. The high yield, chemoselectivity, convenience, and broad applicability of this triazole formation reaction make such a modular assembly strategy very attractive. Electron-transfer rate constants from greater than 60,000 to 1 s−1 are obtained by varying the length and conjugation of the electron-transfer bridge and by varying the surrounding diluent thiols in the monolayer. Triazole and the triazole carbonyl linkages provide similar electronic coupling for electron transfer as esters. The ability to vary the rate of electron transfer to many different redox species over many orders of magnitude by using modular coupling chemistry provides a convenient way to study and control the delivery of electrons to multielectron redox catalysts and similar interfacial systems that require controlled delivery of electrons. PMID:16898751

Synthesis of avibactam derivatives and activity on β-lactamases and peptidoglycan biosynthesis enzymes of mycobacteria.

PubMed

Edoo, Zainab; Iannazzo, Laura; Compain, Fabrice; Li de la Sierra Gallay, Inès; van Tilbeurgh, Herman; Fonvielle, Matthieu; Bouchet, Flavie; Le Run, Eva; Mainardi, Jean-Luc; Arthur, Michel; Ethève-Quelquejeu, Mélanie; Hugonnet, Jean-Emmanuel

2018-03-30

There is a renewed interest for β-lactams for treating infections due to Mycobacterium tuberculosis and M. abscessus since their β-lactamases are inhibited by classical (clavulanate) or new generation (avibactam) inhibitors, respectively. Here, we report access to an azido derivative of the diazabicyclooctane (DBO) scaffold of avibactam for functionalization by the Huisgen-Sharpless cycloaddition reaction. The amoxicillin-DBO combinations were active indicating that the triazole ring is compatible with drug penetration (minimal inhibitory concentration of 16 µg/ml for both species). Mechanistically, β-lactamase inhibition was not sufficient to account for the potentiation of amoxicillin by DBOs. Thus, we investigated the latter compounds as inhibitors of L,D-transpeptidases (LDTs), which are the main peptidoglycan polymerases in mycobacteria. The DBOs acted as slow-binding inhibitors of LDTs by S-carbamoylation indicating that optimization of DBOs for LDT inhibition is an attractive strategy to obtain drugs selectively active on mycobacteria. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Short- and long-term modulation of the lutein epoxide and violaxanthin cycles in two species of the Lauraceae: sweet bay laurel (Laurus nobilis L.) and avocado (Persea americana Mill.).

PubMed

Esteban, R; Jiménez, M S; Morales, D; Jiménez, E T; Hormaetxe, K; Becerril, J M; Osmond, B; García-Plazaola, J I

2008-05-01

Short- and long-term responses of the violaxanthin (V) and lutein epoxide (Lx) cycles were studied in two species of Lauraceae: sweet bay laurel (Laurus nobilis L.) and avocado (Persea americana L.). The Lx content exceeded the V content in shade leaves of both species. Both Lx and V were de-epoxidised on illumination, but only V was fully restored by epoxidation in low light. Violaxanthin was preferentially de-epoxidised in low light in L. nobilis. This suggests that Lx accumulates with leaf ageing, partly because its conversion to lutein is limited in shade. After exposure to strong light, shade leaves of avocado readjusted the total pools of alpha- and beta-xanthophyll cycles by de novo synthesis of antheraxanthin, zeaxanthin and lutein. This occurred in parallel with a sustained depression of F(v)/F(m). In Persea indica, a closely related but low Lx species, F(v)/F(m) recovered faster after a similar light treatment, suggesting the involvement of the Lx cycle in sustained energy dissipation. Furthermore, the seasonal correlation between non-reversible Lx and V photoconversions and pre-dawn F(v)/F(m) in sun leaves of sweet bay supported the conclusion that the Lx cycle is involved in a slowly reversible downregulation of photosynthesis analogous to the V cycle.

The coupling of carbon dioxide and epoxides by phenanthroline derivatives containing different Cu(II) complexes as catalyst

NASA Astrophysics Data System (ADS)

Kilic, Ahmet; Palali, Ahmet Arif; Durgun, Mustafa; Tasci, Zeynep; Ulusoy, Mahmut

2013-09-01

A series of the mononuclear Cu(II) metal complexes containing the ligand Bdppz [(9a,13a-dihydro-4,5,9,14-tetraaza-benzo[b]triphenylene-11-yl)-phenyl-methanone] (L1) and Aqphen [(12,17-dihydronaphthol[2,3-h]dipyrido[3,2-a:2‧,3‧-c]-phenazine-12,17-dione)] (L2) were synthesized and used as catalyst for the coupling of carbon dioxide (CO2) and liquid epoxide which served as both reactant and solvent. Dimethylamino pyridine (DMAP) was used as co-catalyst. The yields of epoxides to corresponding cyclic carbonates were determined by comparing the ratio of product to substrate in the 1H NMR spectrum of an aliquot of the reaction mixture. The mononuclear Cu(II) complexes of these ligands were synthesized by treating an ethanol solvent of the appropriate ligand with a different molar amount of CuCl2·2H2O. The Cu(II) complexes were characterized by FT-IR, UV-Vis, elemental analysis, melting point analysis, mass spectra, molar conductivity measurements and magnetic susceptibility techniques. The reaction of the Bdppz and Aqphen ligands in a 1:1, 1:2 or 1:3 mole ratio with CuCl2·2H2O afforded ionic Cu(II) complexes in the presence of Et3N.

Isolation and characterization of 9-lipoxygenase and epoxide hydrolase 2 genes: Insight into lactone biosynthesis in mango fruit (Mangifera indica L.).

PubMed

Deshpande, Ashish B; Chidley, Hemangi G; Oak, Pranjali S; Pujari, Keshav H; Giri, Ashok P; Gupta, Vidya S

2017-06-01

Uniqueness and diversity of mango flavour across various cultivars are well known. Among various flavour metabolites lactones form an important class of aroma volatiles in certain mango varieties due to their ripening specific appearance and lower odour detection threshold. In spite of their biological and biochemical importance, lactone biosynthetic pathway in plants remains elusive. Present study encompasses quantitative real-time analysis of 9-lipoxygenase (Mi9LOX), epoxide hydrolase 2 (MiEH2), peroxygenase, hydroperoxide lyase and acyl-CoA-oxidase genes during various developmental and ripening stages in fruit of Alphonso, Pairi and Kent cultivars with high, low and no lactone content and explains their variable lactone content. Study also covers isolation, recombinant protein characterization and transient over-expression of Mi9LOX and MiEH2 genes in mango fruits. Recombinant Mi9LOX utilized linoleic and linolenic acids, while MiEH2 utilized aromatic and fatty acid epoxides as their respective substrates depicting their role in fatty acid metabolism. Significant increase in concentration of δ-valerolactone and δ-decalactone upon Mi9LOX over-expression and that of δ-valerolactone, γ-hexalactone and δ-hexalactone upon MiEH2 over-expression further suggested probable involvement of these genes in lactone biosynthesis in mango. Copyright © 2017 Elsevier Ltd. All rights reserved.

Carbamazepine and its 10,11-epoxide metabolite in acute mania: clinical and pharmacokinetic correlates.

PubMed

Petit, P; Lonjon, R; Cociglio, M; Sluzewska, A; Blayac, J P; Hue, B; Alric, R; Pouget, R

1991-01-01

The study was designed to investigate the antimanic profile of carbamazepine as a first-line drug in affective or schizoaffective disorders, to correlate the clinical efficacy with the plasma level of carbamazepine and its 10,11-epoxide metabolite, and to test the potential value of monitoring the salivary level. It was administered alone for 3 weeks to 21 acute manic inpatients. During the first week, the dosage was rapidly increased to 800 mg/day in order to produce steady-state plasma levels of carbamazepine on Day 7. The individual dose was then adjusted to maintain the therapeutic range of 8-12 mg/l. Plasma and saliva levels of the drug and its metabolite, as well as clinical status were assessed weekly. Overall, there was 62% globally improved patients and 77% in affective disorders. The improvement of manic symptoms was significantly lower in schizoaffective than in affective disorders, whereas the dropout rate and the need for antipsychotic medication was higher in the former group. The antimanic response was significantly correlated with the plasma levels both of carbamazepine and its epoxide metabolite, with a time-lag consistent with a delayed drug effect. Drug and metabolite concentrations in saliva were close to their plasma free fraction and were strongly correlated with their plasma levels, suggesting the potential value of salivary drug monitoring.

Insights into carotenoid dynamics in non-foliar photosynthetic tissues of avocado.

PubMed

Esteban, Raquel; Olascoaga, Beñat; Becerril, José M; García-Plazaola, José I

2010-09-01

Leaves are the main photosynthetically active tissues in most plants. However, stems and fruits are also important for the overall carbon balance of the plant because of their contribution to fixation of the CO(2) released by respiration. Photosynthesis could not be possible without a complete set of photoprotection mechanisms, which include the ubiquitous violaxanthin (V) cycle and the taxonomically restricted lutein epoxide (Lx) cycle. In this work, we characterise carotenoid stoichiometry in photosynthetic stems and fruits of avocado in comparison with that of leaves and specifically whether Lx is present in these tissues and also whether it is involved in a light-driven cycle. Avocado was selected as model species to study whether both cycles were functional in non-foliar photosynthetic structures (stems and fruits). An unusual pigment composition was observed in avocado fruit, with a high content of cis-V and cis-Lx, suggesting a different photosynthetic function. In stems, both xanthophylls de-epoxidated upon illumination, but only V recovered in the dark, indicating the existence of a possible 'truncated' Lx cycle. Lx in fruits was de-epoxidated only when its pool was higher than a threshold of 30 mmol mol(-1) chlorophyll, indicating a high non-photoconvertible pool of Lx. We conclude that, at least in stems, the dynamic regulation of photosynthetic activity could also depend on the Lx cycle.

Microdroplets Accelerate Ring Opening of Epoxides

NASA Astrophysics Data System (ADS)

Lai, Yin-Hung; Sathyamoorthi, Shyam; Bain, Ryan M.; Zare, Richard N.

2018-05-01

The nucleophilic opening of an epoxide is a classic organic reaction that has widespread utility in both academic and industrial applications. We have studied the reaction of limonene oxide with morpholine to form 1-methyl-2-morpholino-4-(prop-1-en-2-yl) cyclohexan-1-ol in bulk solution and in electrosprayed microdroplets with a 1:1 v/ v water/methanol solvent system. We find that even after 90 min at room temperature, there is no product detected by nuclear magnetic resonance spectroscopy in bulk solution whereas in room-temperature microdroplets (2-3 μm in diameter), the yield is already 0.5% in a flight time of 1 ms as observed by mass spectrometry. This constitutes a rate acceleration of 105 in the microdroplet environment, if we assume that as much as 5% of product is formed in bulk after 90 min of reaction time. We examine how the reaction rate depends on droplet size, solvent composition, sheath gas pressure, and applied voltage. These factors profoundly influence the extent of reaction. This dramatic acceleration is not limited to just one system. We have also found that the nucleophilic opening of cis-stilbene oxide by morpholine is similarly accelerated. Such large acceleration factors in reaction rates suggest the use of microdroplets for ring opening of epoxides in other systems, which may have practical significance if such a procedure could be scaled. [Figure not available: see fulltext.

Kinetic and Mechanistic Study of the pH-Dependent Activation (Epoxidation) of Prodrug Treosulfan Including the Reaction Inhibition in a Borate Buffer.

PubMed

Romański, Michał; Ratajczak, Whitney; Główka, Franciszek

2017-07-01

A prodrug treosulfan (T) undergoes a pH-dependent activation to epoxide derivatives. The process seems to involve an intramolecular Williamson reaction (IWR) but clear kinetic evidence is lacking. Moreover, a cis-diol system present in the T structure is expected to promote complexation with boric acid. As a result, the prodrug epoxidation would be inhibited; however, this phenomenon has not been investigated. In this article, the effect of pH on the kinetics of T conversion to its monoepoxide was studied from a mechanistic point of view. Also, the influence of boric acid on the reaction kinetics was examined. The rate constants observed for the activation of T (k obs ) in acetate, phosphate, and carbonate buffers satisfied the equation logk obs  = -7.48 + 0.96 pH. The reaction was inhibited in the excess of boric acid over T, and the k obs decreased with increasing borate buffer concentration. The experimental results were consistent with the inhibition model that included the formation of a tetrahedral, anionic T-boric acid monoester. To conclude, in nonborate buffers, the T activation to (2S,3S)-1,2-epoxybutane-3,4-diol 4-methanesulfonate follows IWR mechanism. A borate buffer changes the reaction kinetics and complicates kinetic analysis. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Epigallocatechin-3-gallate reduces DNA damage induced by benzo[a]pyrene diol epoxide and cigarette smoke condensate in human mucosa tissue cultures.

PubMed

Baumeister, Philipp; Reiter, Maximilian; Kleinsasser, Norbert; Matthias, Christoph; Harréus, Ulrich

2009-06-01

Although epidemiological studies indicate cancer preventive effects of diets rich in fruit and vegetables, large clinical intervention studies conducted to evaluate dietary supplementation with micronutrients, mostly vitamins, showed disappointing results in large parts. In contrast, there is encouraging epidemiologic data indicating great chemopreventive potential of a large group of phytochemicals, namely polyphenols. This study shows the DNA protective effect epigallocatechin-3-gallate, a tea catechin, and one of the best-studied substances within this group, on carcinogen-induced DNA fragmentation in upper aerodigestive tract cells. Cell cultures from fresh oropharyngeal mucosa biopsies were preincubated with epigallocatechin-3-gallate in different concentrations before DNA damage was introduced with the metabolically activated carcinogen benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide or cigarette smoke condensate. Effects on resulting DNA fragmentation were measured using the alkaline single-cell microgel electrophoresis (comet assay). Epigallocatechin-3-gallate significantly reduced benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide-induced DNA damage by up to 51% (P<0.001). Fragmentation induced by cigarette smoke condensate could be lowered by 47% (P<0.001). Data suggest a cancer preventive potential of epigallocatechin-3-gallate as demonstrated on a subcellular level. An additional mechanism of tea catechin action is revealed by using a primary mucosa culture model.

