Sample records for absolute asymmetric synthesis

  1. Asymmetric total synthesis and absolute stereochemistry of the neuroactive marine macrolide palmyrolide A.

    PubMed

    Tello-Aburto, Rodolfo; Johnson, Emily M; Valdez, Cheyenne K; Maio, William A

    2012-04-20

    The first asymmetric total synthesis and determination of the absolute configuration for the neuroactive marine macrolide palmyrolide A is described. The highlight of the synthesis is macrocyclization via trans-enamide formation catalyzed by copper(I) iodide and cesium carbonate. Comparison with the authentic spectral data confirms the synthesis of (+)-ent-palmyrolide A. PMID:22475318

  2. Asymmetric Total Synthesis and Absolute Stereochemistry of the Neuroactive Marine Macrolide Palmyrolide A†

    PubMed Central

    Tello-Aburto, Rodolfo; Johnson, Emily M.; Valdez, Cheyenne K.

    2012-01-01

    The first asymmetric total synthesis and determination of the absolute configuration for the neuroactive marine macrolide Palmyrolide A is described. The highlight of the synthesis is macrocyclization via trans-enamide formation catalyzed by copper (I) iodide and cesium carbonate. Comparison with the authentic spectral data confirms the synthesis of (+)-ent-Palmyrolide A. PMID:22475318

  3. (-)-(2S,3R,Z)-Nakinadine A: first asymmetric synthesis and absolute configuration assignment.

    PubMed

    Davies, Stephen G; Fletcher, Ai M; Roberts, Paul M; Shah, Rushabh S; Thompson, Amber L; Thomson, James E

    2014-03-01

    Mannich-type reaction of methyl phenylacetate with the N-tert-butylsulfinyl imine derived from (R)-tert-butylsulfinamide and (Z)-14-(pyridin-3'-yl)tetradec-11-enal has been used as the key step in the first asymmetric synthesis of (-)-nakinadine A. Both the 2,3-syn- and 2,3-anti-diastereoisomers were prepared; comparison of spectroscopic and specific rotation data facilitated assignment of the absolute (2S,3R,Z)-configuration within the natural product. (-)-(2S,3R,Z)-Nakinadine A was prepared in 10 steps from 11-bromoundecan-1-ol, in 10% overall yield, 97:3 dr [(Z):(E) ratio], and >98% ee. PMID:24564566

  4. ABSOLUTE ASYMMETRIC SYNTHESIS. I. ON THE MECHANISM OF THEPHOTOCHEMICAL ABSOLUTE ASYMMETRIC SYNTHESIS OF HELICENES WITH CIRCULARLYPOLARIZED LIGHT. . WAVELENGTH DEPENDENCE OF THE OPTICAL YIELD OFOCTAHELICENE.

    SciTech Connect

    Bernstein, William J.; Calvin, Melvin; Buchardt, Ole.

    1971-05-01

    The synthesis of nonracemic yields of hexa-, hepta-, octa-, and nonhelicene with circular light was observed, and the structural and wavelength dependence of the induced optical yields was examined. The results obtained, together with a detailed consideration of the mechanism of helicene synthesis from the parent diarylolefins, indicate that the induced optical activity is due to selective reaction of enantiomeric conformations of the parent cis diarylolefins by circular light.

  5. A chiral 1,4-oxazin-2-one: asymmetric synthesis versus resolution, structure, conformation and VCD absolute configuration

    Microsoft Academic Search

    A. Solladié-Cavallo; O. Sedy; M. Salisova; M. Biba; C. J. Welch; L. Nafié; T. Freedman

    2001-01-01

    1,4-Oxazin-2-one 3 is obtained from 2-pinanone in 4 steps and 78% overall yield. Enantiopure (e.e. >99%) (R)-(+)-3 and (S)-(?)-3 were obtained through chiral supercritical fluid chromatography (using a semi preparative Chiralpak AS column) with almost quantitative recovery of material. The structure and the boat-conformation of the lactone ring have been determined by NMR and the absolute configuration determined by VCD.

  6. Frontispiece: Absolute Asymmetric Synthesis: Viedma Ripening of [Co(bpy)3 ](2+) and Solvent-Free Oxidation to [Co(bpy)3 ](3.).

    PubMed

    Björemark, Per Martin; Jönsson, Johan; Håkansson, Mikael

    2015-07-20

    Asymmetric Synthesis Syntheses of [Co(bpy)3 ](2+) yield racemic solutions because the ?- and ?-enantiomers are stereochemically labile. However, crystallization and attrition-enhanced deracemization can give homochiral crystal batches of either handedness in quantitative yield. Subsequently, solvent-free oxidation with bromine vapour fixes the chirality because [Co(bipy)3 ](3+) does not enantiomerize in solution at ambient temperature. For more details, see the Communication by M. Håkansson et?al. on page?10630?ff. PMID:26171695

  7. Asymmetric total synthesis of (+)-dragmacidin D reveals unexpected stereocomplexity.

    PubMed

    Zhang, Fengying; Wang, Bin; Prasad, Pritesh; Capon, Robert J; Jia, Yanxing

    2015-03-20

    The first asymmetric total synthesis of the bis-indole marine alkaloid (+)-dragmacidin D (1) has been achieved. This synthesis revises an earlier configurational assignment based on biosynthetic considerations and assigns an R absolute configuration to (+)-1. The current studies reveal that natural dragmacidin D is isolated as either a racemate or a scalemic mixture (39% ee). PMID:25730523

  8. A Unique Asymmetrical Stroop Effect in Absolute Pitch Possessors

    Microsoft Academic Search

    Lilach Akiva-Kabiri; Avishai Henik

    2012-01-01

    The Stroop task has been employed to study automaticity or failures of selective attention for many years. The effect is known to be asymmetrical, with words affecting color naming but not vice versa. In the current work two auditory-visual Stroop-like tasks were devised in order to study the automaticity of pitch processing in both absolute pitch (AP) possessors and musically

  9. Spontaneous chiral crystallization of achiral materials and absolute asymmetric transformation in the chiral crystalline environment

    Microsoft Academic Search

    Masami Sakamoto

    Recently, the combination of chiral crystallization and the solid-state photoreaction has provided many successful examples\\u000a of absolute asymmetric synthesis.[1] In these reactions achiral materials adopted chiral arrangement only by spontaneous crystallization,\\u000a and optically active products are obtained from the topochemically controlled reaction with high ees (Figure 1).[2,3] This\\u000a method incurs a problem in crystallization of achiral molecules in chiral space

  10. Hydroxamic Acids in Asymmetric Synthesis

    PubMed Central

    Li, Zhi; Yamamoto, Hisashi

    2012-01-01

    Metal-catalyzed stereoselective reactions are a central theme in organic chemistry research. In these reactions, the stereoselection is achieved predominantly by introducing chiral ligands at the metal catalyst’s center. For decades, researchers have sought better chiral ligands for asymmetric catalysis and have made great progress. Nevertheless, to achieve optimal stereoselectivity and to catalyze new reactions, new chiral ligands are needed. Due to their high metal affinity, hydroxamic acids play major roles across a broad spectrum of fields from biochemistry to metal extraction. Dr. K. Barry Sharpless first revealed their potential as chiral ligands for asymmetric synthesis in 1977: He published the chiral vanadium-hydroxamic-acid-catalyzed, enantioselective epoxidation of allylic alcohols before his discovery of Sharpless Asymmetric Epoxidation, which uses titanium-tartrate complex as the chiral reagent. However, researchers have reported few highly enantioselective reactions using metal-hydroxamic acid as catalysts since then. This Account summarizes our research on metal-catalyzed asymmetric epoxidation using hydroxamic acids as chiral ligands. We designed and synthesized a series of new hydroxamic acids, most notably the C2-symmetric bis-hydroxamic acid (BHA) family. V-BHA-catalyzed epoxidation of allylic and homoallylic alcohols achieved higher activity and stereoselectivity than Sharpless Asymmetric Epoxidation in many cases. Changing the metal species led to a series of unprecedented asymmetric epoxidation reactions, such as (i) single olefins and sulfides with Mo-BHA, (ii) homoallylic and bishomoallylic alcohols with Zr- and Hf-BHA, and (iii) N-alkenyl sulfonamides and N-sulfonyl imines with Hf-BHA. These reactions produce uniquely functionalized chiral epoxides with good yields and enantioselectivities. PMID:23157425

  11. Asymmetric, stereocontrolled total synthesis of paraherquamide A.

    PubMed

    Williams, Robert M; Cao, Jianhua; Tsujishima, Hidekazu; Cox, Rhona J

    2003-10-01

    The first total synthesis of paraherquamide A, a potent anthelmintic agent isolated from various Penicillium sp. with promising activity against drug-resistant intestinal parasites, is reported. Key steps in this asymmetric, stereocontrolled total synthesis include a new enantioselective synthesis of alpha-alkylated-beta-hydroxyproline derivatives to access the substituted proline nucleus and a highly diastereoselective intramolecular S(N)2' cyclization to generate the core bicyclo[2.2.2]diazaoctane ring system. PMID:14519003

  12. De novo asymmetric synthesis of 8a-epi-swainsonine.

    PubMed

    Abrams, Jason N; Babu, Ravula Satheesh; Guo, Haibing; Le, Dianna; Le, Jennifer; Osbourn, Joshua M; O'Doherty, George A

    2008-03-01

    An enantioselective and diastereocontrolled approach to 8a-epi-d-swainsonine has been developed from achiral furfural. The key step to this synthesis was a one-pot procedure for the hydrogenolytic removal of two protecting groups and two intramolecular reductive amination reactions. The absolute stereochemistry was introduced by asymmetric Noyori reduction of furfuryl ketone. This route relies on diastereoselective palladium-catalyzed glycosylation to install the anomeric bond, and Luche reduction, diastereoselective dihydroxylation to set up the manno-stereochemistry of the indolizidine precursor. PMID:18237188

  13. Asymmetric synthesis of tertiary thiols and thioethers

    PubMed Central

    MacLellan, Paul

    2011-01-01

    Summary Enantiomerically pure tertiary thiols provide a major synthetic challenge, and despite the importance of chiral sulfur-containing compounds in biological and medicinal chemistry, surprisingly few effective methods are suitable for the asymmetric synthesis of tertiary thiols. This review details the most practical of the methods available. PMID:21647256

  14. Combined Acid Catalysis for Asymmetric Synthesis

    E-print Network

    Johnson, Jeff S.