The hydrolysis of epoxides catalyzed by inorganic ammonium salts in water: kinetic evidence for hydrogen bond catalysis.

PubMed

Nozière, B; Fache, F; Maxut, A; Fenet, B; Baudouin, A; Fine, L; Ferronato, C

2018-01-17

Naturally-occurring inorganic ammonium ions have been recently reported as efficient catalysts for some organic reactions in water, which contributes to the understanding of the chemistry in some natural environments (soils, seawater, atmospheric aerosols, …) and biological systems, and is also potentially interesting for green chemistry as many of their salts are cheap and non-toxic. In this work, the effect of NH 4 + ions on the hydrolysis of small epoxides in water was studied kinetically. The presence of NH 4 + increased the hydrolysis rate by a factor of 6 to 25 compared to pure water and these catalytic effects were shown not to result from other ions, counter-ions or from acid or base catalysis, general or specific. The small amounts of amino alcohols produced in the reactions were identified as the actual catalysts by obtaining a strong acceleration of the reactions when adding these compounds directly to the epoxides in water. Replacing the amino alcohols by other strong hydrogen-bond donors, such as trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) gave the same results, demonstrating that the kinetics of these reactions was driven by hydrogen-bond catalysis. Because of the presence of many hydrogen-bond donors in natural environments (for instance amines and hydroxy-containing compounds), hydrogen-bond catalysis is likely to contribute to many reaction rates in these environments.

MODULATION BY IONIC STRENGTH AND SUPERHELICITY OF BENZO[a]PYRENE DIOL EPOXIDE INDUCED DNA ALKYLATION AND UNWINDING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamper, Howard B.; Straub, Kenneth; Calvin, Melvin

Superhelical and partially relaxed SV40 DNA were reacted in vitro with (+)7{beta}, 8{alpha}-dihydroxy-9{alpha},10{alpha}-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BaP diol epoxide). The modified DNA contained N{sup 2} guanine and N{sup 6} adeninte hydrocarbon adducts in the ratio 86:14. Superhelical SV40 DNA was approximately 6% more susceptible to modification than partially relaxed viral DNA. Counterions inhibited DNA alkylation by up to 90%, Mg{sup 2+} being 50-fold more effective than Na{sup +}. The sensitivity of covalent binding to helix stability is consistent with a reaction complex in which BaP diol epoxide is intercalated. The superhelical density of the modified DNA substrates was determined electrophoretically relative to partiallymore » relaxed standards and an unwinding angle for the hydrocarbon adducts was calculated. The angle was dependent upon the superhelicity of the DNA molecule and ranged from 330{sup o} to 30{sup o}. This data indicates that the modified base pairs are disrupted and, in the presence of torsional strain, act as centers for the further denaturation of up to 8 adjacent base pairs. In the absence of such strain the alkylation sites have an ordered structure with the attached hydrocarbon probably oriented in the minor or major groove of the helix.« less

Ethylene Epoxidation with Nitrous Oxide over Fe-BTC Metal-Organic Frameworks: A DFT Study.

PubMed

Maihom, Thana; Choomwattana, Saowapak; Wannakao, Sippakorn; Probst, Michael; Limtrakul, Jumras

2016-11-04

The epoxidation of ethylene with N 2 O over the metal-organic framework Fe-BTC (BTC=1,3,5-benzentricarboxylate) is investigated by means of density functional calculations. Two reaction paths for the production of ethylene oxide or acetaldehyde are systematically considered in order to assess the efficiency of Fe-BTC for the selective formation of ethylene oxide. The reaction starts with the decomposition of N 2 O to form an active surface oxygen atom on the Fe site of Fe-BTC, which subsequently reacts with an ethylene molecule to form an ethyleneoxy intermediate. This intermediate can then be selectively transformed either by 1,2-hydride shift into the undesired product acetaldehyde or into the desired product ethylene oxide by way of ring closure of the intermediate. The production of ethylene oxide requires an activation energy of 5.1 kcal mol -1 , which is only about one-third of the activation energy of acetaldehyde formation (14.3 kcal mol -1 ). The predicted reaction rate constants for the formation of ethylene oxide in the relevant temperature range are approximately 2-4 orders of magnitude higher than those for acetaldehyde. Altogether, the results suggest that Fe-BTC is a good candidate catalyst for the epoxidation of ethylene by molecular N 2 O. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Binding on Enantioselectivity of Epoxide Hydrolase.

PubMed

Zaugg, Julian; Gumulya, Yosephine; Bodén, Mikael; Mark, Alan E; Malde, Alpeshkumar K

2018-03-26

Molecular dynamics simulations and free energy calculations have been used to investigate the effect of ligand binding on the enantioselectivity of an epoxide hydrolase (EH) from Aspergillus niger. Despite sharing a common mechanism, a wide range of alternative mechanisms have been proposed to explain the origin of enantiomeric selectivity in EHs. By comparing the interactions of ( R)- and ( S)-glycidyl phenyl ether (GPE) with both the wild type (WT, E = 3) and a mutant showing enhanced enantioselectivity to GPE (LW202, E = 193), we have examined whether enantioselectivity is due to differences in the binding pose, the affinity for the ( R)- or ( S)- enantiomers, or a kinetic effect. The two enantiomers were easily accommodated within the binding pockets of the WT enzyme and LW202. Free energy calculations suggested that neither enzyme had a preference for a given enantiomer. The two substrates sampled a wide variety of conformations in the simulations with the sterically hindered and unhindered carbon atoms of the GPE epoxide ring both coming in close proximity to the nucleophilic aspartic acid residue. This suggests that alternative pathways could lead to the formation of a ( S)- and ( R)-diol product. Together, the calculations suggest that the enantioselectivity is due to kinetic rather than thermodynamic effects and that the assumption that one substrate results in one product when interpreting the available experimental data and deriving E-values may be inappropriate in the case of EHs.

ELONGATED UPPERMOST INTERNODE Encodes a Cytochrome P450 Monooxygenase That Epoxidizes Gibberellins in a Novel Deactivation Reaction in RiceW⃞

PubMed Central

Zhu, Yongyou; Nomura, Takahito; Xu, Yonghan; Zhang, Yingying; Peng, Yu; Mao, Bizeng; Hanada, Atsushi; Zhou, Haicheng; Wang, Renxiao; Li, Peijin; Zhu, Xudong; Mander, Lewis N.; Kamiya, Yuji; Yamaguchi, Shinjiro; He, Zuhua

2006-01-01

The recessive tall rice (Oryza sativa) mutant elongated uppermost internode (eui) is morphologically normal until its final internode elongates drastically at the heading stage. The stage-specific developmental effect of the eui mutation has been used in the breeding of hybrid rice to improve the performance of heading in male sterile cultivars. We found that the eui mutant accumulated exceptionally large amounts of biologically active gibberellins (GAs) in the uppermost internode. Map-based cloning revealed that the Eui gene encodes a previously uncharacterized cytochrome P450 monooxygenase, CYP714D1. Using heterologous expression in yeast, we found that EUI catalyzed 16α,17-epoxidation of non-13-hydroxylated GAs. Consistent with the tall and dwarfed phenotypes of the eui mutant and Eui-overexpressing transgenic plants, respectively, 16α,17-epoxidation reduced the biological activity of GA4 in rice, demonstrating that EUI functions as a GA-deactivating enzyme. Expression of Eui appeared tightly regulated during plant development, in agreement with the stage-specific eui phenotypes. These results indicate the existence of an unrecognized pathway for GA deactivation by EUI during the growth of wild-type internodes. The identification of Eui as a GA catabolism gene provides additional evidence that the GA metabolism pathway is a useful target for increasing the agronomic value of crops. PMID:16399803

Hybrid networks based on epoxidized camelina oil

PubMed Central

Balanuca, Brindusa; Stan, Raluca; Lungu, Adriana; Vasile, Eugeniu; Iovu, Horia

2017-01-01

Abstract Lately, renewable resources received great attention in the macromolecular compounds area, regarding the design of the monomers and polymers with different applications. In this study the capacity of several modified vegetable oil-based monomers to build competitive hybrid networks was investigate, taking into account thermal and mechanical behavior of the designed materials. In order to synthesize such competitive nanocomposites, the selected renewable raw material, camelina oil, was employed due to the non-toxicity and biodegradability behavior. General properties of epoxidized camelina oil-based materials were improved by loading of different types of organic-inorganic hybrid compounds – polyhedral oligomeric silsesquioxane (POSS) bearing one (POSS1Ep) or eight (POSS8Ep) epoxy rings on the cages. In order to identify the chemical changes occurring after the thermal curing reactions, FT-IR spectrometry was employed. The new synthesized nanocomposites based on epoxidized camelina oil (ECO) were characterized by dynamic mechanical analyze and thermogravimetric analyze. The morphology of the ECO-based materials was investigate by scanning electron microscopy and supplementary information regarding the presence of the POSS compounds were establish by energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The smooth materials without any separation phase indicates a well dispersion of the Si–O–Si cages within the organic matrix and the incorporation of this hybrid compounds into the ECO network demonstrates to be a well strategy to improve the thermal and mechanical properties, simultaneously. PMID:29491775

Effect of epoxidation on 30% poly(methyl methacrylate)-grafted natural rubber polymer electrolytes

NASA Astrophysics Data System (ADS)

Nazir, Khuzaimah; Aziz, Ahmad Fairoz; Adam, Nurul Ilham; Yahya, Muhd Zu Azhan; Ali, Ab Malik Marwan

2015-08-01

Epoxidized 30% poly(methyl methacrylate)-grafted natural rubber (EMG 30) as a polymer host in solid polymer electrolytes (SPEs) has been investigated. EMG30 was synthesized via performicepoxidation method onto 30% poly(methyl methacrylate)-grafted natural rubber (MG30) and the formations of epoxy group were discussed. The EMG30 were characterized by proton nuclear magnetic resonance (1HNMR) to investigate their chemical structure and differential scanning calorimeter to determine their crystallinity. A new peak in 1HNMR spectra (2.71 ppm) confirmed the appearance of epoxy group. SPE based on EMG30 doped with 40 wt% LiCF3SO3 show the highest conductivity. The complexation between EMG30 and LiCF3SO3 were confirmed by attenuated total reflection Fourier transform infrared (ATR-FTIR).

Thermoset coatings from epoxidized sucrose soyate and blocked, bio-based dicarboxylic acids.

PubMed

Kovash, Curtiss S; Pavlacky, Erin; Selvakumar, Sermadurai; Sibi, Mukund P; Webster, Dean C

2014-08-01

A new 100% bio-based thermosetting coating system was developed from epoxidized sucrose soyate crosslinked with blocked bio-based dicarboxylic acids. A solvent-free, green method was used to block the carboxylic acid groups and render the acids miscible with the epoxy resin. The thermal reversibility of this blocking allowed for the formulation of epoxy-acid thermoset coatings that are 100% bio-based. This was possible due to the volatility of the vinyl ethers under curing conditions. These systems have good adhesion to metal substrates and perform well under chemical and physical stress. Additionally, the hardness of the coating system is dependent on the chain length of the diacid used, making it tunable. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactive Metabolites in the Biotransformation of Molecules Containing a Furan Ring

PubMed Central

Peterson, Lisa A.

2012-01-01

Many xenobiotics containing a furan ring are toxic and/or carcinogenic. The harmful effects of these compounds require furan ring oxidation. This reaction generates an electrophilic intermediate. Depending on the furan ring substituents, the intermediate is either an epoxide or a cis-enedione with more ring substitution favoring epoxide formation. Either intermediate reacts with cellular nucleophiles such as protein or DNA to trigger toxicities. The reactivity of the metabolite determines which cellular nucleophiles are targeted. The toxicity of a particular furan is also influenced by the presence of competing metabolic pathways or efficient detoxification routes. GSH plays an important role in modulating the harmful effects of this class of compound by reacting with the reactive metabolite. However, this may not represent a detoxification step in all cases. PMID:23061605

Quetol 651: Not just a low viscosity resin.

PubMed

Ellis, E Ann

2016-01-01

Quetol 651, a low viscosity epoxy resin, is miscible with alcohols, acetone, and water. It is versatile and can be used as a single epoxide or mixed with other epoxides and anhydrides. The most important characteristic is that the addition of Quetol 651 to a formulation results in a lower viscosity embedding medium and allows for good detection of antigenic activity. Properly formulated and mixed resins containing Quetol 651 have excellent sectioning properties and good beam stability. The decrease in viscosity lends to lower specific gravity of the embedding medium and less interfering electron density between specimen elements resulting in better spatial resolution. New formulations and viscosity data are presented and compared to long used, embedding formulations and the extensive uses of Quetol 651 are reviewed. © 2015 Wiley Periodicals, Inc.

Structural evolution of fluorinated graphene upon molten-alkali treatment probed by X-ray absorption near-edge structure spectroscopy

NASA Astrophysics Data System (ADS)

Liang, Xianqing; Pan, Deyou; Lao, Ming; Liang, Shuiying; Huang, Dan; Zhou, Wenzheng; Guo, Jin

2017-05-01

The structural evolution of fluorinated graphene (FG) nanosheets upon molten-alkali treatment has been systematically investigated utilizing X-ray absorption near-edge structure (XANES) spectroscopy. It is found that the hydroxyl groups can progressively displace fluorine atoms to form covalent bonds to the graphene sheets under designed molten-alkali condition. The XANES spectra also reveal the formation of epoxide groups through intramolecular dehydration of neighbouring hydroxyl groups after substitution reaction. At high alkali-FG weight ratio, the restoration of the π-conjugated structure in graphene sheets can be observed due to the gradual decomposition of epoxide groups. Our experimental results indicate that the surface chemistry and electronic structure of hydroxyl-functionalized FG (HFG) can be readily tuned by varying the ratio of reactants.

Radiation polymerisable compositions containing 3-sorboyloxy-2-hydroxypropyl groups

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, G.E.

1976-02-03

Compounds having at least three 3-sorboyloxy-2-hydroxypropyl groups directly attached to ether oxygen atoms are polymerised by exposure to actinic radiation, preferably in the presence of a sensitizer such as Michler's ketone or benzoin. The compounds may be obtained by the reaction either of sorbic acid with a substance having at least three glycidyl ether groups or of glycidyl sorbate with a substance having at least three phenolic or alcoholic hydroxyl groups: if desired, not all of the glycidyl groups may be consumed, so that, after actinically induced polymerisation, the epoxide-containing polymer may be cross-linked by reaction with a curing agentmore » for epoxide resins. The compounds are useful in making printed circuits or printing plates for offset printing.« less

Rational Catalyst Design of Titanium-Silica Materials Aided by Site-Specific Titration Tools

NASA Astrophysics Data System (ADS)

Eaton, Todd Robert

Silica-supported titanium materials are widely used for thermocatalytic applications such as hydroxylation of alkanes and aromatics, oxidation of alcohols and ethers, ammoximation of carbonyls, and sulfoxidations, while Ti-based materials are widely studied for photocatalytic applications such as photo-oxidation of organic substrates and photo-reduction of CO 2. However, the underlying phenomena of how to synthesize, identify, and control the active structures in these materials is not well understood because of the narrow scope of previous work. Studies of titanium-based catalysts typically focus on materials where the metal is present as either highly-dispersed Ti cations or in bulk crystalline TiO2 form, neglecting the numerous and potentially useful intermediate structures. Furthermore, these works typically focus on a single synthesis technique and rely upon bulk characterization techniques to understand the materials. Here rigorous titanium-silica synthesis-structure-function relationships are established by examining several different synthetic method and utilizing characterization techniques that enable an atomic-level understanding of the materials. The materials studied span the range from isolated Ti cations to clustered TiOx domains, polymeric TiO x domains, anatase-like 2D TiO2 domains, and 3D crystalline TiO2. Tools to quantify accessible TiO x and tetrahedral Ti sites are developed, utilizing the selective titration of titanium with phenylphosphonic acid (PPA). Catalytic properties are probed with the photocatalytic oxidation of benzyl alcohol and the thermocatalytic epoxidation of cis-cyclooctene with H2O2 . PPA titration data indicate that the rate of benzyl alcohol photo-oxidation is independent of titanium coordination, while the rate of alkene epoxidation with H2O2 is proportional to the number of tetrahedral titanium sites on the catalyst. PPA titration data also enables the estimation of TiO2 particle size and reveals an important distinction between particle and crystal size, as obtained from XRD. In the course of establishing these relationships we've gained the knowledge of how to control TiO x structure, which enables the design of new and better catalysts. Understanding the synthesis-structure-function relationships allow for the design of a tandem photo/thermocatalytic reaction system for producing and consuming H2O2. By partially overcoating a TiO 2 photocatalyst with a ˜2 nm silica layer we observe a 56-fold rate improvement compared to bare-TiO2 for H2O2 synthesis from the proton-assisted reduction of O2. Addition of metal-SiO2 thermocatalysts (metal=Ti, Nb, or Ta) with sites needed for H2O2 activation creates a tandem system wherein the H2O2 produced in situ is utilized for alkene epoxidation. Compared to a thermocatalytic-only system, the tandem system accelerates epoxidation for cis-cyclooctene(11x faster), styrene(20x) and 1-octene(30x). This approach demonstrates a means for epoxidation with O2 that avoids H2O2 purification and transport, simplifies the total process, provides new opportunities for control by independent H2O2 production and consumption in the same reactor, and enhances rates relative to thermocatalytic-only epoxidation by intimately coupling H2O2 generation and consumption. Critically, establishment of titanium-silica synthesis-structure-function relationships enables the design of new catalysts and systems that are less energy- and material-intensive, leading towards more sustainable chemistry.

Induction of rat liver microsomal epoxide hydrolase by thiazole and pyrazine: hydrolysis of 2-cyanoethylene oxide.

PubMed

Kim, S G; Kedderis, G L; Batra, R; Novak, R F

1993-08-01

Liver microsomal epoxide hydrolase (mEH) is active in the detoxification of epoxide-containing carcinogens. The effects of thiazole and pyrazine, constituents of tobacco and tobacco smoke as well as of a variety of foods, on the expression and regulation of mEH were examined in rats (200 mg/kg body wt/day, i.p., 1-3 days). Immunoblot analyses using rabbit anti-rat mEH antibody revealed a significant increase in mEH levels in hepatic microsomes isolated from either thiazole- or pyrazine-treated animals. Another protein (approximately 43 kd) cross-reacting with polyclonal mEH antibody was found to be increased concomitantly following pyrazine treatment. Northern and slot blot analyses showed substantial increases in mEH mRNA following either thiazole or pyrazine treatment. The level of mEH mRNA increased 17-fold at 24 h following thiazole treatment, relative to control. Approximately 20- and 16-fold increases in mEH mRNA were also observed at 48 and 72 h respectively following treatment with pyrazine. The level of polymerase chain reaction (PCR)-amplified mEH DNA derived from poly(A)+ RNA was clearly elevated following either thiazole or pyrazine treatment relative to that from untreated animals. Both sense and antisense strands of PCR-amplified mEH DNA were cloned into an M13mp19 phage vector in order to examine the nucleotide sequences of PCR-amplified mEH DNA derived from the poly(A)+ RNA isolated from thiazole- or pyrazine-treated animals. Sequence analyses revealed that the sequence of PCR-amplified DNA from the induced mRNA was identical to that published for mEH cDNA. Epoxide hydrolase activity toward the hydrolysis of 2-cyanoethylene oxide (CEO), the epoxide metabolite of the rat carcinogen acrylonitrile, was not significant in hepatic microsomes from untreated rats, but was substantially induced by treatment with thiazole or pyrazine. Microsomal hydrolysis activity was heat-sensitive and potently inhibited by 1,1,1-trichloropropene-2,3-oxide, indicating that mEH was the catalyst. The Vmax for the hydrolysis of CEO by hepatic microsomes from thiazole-treated rats (13.4 nmol/min/mg protein) was 1.5-fold greater than that with microsomes from pyrazine-treated rats, whereas similar Km values (approximately 1 mM) were observed for both microsomal preparations. These kinetic data correlate well with the increases in mEH mRNA observed after administration of thiazole or pyrazine to rats. These results provide evidence that administration of thiazole or pyrazine induces mEH with a large increase in mEH mRNA, and that the induced mEH catalyzes the hydrolysis of CEO.

Direct valorisation of waste cocoa butter triglycerides via catalytic epoxidation, ring-opening and polymerisation.

PubMed

Plaza, Dorota D; Strobel, Vinzent; Heer, Parminder Kaur Ks; Sellars, Andrew B; Hoong, Seng-Soi; Clark, Andrew J; Lapkin, Alexei A

2017-09-01

Development of circular economy requires significant advances in the technologies for valorisation of waste, as waste becomes new feedstock. Food waste is a particularly important feedstock, containing large variation of complex chemical functionality. Although most food waste sources are complex mixtures, waste from food processing, no longer suitable for the human food chain, may also represent relatively clean materials. One such material requiring valorisation is cocoa butter. Epoxidation of a triglyceride from a food waste source, processing waste cocoa butter, into the corresponding triglyceride epoxide was carried out using a modified Ishii-Venturello catalyst in batch and continuous flow reactors. The batch reactor achieved higher yields due to the significant decomposition of hydrogen peroxide in the laminar flow tubular reactor. Integral and differential models describing the reaction and the phase transfer kinetics were developed for the epoxidation of cocoa butter and the model parameters were estimated. Ring-opening of the epoxidised cocoa butter was undertaken to provide polyols of varying molecular weight (M w = 2000-84 000 Da), hydroxyl value (27-60 mg KOH g -1 ) and acid value (1-173 mg KOH g -1 ), using either aqueous ortho-phosphoric acid (H 3 PO 4 ) or boron trifluoride diethyl etherate (BF 3 · OEt 2 )-mediated oligomerisation in bulk, using hexane or tetrahydrofuran (THF) as solvents. The thermal and tensile properties of the polyurethanes obtained from the reaction of these polyols with 4,4'-methylene diphenyl diisocyanate (MDI) are described. The paper presents a complete valorisation scheme for a food manufacturing industry waste stream, starting from the initial chemical transformation, developing a process model for the design of a scaled-up process, and leading to synthesis of the final product, in this case a polymer. This work describes aspects of optimisation of the conversion route, focusing on clean synthesis and also demonstrates the interdisciplinary nature of the development projects, requiring input from different areas of chemistry, process modelling and process design. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Crystal Structure and Catalytic Behavior in Olefin Epoxidation of a One-Dimensional Tungsten Oxide/Bipyridine Hybrid.

PubMed

Amarante, Tatiana R; Antunes, Margarida M; Valente, Anabela A; Paz, Filipe A Almeida; Pillinger, Martyn; Gonçalves, Isabel S

2015-10-19

The tungsten oxide/2,2'-bipyridine hybrid material [WO3(2,2'-bpy)]·nH2O (n = 1-2) (1) has been prepared in near quantitative yield by the reaction of H2WO4, 2,2'-bpy, and H2O in the mole ratio of ca. 1:2:700 at 160 °C for 98 h in a rotating Teflon-lined digestion bomb. The solid-state structure of 1 was solved and refined through Rietveld analysis of high-resolution synchrotron X-ray diffraction data collected for the microcrystalline powder. The material, crystallizing in the orthorhombic space group Iba2, is composed of a one-dimensional organic-inorganic hybrid polymer, ∞(1)[WO3(2,2'-bpy)], topologically identical to that found in the previously reported anhydrous phases [MO3(2,2'-bpy)] (M = Mo, W). While in the latter the N,N'-chelated 2,2'-bpy ligands of adjacent corner-shared {MO4N2} octahedra are positioned on the same side of the 1D chain, in 1 the 2,2'-bpy ligands alternate above and below the chain. The catalytic behavior of compound 1 for the epoxidation of cis-cyclooctene was compared with that for several other tungsten- or molybdenum-based (pre)catalysts, including the hybrid polymer [MoO3(2,2'-bpy)]. While the latter exhibits superior performance when tert-butyl hydroperoxide (TBHP) is used as the oxidant, compound 1 is superior when aqueous hydrogen peroxide is used, allowing near-quantitative conversion of the olefin to the epoxide. With H2O2, compounds 1 and [MoO3(2,2'-bpy)] act as sources of soluble active species, namely, the oxodiperoxo complex [MO(O2)2(2,2'-bpy)], which is formed in situ. Compounds 1 and [WO(O2)2(2,2'-bpy)] (2) were further tested in the epoxidation of cyclododecene, trans-2-octene, 1-octene, (R)-limonene, and styrene. The structure of 2 was determined by single-crystal X-ray diffraction and found to be isotypical with the molybdenum analogue.

Hardness and swelling behaviour of epoxidized natural rubber/recycled acrylonitrile-butadiene rubber (ENR 50/NBRr) blends

NASA Astrophysics Data System (ADS)

Ahmad, Hazwani Syaza; Ismail, Hanafi; Rashid, Azura A.

2017-07-01

This recent work is to investigate the hardness and swelling behaviour of epoxidized natural rubber/recycled acrylonitrile-butadiene rubber (ENR 50/NBRr) blends. ENR 50/NBRr blends were prepared by two-roll mills with five different loading of NBRr from 5 to 35 phr. Results indicated that the hardness of ENR 50/NBRr blends increased as recycled NBR increased due to the improvement in crosslink density of the blends. Increasing NBRr content gives ENR 50/NBRr blends better resistance towards swelling. Higher degree of crosslinking will increase the swelling resistance and reduce the penetration of toluene into the blends. The presence of polar group in ENR 50 and NBRr give better hardness properties and swelling behaviour of the ENR 50/NBRr blends compared to the NR/NBRr blends.

Analogues of the epoxy resin monomer diglycidyl ether of bisphenol F: effects on contact allergenic potency and cytotoxicity.