    Combined Acid Catalysis for Asymmetric Synthesis Michael T. Corbett University of North Carolina, 44, 1924­1942. Limitations of classical Brønsted/Lewis Acid catalysis: · Poor reactivity (low acidity) · Low selectivity · High catalyst loading R X R X HMLn X Lewis Acid Catalysis Brønsted Acid Catalysis X

  15. Catalytic asymmetric synthesis of febrifugine and isofebrifugine

    Microsoft Academic Search

    Sh? Kobayashi; Masaharu Ueno; Ritsu Suzuki; Haruro Ishitani

    1999-01-01

    Antimalarial alkaloids, febrifugine (1) and isofebrifugine (2), were synthesized from simple achiral starting materials using tin(II)-catalyzed catalytic asymmetric aldol reaction and lanthanide-catalyzed aqueous three-component reaction as the key steps. These unambiguous total syntheses revealed that the absolute configurations of febrifugine and isofebrifugine were not (2?S, 3?R) and (2?R, 3?R) as reported previously but (2?R, 3?S) and (2?S, 3?S), respectively.

  16. Asymmetric Silver "Nanocarrot" Structures: Solution Synthesis and Their Asymmetric Plasmonic Resonances

    E-print Network

    Asymmetric Silver "Nanocarrot" Structures: Solution Synthesis and Their Asymmetric Plasmonic the wet-chemical synthesis of asymmetric one-dimensional (1D) silver "nanocarrot" structures that exhibit of the longitudinal surface plasmon resonance peaks. The silver nanocarrots also show very high sensitivity

  17. Asymmetric Total Synthesis of ent-Pyripyropene?A.

    PubMed

    Fuse, Shinichiro; Ikebe, Ayako; Oosumi, Kazuya; Karasawa, Tomoya; Matsumura, Keisuke; Izumikawa, Miho; Johmoto, Kohei; Uekusa, Hidehiro; Shin-Ya, Kazuo; Doi, Takayuki; Takahashi, Takashi

    2015-06-22

    An asymmetric total synthesis of ent-pyripyropene?A was achieved by a convergent synthetic route. We used our originally developed Ti(III) -catalyzed radical cyclization to construct an AB-ring portion that consisted of a trans-decalin skeleton with five contiguous stereogenic centers. The coupling between the AB-ring and the DE-ring portions, and a subsequent C-ring cyclization, led to the total synthesis of ent-pyripyropene?A. An evaluation of the insecticidal activity of ent-pyripyropene?A against two aphid species revealed that ent-pyripyropene?A was 35-175 times less active than naturally occurring pyripyropene?A. This result indicated that the biological target of pyripyropene?A recognizes the absolute configuration of pyripyropene?A. PMID:26014374

  18. Asymmetric Total Synthesis of Bioactive Natural Lipid Mycalol.

    PubMed

    Das, Subhendu; Kuilya, Tapan Kumar; Goswami, Rajib Kumar

    2015-06-19

    A concise and convergent route for stereoselective total synthesis of promising anticancer natural lipid mycalol has been achieved using cheap and readily available l-arabinose as a chiral pool. The notable features of our synthesis comprised regioselective Wacker oxidation, Sharpless asymmetric dihydroxylation, Julia-Kocienski olefination, Wittig olefination, Zipper reaction, and Sonogashira reaction. Comparison of the spectroscopic data on a series of isomers supports the revised structure (Org. Lett. 2015, 17, 1652) instead of the one originally proposed. PMID:25992780

  19. Pseudoephenamine: A Practical Chiral Auxiliary for Asymmetric Synthesis

    PubMed Central

    Morales, Marvin R.; Mellem, Kevin T.; Myers, Andrew G.

    2013-01-01

    Pseudoephenamine is shown to be a versatile chiral auxiliary for asymmetric synthesis. It is free from regulatory restrictions and exhibits remarkable stereocontrol in alkylation reactions, especially those that form quaternary carbon centers. Amides derived from pseudoephenamine exhibit a high propensity to be crystalline substances and provide sharp, well-defined peaks in NMR spectra. PMID:22461381

  20. Magnetically Retrievable Catalysts for Asymmetric Synthesis

    EPA Science Inventory

    Surface modification of magnetic nanoparticles with chiral scaffolds for asymmetric catalytic applications is an elegant way of providing a special pseudo homogenous phase which could be separated using an external magnet. In this review, we summarize the use of magnetic nanopart...

  1. Asymmetric Synthesis of the Aminocyclitol Pactamycin, a Universal Translocation Inhibitor

    PubMed Central

    Sharpe, Robert J.; Malinowski, Justin T.; Johnson, Jeffrey S.

    2014-01-01

    An asymmetric total synthesis of the aminocyclopentitol pactamycin is described, which delivers the title compound in 15 steps from 2,4-pentanedione. Critical to this approach was the exploitation of a complex symmetry-breaking reduction strategy to assemble the C1, C2, and C7 relative stereochemistry within the first four steps of the synthesis. Multiple iterations of this reduction strategy are described, and a thorough analysis of stereochemical outcomes is detailed. In the final case, an asymmetric Mannich reaction was developed to install a protected amine directly at the C2 position. Symmetry-breaking reduction of this material gave way to a remarkable series of stereochemical outcomes leading to the title compound without recourse to non-strategic downstream manipulations. This synthesis is immediately accommodating to the facile preparation of structural analogs. PMID:24245656

  2. Asymmetric synthesis of the aminocyclitol pactamycin, a universal translocation inhibitor.

    PubMed

    Sharpe, Robert J; Malinowski, Justin T; Johnson, Jeffrey S

    2013-11-27

    An asymmetric total synthesis of the aminocyclopentitol pactamycin is described. The title compound is delivered in 15 steps from 2,4-pentanedione. Critical to this approach was the exploitation of a complex symmetry-breaking reduction strategy to assemble the C1, C2, and C7 relative stereochemistry within the first four steps of the synthesis. Multiple iterations of this reduction strategy are described, and a thorough analysis of stereochemical outcomes is detailed. In the final case, an asymmetric Mannich reaction was developed to install a protected amine directly at the C2 position. Symmetry-breaking reduction of this material gave way to a remarkable series of stereochemical outcomes leading to the title compound without recourse to nonstrategic downstream manipulations. This synthesis is immediately accommodating to the preparation of structural analogs. PMID:24245656

  3. First asymmetric total synthesis of (+)-sparteine.

    PubMed

    Smith, Brenton T; Wendt, John A; Aubé, Jeffrey

    2002-07-25

    [reaction: see text] The total synthesis of (+)-sparteine was accomplished from 2,5-norbornadione in 15 steps and 15.7% overall yield. The key steps were two ring-expansion reactions, one involving an intramolecular Schmidt reaction and one using a novel variant of the photo-Beckmann rearrangement. PMID:12123380

  4. The role of biocatalysis in the asymmetric synthesis of alkaloids

    PubMed Central

    2013-01-01

    Alkaloids are not only one of the most intensively studied classes of natural products, their wide spectrum of pharmacological activities also makes them indispensable drug ingredients in both traditional and modern medicine. Among the methods for their production, biotechnological approaches are gaining importance, and biocatalysis has emerged as an essential tool in this context. A number of chemo-enzymatic strategies for alkaloid synthesis have been developed over the years, in which the biotransformations nowadays take an increasingly ‘central’ role. This review summarises different applications of biocatalysis in the asymmetric synthesis of alkaloids and discusses how recent developments and novel enzymes render innovative and efficient chemo-enzymatic production routes possible. PMID:25580241

  5. Asymmetric total synthesis of mycoleptodiscin?a.

    PubMed

    Zhou, Shupeng; Chen, Hao; Luo, Yijie; Zhang, Wenhao; Li, Ang

    2015-06-01

    The first total synthesis of mycoleptodiscin?A, a structurally unusual indolosesquiterpenoid possessing an ortho-benzoquinone motif, has been accomplished. A sulfone alkylation coupled two readily available fragments to give an aryl triene intermediate. The tetracyclic core of the molecule was assembled through a highly enantioselective iridium-catalyzed polyene cyclization. The benzylic homologation was achieved by a cationic cyanation. The indole motif was constructed via a copper-mediated intramolecular C?N bond formation at a late stage. PMID:25907827

  6. Catalytic Asymmetric Synthesis of Antimalarial Alkaloids Febrifugine and Isofebrifugine and Their Biological Activity.