PubMed

O'Boyle, Niamh M; Delaine, Tamara; Luthman, Kristina; Natsch, Andreas; Karlberg, Ann-Therese

2012-11-19

Diglycidyl ethers of bisphenol A (DGEBA) and bisphenol F (DGEBF) are widely used as components in epoxy resin thermosetting products. They are known to cause occupational and nonoccupational allergic contact dermatitis. The aim of this study is to investigate analogues of DGEBF with regard to contact allergy and cytotoxicity. A comprehensive knowledge of the structural features that contribute to the allergenic and cytotoxic effects of DGEBF will guide the development of future novel epoxy resin systems with reduced health hazards for those coming into contact with them. It was found that the allergenic effects of DGEBF were dependent on its terminal epoxide groups. In contrast, it was found that the cytotoxicity in monolayer cell culture was dependent not only on the presence of epoxide groups but also on other structural features.

Synthesis of chlorophyll-amino acid conjugates as models for modification of proteins with chromo/fluorophores.

PubMed

Tamiaki, Hitoshi; Isoda, Yasuaki; Tanaka, Takuya; Machida, Shinnosuke

2014-02-15

A chlorophyll-a derivative bonded directly with epoxide at the peripheral position of the chlorin π-system was reacted with N-urethane and C-ester protected amino acids bearing an alcoholic or phenolic hydroxy group as well as a carboxy group at the residue to give chlorophyll-amino acid conjugates. The carboxy residues of N,C-protected aspartic and glutamic acids were esterified with the epoxide in high yields. The synthetic conjugates in dichloromethane had absorption bands throughout the visible region including intense red-side Qy and blue-side Soret bands. By their excitation at the visible bands, strong and efficient fluorescence emission was observed up to the near-infrared region. The chromo/fluorophores are promising for preparation of functional peptides and modification of proteins. Copyright © 2013 Elsevier Ltd. All rights reserved.

Epoxidized soy bean oil migrating from the gaskets of lids into food packed in glass jars. Analysis by on-line liquid chromatography-gas chromatography.

PubMed

Fankhauser-Noti, Anja; Fiselier, Katell; Biedermann-Brem, Sandra; Grob, Koni

2005-08-05

The migration of epoxidized soy bean oil (ESBO) from the gasket in the lids of glass jars into foods, particularly those rich in edible oil, often far exceeds the legal limit (60 mg/kg). ESBO was determined through a methyl ester isomer of diepoxy linoleic acid. Transesterification occurred directly in the homogenized food. From the extracted methyl esters, the diepoxy components were isolated by normal-phase LC and transferred on-line to gas chromatography with flame ionization detection using the on-column interface in the concurrent solvent evaporation mode. The method involves verification elements to ensure the reliability of the results for every sample analyzed. The detection limit is 2-5 mg/kg, depending on the food. Uncertainty of the procedure is below 10%.

Nanostructured bio-functional polymer brushes.

PubMed

Padeste, Celestino; Farquet, Patrick; Potzner, Christian; Solak, Harun H

2006-01-01

Structured poly(glycidyl methracrylate) (poly-GMA) brushes have been grafted onto flexible fluoro-polymer films using a radiation grafting process. The reactive epoxide of poly-GMA provides the basis for a versatile biofunctionalization of the grafted brushes. Structure definition by extreme ultraviolet (EUV) exposure allowed nanometer-scale resolution of periodic patterns. By variation of the exposure dose the height of the grafted structures can be adapted in a wide range. Derivatization of the grafted brushes included reaction with various amines with different side chains, hydrolysis of the epoxide to diols to increase protein resistance and introduction of ionic groups to yield poly-electrolytes. As an example for biofunctionalization, biotin was linked to the grafted brush and biofunctionality was demonstrated in a competitive biotin-streptavidin assay. In this article we also present a brief review of other approaches to obtain structured biofunctional polymer brushes.

The mutagenicities of safrole, estragole, eugenol, trans-anethole, and some of their known or possible metabolites for Salmonella typhimurium mutants.

PubMed

Swanson, A B; Chambliss, D D; Blomquist, J C; Miller, E C; Miller, J A

1979-04-01

Safrole, estragole, anethole, and eugenol and some of their known or possible metabolites were tested for mutagenic activity for S. typhimurium TA1535, TA100, and TA98. Highly purified 1'-hydroxyestragole and 1'-hydroxysafrole were mutagenic (approximately 15 and 10 revertants/micromole, respectively) for strain TA100 in the absence of fortified liver microsomes; trans-anethole and estragole appeared to have very weak activity. 3'-Hydroxyanethole was too toxic for an adequate test. Supplementation with NADPH-fortified rat-liver microsomes and cytosol converted 3'-hydroxyanethole to a mutagen(s) and increased the mutagenic activities for strain TA100 of 1'-hydroxyestragole, 1'-hydroxysafrole, estragole, and anethole. No mutagenicity was detected for safrole or eugenol with or without added NADPH-fortified liver preparations. The electrophilic 2',3'-oxides of safrole, 1'-hydroxysafrole, 1'-acetoxysafrole, 1'-oxosafrole, estragole, 1'-hydroxyestragole, and eugenol showed dose-dependent mutagenic activities for strain TA1535 in the absence of fortified liver microsomes. These mutagenic activities ranged from about 330 revertants/micromole for 1'-oxosafrole-2',3'-oxide to about 7000 revertants/micromole for safrole-2',3'-oxide. The arylalkenes, their hydroxylated derivatives, or their epoxides did not show mutagenic activity for strain TA98, except for 1'-oxosafrole-2',3'-oxide, which had weak activity. Since the arylalkenes are hydroxylated and/or epoxidized by hepatic microsomes, hydroxy and epoxide derivatives appear to be proximate and ultimate mutagenic metabolites, respectively, of the arylalkenes.

Epoxide as a precursor to secondary organic aerosol formation from isoprene photooxidation in the presence of nitrogen oxides

PubMed Central

Lin, Ying-Hsuan; Zhang, Haofei; Pye, Havala O. T.; Zhang, Zhenfa; Marth, Wendy J.; Park, Sarah; Arashiro, Maiko; Cui, Tianqu; Budisulistiorini, Sri Hapsari; Sexton, Kenneth G.; Vizuete, William; Xie, Ying; Luecken, Deborah J.; Piletic, Ivan R.; Edney, Edward O.; Bartolotti, Libero J.; Gold, Avram; Surratt, Jason D.

2013-01-01

Isoprene is a substantial contributor to the global secondary organic aerosol (SOA) burden, with implications for public health and the climate system. The mechanism by which isoprene-derived SOA is formed and the influence of environmental conditions, however, remain unclear. We present evidence from controlled smog chamber experiments and field measurements that in the presence of high levels of nitrogen oxides (NOx = NO + NO2) typical of urban atmospheres, 2-methyloxirane-2-carboxylic acid (methacrylic acid epoxide, MAE) is a precursor to known isoprene-derived SOA tracers, and ultimately to SOA. We propose that MAE arises from decomposition of the OH adduct of methacryloylperoxynitrate (MPAN). This hypothesis is supported by the similarity of SOA constituents derived from MAE to those from photooxidation of isoprene, methacrolein, and MPAN under high-NOx conditions. Strong support is further derived from computational chemistry calculations and Community Multiscale Air Quality model simulations, yielding predictions consistent with field observations. Field measurements taken in Chapel Hill, North Carolina, considered along with the modeling results indicate the atmospheric significance and relevance of MAE chemistry across the United States, especially in urban areas heavily impacted by isoprene emissions. Identification of MAE implies a major role of atmospheric epoxides in forming SOA from isoprene photooxidation. Updating current atmospheric modeling frameworks with MAE chemistry could improve the way that SOA has been attributed to isoprene based on ambient tracer measurements, and lead to SOA parameterizations that better capture the dependency of yield on NOx. PMID:23553832

Modular, Metal-Catalyzed Cycloisomerization Approach to Angularly Fused Polycyclic Aromatic Hydrocarbons and Their Oxidized Derivatives

PubMed Central

Thomson, Paul F.; Parrish, Damon; Pradhan, Padmanava; Lakshman, Mahesh K.

2015-01-01

Palladium-catalyzed cross-coupling reactions of 2-bromobenzaldehyde and 6-bromo-2,3-dimethoxybenzaldehyde with 4-methyl-1-naphthaleneboronic acid and acenaphthene-5-boronic acid gave corresponding o-naphthyl benzaldehydes. Corey–Fuchs olefination followed by reaction with n-BuLi led to various 1-(2-ethynylphenyl)naphthalenes. Cycloisomerization of individual 1-(2-ethynylphenyl)naphthalenes to various benzo[c]phenanthrene (BcPh) analogues was accomplished smoothly with catalytic PtCl2 in PhMe. In the case of 4,5-dihydrobenzo[l]acephenanthrylene, oxidation with DDQ gave benzo[l]acephenanthrylene. The dimethoxy-substituted benzo[c]phenanthrenes were demethylated with BBr3 and oxidized to the ortho-quinones with PDC. Reduction of these quinones with NaBH4 in THF/EtOH in an oxygen atmosphere gave the respective dihydrodiols. Exposure of the dihydrodiols to N-bromoacetamide in THF-H2O led to bromohydrins that were cyclized with Amberlite IRA 400 HO− to yield the series 1 diol epoxides. Epoxidation of the dihydrodiols with mCPBA gave the isomeric series 2 diol epoxides. All of the hydrocarbons as well as the methoxy-substituted ones were crystallized and analyzed by X-ray crystallography, and these data are compared to other previously studied BcPh derivatives. The methodology described is highly modular and can be utilized for the synthesis of a wide variety of angularly fused polycyclic aromatic hydrocarbons and their putative metabolites and/or other derivatives. PMID:26196673

Lycopene cyclase paralog CruP protects against reactive oxygen species in oxygenic photosynthetic organisms.

PubMed

Bradbury, Louis M T; Shumskaya, Maria; Tzfadia, Oren; Wu, Shi-Biao; Kennelly, Edward J; Wurtzel, Eleanore T

2012-07-03

In photosynthetic organisms, carotenoids serve essential roles in photosynthesis and photoprotection. A previous report designated CruP as a secondary lycopene cyclase involved in carotenoid biosynthesis [Maresca J, et al. (2007) Proc Natl Acad Sci USA 104:11784-11789]. However, we found that cruP KO or cruP overexpression plants do not exhibit correspondingly reduced or increased production of cyclized carotenoids, which would be expected if CruP was a lycopene cyclase. Instead, we show that CruP aids in preventing accumulation of reactive oxygen species (ROS), thereby reducing accumulation of β-carotene-5,6-epoxide, a ROS-catalyzed autoxidation product, and inhibiting accumulation of anthocyanins, which are known chemical indicators of ROS. Plants with a nonfunctional cruP accumulate substantially higher levels of ROS and β-carotene-5,6-epoxide in green tissues. Plants overexpressing cruP show reduced levels of ROS, β-carotene-5,6-epoxide, and anthocyanins. The observed up-regulation of cruP transcripts under photoinhibitory and lipid peroxidation-inducing conditions, such as high light stress, cold stress, anoxia, and low levels of CO(2), fits with a role for CruP in mitigating the effects of ROS. Phylogenetic distribution of CruP in prokaryotes showed that the gene is only present in cyanobacteria that live in habitats characterized by large variation in temperature and inorganic carbon availability. Therefore, CruP represents a unique target for developing resilient plants and algae needed to supply food and biofuels in the face of global climate change.

Epoxide as a precursor to secondary organic aerosol formation from isoprene photooxidation in the presence of nitrogen oxides.

PubMed

Lin, Ying-Hsuan; Zhang, Haofei; Pye, Havala O T; Zhang, Zhenfa; Marth, Wendy J; Park, Sarah; Arashiro, Maiko; Cui, Tianqu; Budisulistiorini, Sri Hapsari; Sexton, Kenneth G; Vizuete, William; Xie, Ying; Luecken, Deborah J; Piletic, Ivan R; Edney, Edward O; Bartolotti, Libero J; Gold, Avram; Surratt, Jason D

2013-04-23

Isoprene is a substantial contributor to the global secondary organic aerosol (SOA) burden, with implications for public health and the climate system. The mechanism by which isoprene-derived SOA is formed and the influence of environmental conditions, however, remain unclear. We present evidence from controlled smog chamber experiments and field measurements that in the presence of high levels of nitrogen oxides (NO(x) = NO + NO2) typical of urban atmospheres, 2-methyloxirane-2-carboxylic acid (methacrylic acid epoxide, MAE) is a precursor to known isoprene-derived SOA tracers, and ultimately to SOA. We propose that MAE arises from decomposition of the OH adduct of methacryloylperoxynitrate (MPAN). This hypothesis is supported by the similarity of SOA constituents derived from MAE to those from photooxidation of isoprene, methacrolein, and MPAN under high-NOx conditions. Strong support is further derived from computational chemistry calculations and Community Multiscale Air Quality model simulations, yielding predictions consistent with field observations. Field measurements taken in Chapel Hill, North Carolina, considered along with the modeling results indicate the atmospheric significance and relevance of MAE chemistry across the United States, especially in urban areas heavily impacted by isoprene emissions. Identification of MAE implies a major role of atmospheric epoxides in forming SOA from isoprene photooxidation. Updating current atmospheric modeling frameworks with MAE chemistry could improve the way that SOA has been attributed to isoprene based on ambient tracer measurements, and lead to SOA parameterizations that better capture the dependency of yield on NO(x).

Identification of α-tocotrienolquinone epoxides and development of an efficient molecular distillation procedure for quantitation of α-tocotrienol oxidation products in food matrices by high-performance liquid chromatography with diode array and fluorescence detection.