    PubMed

    Kobayashi, Shū; Ueno, Masaharu; Suzuki, Ritsu; Ishitani, Haruro; Kim, Hye-Sook; Wataya, Yusuke

    1999-09-01

    Antimalarial alkaloids febrifugine (1) and isofebrifugine (2) were efficiently synthesized from simple achiral starting materials on the basis of the catalytic asymmetric synthesis. The first key reaction was performed using the tin(II)-mediated catalytic asymmetric aldol protocol to afford chiral aldehyde 3 in high yield with high diastereo- and enantioselectivities. The second key step, a Mannich-type reaction, did not give satisfactory results according to the conventional methods. We then developed a novel aqueous Mannich-type three-component reaction of an aldehyde, an amine, and a vinyl ether using a Lewis acid-surfactant combined catalyst (LASC), and the key intermediates 16 and 17 were obtained in high yields. The final coupling reactions of bromoacetone 14 with 4-hydroxyquinazoline were carried out using basic conditions, and successive deprotection gave 1 and 2, respectively, without any isomerization. These unambiguous total asymmetric syntheses revealed that the absolute configurations of febrifugine and isofebrifugine were not (2'S,3'R) and (2'R,3'R) as reported previously but (2'R,3'S) and (2'S,3'S), respectively (1' and 2'). Finally, antimalarial activities of the synthesized febrifugine and isofebrifugine, and their antipodes, were examined. It was revealed that the activities and selectivities of natural febrifugine and isofebrifugine were much higher than those of the antipodes. PMID:11674693

  7. Enantioselective total synthesis and assignment of the absolute configuration of (+)-laurokamurene B

    Microsoft Academic Search

    Adusumilli Srikrishna; Baire Beeraiah; R. Ramesh Babu

    2008-01-01

    The first enantioselective total synthesis of the rearranged aromatic sesquiterpene (+)-laurokamurene B, isolated from the Chinese red algae Laurencia okamurai Yamada, has been accomplished starting from (S)-campholenaldehyde, establishing the absolute configuration of laurokamurenes.

  8. De novo asymmetric synthesis of an alpha-6-deoxyaltropyranoside as well as its 2-/3-deoxy and 2,3-dideoxy congeners.

    PubMed

    Shan, Mingde; Xing, Yalan; O'Doherty, George A

    2009-08-21

    A highly divergent de novo asymmetric synthesis of benzyl alpha-6-deoxyaltropyranoside, benzyl alpha-ascarylopyranoside, benzyl alpha-amicetopyranoside, and benzyl alpha-digitoxopyranoside has been achieved via a common pyranone intermediate. The routes rely upon a palladium(0)-catalyzed glycosylation reaction and corresponding post-glycosylation transformations. The control of the absolute and relative stereochemical configuration came from a Noyori reduction of 2-acylfuran and subsequent diastereoselective introduction of other stereogenic centers. PMID:20560564

  9. Catalytic asymmetric synthesis of sterically hindered tertiary ?-aryl ketones.

    PubMed

    Doran, Robert; Guiry, Patrick J

    2014-10-01

    The catalytic asymmetric synthesis of a series of tertiary ?-aryl cyclopentanones and cyclohexanones has been accomplished via a Pd-catalyzed decarboxylative protonation of the corresponding ?-aryl-?-keto allyl esters. Enantioselectivities of up to 92% ee and 74% ee were achieved for cyclopentanone and cyclohexanone substrates, respectively. The route described gives access to these important structural motifs in moderate to high levels of enantioselectivity. In particular, this is only the second direct approach for the preparation of tertiary ?-aryl cyclopentanones. The synthetic approach allows for simple modification of the aryl group. Significantly, substrates containing sterically hindered aryl groups gave the highest levels of enantioselectivity, and these aryl groups were readily installed by a Pb-mediated arylation of a ?-keto allyl ester. PMID:25233274

  10. Asymmetric Synthesis of Inhibitors of Glycinamide Ribonucleotide Transformylase

    PubMed Central

    DeMartino, Jessica K.; Hwang, Inkyu; Connelly, Stephen; Wilson, Ian A.; Boger, Dale L.

    2008-01-01

    Glycinamide ribonucleotide transformylase (GAR Tfase) catalyzes the first of two formyl transfer steps in the de novo purine biosynthetic pathway that require folate cofactors and has emerged as a productive target for antineoplastic therapeutic intervention. The asymmetric synthesis and evaluation of the two diastereomers of 10-methylthio-DDACTHF (10R-3 and 10S-3) and related analogues as potential inhibitors of GAR Tfase are reported. This work, which defines the importance of the C10 stereochemistry for this class of inhibitors of GAR Tfase, revealed that both diastereomers are potent inhibitors of rhGAR Tfase (10R-3 Ki = 210 nM, 10S-3 Ki = 180 nM) that exhibit effective cell growth inhibition (CCRF-CEM IC50 = 80 and 50 nM, respectively) which is dependent on intracellular polyglutamation by folylpolyglutamate synthetase (FPGS), but not intracellular transport by the reduced folate carrier. PMID:18686942

  11. Catalytic, Asymmetric Indolizidinone Aza-Quaternary Stereocenter Synthesis: Expedient Synthesis of the Cylindricine Alkaloids Core

    PubMed Central

    Dalton, Derek M.; Rovis, Tomislav

    2013-01-01

    The Rh(I)•CKphos catalyzed [2+2+2] cycloaddition of 1,1-disubstituted alkenyl isocyanates and alkyl alkynes selectively forms previously inaccessible vinylogous amide indolizidinone cycloadducts, establishing an azaquaternery stereocenter with excellent enantioselectivies (up to 98% ee). This advance enables a seven step catalytic, asymmetric synthesis of the tricyclic core of the cylindricine alkaloids with excellent control of product-, regio- and enantioselectivity. PMID:23631448

  12. Asymmetric Synthesis of trans-2,5-Disubstituted Pyrrolidines from Enantiopure Homoallylic Amines. Synthesis of Pyrrolidine (?)-197B

    PubMed Central

    Davis, Franklin A.; Song, Minsoo; Augustine, Alexander

    2008-01-01

    Iodocyclization of sulfinimine-derived enantiopure homoallylic sulfonamides affords trans-2,5-disubstituted 3-iodopyrrolidines and represents valuable methodology for the asymmetric synthesis of this important heterocyclic ring system. PMID:16555832

  13. Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step

    PubMed Central

    Fronert, Jeanne; Bisschops, Tom; Boeck, Florian

    2012-01-01

    Summary The first organocatalytic asymmetric synthesis of smyrindiol, by using an (S)-proline catalyzed enantioselective intramolecular aldol reaction as the key step, is described. Smyrindiol was synthesized from commercially available 2,4-dihydroxybenzaldehyde in 15 steps, with excellent stereoselectivity (de = 99%, ee = 99%). In the course of this total synthesis a new and mild coumarin assembly was developed. PMID:23019438

  14. Synthesis of asymmetric tetracarboxylic acids and corresponding dianhydrides

    NASA Technical Reports Server (NTRS)

    Chuang, Chun-Hua (Inventor)

    2008-01-01

    This invention relates to processes for preparing asymmetrical biphenyl tetracarboxylic acids and the corresponding asymmetrical dianhydrides, namely 2,3,3',4'-biphenyl dianhydride (a-BPDA), 2,3,3',4'-benzophenone dianhydride (a-BTDA) and 3,4'-methylenediphthalic anhydride (-MDPA). By cross-coupling reactions of reactive metal substituted o-xylenes or by cross-coupling o-xylene derivatives in the presence of catalysts, this invention specifically produces asymmetrical biphenyl intermediates that are subsequently oxidized or hydrolyzed and oxidized to provide asymmetric biphenyl tetracarboxylic acids in comparatively high yields. These asymmetrical biphenyl tetracarboxylic acids are subsequently converted to the corresponding asymmetrical dianhydrides without contamination by symmetrical biphenyl dianhydrides.