PubMed

Büsing, Anne; Drotleff, Astrid M; Ternes, Waldemar

2012-08-29

The aim of this study was to investigate the most important oxidation products of α-tocotrienol (α-T3) along with other tocochromanols in lipid matrices and tocotrienol-rich foods. For this purpose, an efficient molecular distillation procedure was developed for the extraction of analytes, and α-T3-spiked and thermally oxidized natural lipids (lard and wheat germ oil) and α-T3-rich foods (wholemeal rye bread and oil from dried brewer's spent grain) were investigated through HPLC-DAD-F. The following α-T3 oxidation products were extractable from lipid matrices along with tocochromanols: α-tocotrienolquinone (α-T3Q), α-tocotrienolquinone-4a,5-epoxide (α-T3Q-4a,5-E), α-tocotrienolquinone-7,8-epoxide (α-T3Q-7,8-E), 7-formyl-β-tocotrienol (7-FβT3), and 5-formyl-γ-tocotrienol (5-FγT3). Recovery rates were as high as 88% and enrichment factors up to 124. The proposed method allows the investigation of α-T3Q, α-T3Q-4a,5-E, α-T3Q-7,8-E, 7-FβT3, and 5-FγT3 in small quantities (<0.78 μg/g) in lipid matrices, which is necessary for the investigation and analysis of the formation kinetics of these oxidation products in fat, oils, and tocotrienol-rich foods.

Potential Metabolic Activation of a Representative C2-Alkylated Polycyclic Aromatic Hydrocarbon 6-Ethylchrysene Associated with the Deepwater Horizon Oil Spill in Human Hepatoma (HepG2) Cells

PubMed Central

2016-01-01

Exposure to polycyclic aromatic hydrocarbons (PAHs) is the major human health hazard associated with the Deepwater Horizon oil spill. C2-Chrysenes are representative PAHs present in crude oil and could contaminate the food chain. We describe the metabolism of a C2-chrysene regioisomer, 6-ethylchrysene (6-EC), in human HepG2 cells. The structures of the metabolites were identified by HPLC-UV-fluorescence detection and LC-MS/MS. 6-EC-tetraol isomers were identified as signature metabolites of the diol-epoxide pathway. O-Monomethyl-O-monosulfonated-6-EC-catechol, its monohydroxy products, and N-acetyl-l-cysteine(NAC)-6-EC-ortho-quinone were discovered as signature metabolites of the ortho-quinone pathway. Potential dual metabolic activation of 6-EC involving the formation of bis-electrophiles, i.e., a mono-diol-epoxide and a mono-ortho-quinone within the same structure, bis-diol-epoxides, and bis-ortho-quinones was observed as well. The identification of 6-EC-tetraol, O-monomethyl-O-monosulfonated-6-EC-catechol, its monohydroxy products, and NAC-6-EC-ortho-quinone supports potential metabolic activation of 6-EC by P450 and AKR enzymes followed by metabolic detoxification of the ortho-quinone through interception of its redox cycling capability by catechol-O-methyltransferase and sulfotransferase enzymes. The tetraols and catechol conjugates could be used as biomarkers of human exposure to 6-EC resulting from oil spills. PMID:27054409

Organic reactions catalyzed by methylrhenium trioxide: Reactions of ethyl diazoacetate and organic azides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Z.; Espenson, J.H.

1996-10-16

Methylrhenium trioxide (CH{sub 3}ReO{sub 3} or MTO) catalyzes several classes of reactions of ethyl diazoacetate, EDA. It is the first high valent oxo complex for carbene transfer. Under mild conditions and in the absence of other substrates, EDA was converted to a 9:1 mixture of diethyl maleate and diethyl fumarate. In the presence of alcohols, {alpha}-alkoxy ethyl acetates were obtained in good yield. The yields dropped for the larger and more branched alcohols, the balance of material being diethyl maleate and fumarate. An electron-donating group in the para position of phenols favors the formation of {alpha}-phenoxy ethyl acetates. The usemore » of EDA to form {alpha}-thio ethyl acetates and N-substituted glycine ethyl esters, on the other hand, is hardly affected by the size or structure of the parent thiol or amine, with all of these reactions proceeding in high yield. MTO-catalyzed cycloaddition reactions occur between EDA and aromatic imines, olefins, and carbonyl compounds. Three-membered ring products are formed: aziridines, cyclopropanes, and epoxides, respectively. The reactions favor the formation of trans products, and provide a convenient route for the preparation of aziridines. Intermediate carbenoid and nitrenoid species have been proposed. In the presence of an oxygen source such as an epoxide, ethyl diazoacetate and azibenzil are converted to an oxalic acid monoethyl ester and to benzil; at the same time the epoxide was converted to an olefin. 75 refs., 1 fig., 7 tabs.« less

Cytotoxic Constituents from the Rhizomes of Curcuma zedoaria

PubMed Central

Ahmed Hamdi, Omer Abdalla; Syed Abdul Rahman, Syarifah Nur; Awang, Khalijah; Abdul Wahab, Norhanom; Looi, Chung Yeng; Thomas, Noel Francis; Abd Malek, Sri Nurestri

2014-01-01

Curcuma zedoaria also known as Temu putih is traditionally used in food preparations and treatment of various ailments including cancer. The cytotoxic activity of hexane, dichloromethane, ethyl acetate, methanol, and the methanol-soxhlet extracts of Curcuma zedoaria rhizomes was tested on two human cancer cell lines (Ca Ski and MCF-7) and a noncancer cell line (HUVEC) using MTT assay. Investigation on the chemical components in the hexane and dichloromethane fractions gave 19 compounds, namely, labda-8(17),12 diene-15,16 dial (1), dehydrocurdione (2), curcumenone (3), comosone II (4), curcumenol (5), procurcumenol (6), germacrone (7), zerumbone epoxide (8), zederone (9), 9-isopropylidene-2,6-dimethyl-11-oxatricyclo[6.2.1.01,5]undec-6-en-8-ol (10), furanodiene (11), germacrone-4,5-epoxide (12), calcaratarin A (13), isoprocurcumenol (14), germacrone-1,10-epoxide (15), zerumin A (16), curcumanolide A (17), curcuzedoalide (18), and gweicurculactone (19). Compounds (1–19) were evaluated for their antiproliferative effect using MTT assay against four cancer cell lines (Ca Ski, MCF-7, PC-3, and HT-29). Curcumenone (3) and curcumenol (5) displayed strong antiproliferative activity (IC50 = 8.3 ± 1.0 and 9.3 ± 0.3 μg/mL, resp.) and were found to induce apoptotic cell death on MCF-7 cells using phase contrast and Hoechst 33342/PI double-staining assay. Thus, the present study provides basis for the ethnomedical application of Curcuma zedoaria in the treatment of breast cancer. PMID:25126594

A Sensitive Gel-based Method Combining Distinct Cyclophellitol-based Probes for the Identification of Acid/Base Residues in Human Retaining β-Glucosidases*

PubMed Central

Kallemeijn, Wouter W.; Witte, Martin D.; Voorn-Brouwer, Tineke M.; Walvoort, Marthe T. C.; Li, Kah-Yee; Codée, Jeroen D. C.; van der Marel, Gijsbert A.; Boot, Rolf G.; Overkleeft, Herman S.; Aerts, Johannes M. F. G.

2014-01-01

Retaining β-exoglucosidases operate by a mechanism in which the key amino acids driving the glycosidic bond hydrolysis act as catalytic acid/base and nucleophile. Recently we designed two distinct classes of fluorescent cyclophellitol-type activity-based probes (ABPs) that exploit this mechanism to covalently modify the nucleophile of retaining β-glucosidases. Whereas β-epoxide ABPs require a protonated acid/base for irreversible inhibition of retaining β-glucosidases, β-aziridine ABPs do not. Here we describe a novel sensitive method to identify both catalytic residues of retaining β-glucosidases by the combined use of cyclophellitol β-epoxide- and β-aziridine ABPs. In this approach putative catalytic residues are first substituted to noncarboxylic amino acids such as glycine or glutamine through site-directed mutagenesis. Next, the acid/base and nucleophile can be identified via classical sodium azide-mediated rescue of mutants thereof. Selective labeling with fluorescent β-aziridine but not β-epoxide ABPs identifies the acid/base residue in mutagenized enzyme, as only the β-aziridine ABP can bind in its absence. The Absence of the nucleophile abolishes any ABP labeling. We validated the method by using the retaining β-glucosidase GBA (CAZy glycosylhydrolase family GH30) and then applied it to non-homologous (putative) retaining β-glucosidases categorized in GH1 and GH116: GBA2, GBA3, and LPH. The described method is highly sensitive, requiring only femtomoles (nanograms) of ABP-labeled enzymes. PMID:25344605

Some Stereochemical Principles from Polymers: Molecular Symmetry and Molecular Flexibility

ERIC Educational Resources Information Center

Price, Charles C.

1973-01-01

Discusses the use of the properties of polyethylene, polypropylene, polyisobutylene, and their three epoxides to illustrate the relationships of entropy to molecular properties and the concepts of molecular chirality, geometry, and flexibility. (CC)

Titanium-based zeolitic imidazolate framework for chemical fixation of carbon dioxide

EPA Science Inventory

A titanium-based zeolitic imidazolate framework (Ti-ZIF) with high surface area and porous morphology was synthesized and itsefficacy was demonstrated in the synthesis of cyclic carbonates from epoxides and carbon dioxide.

Photoredox Catalysis for the Generation of Carbon Centered Radicals.

PubMed

Goddard, Jean-Philippe; Ollivier, Cyril; Fensterbank, Louis

2016-09-20

Radical chemistry has witnessed over the last decades important advances that have positioned it as a methodology of choice in synthetic chemistry. A number of great attributes such as specific reactivities, the knowledge of the kinetics of most elementary processes, the functional group tolerance, and the possibility to operate cascade sequences are clearly responsible for this craze. Nevertheless, at the end of the last century, radical chemistry appeared plagued by several hurdles to overcome such as the use of environmentally problematic mediators or the impossibility of scale up. While the concept of photocatalysis was firmly established in the coordination chemistry community, its diffusion in organic synthetic chemistry remained sporadic for decades until the end of the 2000s with the breakthrough merging of organocatalysis and photocatalysis by the MacMillan group and contemporary reports by the groups of Yoon and Stephenson. Since then, photoredox catalysis has enjoyed particularly active and intense developments. It is now the topic of a still increasing number of publications featuring various applications from asymmetric synthesis, total synthesis of natural products, and polymerization to process (flow) chemistry. In this Account, we survey our own efforts in this domain, focusing on the elaboration of new photocatalytic pathways that could lead to the efficient generation of C-centered functionalized alkyl and aryl radicals. Both reductive and oxidative manifolds are accessible through photoredox catalysis, which has guided us along these lines in our projects. Thus, we studied the photocatalytic reduction of onium salts such as sulfoniums and iodoniums for the production of the elusive aryl radical intermediates. Progressing to more relevant chemistry for synthesis, we examined the cleavage of C-O and the C-Br bonds for the generation of alkyl C-centered radicals. Activated epoxides could serve as valuable substrates of a photocatalyzed variant of the Nugent-RajanBabu-Gansäuer homolytic cleavage of epoxides. Using imidazole based carbamates, we could also devise the first photocatalyzed Barton-McCombie deoxygenation reaction. Finally, bromophenylacetate can be reduced using the [Au2(μ-dppm)2]Cl2 photocatalyst under UVA or visible-light. This was used for the initiation of the controlled atom transfer radical polymerization of methacrylates and acrylates in solution or laminate. Our next endeavors concerned the photocatalyzed oxidation of stabilized carbanions such as enolates of 1,3-dicarbonyl substrates, trifluoroborates, and more extensively bis-catecholato silicates. Because of their low oxidation potentials, the later have proved to be exquisite sources of radical entities, which can be engaged in diverse intermolecular reactions such as vinylation, alkynylation, and conjugate additions. The bis-catecholato silicates were also shown to behave as excellent partners of dual photoredox-nickel catalysis leading in an expeditious manner to libraries of cross coupling products.

Essential Oils in Foods: From Ancient Times to the 21st Century.

PubMed

Sendra, Esther

2016-06-14

Medicinal plants and culinary herbs have been used since ancient times. Essential oils (EO) are a mixture of numerous compounds, mainly terpenes, alcohols, acids, esters, epoxides, aldehydes, ketones,aminesandsulfides,thatareprobablyproducedbyplantsasaresponsetostress[1].[...].

Effect of epoxidation on 30% poly(methyl methacrylate)-grafted natural rubber polymer electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nazir, Khuzaimah; Aziz, Ahmad Fairoz; Adam, Nurul Ilham

Epoxidized 30% poly(methyl methacrylate)-grafted natural rubber (EMG 30) as a polymer host in solid polymer electrolytes (SPEs) has been investigated. EMG30 was synthesized via performicepoxidation method onto 30% poly(methyl methacrylate)-grafted natural rubber (MG30) and the formations of epoxy group were discussed. The EMG30 were characterized by proton nuclear magnetic resonance ({sup 1}HNMR) to investigate their chemical structure and differential scanning calorimeter to determine their crystallinity. A new peak in {sup 1}HNMR spectra (2.71 ppm) confirmed the appearance of epoxy group. SPE based on EMG30 doped with 40 wt% LiCF{sub 3}SO{sub 3} show the highest conductivity. The complexation between EMG30 and LiCF{submore » 3}SO{sub 3} were confirmed by attenuated total reflection Fourier transform infrared (ATR-FTIR)« less

A Polyoxovanadate-Resorcin[4]arene-Based Porous Metal-Organic Framework as an Efficient Multifunctional Catalyst for the Cycloaddition of CO2 with Epoxides and the Selective Oxidation of Sulfides.