  15. A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

    PubMed Central

    2013-01-01

    Summary A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities. PMID:24367413

  16. An absolute requirement for serum macromolecules in phytohaemagglutinin-induced human lymphocyte DNA synthesis.

    PubMed Central

    Yachnin, S; Raymond, J

    1975-01-01

    We have examined the effect of different variables such as tissue culture media, with or without various supplements, lymphocyte isolation techniques, lymphocyte contamination by autologous red blood cells and platelets, and lymphocyte numbers, on the requirement for serum during phytohaemagglutinin (PHA) induced DNA synthesis in human lymphocytes. At all mitogen doses tested, we have found that dialysable constituents of serum enrich the ability of all tissue culture media to support lymphocyte DNA synthesis; however, human lymphocytes display an absolute requirement for nondialysable macromolecular constituents of serum in order to synthesize DNA. PMID:1212814

  17. Phosphonic Acid Functionalized Asymmetric Phthalocyanines: Synthesis, Modification of Indium Tin Oxide (ITO), and Charge Transfer

    SciTech Connect

    Polaske, Nathan W. [Univ. of Arizona, Tucson, AZ (United States); Lin, Hsiao-Chu [Univ. of Arizona, Tucson, AZ (United States); Tang, Anna [Univ. of Arizona, Tucson, AZ (United States); Mayukh, Mayank [Univ. of Arizona, Tucson, AZ (United States); Oquendo, Luis E. [Univ. of Arizona, Tucson, AZ (United States); Green, John [Univ. of Arizona, Tucson, AZ (United States); Ratcliff, Erin L. [Univ. of Arizona, Tucson, AZ (United States); Armstrong, Neal R. [Univ. of Arizona, Tucson, AZ (United States); Saavedra, S. Scott [Univ. of Arizona, Tucson, AZ (United States); McGrath, Dominic V. [Univ. of Arizona, Tucson, AZ (United States)

    2011-12-20

    Metalated and free-base A?B-type asymmetric phthalocyanines (Pcs) bearing, in the asymmetric quadrant, a flexible alkyl linker of varying chain lengths terminating in a phosphonic acid (PA) group have been synthesized. Two parallel series of asymmetric Pc derivatives bearing aryloxy and arylthio substituents are reported, and their synthesis and characterization through NMR, combustion analysis, and MALDI-MS are described. We also demonstrate the modification of indium tin oxide (ITO) substrates using the PA functionalized asymmetric Pc derivatives and monitoring their electrochemistry. The PA functionalized asymmetric Pcs were anchored to the ITO surface through chemisorption and their electrochemical properties characterized using cyclic voltammetry to investigate the effects of PA structure on the thermodynamics and kinetics of charge transfer. Ionization energies of the modified ITO surfaces were measured using ultraviolet photoemission spectroscopy.

  18. Asymmetric synthesis of (+)-febrifugine and (+)-isofebrifugine using yeast reduction

    Microsoft Academic Search

    Yasuo Takeuchi; Kumiko Azuma; Kentaro Takakura; Hitoshi Abe; Hye-Sook Kim; Yusuke Wataya; Takashi Harayama

    2001-01-01

    The antimalarial agents febrifugine (d-1) and isofebrifugine (d-2) were synthesized from chiral 3-piperidinol (d-4), which was asymmetrically prepared by the yeast reduction of 3-piperidone derivatives (dl-3), with dynamic optical resolution.

  19. Asymmetric synthesis of N-allylic indoles via regio- and enantioselective allylation of aryl hydrazines.

    PubMed

    Xu, Kun; Gilles, Thomas; Breit, Bernhard

    2015-01-01

    The asymmetric synthesis of N-allylic indoles is important for natural product synthesis and pharmaceutical research. The regio- and enantioselective N-allylation of indoles is a true challenge due to the favourable C3-allylation. We develop here a new strategy to the asymmetric synthesis of N-allylic indoles via rhodium-catalysed N-selective coupling of aryl hydrazines with allenes followed by Fischer indolization. The exclusive N-selectivities and good to excellent enantioselectivities are achieved applying a rhodium(I)/DTBM-Segphos or rhodium(I)/DTBM-Binap catalyst. This method permits the practical synthesis of valuable chiral N-allylated indoles, and avoids the N- or C-selectivity issue. PMID:26137886

  20. Asymmetric synthesis of N-allylic indoles via regio- and enantioselective allylation of aryl hydrazines

    PubMed Central

    Xu, Kun; Gilles, Thomas; Breit, Bernhard

    2015-01-01

    The asymmetric synthesis of N-allylic indoles is important for natural product synthesis and pharmaceutical research. The regio- and enantioselective N-allylation of indoles is a true challenge due to the favourable C3-allylation. We develop here a new strategy to the asymmetric synthesis of N-allylic indoles via rhodium-catalysed N-selective coupling of aryl hydrazines with allenes followed by Fischer indolization. The exclusive N-selectivities and good to excellent enantioselectivities are achieved applying a rhodium(I)/DTBM-Segphos or rhodium(I)/DTBM-Binap catalyst. This method permits the practical synthesis of valuable chiral N-allylated indoles, and avoids the N- or C-selectivity issue. PMID:26137886

  1. Catalytic asymmetric synthesis of 4-nitropyrazolidines: an access to optically active 1,2,3-triamines.

    PubMed

    Lykke, Lennart; Carlsen, Bjørn Dreiø; Rambo, Raoní Scheibler; Jørgensen, Karl Anker

    2014-08-13

    The first catalytic enantio- and diastereoselective synthesis of 4-nitropyrazolidines is presented. Asymmetric hydrogen-bonding activation of nitro-olefins facilitated the 1,3-dipolar cycloaddition with hydrazones, affording optically active 4-nitropyrazolidines containing three continuous stereogenic centers as a single diastereomer in up to 99% ee. Furthermore, it is demonstrated that the optically active 4-nitropyrazolidines can be applied as precursors for the synthesis of highly interesting 1,2,3-triamines. PMID:25072940

  2. Synthesis and photodynamic activity of novel asymmetrically substituted fluorinated phthalocyanines.

    PubMed

    Sharman, Wesley M; van Lier, Johan E

    2005-01-01

    A series of asymmetrically substituted dodecafluorinated phthalocyanines has been synthesized via the Kobayashi ring expansion reaction of the corresponding dodecafluorinated boron subphthalocyanine with differently substituted 1,3-diiminoisoindolines. The mild reaction conditions employed during this ring expansion reaction gave rise exclusively to 3:1 asymmetrically substituted dodecafluorinated phthalocyanines. Metal insertion into the metal-free phthalocyanines was accomplished by heating at 40 degrees C in N,N-dimethylformamide in the presence of zinc bromide. The resulting zinc dodecafluorophthalocyanines were formulated as Cremophor EL oil-water emulsions and evaluated as photosensitizers in vitro against EMT-6 mouse mammary tumor cells. As compared to the previously studied zinc hexadecafluorophthalocyanine, these new asymmetrical zinc dodecafluorophthalocyanines exhibited improved photodynamic activity. PMID:16173794

  3. Asymmetric synthesis of Crispine A: constructing tetrahydroisoquinoline scaffolds using pummerer cyclizations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For the first time, a concise, linear and protecting group-free stereoselective synthesis of both enantiomers of crispine A have been achieved in six steps with an overall yield of less than or equal to 20%,starting from commercially available veratraldehyde. Asymmetric Keck allylation and trifluoro...

  4. Necessary and Sufficient Conditions for the Asymmetric Synthesis of Chiral Amines Using

    E-print Network

    Lee, Jooyoung

    ARTICLE Necessary and Sufficient Conditions for the Asymmetric Synthesis of Chiral Amines Using v activities of substrates. In the reaction generating PMP-Enz from PLP-Enz using L- alanine as an amine donor). However, in the subsequent half reaction recycling PLP-Enz from PMP-Enz using acetophenone as an amine

  5. Multistep One-Pot Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis

    E-print Network

    Zhao, Huimin

    Multistep One-Pot Reactions Combining Biocatalysts and Chemical Catalysts for Asymmetric Synthesis Carl A. Denard, John F. Hartwig,*, and Huimin Zhao*,,§ Department of Chemical and Biomolecular of chemical catalysts. Over the last 20 years, research in this area has provided us with proof of concept

  6. Concise and Practical Asymmetric Synthesis of a Challenging Atropisomeric HIV Integrase Inhibitor.

    PubMed

    Fandrick, Keith R; Li, Wenjie; Zhang, Yongda; Tang, Wenjun; Gao, Joe; Rodriguez, Sonia; Patel, Nitinchandra D; Reeves, Diana C; Wu, Jiang-Ping; Sanyal, Sanjit; Gonnella, Nina; Qu, Bo; Haddad, Nizar; Lorenz, Jon C; Sidhu, Kanwar; Wang, June; Ma, Shengli; Grinberg, Nelu; Lee, Heewon; Tsantrizos, Youla; Poupart, Marc-André; Busacca, Carl A; Yee, Nathan K; Lu, Bruce Z; Senanayake, Chris H

    2015-06-01

    A practical and efficient synthesis of a complex chiral atropisomeric HIV integrase inhibitor has been accomplished. The combination of a copper-catalyzed acylation along with the implementation of the BI-DIME ligands for a ligand-controlled Suzuki cross-coupling and an unprecedented bis(trifluoromethane)sulfonamide-catalyzed tert-butylation renders the synthesis of this complex molecule robust, safe, and economical. Furthermore, the overall synthesis was conducted in an asymmetric and diastereoselective fashion with respect to the imbedded atropisomer. PMID:25939331

  7. Total synthesis and absolute configuration assignment of MRSA active garcinol and isogarcinol.

    PubMed

    Socolsky, Cecilia; Plietker, Bernd

    2015-02-01

    A short total synthesis of (±)-garcinol and (±)-isogarcinol, two endo-type?B PPAPs with reported activity against methiciline resistant Staphylococcus aureus (MRSA), is presented. The separation of framework-constructing from framework-decorating steps and the application of two highly regio- and stereoselective Pd-catalysed allylations, that is, the Pd-catalysed decarboxylative Tsuji-Trost allylation and the diastereoselective Pd-catalysed allyl-allyl cross-coupling, are key elements that allowed the total synthesis to be accomplished within 13 steps starting from acetylacetone. After separation of the enantiomers the absolute configurations of the four natural products (i.e., (-)-garcinol, (+)-guttiferone?E (i.e., ent-garcinol), (-)-isogarcinol, and (+)-isoxanthochymol (i.e., ent-isogarcinol)) were assigned based on ECD spectroscopy. PMID:25537962

  8. Chemoenzymatic Asymmetric Synthesis of Pregabalin Precursors via Asymmetric Bioreduction of ?-Cyanoacrylate Esters Using Ene-Reductases

    PubMed Central

    2013-01-01

    The asymmetric bioreduction of a library of ?-cyanoacrylate esters using ene-reductases was studied with the aim to provide a biocatalytic route to precursors for GABA analogues, such as pregabalin. The stereochemical outcome could be controlled by substrate-engineering through size-variation of the ester moiety and by employing stereochemically pure (E)- or (Z)-isomers, which allowed to access both enantiomers of each product in up to quantitative conversion in enantiomerically pure form. In addition, stereoselectivities and conversions could be improved by mutant variants of OPR1, and the utility of the system was demonstrated by preparative-scale applications. PMID:23316696

  9. Inherently Chiral Calixarenes: Synthesis, Optical Resolution, Chiral Recognition and Asymmetric Catalysis

    PubMed Central

    Li, Shao-Yong; Xu, Yao-Wei; Liu, Jun-Min; Su, Cheng-Yong

    2011-01-01

    Inherently chiral calixarenes, whose chirality is based on the absence of a planar symmetry or an inversion center in the molecules as a whole through the asymmetric array of several achiral groups upon the three-dimensional calix-skeletons, are challenging and attractive chiral molecules, because of their potential in supramolecular chemistry. The synthesis and optical resolution of all varieties of inherently chiral calixarenes are systematically discussed and classified, and their applications in chiral recognition and asymmetric catalysis are thoroughly illustrated in this review. PMID:21339996

  10. Vanadium in asymmetric synthesis: emerging concepts in catalyst design and applications.

    PubMed

    Takizawa, Shinobu; Gröger, Harald; Sasai, Hiroaki

    2015-06-15

    In recent years vanadium catalysis has been extended to a range of different and even complementary directions in asymmetric synthesis. Inspired by nature's way to activate both substrate and reagent in many cases, the design of efficient bifunctional and dinuclear vanadium catalysts has been achieved. Furthermore, vanadium catalysis has been an early field in which "hybrid catalysts" have been studied in detail by incorporation of oxovanadium complexes into proteins, thus giving artificial enzymes. In addition, a high compatibility of vanadium with proteins enabled the use of vanadium chemocatalysts for combinations with enzyme catalysis in one-pot, thus leading to dynamic kinetic resolutions. In this contribution, these three concepts of vanadium catalysis opening up new perspectives for asymmetric synthesis are reviewed. PMID:25809123

  11. Catalytic Asymmetric Synthesis of Enantioenriched Heterocycles Bearing a C?CF3 Stereogenic Center.

    PubMed

    Huang, Yi-Yong; Yang, Xing; Chen, Zhuo; Verpoort, Francis; Shibata, Norio

    2015-06-01

    Given the important agricultural and medicinal application of optically pure heterocycles bearing a trifluoromethyl group at the stereogenic carbon center in the heterocyclic framework, the exploration of efficient and practical synthetic strategies to such types of molecules remains highly desirable. Catalytic enantioselective synthesis has one clear advantage that it is more cost-effective than other synthetic methods, but remains limited by challenges in achieving excellent yield and stereoselectivities with a low catalyst loading. Thus far, numerous models of organo- and organometal-catalyzed asymmetric reactions have been exploited to achieve this elusive goal over the past decade. This review article describes recent progress on this research topic, and focuses on an understanding of the catalytic asymmetric protocols exemplified in the catalytic enantioselective synthesis of a wide range of complex enantioenriched trifluoromethylated heterocycles. PMID:25736019

  12. Asymmetric synthesis of gem-difluoromethylenated linear triquinanes via cascade gem-difluoroalkyl radical cyclization.

    PubMed

    Thaharn, Watcharaporn; Soorukram, Darunee; Kuhakarn, Chutima; Tuchinda, Patoomratana; Pakawatchai, Chaveng; Saithong, Saowanit; Reutrakul, Vichai; Pohmakotr, Manat

    2015-01-16

    An asymmetric synthesis of gem-difluoromethylenated linear triquinanes is described exploiting the synthetic utilities of PhSCF2TMS (5) as a "(•)CF2(-)'' building block. The strategy involves fluoride-catalyzed nucleophilic addition of PhSCF2TMS (5) to chiral ketocyclopentenes 6 to provide silylated adducts 9 or alcohol derivatives 10 and 11. Subsequent cascade radical cyclization of the gem-difluoroalkyl radical generated from silylated adducts 9 or alcohols 10 and 11 afforded gem-difluoromethylenated linear triquinanes 16 as an approximate 1:1 mixture of two diastereomers (16A and 16B). Alternatively, a convenient asymmetric synthesis of gem-difluoromethylenated linear triquinanes 16A can be accomplished by oxidation of 16a (R = H) to provide ketotriquinane 17 followed by a highly stereoselective nucleophilic addition to 17 employing DIBAL, NaBH4, and various Grignard reagents. PMID:25517014

  13. Organocatalytic asymmetric cascade reactions of 7-vinylindoles: diastereo- and enantioselective synthesis of C7-functionalized indoles.

    PubMed

    Shi, Feng; Zhang, Hong-Hao; Sun, Xiao-Xue; Liang, Jing; Fan, Tao; Tu, Shu-Jiang

    2015-02-16

    The first catalytic asymmetric cascade reaction of 7-vinylindoles has been established by the rational design of such substrates. Cascade reactions with isatin-derived 3-indolylmethanols in the presence of a chiral phosphoric acid derivative allow the diastereo- and enantioselective synthesis of C7-functionalized indoles as well as the construction of cyclopenta[b]indole and spirooxindole frameworks (all >95:5 d.r., 94->99?% ee). This approach not only addresses the great challenge of the catalytic asymmetric synthesis of C7-functionalized indoles, but also provides an efficient method for constructing biologically important cyclopenta[b]indole and spirooxindole scaffolds with excellent optical purity. Investigation of the reaction pathway and activation mode has suggested that this cascade reaction proceeds through a vinylogous Michael addition/Friedel-Crafts process, in which dual H-bonding activation of the two reactants plays a crucial role. PMID:25521722

  14. Studies Toward the Asymmetric Synthesis of the Right Part of the Mycalamides

    PubMed Central

    Zhong, H. Marlon; Sohn, Jeong-Hun; Rawal, Viresh H.

    2008-01-01

    Described herein is the asymmetric synthesis of a functionalized, trioxadecalin unit that comprises the right-hand part of the mycalamides and related natural products. The synthetic route involves a 16-step sequence that accomplishes the formation of two heterocyclic rings and the generation of five stereocenters. The synthesis commenced with a C2 symmetric starting material, diethyl D-tartrate, and took advantage of a relay of diastereoselective reactions to extend this four-carbon chain and introduce new chiral centers. Subsequent electrophile mediated cyclization afforded the desired pyran ring, which was then transformed into the desired, functionalized trioxadecalin skeleton. PMID:17221953

  15. Asymmetric synthesis of fully substituted cyclopentane-oxindoles through an organocatalytic triple Michael domino reaction.