PubMed

Lu, Bing-Bing; Yang, Jin; Liu, Ying-Ying; Ma, Jian-Fang

2017-10-02

In this work, we report a new polyoxovanadate-resorcin[4]arene-based metal-organic framework (PMOF), [Co 2 L 0.5 V 4 O 12 ]·3DMF·5H 2 O (1), assembled with a newly functionalized wheel-like resorcin[4]arene ligand (L). 1 features an elegant porous motif and represents a rare example of PMOFs composed of both a resorcin[4]arene ligand and polyoxovanadate. Remarkably, 1 shows open V sites in the channel, which makes 1 an efficient heterogeneous Lewis acid catalyst for the cycloaddition of carbon dioxide to epoxides with high conversion and selectivity. Strikingly, 1 also exhibits high catalytic activity for the heterogeneous oxidative desulfurization of sulfides. Particularly, the heterogeneous catalyst 1 can be easily separated and reused with good catalytic activity.

Takovite-aluminosilicate-Cr materials prepared by adsorption of Cr3+ from industrial effluents as catalysts for hydrocarbon oxidation reactions.

PubMed

Ciuffi, Katia J; de Faria, Emerson H; Marçal, Liziane; Rocha, Lucas A; Calefi, Paulo S; Nassar, Eduardo J; Pepe, Iuri; da Rocha, Zênis N; Vicente, Miguel A; Trujillano, Raquel; Gil, Antonio; Korili, Sophia A

2012-05-01

The catalytic efficiency of takovite-aluminosilicate-chromium catalysts obtained by adsorption of Cr(3+) ions from aqueous solutions by a takovite-aluminosilicate nanocomposite adsorbent is reported. The adsorbent was synthesized by the coprecipitation method. The catalytic activity of the final Cr-catalysts depended on the amount of adsorbed chromium. (Z)-cyclooctene conversion up to 90% with total selectivity for the epoxide was achieved when the oxidation was carried out with hydrogen peroxide, at room temperature. After five consecutive runs, the catalysts maintained high activity, although after the sixth reuse, the epoxide yields strongly decreased to 35%. The catalysts were also efficient for cyclohexane oxidation, reaching up to 18% conversion, with cyclohexanone/cyclohexanol selectivity close to 1.2. On the whole, their use as catalysts gives a very interesting application for the solids obtained by adsorption of a contaminant cation such as Cr(3+).

Structural Modeling Insights into Human VKORC1 Phenotypes

PubMed Central

Czogalla, Katrin J.; Watzka, Matthias; Oldenburg, Johannes

2015-01-01

Vitamin K 2,3-epoxide reductase complex subunit 1 (VKORC1) catalyses the reduction of vitamin K and its 2,3-epoxide essential to sustain γ-carboxylation of vitamin K-dependent proteins. Two different phenotypes are associated with mutations in human VKORC1. The majority of mutations cause resistance to 4-hydroxycoumarin- and indandione-based vitamin K antagonists (VKA) used in the prevention and therapy of thromboembolism. Patients with these mutations require greater doses of VKA for stable anticoagulation than patients without mutations. The second phenotype, a very rare autosomal-recessive bleeding disorder caused by combined deficiency of vitamin K dependent clotting factors type 2 (VKCFD2) arises from a homozygous Arg98Trp mutation. The bleeding phenotype can be corrected by vitamin K administration. Here, we summarize published experimental data and in silico modeling results in order to rationalize the mechanisms of VKA resistance and VKCFD2. PMID:26287237

Synthesis, reactivity and application studies for different biolubricants

PubMed Central

2014-01-01

Vegetable oils have different unique properties owing to their unique chemical structure. Vegetable oils have a greater ability to lubricate and have higher viscosity indices. Therefore, they are being more closely examined as base oil for biolubricants and functional fluids. In spite of their many advantages, vegetable oils suffer from two major drawbacks of inadequate oxidative stability and poor low-temperature properties, which hinder their utilization as biolubricant base oils. Transforming alkene groups in fatty acids to other stable functional groups could improve the oxidative stability, whereas reducing structural uniformity of the oil by attaching alkyl side chains could improve the low-temperature performance. In that light, the epoxidation of unsaturated fatty acids is very interesting as it can provide diverse side chains arising from the mono- or di-epoxidation of the unsaturated fatty acid. Oxirane ring opening by an acid-catalyzed reaction with a suitable reagent provides interesting polyfunctional compounds. PMID:24612780

Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprika.

PubMed

Deli, J; Molnár, P; Matus, Z; Tóth, G

2001-03-01

The changes in the carotenoid pigments of the Capsicum annuum var. lycopersiciforme rubrum during maturation have been investigated quantitatively by means of a HPLC technique. In all of the chromatograms, 40 peaks were detected; 34 carotenoids were identified. The total carotenoid content of the ripe fruits was about 1.3 g/100 g of dry weight, of which capsanthin constituted 37%, zeaxanthin was 8%, cucurbitaxanthin A was 7%, capsorubin constituted 3.2%, and beta-carotene accounted for 9%. The remainder was composed of capsanthin 5,6-epoxide, capsanthin 3,6-epoxide, 5,6-diepikarpoxanthin, violaxanthin, antheraxanthin, beta-cryptoxanthin, and several cis isomers and furanoid oxides. The possible biosynthetic routes for the formation of minor carotenoids containing 3,5,6-trihydroxy-beta-, 3,6-epoxy-beta-, and 6-hydroxy-gamma-end groups are described.

Performance of magnetorheological elastomer based green epoxidized natural rubber/sucrose acetate isobutyrate hybrid matrix

NASA Astrophysics Data System (ADS)

Khairi, Muntaz Hana Ahmad; Amri Mazlan, Saiful; Aziz, Siti Aishah Abdul; Ubaidillah; Tan Shilan, Salihah

2018-04-01

This study introduces a sucrose acetate isobutyrate (SAIB) as a novel additive of magnetorheological elastomers (MREs). The MREs utilized an epoxidized natural rubber (ENR) as the matrix and carbonyl iron particles (CIPs) as their filler. The CIPs were fixed at 60 wt%. The viscosity of the compound was observed using a viscometer. Meanwhile, the microstructures were observed by using field emission scanning electron microscope (FESEM). Rheological properties regarding shear storage modulus were measured by using a rheometer (MCR 302, Anton Paar). The experimental results demonstrated that the MREs-based ENR/SAIB had a decrement in their viscosity by 40% reduction. Moreover, the magnetorheological (MR) effect increased by 23% as the increment of magnetic fields. The morphological photograph showed that the CIPs embedded well within the matrix. The fabricated MREs samples were strain dependent, where all MREs samples exhibit the deteriorating trend when increasing the strain amplitude.

Epoxide pathways improve model predictions of isoprene markers and reveal key role of acidity in aerosol formation.

PubMed

Pye, Havala O T; Pinder, Robert W; Piletic, Ivan R; Xie, Ying; Capps, Shannon L; Lin, Ying-Hsuan; Surratt, Jason D; Zhang, Zhenfa; Gold, Avram; Luecken, Deborah J; Hutzell, William T; Jaoui, Mohammed; Offenberg, John H; Kleindienst, Tadeusz E; Lewandowski, Michael; Edney, Edward O

2013-10-01

Isoprene significantly contributes to organic aerosol in the southeastern United States where biogenic hydrocarbons mix with anthropogenic emissions. In this work, the Community Multiscale Air Quality model is updated to predict isoprene aerosol from epoxides produced under both high- and low-NOx conditions. The new aqueous aerosol pathways allow for explicit predictions of two key isoprene-derived species, 2-methyltetrols and 2-methylglyceric acid, that are more consistent with observations than estimates based on semivolatile partitioning. The new mechanism represents a significant source of organic carbon in the lower 2 km of the atmosphere and captures the abundance of 2-methyltetrols relative to organosulfates during the simulation period. For the parametrization considered here, a 25% reduction in SOx emissions effectively reduces isoprene aerosol, while a similar reduction in NOx leads to small increases in isoprene aerosol.

Two conformers of 10,11-dihydro-5H-dibenzo[a,d]cycloheptene spiro-linked with homobenzoquinone epoxide.

PubMed

Asahara, Haruyasu; Koizumi, Takuya; Mochizuki, Eiko; Oshima, Takumi

2006-03-01

The crystal structures of the two thermally equilibrated conformational isomers of the epoxide 1',5'-dimethylspiro[10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5,8'-4'-oxatricyclo[5.1.0.0(3,5)]octane]-2',6'-dione, C23H20O3, have been determined by X-ray diffraction. In the tricyclic dione skeleton, the oxirane and cyclopropane rings adopt an anti structure with respect to the conjunct quinone frame. The spiro-linked 10,11-dihydro-5H-dibenzo[a,d]cycloheptene ring of the major isomer has a fairly twisted boat form, folding opposite to the adjoining cyclopropane methyl substituent, whereas the seven-membered ring of the minor isomer has an almost ideal twist-boat form, inversely folding to the side of the relevant methyl group. The conformational structures of these isomers have been compared with those of the corresponding isomers of the unepoxidized homobenzoquinone.

Tuning graphitic oxide for initiator- and metal-free aerobic epoxidation of linear alkenes

NASA Astrophysics Data System (ADS)

Pattisson, Samuel; Nowicka, Ewa; Gupta, Upendra N.; Shaw, Greg; Jenkins, Robert L.; Morgan, David J.; Knight, David W.; Hutchings, Graham J.

2016-09-01

Graphitic oxide has potential as a carbocatalyst for a wide range of reactions. Interest in this material has risen enormously due to it being a precursor to graphene via the chemical oxidation of graphite. Despite some studies suggesting that the chosen method of graphite oxidation can influence the physical properties of the graphitic oxide, the preparation method and extent of oxidation remain unresolved for catalytic applications. Here we show that tuning the graphitic oxide surface can be achieved by varying the amount and type of oxidant. The resulting materials differ in level of oxidation, surface oxygen content and functionality. Most importantly, we show that these graphitic oxide materials are active as unique carbocatalysts for low-temperature aerobic epoxidation of linear alkenes in the absence of initiator or metal. An optimum level of oxidation is necessary and materials produced via conventional permanganate-based methods are far from optimal.

Identification and characterization of epoxide hydrolase activity of polycyclic aromatic hydrocarbon-degrading bacteria for biocatalytic resolution of racemic styrene oxide and styrene oxide derivatives.

PubMed

Woo, Jung-Hee; Kwon, Tae-Hyung; Kim, Jun-Tae; Kim, Choong-Gon; Lee, Eun Yeol

2013-04-01

A novel epoxide hydrolase (EHase) from polycyclic aromatic hydrocarbon (PAH)-degrading bacteria was identified and characterized. EHase activity was identified in four strains of PAH-degrading bacteria isolated from commercial gasoline and oil-contaminated sediment based on their growth on styrene oxide and its derivatives, such as 2,3- and 4-chlorostyrene oxides, as a sole carbon source. Gordonia sp. H37 exhibited high enantioselective hydrolysis activity for 4-chlorostyrene oxide with an enantiomeric ratio of 27. Gordonia sp. H37 preferentially hydrolyzed the (R)-enantiomer of styrene oxide derivatives resulting in the preparation of a (S)-enantiomer with enantiomeric excess greater than 99.9 %. The enantioselective EHase activity was identified and characterized in various PAH-degrading bacteria, and whole cell Gordonia sp. H37 was employed as a biocatalyst for preparing enantiopure (S)-styrene oxide derivatives.

Structure of a bacterial homologue of vitamin K epoxide reductase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Weikai; Schulman, Sol; Dutton, Rachel J.

Vitamin K epoxide reductase (VKOR) generates vitamin K hydroquinone to sustain {gamma}-carboxylation of many blood coagulation factors. Here, we report the 3.6 {angstrom} crystal structure of a bacterial homologue of VKOR from Synechococcus sp. The structure shows VKOR in complex with its naturally fused redox partner, a thioredoxin-like domain, and corresponds to an arrested state of electron transfer. The catalytic core of VKOR is a four transmembrane helix bundle that surrounds a quinone, connected through an additional transmembrane segment with the periplasmic thioredoxin-like domain. We propose a pathway for how VKOR uses electrons from cysteines of newly synthesized proteins tomore » reduce a quinone, a mechanism confirmed by in vitro reconstitution of vitamin K-dependent disulphide bridge formation. Our results have implications for the mechanism of the mammalian VKOR and explain how mutations can cause resistance to the VKOR inhibitor warfarin, the most commonly used oral anticoagulant.« less

Characteristics of polyaniline cobalt supported catalysts for epoxidation reactions.

PubMed

Kowalski, Grzegorz; Pielichowski, Jan; Grzesik, Mirosław

2014-01-01

A study of polyaniline (PANI) doping with various cobalt compounds, that is, cobalt(II) chloride, cobalt(II) acetate, and cobalt(II) salen, is presented. The catalysts were prepared by depositing cobalt compounds onto the polymer surface. PANI powders containing cobalt ions were obtained by one- or two-step method suspending PANI in the following acetonitrile/acetic acid solution or acetonitrile and then acetic acid solution. Moreover different ratios of Co(II) : PANI were studied. Catalysts obtained with both methods and at all ratios were investigated using various techniques including AAS and XPS spectroscopy. The optimum conditions for preparation of PANI/Co catalysts were established. Catalytic activity of polyaniline cobalt(II) supported catalysts was tested in dec-1-ene epoxidation with molecular oxygen at room temperature. The relationship between the amount of cobalt species, measured with both AAS and XPS techniques, and the activity of PANI-Co catalysts has been established.