    PubMed

    Zou, Liang-Hua; Philipps, Arne R; Raabe, Gerhard; Enders, Dieter

    2015-01-12

    An efficient, highly stereoselective asymmetric synthesis of fully functionalized cyclopentanes bearing an oxindole moiety and several other functional groups in one pot has been developed. Key step is an organocatalytic triple Michael domino reaction forming three C-C bonds and six stereocenters, including a quaternary one. Starting from equimolar amounts of simple substrates, a high molecular complexity can be reached after a Wittig olefination in one pot. The new protocol can easily be scaled up to gram amounts. PMID:25470781

  16. Large-scale asymmetric synthesis of a cathepsin S inhibitor.

    PubMed

    Lorenz, Jon C; Busacca, Carl A; Feng, XuWu; Grinberg, Nelu; Haddad, Nizar; Johnson, Joe; Kapadia, Suresh; Lee, Heewon; Saha, Anjan; Sarvestani, Max; Spinelli, Earl M; Varsolona, Rich; Wei, Xudong; Zeng, Xingzhong; Senanayake, Chris H

    2010-02-19

    A potent reversible inhibitor of the cysteine protease cathepsin-S was prepared on large scale using a convergent synthetic route, free of chromatography and cryogenics. Late-stage peptide coupling of a chiral urea acid fragment with a functionalized aminonitrile was employed to prepare the target, using 2-hydroxypyridine as a robust, nonexplosive replacement for HOBT. The two key intermediates were prepared using a modified Strecker reaction for the aminonitrile and a phosphonation-olefination-rhodium-catalyzed asymmetric hydrogenation sequence for the urea. A palladium-catalyzed vinyl transfer coupled with a Claisen reaction was used to produce the aldehyde required for the side chain. Key scale up issues, safety calorimetry, and optimization of all steps for multikilogram production are discussed. PMID:20102230

  17. Psi[CH2O] pseudodipeptide synthesis. An improved approach which allows absolute configuration determination.

    PubMed

    Breton, P; Monsigny, M; Mayer, R

    1990-04-01

    An improved way to obtain psi[CH2O] pseudodipeptide units is proposed, involving an intramolecular Williamson's reaction, with displacement of bromine by an alkoxide, instead of the classical intermolecular one. Until now, psi[CH2O] pseudodipeptide synthesis done by this new method, has used a protected form of the amino alcohol hydroxyl group to prepare the acyclic precursor. In the present paper, the use of an active ester of the brominated carboxylic acid avoids this protection step. The pseudodipeptides AcGly psi[CH2O]-D,L-Ala-OH and Ac-Ser(Bzl) psi [CH2O]-D,L-Ala-OH were obtained in high yields, through a delta-lactam intermediate, which furthermore allows the determination of the absolute configuration of compounds using HPLC and appropriate nuclear magnetic resonance (NMR) techniques. PMID:2345056

  18. Synthesis and spectroscopic properties of novel asymmetric Schiff bases.

    PubMed

    Güngör, Ozlem; Gürkan, Perihan

    2010-09-15

    Three novel diimine Schiff bases including two asymmetric imines (2-OH)R-CHN-C(6)H(4)-CHN-R'(2-OH) type [where R=R'=phenyl for H(2)L(1); R=naphthyl, R'=phenyl for H(2)L(2) and R=R'=naphthyl for H(2)L(3)] have been synthesized with a new two step method. For this purpose, the starting Schiff bases 4-nitrobenzylidene-2-hydroxyaniline (SB(1)-NO(2)) and 4-nitrobenzylidene-2-hydroxy-3-naphthylamine (SB(2)-NO(2)) have been synthesized, previously. Nitro groups of them have been reduced into their amino derivatives (SB(1)-NH(2) and SB(2)-NH(2)) with sodium dithionite as selective reductant and the other imino groups have been formed by adding salicylaldehyde or 2-hydroxy-1-naphthaldehyde to the same solutions. The structures of the diimine Schiff bases were confirmed by elemental analyses, ESI-MS, FT-IR, (1)H NMR and (13)C NMR spectroscopy. The phenol-imine and keto-amine tautomerism of the Schiff bases were investigated by FT-IR, (1)H NMR, (13)C NMR techniques and UV-vis spectra in different solvents (DMSO, methanol, chloroform, toluene and cyclohexane). The effects of acidic and basic media on the tautomeric equilibria were discussed. PMID:20541456

  19. Synthesis and spectroscopic properties of novel asymmetric Schiff bases

    NASA Astrophysics Data System (ADS)

    Güngör, Özlem; Gürkan, Perihan

    2010-09-01

    Three novel diimine Schiff bases including two asymmetric imines (2-OH)R-CH dbnd N-C 6H 4-CH dbnd N-R'(2-OH) type [where R = R' = phenyl for H 2L 1; R = naphthyl, R' = phenyl for H 2L 2 and R = R' = naphthyl for H 2L 3] have been synthesized with a new two step method. For this purpose, the starting Schiff bases 4-nitrobenzylidene-2-hydroxyaniline (SB 1-NO 2) and 4-nitrobenzylidene-2-hydroxy-3-naphthylamine (SB 2-NO 2) have been synthesized, previously. Nitro groups of them have been reduced into their amino derivatives (SB 1-NH 2 and SB 2-NH 2) with sodium dithionite as selective reductant and the other imino groups have been formed by adding salicylaldehyde or 2-hydroxy-1-naphthaldehyde to the same solutions. The structures of the diimine Schiff bases were confirmed by elemental analyses, ESI-MS, FT-IR, 1H NMR and 13C NMR spectroscopy. The phenol-imine and keto-amine tautomerism of the Schiff bases were investigated by FT-IR, 1H NMR, 13C NMR techniques and UV-vis spectra in different solvents (DMSO, methanol, chloroform, toluene and cyclohexane). The effects of acidic and basic media on the tautomeric equilibria were discussed.

  20. Totally asymmetric exclusion process with extended objects: A model for protein synthesis Leah B. Shaw,1,2,

    E-print Network

    Shaw, Leah B.

    Totally asymmetric exclusion process with extended objects: A model for protein synthesis Leah B February 2003; published 18 August 2003 The process of protein synthesis in biological systems resembles a one dimensional driven lattice gas in which the particles have spatial extent, covering more than one

  1. Synthesis of non-racemic ?-hydroxyphosphonates via asymmetric phospho-aldol reaction.

    PubMed

    Spilling, Christopher D; Malla, Raj K

    2015-01-01

    It has been more than 50 years since the first phospho-aldol reactions of dialkyl phosphites were reported. These efficient P-C bond-forming reactions have become the cornerstone of methods for the synthesis of ?-hydroxyphosphonates and, by numerous available substitution reactions, the synthesis of other ?- and ?-substituted phosphonates and phosphonic acids. Much of the interest in ?- and ?-substituted phosphonates and phosphonic acids has been stimulated by reports of their biological activity, which is often dependent upon their absolute and relative stereochemistry. In this chapter, we review diastereoselective and enantioselective additions of dialkyl phosphites to aldehydes and ketones, otherwise called the phospho-aldol, Pudovik or Abramov reactions. PMID:25467537

  2. Asymmetric total synthesis and antiproliferative activity of goniothalamin oxide isomers.

    PubMed

    Marquissolo, Cilene; de Fátima, Angelo; Kohn, Luciana K; Ruiz, Ana Lúcia T G; de Carvalho, João Ernesto; Pilli, Ronaldo A

    2009-04-01

    Goniothalamin oxide (1) is a styryl lactone which was isolated from bark and leaves of several Goniothalamus species. This natural product has some interesting biological properties such as larvicidal and tripanocidal activities. However, no studies on the antiproliferative profile of goniothalamin oxide (1) and its stereoisomers have been reported yet. Here, goniothalamin epoxide (1), isogoniothalamin epoxide (2) and their enantiomers were prepared via epoxidation of (R)-and (S)-goniothalamin (4). A 3:2 molar ratio in favor of goniothalamin oxide (1) and ent-1 was observed from (R)- and (S)-4, respectively, when 3-chloroperbenzoic acid (mCPBA) was employed while an increase to 6:1 molar ratio was achieved with (S,S)-Jacobsen's catalyst. Antiproliferative activity of these epoxides revealed that ent-isogoniothalamin oxide (ent-2) was the most active against the eight cancer cell lines studied. These results indicate that 6S, 7R and 8R absolute configurations are beneficial for the activity of these epoxides. PMID:19185327

  3. Practical catalytic asymmetric synthesis of diaryl-, aryl heteroaryl-, and diheteroarylmethanols.

    PubMed

    Salvi, Luca; Kim, Jeung Gon; Walsh, Patrick J

    2009-09-01

    Enantioenriched diaryl-, aryl heteroaryl-, and diheteroarylmethanols exhibit important biological and medicinal properties. One-pot catalytic asymmetric syntheses of these compounds beginning from readily available aryl bromides are introduced. Thus, lithium-bromide exchange with commercially available aryl bromides and n-BuLi was followed by salt metathesis with ZnCl(2) to generate ArZnCl. A second equivalent of n-BuLi was added to form the mixed organozinc, ArZnBu. In the presence of enantioenriched amino alcohol-based catalysts, ArZnBu adds to aldehydes to afford essentially racemic diarylmethanols. The low enantioselectivities were attributed to a LiCl-promoted background reaction. To inhibit this background reaction, the chelating diamine TEEDA (tetraethylethylene diamine) was introduced prior to aldehyde addition. Under these conditions, enantioenriched diarylmethanols were obtained with >90% ee. Arylations of enals generated allylic alcohols with 81-90% ee. This procedure was unsuccessful, however, when applied to heteroaryl bromides, which was attributed to decomposition of the heteroaryl lithium under the salt metathesis conditions. To avoid this problem, the metathesis was conducted with EtZnCl, which enabled the salt metathesis to proceed at low temperatures. The resulting EtZn(Ar(Hetero)) intermediates (Ar(Hetero) = 2- and 3-thiophenyl, 2-benzothiophenyl, 3-furyl, and 5-indolyl) were successfully added to aldehydes and heteroaryl aldehydes with enantioselectivities between 81-99%. These are the first examples of catalytic and highly enantioselective syntheses of diheteroarylmethanols. In a similar fashion, ferrocenyl bromide was used to generate FcZnEt and the ferrocenyl group added to benzaldehyde and heteroaromatic aldehydes to form ferrocene-based ligand precursors in 86-95% yield with 96-98% ee. It was also found that the arylation and heteroarylation of enals could be followed by diastereoselective epoxidations to provide epoxy alcohols with high enantio- and diastereoselectivities in a one-pot procedure. PMID:19653691

  4. The origins of homochirality examined by using asymmetric autocatalysis.

    PubMed

    Soai, Kenso; Kawasaki, Tsuneomi; Matsumoto, Arimasa

    2014-02-01

    Pyrimidyl alkanol was found to act as an asymmetric autocatalyst in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde. Asymmetric autocatalysis of 2-alkynylpyrimidyl alkanol with an extremely low enantiomeric excess (ca. 0.00005% ee) exhibits enormous asymmetric amplification to afford the same compound with >99.5% ee. This asymmetric autocatalysis with amplification of ee has been employed to examine the validity of proposed theories of the origins of homochirality. Circularly polarized light, quartz, sodium chlorate, cinnabar, chiral organic crystals and spontaneous absolute asymmetric synthesis were considered as possible candidates for the origin of chirality; each could act as a chiral source in asymmetric autocatalysis. Asymmetric autocatalysis can discriminate the isotope chirality arising from the small difference between carbon (carbon-13/carbon-12) and hydrogen (D/H) isotopes. Cryptochiral compounds were also discriminated by asymmetric autocatalysis. PMID:24449510

  5. Asymmetric synthesis of 3-substituted tetrahydro-2-benzazepines.

    PubMed

    Quick, Matthias P; Fröhlich, Roland; Schepmann, Dirk; Wünsch, Bernhard

    2015-07-14

    The enantiomerically and diastereomerically pure tricyclic oxazolidine cis-10 was prepared in a five step synthesis starting with 1-bromo-2-iodobenzene. Me3SiCN and allylSiMe3 reacted with cis-10 in the presence of TiCl4 to form the nitrile (3S)-11 and the allyl derivative (3S)-12 with high diastereoselectivity. The hydrogenolytic removal of the chiral auxiliary failed, since the endocyclic benzyl-N-bond was cleaved simultaneously. Therefore the N-(hydroxyethyl)amide of (3S)-12 was transformed into the enamide 27, which was hydrolyzed to afford the secondary amide 28. The enamide strategy to remove the chiral auxiliary from (3S)-11 led to complete racemization due to fast deprotonation in ?-position of the cyano moiety. Two pairs of enantiomers 30a-b/ent-30a-b with prototypical ? substituents at the N-atom were prepared. The low ?1 affinity of the tetrahydro-2-benzazepines (ent-30b, Ki = 407 nM) is attributed to the short distance between the two lipophilic aromatic moieties. PMID:26055189

  6. An Ultimate Stereocontrol in Asymmetric Synthesis of Optically Pure Fully Aromatic Helicenes.

    PubMed

    Šámal, Michal; Chercheja, Serghei; Rybá?ek, Ji?í; Vacek Chocholoušová, Jana; Vacek, Jaroslav; Bednárová, Lucie; Šaman, David; Stará, Irena G; Starý, Ivo

    2015-07-01

    The role of the helicity of small molecules in enantioselective catalysis, molecular recognition, self-assembly, material science, biology, and nanoscience is much less understood than that of point-, axial-, or planar-chiral molecules. To uncover the envisaged potential of helically chiral polyaromatics represented by iconic helicenes, their availability in an optically pure form through asymmetric synthesis is urgently needed. We provide a solution to this problem present since the birth of helicene chemistry in 1956 by developing a general synthetic methodology for the preparation of uniformly enantiopure fully aromatic [5]-, [6]-, and [7]helicenes and their functionalized derivatives. [2 + 2 + 2] Cycloisomerization of chiral triynes combined with asymmetric transformation of the first kind (ultimately controlled by the 1,3-allylic-type strain) is central to this endeavor. The point-to-helical chirality transfer utilizing a traceless chiral auxiliary features a remarkable resistance to diverse structural perturbations. PMID:25928194

  7. Asymmetric synthesis of 4-deoxyverrucarol via two types of ring expansion reactions

    PubMed

    Miyata; Nemoto; Ihara

    2000-01-28

    Asymmetric synthesis of a trichothecane analogue, 4-deoxyverrucarol (2), was carried out through two types of ring expansion reactions. First, synthesis of the racemate of 2 was investigated. Thus, 1-[1-(tert-butyldimethylsiloxy)-ethyl]-1-methoxycarbonyl-2-hexen-4-on e (10), prepared by Diels-Alder reaction, was converted into the cyclopropylidene 15. The cyclobutanone (+/-)-18 was obtained from 15 via dihydroxylation, followed by successive treatments with SO(2)Cl(2) in the presence of imidazole and Florisil. After transformation of (+/-)-18 into the vinylcyclobutanol (+/-)-19, the second ring expansion reaction was performed with Pd(OAc)(2) to provide the cyclopentanone (+/-)-20. The product was converted into the racemate of 4-deoxyverrucarol (2) through the cyclohexenone (+/-)-22, but the diastereoselectivity during the introduction of the double bond was unsatisfactory. The selectivity was improved in the case of the asymmetric synthesis. The optically active cyclobutanone (+)-18 was prepared via AD reaction of 15 with 73% ee. After the transformation of (+)-18 into the cyclohexanone (-)-30 through the palladium-mediated ring expansion reaction, (-)-30 was subjected to the diastereoselective deprotonation reaction using the chiral amide. The key synthetic intermediate (-)-25 of 4-deoxyverrucarol (2) was synthesized in an optically pure form by taking advantage of a kind of kinetic resolution that occurred during the deprotonation step. PMID:10813964

  8. An enantioselective synthesis of the key intermediate for triazole antifungal agents; application to the catalytic asymmetric synthesis of efinaconazole (Jublia).

    PubMed

    Tamura, Keiji; Kumagai, Naoya; Shibasaki, Masakatsu

    2014-04-01

    A new synthetic route, the shortest reported to date, to access a key intermediate for the synthesis of various triazole antifungal agents was developed. The elusive tetrasubstituted stereogenic center that is essential in advanced triazole antifungal agents was constructed via the catalytic asymmetric cyanosilylation of a ketone. The subsequent transformations were performed in two one-pot operations, enhancing the overall synthetic efficiency toward the intermediate. This streamlined synthetic approach was successfully applied to efficient enantioselective syntheses of efinaconazole (Jublia) and ravuconazole. PMID:24635354

  9. Highly enantioselective synthesis of ?-, ?-, and ?-chiral 1-alkanols via Zr-catalyzed asymmetric carboalumination of alkenes (ZACA)–Cu- or Pd-catalyzed cross-coupling

    PubMed Central

    Xu, Shiqing; Oda, Akimichi; Kamada, Hirofumi; Negishi, Ei-ichi

    2014-01-01

    Despite recent advances of asymmetric synthesis, the preparation of enantiomerically pure (?99% ee) compounds remains a challenge in modern organic chemistry. We report here a strategy for a highly enantioselective (?99% ee) and catalytic synthesis of various ?- and more-remotely chiral alcohols from terminal alkenes via Zr-catalyzed asymmetric carboalumination of alkenes (ZACA reaction)–Cu- or Pd-catalyzed cross-coupling. ZACA–in situ oxidation of tert-butyldimethylsilyl (TBS)-protected ?-alkene-1-ols produced both (R)- and (S)-?,?-dioxyfunctional intermediates (3) in 80–88% ee, which were readily purified to the ?99% ee level by lipase-catalyzed acetylation through exploitation of their high selectivity factors. These ?,?-dioxyfunctional intermediates serve as versatile synthons for the construction of various chiral compounds. Their subsequent Cu-catalyzed cross-coupling with various alkyl (primary, secondary, tertiary, cyclic) Grignard reagents and Pd-catalyzed cross-coupling with aryl and alkenyl halides proceeded smoothly with essentially complete retention of stereochemical configuration to produce a wide variety of ?-, ?-, and ?-chiral 1-alkanols of ?99% ee. The M?NP ester analysis has been applied to the determination of the enantiomeric purities of ?- and ?-chiral primary alkanols, which sheds light on the relatively undeveloped area of determination of enantiomeric purity and/or absolute configuration of remotely chiral primary alcohols. PMID:24912191

  10. Stereocontrolled asymmetric synthesis of alpha-hydroxy-beta-amino acids. A stereodivergent approach.

    PubMed

    Aoyagi, Y; Jain, R P; Williams, R M

    2001-04-18

    The stereocontrolled asymmetric synthesis of alpha-hydroxy-beta-amino acids has been investigated via the Lewis acid-promoted cyanation of (5R,6S)-2-acetoxy-4-(benzyloxycarbonyl)-5,6-diphenyl-2,3,5,6-tetrahydro-4H-1,4-oxazines with trimethylsilyl cyanide. Base-catalyzed hydrolysis of the resulting cyano compounds proceeds with excellent stereoselectivity, providing access to diastereomerically pure oxazine-2-carboxylic acids which were readily converted to each enantiomer of the alpha-hydroxy-beta-amino acids isothreonine and nor-C-statine. PMID:11472118