Characteristics of Polyaniline Cobalt Supported Catalysts for Epoxidation Reactions

PubMed Central

Kowalski, Grzegorz; Pielichowski, Jan; Grzesik, Mirosław

2014-01-01

A study of polyaniline (PANI) doping with various cobalt compounds, that is, cobalt(II) chloride, cobalt(II) acetate, and cobalt(II) salen, is presented. The catalysts were prepared by depositing cobalt compounds onto the polymer surface. PANI powders containing cobalt ions were obtained by one- or two-step method suspending PANI in the following acetonitrile/acetic acid solution or acetonitrile and then acetic acid solution. Moreover different ratios of Co(II) : PANI were studied. Catalysts obtained with both methods and at all ratios were investigated using various techniques including AAS and XPS spectroscopy. The optimum conditions for preparation of PANI/Co catalysts were established. Catalytic activity of polyaniline cobalt(II) supported catalysts was tested in dec-1-ene epoxidation with molecular oxygen at room temperature. The relationship between the amount of cobalt species, measured with both AAS and XPS techniques, and the activity of PANI-Co catalysts has been established. PMID:24701183

Extremely efficient crystallization of HKUST-1 and Keggin-loaded related phases through the epoxide route.

PubMed

Oestreicher, Víctor; Jobbágy, Matías

2017-03-25

Highly crystalline HKUST-1 and COK-16-like phases were obtained based on a mild in situ alkalinization one-pot epoxide driven method. A slurry composed of finely ground trimesic acid, H 3 BTC, dispersed in a CuCl 2 aqueous solution quantitatively developed well crystallized HKUST-1 after the addition of propylene oxide. The use of solid H 3 BTC ensures a low concentration of free linker, favoring crystalline growth over the precipitation of amorphous or metastable impurities. An extreme space-time yield of 2.1 × 10 5 kg m -3 day -1 was reached, with no linker excess and minimum use of solvent. The method was equally efficient in the achievement of pure NENU/COK-16 phases, containing [PW 12 O 40 ] 3- , [PMo 12 O 40 ] 3- and [SiMo 12 O 40 ] 4- polyoxometalates.

A One-Step Route to CO2 -Based Block Copolymers by Simultaneous ROCOP of CO2 /Epoxides and RAFT Polymerization of Vinyl Monomers.

PubMed

Wang, Yong; Zhao, Yajun; Ye, Yunsheng; Peng, Haiyan; Zhou, Xingping; Xie, Xiaolin; Wang, Xianhong; Wang, Fosong

2018-03-26

The one-step synthesis of well-defined CO 2 -based diblock copolymers was achieved by simultaneous ring-opening copolymerization (ROCOP) of CO 2 /epoxides and RAFT polymerization of vinyl monomers using a trithiocarbonate compound bearing a carboxylic group (TTC-COOH) as the bifunctional chain transfer agent (CTA). The double chain-transfer effect allows for independent and precise control over the molecular weight of the two blocks and ensures narrow polydispersities of the resultant block copolymers (1.09-1.14). Notably, an unusual axial group exchange reaction between the aluminum porphyrin catalyst and TTC-COOH impedes the formation of homopolycarbonates. By taking advantage of the RAFT technique, it is able to meet the stringent demand for functionality control to well expand the application scopes of CO 2 -based polycarbonates. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gd(OTf)3-catalyzed synthesis of geranyl esters for the intramolecular radical cyclization of their epoxides mediated by titanocene(III).

PubMed

García Santos, William H; Puerto Galvis, Carlos E; Kouznetsov, Vladimir V

2015-02-07

A selective and mild method for the esterification of a variety of carboxylic acids with geraniol is developed. We demonstrated that the use of triphenylphosphine, I2, 2-methylimidazole or imidazole and a catalytic amount of Gd(OTf)3 resulted to be more active than the previous protocols, providing a 16-membered library of geranyl esters in higher yields and in shorter reaction times. The use of essential oil of palmarosa (Cymbopogon martinii), enriched with geraniol, as a raw material for the synthesis of the target compounds complemented and proved how sustainable and eco-friendly this protocol is. Finally, the selective 6,7-epoxidation of the obtained geranyl esters led us to study their regio-controlled radical cyclization mediated by titanocene(III) for the synthesis of novel (8-hydroxy-9,9-dimethyl-5-methylene cyclohexyl)methyl esters in moderate yields and with excellent stereoselectivities.

Discovery of potent inhibitors of soluble epoxide hydrolase by combinatorial library design and structure-based virtual screening.

PubMed

Xing, Li; McDonald, Joseph J; Kolodziej, Steve A; Kurumbail, Ravi G; Williams, Jennifer M; Warren, Chad J; O'Neal, Janet M; Skepner, Jill E; Roberds, Steven L

2011-03-10

Structure-based virtual screening was applied to design combinatorial libraries to discover novel and potent soluble epoxide hydrolase (sEH) inhibitors. X-ray crystal structures revealed unique interactions for a benzoxazole template in addition to the conserved hydrogen bonds with the catalytic machinery of sEH. By exploitation of the favorable binding elements, two iterations of library design based on amide coupling were employed, guided principally by the docking results of the enumerated virtual products. Biological screening of the libraries demonstrated as high as 90% hit rate, of which over two dozen compounds were single digit nanomolar sEH inhibitors by IC(50) determination. In total the library design and synthesis produced more than 300 submicromolar sEH inhibitors. In cellular systems consistent activities were demonstrated with biochemical measurements. The SAR understanding of the benzoxazole template provides valuable insights into discovery of novel sEH inhibitors as therapeutic agents.

Transition State Geometry Measurements from 13C Isotope Effects. The Experimental Transition State for the Epoxidation of Alkenes with Oxaziridines

PubMed Central

Hirschi, Jennifer S.; Takeya, Tetsuya; Hang, Chao; Singleton, Daniel A.

2009-01-01

We suggest here and evaluate a methodology for the measurement of specific interatomic distances from a combination of theoretical calculations and experimentally measured 13C kinetic isotope effects. This process takes advantage of a broad diversity of transition structures available for the epoxidation of 2-methyl-2-butene with oxaziridines. From the isotope effects calculated for these transition structures, a theory-independent relationship between the C-O bond distances of the newly forming bonds and the isotope effects is established. Within the precision of the measurement, this relationship in combination with the experimental isotope effects provides a highly accurate picture of the C-O bonds forming at the transition state. The diversity of transition structures also allows an evaluation of the Schramm process for defining transition state geometries based on calculations at non-stationary points, and the methodology is found to be reasonably accurate. PMID:19146405

Identification of an Epoxide Metabolite of Lycopene in Human Plasma Using 13C-Labeling and QTOF-MS.

PubMed

Cichon, Morgan J; Moran, Nancy E; Riedl, Ken M; Schwartz, Steven J; Clinton, Steven K

2018-03-20

The carotenoid lycopene is a bioactive component of tomatoes and is hypothesized to reduce risk of several chronic diseases, such as prostate cancer. The metabolism of lycopene is only beginning to be understood and some studies suggest that metabolites of lycopene may be partially responsible for bioactivity associated with the parent compound. The detection and characterization of these compounds in vivo is an important step in understanding lycopene bioactivity. The metabolism of lycopene likely involves both chemical and enzymatic oxidation. While numerous lycopene metabolites have been proposed, few have actually been identified in vivo following lycopene intake. Here, LC-QTOF-MS was used along with 13 C-labeling to investigate the post-prandial oxidative metabolism of lycopene in human plasma. Previously reported aldehyde cleavage products were not detected, but a lycopene 1,2-epoxide was identified as a new candidate oxidative metabolite.

Kinetic Studies on the Xanthophyll Cycle in Barley Leaves (Influence of Antenna Size and Relations to Nonphotochemical Chlorophyll Fluorescence Quenching).

PubMed Central

Hartel, H.; Lokstein, H.; Grimm, B.; Rank, B.

1996-01-01

Xanthophyll-cycle kinetics as well as the relationship between the xanthophyll de-epoxidation state and Stern-Volmer type nonphotochemical chlorophyll (Chl) fluorescence quenching (qN) were investigated in barley (Hordeum vulgare L.) leaves comprising a stepwise reduced antenna system. For this purpose plants of the wild type (WT) and the Chl b-less mutant chlorina 3613 were cultivated under either continuous (CL) or intermittent light (IML). Violaxanthin (V) availability varied from about 70% in the WT up to 97 to 98% in the mutant and IML-grown plants. In CL-grown mutant leaves, de-epoxidation rates were strongly accelerated compared to the WT. This is ascribed to a different accessibility of V to the de-epoxidase due to the existence of two V pools: one bound to light-harvesting Chl a/b-binding complexes (LHC) and the other one not bound. Epoxidation rates (k) were decreased with reduction in LHC protein contents: kWT > kmutant >> kIML plants. This supports the idea that the epoxidase activity resides on certain LHC proteins. Irrespective of huge zeaxanthin and antheraxanthin accumulation, the capacity to develop qN was reduced stepwise with antenna size. The qN level obtained in dithiothreitol-treated CL- and IML-grown plants was almost identical with that in untreated IML-grown plants. The findings provide evidence that structural changes within the LHC proteins, mediated by xanthophyll-cycle operation, render the basis for the development of a major proportion of qN. PMID:12226199

Identification of a tumor-promoter cholesterol metabolite in human breast cancers acting through the glucocorticoid receptor

PubMed Central

Voisin, Maud; de Medina, Philippe; Mallinger, Arnaud; Dalenc, Florence; Huc-Claustre, Emilie; Leignadier, Julie; Serhan, Nizar; Soules, Régis; Ségala, Grégory; Mougel, Aurélie; Noguer, Emmanuel; Mhamdi, Loubna; Bacquié, Elodie; Iuliano, Luigi; Zerbinati, Chiara; Lacroix-Triki, Magali; Chaltiel, Léonor; Filleron, Thomas; Cavaillès, Vincent; Al Saati, Talal; Rochaix, Philippe; Duprez-Paumier, Raphaelle; Franchet, Camille; Ligat, Laetitia; Lopez, Fréderic; Record, Michel; Poirot, Marc; Silvente-Poirot, Sandrine

2017-01-01

Breast cancer (BC) remains the primary cause of death from cancer among women worldwide. Cholesterol-5,6-epoxide (5,6-EC) metabolism is deregulated in BC but the molecular origin of this is unknown. Here, we have identified an oncometabolism downstream of 5,6-EC that promotes BC progression independently of estrogen receptor α expression. We show that cholesterol epoxide hydrolase (ChEH) metabolizes 5,6-EC into cholestane-3β,5α,6β-triol, which is transformed into the oncometabolite 6-oxo-cholestan-3β,5α-diol (OCDO) by 11β-hydroxysteroid-dehydrogenase-type-2 (11βHSD2). 11βHSD2 is known to regulate glucocorticoid metabolism by converting active cortisol into inactive cortisone. ChEH inhibition and 11βHSD2 silencing inhibited OCDO production and tumor growth. Patient BC samples showed significant increased OCDO levels and greater ChEH and 11βHSD2 protein expression compared with normal tissues. The analysis of several human BC mRNA databases indicated that 11βHSD2 and ChEH overexpression correlated with a higher risk of patient death, highlighting that the biosynthetic pathway producing OCDO is of major importance to BC pathology. OCDO stimulates BC cell growth by binding to the glucocorticoid receptor (GR), the nuclear receptor of endogenous cortisol. Interestingly, high GR expression or activation correlates with poor therapeutic response or prognosis in many solid tumors, including BC. Targeting the enzymes involved in cholesterol epoxide and glucocorticoid metabolism or GR may be novel strategies to prevent and treat BC. PMID:29078321

Synthesis, docking, cytotoxicity, and LTA4H inhibitory activity of new gingerol derivatives as potential colorectal cancer therapy.

PubMed

El-Naggar, Mai H; Mira, Amira; Abdel Bar, Fatma M; Shimizu, Kuniyoshi; Amer, Mohamed M; Badria, Farid A

2017-02-01

Leukotriene A4 hydrolase (LTA 4 H) is a proinflammatory enzyme that generates the inflammatory mediator leukotriene which may play an important role in chronic inflammation associated carcinogenesis. [6]-gingerol, the major bioactive compound of Zingiber officinale, is a potential inhibitor of LTA 4 H, a highly expressed enzyme in colorectal carcinoma. Eighteen compounds; seven of natural origin (including [4]-, [6]-, [8]-, and [10]-gingerol), five new and six known semi-synthesized [6]-gingerol derivatives were examined using docking, in vitro cytotoxicity against human colon cancer cells (HCT-116) and LTA 4 H aminopeptidase and epoxide hydrolase inhibitory studies. Methyl shogoal (D8) showed to be the most potent compound against HCT-116 cells (IC 50 ; 1.54μM). Remarkably, D8 proved to be non-cytotoxic to normal cells; (TIG-1) and (HF-19) with high selective index (SI; 52.3). Furthermore [6]-gingerol derivatives showed potent LTA 4 H inhibitory activities in comparison to the universal positive controls (bestatin and 4BSA). Among the natural gingerols, [10]-gingerol (N3) exhibited the highest LTA 4 H aminopeptidase and epoxide hydrolase inhibitory activities with IC 50 ; 21.59 and 15.24μM, respectively. Meanwhile, methyl shogoal (D8) and 4'-O-prenyl-[6]-gingerol (D10) retained the highest inhibition with IC 50 ; 4.92 and 3.01μM, for aminopeptidase, and 11.27 and 7.25μM for epoxide hydrolase activities, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Identification of a tumor-promoter cholesterol metabolite in human breast cancers acting through the glucocorticoid receptor.

PubMed

Voisin, Maud; de Medina, Philippe; Mallinger, Arnaud; Dalenc, Florence; Huc-Claustre, Emilie; Leignadier, Julie; Serhan, Nizar; Soules, Régis; Ségala, Grégory; Mougel, Aurélie; Noguer, Emmanuel; Mhamdi, Loubna; Bacquié, Elodie; Iuliano, Luigi; Zerbinati, Chiara; Lacroix-Triki, Magali; Chaltiel, Léonor; Filleron, Thomas; Cavaillès, Vincent; Al Saati, Talal; Rochaix, Philippe; Duprez-Paumier, Raphaelle; Franchet, Camille; Ligat, Laetitia; Lopez, Fréderic; Record, Michel; Poirot, Marc; Silvente-Poirot, Sandrine

2017-10-31

Breast cancer (BC) remains the primary cause of death from cancer among women worldwide. Cholesterol-5,6-epoxide (5,6-EC) metabolism is deregulated in BC but the molecular origin of this is unknown. Here, we have identified an oncometabolism downstream of 5,6-EC that promotes BC progression independently of estrogen receptor α expression. We show that cholesterol epoxide hydrolase (ChEH) metabolizes 5,6-EC into cholestane-3β,5α,6β-triol, which is transformed into the oncometabolite 6-oxo-cholestan-3β,5α-diol (OCDO) by 11β-hydroxysteroid-dehydrogenase-type-2 (11βHSD2). 11βHSD2 is known to regulate glucocorticoid metabolism by converting active cortisol into inactive cortisone. ChEH inhibition and 11βHSD2 silencing inhibited OCDO production and tumor growth. Patient BC samples showed significant increased OCDO levels and greater ChEH and 11βHSD2 protein expression compared with normal tissues. The analysis of several human BC mRNA databases indicated that 11βHSD2 and ChEH overexpression correlated with a higher risk of patient death, highlighting that the biosynthetic pathway producing OCDO is of major importance to BC pathology. OCDO stimulates BC cell growth by binding to the glucocorticoid receptor (GR), the nuclear receptor of endogenous cortisol. Interestingly, high GR expression or activation correlates with poor therapeutic response or prognosis in many solid tumors, including BC. Targeting the enzymes involved in cholesterol epoxide and glucocorticoid metabolism or GR may be novel strategies to prevent and treat BC. Published under the PNAS license.

Compositional profile of α/β-hydrolase fold proteins in mangrove soil metagenomes: prevalence of epoxide hydrolases and haloalkane dehalogenases in oil-contaminated sites

PubMed Central

Jiménez, Diego Javier; Dini-Andreote, Francisco; Ottoni, Júlia Ronzella; de Oliveira, Valéria Maia; van Elsas, Jan Dirk; Andreote, Fernando Dini

2015-01-01

The occurrence of genes encoding biotechnologically relevant α/β-hydrolases in mangrove soil microbial communities was assessed using data obtained by whole-metagenome sequencing of four mangroves areas, denoted BrMgv01 to BrMgv04, in São Paulo, Brazil. The sequences (215 Mb in total) were filtered based on local amino acid alignments against the Lipase Engineering Database. In total, 5923 unassembled sequences were affiliated with 30 different α/β-hydrolase fold superfamilies. The most abundant predicted proteins encompassed cytosolic hydrolases (abH08; ∼ 23%), microsomal hydrolases (abH09; ∼ 12%) and Moraxella lipase-like proteins (abH04 and abH01; < 5%). Detailed analysis of the genes predicted to encode proteins of the abH08 superfamily revealed a high proportion related to epoxide hydrolases and haloalkane dehalogenases in polluted mangroves BrMgv01-02-03. This suggested selection and putative involvement in local degradation/detoxification of the pollutants. Seven sequences that were annotated as genes for putative epoxide hydrolases and five for putative haloalkane dehalogenases were found in a fosmid library generated from BrMgv02 DNA. The latter enzymes were predicted to belong to Actinobacteria, Deinococcus-Thermus, Planctomycetes and Proteobacteria. Our integrated approach thus identified 12 genes (complete and/or partial) that may encode hitherto undescribed enzymes. The low amino acid identity (< 60%) with already-described genes opens perspectives for both production in an expression host and genetic screening of metagenomes. PMID:25171437

21 CFR 172.723 - Epoxidized soybean oil.

Code of Federal Regulations, 2014 CFR

2014-04-01

... incorporation by reference is given in paragraph (b)(1) of this section. (3) The heavy metals (as Pb) content cannot be more than 10 parts per million, as determined by the “Heavy Metals Test,” of the “Food...

Metabolic inactivation of 2-oxiranylmethyl 2-ethyl-2,5-dimethylhexanoate (C10GE) in skin, lung and liver of human, rat and mouse.

PubMed

Boogaard, P J; van Elburg, P A; de Kloe, K P; Watson, W P; van Sittert, N J

1999-10-01

The inactivation of 2-oxiranylmethyl 2-ethyl-2,5-dimethylhexanoate (C10GE), one of the most abundant isomers of the epoxy-resin Carduras E-10 glycidyl ester, was studied in subcellular fractions of human, C3H mouse and F344 rat liver, lung and skin. C10GE is chemically very stable and resistant to aqueous hydrolysis, but it was rapidly metabolized in both cytosolic and microsomal fractions of all organs by epoxide hydrolase (EH)-catalysed hydrolysis of the epoxide moiety as well as carboxylesterase (CE)-catalysed hydrolysis of the ester bond. In cytosol the epoxide group was also efficiently conjugated with glutathione, catalysed by glutathione S-transferase (GST), but this conjugation was much less important than hydrolysis in human as well as rodent samples. Although CE-catalysed hydrolysis of C10GE would theoretically give rise to the formation of glycidol, a directly acting mutagen, it is highly unlikely that any significant level of glycidol would occur in vivo since reported rates of inactivation of glycidol exceed the total rate of hydrolysis of C10GE. The overall rates of inactivation in vitro decreased in the following order: mouse > rat > human. Scaling of the data in vitro to clearances in vivo suggests that the detoxifying capacity in the rodents is similar and about an order of magnitude greater than in human. Nevertheless, the rate of inactivation is 2-3 orders of magnitude greater than for simple epoxides such as butadiene monoxide and about one order of magnitude higher than for the diglycidyl ether of bisphenol A (BADGE). The transdermal penetration and metabolism of [14C]-C10GE was studied in fresh full-thickness mouse, and dermatomized human and rat skin. Of the total radioactivity applied on the skin, only 0.24+/-0.06 (SD), 1.8+/-0.2 and 6.8+/-0.6% penetrated through human, mouse and rat skin respectively. The corresponding apparent skin permeability constants were 0.81, 6.42 and 26.4 x 10(-6) cm/h. During transdermal penetration, [14C]-C10GE was extensively hydrolysed to the corresponding diol and the free acid. Only 0.01, 0.11 and 0.21]% of the applied dose was absorbed unchanged through the human, mouse and rat skin respectively.

Further characterization of benzo[a]pyrene diol-epoxide (BPDE)-induced comet assay effects.

PubMed

Bausinger, Julia; Schütz, Petra; Piberger, Ann Liza; Speit, Günter

2016-03-01

The present study aims to further characterize benzo[a]pyrene diol-epoxide (BPDE)-induced comet assay effects. Therefore, we measured DNA effects by the comet assay and adduct levels by high-performance liquid chromatography (HPLC) in human lymphocytes and A549 cells exposed to (±)-anti-benzo[a]pyrene-7,8-diol 9,10-epoxide [(±)-anti-BPDE] or (+)-anti-benzo[a]pyrene-7,8-diol 9,10-epoxide [(+)-anti-BPDE]. Both, the racemic form and (+)-anti-BPDE, which is the most relevant metabolite with regard to mutagenicity and carcinogenicity, induced DNA migration in cultured lymphocytes in the same range of concentrations to a similar extent in the alkaline comet assay after exposure for 2h. Nevertheless, (+)-anti-BPDE induced significantly enhanced DNA migration after 16 and 18h post-cultivation which was not seen in response to (±)-anti-BPDE. Combination of the comet assay with the Fpg (formamidopyrimidine-DNA glycosylase) protein did not enhance BPDE-induced effects and thus indicated the absence of Fpg-sensitive sites (oxidized purines, N7-guanine adducts, AP-sites). The aphidicolin (APC)-modified comet assay suggested significant excision repair activity of cultured lymphocytes during the first 18h of culture after a 2 h-exposure to BPDE. In contrast to these repair-related effects measured by the comet assay, HPLC analysis of stable adducts did not reveal any significant removal of (+)-anti-BPDE-induced adducts from lymphocytes during the first 22h of culture. On the other hand, HPLC measurements indicated that A549 cells repaired about 70% of (+)-anti-BPDE-induced DNA-adducts within 22h of release. However, various experiments with the APC-modified comet assay did not indicate significant repair activity during this period in A549 cells. The conflicting results obtained with the comet assay and the HPLC-based adduct analysis question the real cause for BPDE-induced DNA migration in the comet assay and the reliability of the APC-modified comet assay for the determination of DNA excision repair activity in response to BPDE in different cell types. © The Author 2015. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Selective Clay Placement Within a Silicate-Clay Epoxy Blend Nanocomposite

NASA Technical Reports Server (NTRS)

Miller, Sandi G (Inventor)

2013-01-01

A clay-epoxy nanocomposite may be prepared by dispersing a layered clay in an alkoxy epoxy, such as a polypropylene oxide based epoxide before combining the mixture with an aromatic epoxy to improve the nanocomposite's thermal and mechanical properties.

Polymerized and functionalized triglycerides

USDA-ARS?s Scientific Manuscript database

Plant oils are useful sustainable raw materials for the development of new chemical products. As part of our research emphasis in sustainability and green polymer chemistry, we have explored a new method for polymerizing epoxidized triglycerides with the use of fluorosulfonic acid. Depending on the ...

21 CFR 172.723 - Epoxidized soybean oil.

Code of Federal Regulations, 2013 CFR

2013-04-01

... given in paragraph (b)(1) of this section. (3) The heavy metals (as Pb) content cannot be more than 10 parts per million, as determined by the “Heavy Metals Test,” of the “Food Chemicals Codex,” 4th ed...

Process for improving moisture resistance of epoxy resins by addition of chromium ions

NASA Technical Reports Server (NTRS)

St.clair, A. K.; Stoakley, D. M.; St.clair, T. L.; Singh, J. J. (Inventor)

1985-01-01

A process for improving the moisture resistance properties of epoxidized TGMDA and DGEBA resin system by chemically incorporating chromium ions is described. The addition of chromium ions is believed to prevent the absorption of water molecules.

Health Assessment Document for Ethylene Oxide

EPA Science Inventory

The largest single use of ethylene oxide is as an intermediate in the synthesis of ethylene glycol. However, small amounts of this epoxide are used as a sterilant or pesticide in commodities, pharmaceuticals, medical devices, tobacco, and other items, representing a considerable ...

VOLATILE ORGANIC CHEMICALS IN 10 PUBLIC-ACCESS BUILDINGS

EPA Science Inventory

The U.S. EPA carried out studies of indoor air quality in 10 buildings. Qualitative analysis identified over 200 aromatics, halogens, esters, alcohols, phenols, ethers, ketones, aldehydes, and epoxides, in addition to several hundred aliphatic hydrocarbons. The total organic load...

NMR spectroscopy for assessment of lipid oxidation during frying

USDA-ARS?s Scientific Manuscript database

Except for total polar compounds (TPC), polymerized triacylglycerols (PTAG) and fatty acid composition, most other current standard methods for lipid oxidation detect very small amounts of oxidation products such as hydroperoxides, conjugated dienes, aldehydes, and epoxides. Therefore, amounts of th...

Ligand-Enabled meta-C–H Activation Using a Transient Mediator

PubMed Central

Wang, Xiao-Chen; Gong, Wei; Fang, Li-Zhen; Zhu, Ru-Yi; Li, Suhua; Engle, Keary M.; Yu, Jin-Quan

2015-01-01

Achieving site selectivity in C–H functionalization reactions is a significant challenge, especially when the target C–H bond is distant from existing functional groups.1–5 Coordination of a functional group to a metal catalyst is often a key driving force and control element in many important reactions including asymmetric hydrogenation,6 epoxidation7, 8, and lithiation9. Exploitation of this effect has led to the development of a broad range of directed C–H activation reactions.10–14 However, such C–H activation methods are limited to proximal C–H bonds, which are spatially and geometrically accessible from the directing functional group. Development of meta-selective C–H functionalizations remains a significant challenge.1–5,15–17 We recently developed a U- shaped template that can be used to overcome this constraint and have shown that it can be used to selectively activate remote meta-C–H bonds.1, 2 While this approach has proven applicable for a diverse set of substrates and catalytic transformations,3–5 the need for a covalently attached complex template is a significant drawback for synthetic applications. In this manuscript, we report an alternative approach, one that employs norbornene as a transient mediator to achieve meta-selective C–H activation with a simple and common ortho-directing group. The use of a newly developed pyridine-based ligand is crucial for relaying the palladium catalyst to the meta position by norbornene following initial ortho- C–H activation. Thus, this catalytic reaction demonstrates the feasibility of switching ortho-selectivity to meta-selectivity in C–H activation of the same substrate by catalyst control. PMID:25754328