  11. Total synthesis of the hydroxyketone kurasoin A using asymmetric phase-transfer alkylation.

    PubMed

    Andrus, Merritt B; Hicken, Erik J; Stephens, Jeffrey C; Bedke, D Karl

    2006-10-27

    The total synthesis of the farnesyltransferase inhibitor kurasoin A has been achieved using a novel asymmetric phase-transfer-catalyzed glycolate alkylation reaction. 2,5-Dimethoxyacetophenone 7 with cinchonidinium catalyst 9(10 mol %) and hydroxide base with pivaloyl benzyl bromide 8 provided S-alkylation product 10 in high yield (80-99%) and excellent enantioselectivity. Baeyer-Villiger oxidation, Weinreb amide formation, and benzyl Grignard addition to the TES-ether 17 gave the protected target. Lithium hydroxide and peroxide generated kurasoin A ([alpha](D) +8.4 degrees ) without isomerization. PMID:17064051

  12. Highly selective asymmetric synthesis of 2-hydroxy fatty acid methyl esters through chiral oxazolidinone carboximides

    Microsoft Academic Search

    Hong-Sik Hwang; Sevim Z. Erhan

    2001-01-01

    Highly selective asymmetric synthesis of 2-hydroxy fatty acid methyl esters has been accomplioshed through chiral imide enolates.\\u000a Five chiral oleic acid imides were prepared by reaction of oleioc acid with pivaloyl chloride followed by reaction with five\\u000a different lithiated chiral oxazolidinones including (R)-(+)-4-benzyl-2-, (S)-(-)-4-benzyl-2-, (4R,5S)-(+)-4-methyl-5-phenyl-2-, (4S,5R)-(-)-4-methyl-5-phenyl-2-, and (R)-(+)-4-isopropyl-2-oxazolidinones in 88–92% yileds. The chiral imides were reacted with NaN(Me3Si)2 at ?78C

  13. Enantioselective total synthesis of (+)-ibophyllidine via an asymmetric phosphine-catalyzed [3 + 2] annulation†

    PubMed Central

    Andrews, Ian P.

    2012-01-01

    In this study we performed the total synthesis of the terpene indole alkaloid (+)-ibophyllidine through a pathway involving asymmetric phosphine catalysis, with our novel l-4-hydroxyproline–derived chiral phosphine mediating the key [3 + 2] annulation. Hydrogenation of the [3 + 2] adduct allowed the rapid formation of the stereochemically dense pyrrolidine ring of (+)-ibophyllidine in excellent yield with exceptionally high levels of both diastereo- and enantioselectivity. We constructed the remainder of the pentacyclic skeleton through an intramolecular alkylation and an intramolecular aza-Morita–Baylis–Hillman reaction. PMID:22798981

  14. Asymmetric synthesis of ?-allyl-?-aryl ?-amino acids by tandem alkylation/?-allylation of ?-iminoesters.

    PubMed

    Curto, John M; Dickstein, Joshua S; Berritt, Simon; Kozlowski, Marisa C

    2014-04-01

    The first asymmetric synthesis of ?-allyl-?-aryl ?-amino acids by means of a three-component coupling of ?-iminoesters, Grignard reagents, and cinnamyl acetate is reported. Notably, the enolate from the tandem process provides a much higher level of reactivity and selectivity than the same enolate generated via direct deprotonation, presumably due to differences in the solvation/aggregation state. A novel method for removal of a homoallylic amine protecting group delivers the free amine congeners. The ?-allyl group offers a means to generate further valuable ?-amino acid structures as exemplified by ring closing metathesis to generate a higher ring homologue of ?-aryl-proline. PMID:24666394

  15. The Development of the Enantioselective Addition of Ethyl Diazoacetate to Aldehydes: Asymmetric Synthesis of 1,2-Diols

    PubMed Central

    Trost, Barry M.; Malhotra, Sushant; Koschker, Philipp; Ellerbrock, Pascal

    2011-01-01

    A novel synthetic strategy towards the asymmetric synthesis of vicinal diols bearing a tertiary center is presented. The method encompasses the dinuclear Mg-catalyzed asymmetric addition of ethyl diazoacetate into several aldehydes, oxidation of the diazo functionality, and diastereoselective alkyl transfer of various organometallics into the resulting chiral ?-hydroxy-?-ketoesters to afford a diverse range of 1,2-diols in high yield, diastereoselectivity, and chirality transfer. PMID:22088096

  16. Engineering methylaspartate ammonia lyase for the asymmetric synthesis of unnatural amino acids

    NASA Astrophysics Data System (ADS)

    Raj, Hans; Szyma?ski, Wiktor; de Villiers, Jandré; Rozeboom, Henriëtte J.; Veetil, Vinod Puthan; Reis, Carlos R.; de Villiers, Marianne; Dekker, Frank J.; de Wildeman, Stefaan; Quax, Wim J.; Thunnissen, Andy-Mark W. H.; Feringa, Ben L.; Janssen, Dick B.; Poelarends, Gerrit J.

    2012-06-01

    The redesign of enzymes to produce catalysts for a predefined transformation remains a major challenge in protein engineering. Here, we describe the structure-based engineering of methylaspartate ammonia lyase (which in nature catalyses the conversion of 3-methylaspartate to ammonia and 2-methylfumarate) to accept a variety of substituted amines and fumarates and catalyse the asymmetric synthesis of aspartic acid derivatives. We obtained two single-active-site mutants, one exhibiting a wide nucleophile scope including structurally diverse linear and cyclic alkylamines and one with broad electrophile scope including fumarate derivatives with alkyl, aryl, alkoxy, aryloxy, alkylthio and arylthio substituents at the C2 position. Both mutants have an enlarged active site that accommodates the new substrates while retaining the high stereo- and regioselectivity of the wild-type enzyme. As an example, we demonstrate a highly enantio- and diastereoselective synthesis of threo-3-benzyloxyaspartate (an important inhibitor of neuronal excitatory glutamate transporters in the brain).

  17. Multi-component Cycloaddition Approaches in the Catalytic Asymmetric Synthesis of Alkaloid Targets†

    PubMed Central

    Perreault, Stéphane; Rovis, Tomislav

    2010-01-01

    Cycloaddition reactions are attractive strategies for rapid formation of molecular complexity in organic synthesis as multiple bonds are formed in a single process. To this end, several research groups have been actively involved in the development of catalytic methods to activate readily accessible ?-components to achieve cycloadditions. However, the use of C-N ?-components for the formation of heterocycles by these processes is less well developed. It has been previously demonstrated that the combination of different isocyanates with two alkynes yields pyridones of several types by metal-catalyzed [2+2+2] cycloadditions. The potential of this chemistry has been extended to alkenes as C-C ?-components, allowing the formation of sp3-stereocenters. In this tutorial review directed towards [n+2+2] cycloaddition of heterocumulenes, alkynes and alkenes, the recent advances in catalytic asymmetric synthesis of indolizidine, quinolizidine and azocine skeletons are discussed. PMID:19847348

  18. Regio- and enantioselective synthesis of N-substituted pyrazoles by rhodium-catalyzed asymmetric addition to allenes.

    PubMed

    Haydl, Alexander M; Xu, Kun; Breit, Bernhard

    2015-06-01

    The rhodium-catalyzed asymmetric N-selective coupling of pyrazole derivatives with terminal allenes gives access to enantioenriched secondary and tertiary allylic pyrazoles, which can be employed for the synthesis of medicinally important targets. The reaction tolerates a large variety of functional groups and labelling experiments gave insights into the reaction mechanism. This new methodology was further applied in a highly efficient synthesis of JAK?1/2 inhibitor (R)-ruxolitinib. PMID:25926026

  19. Asymmetric Synthesis of (-)-Incarvillateine Employing an Intramolecular Alkylation via Rh-Catalyzed Olefinic C-H Bond Activation

    SciTech Connect

    Tsai, Andy; Bergman, Robert; Ellman, Jonathan

    2008-02-18

    An asymmetric total synthesis of (-)-incarvillateine, a natural product having potent analgesic properties, has been achieved in 11 steps and 15.4% overall yield. The key step is a rhodium-catalyzed intramolecular alkylation of an olefinic C-H bond to set two stereocenters. Additionally, this transformation produces an exocyclic, tetrasubstituted alkene through which the bicyclic piperidine moiety can readily be accessed.

  20. Asymmetric synthesis of anti-aldol segments via a nonaldol route: synthetic applications to statines and (-)-tetrahydrolipstatin.

    PubMed

    Ghosh, Arun K; Shurrush, Khriesto; Kulkarni, Sarang

    2009-06-19

    An asymmetric synthesis of anti-aldol segments via a nonaldol route is described. The strategy involves a highly diastereoselective synthesis of functionalized tetrahydrofuran derivatives from optically active 4-phenylbutyrolactone. Treatment of the tetrahydrofuran derivatives with a Lewis acid and acetic anhydride provided the corresponding ring-opened styrene derivatives. Oxidative cleavage of the styrene derivatives provided access to the anti-aldol segments. The utility of this methodology was demonstrated by the synthesis of statine derivatives and pancreatic lipase inhibitor, (-)-tetrahydrolipstatin. PMID:19438217

  1. Development of an Asymmetric Trimethylenemethane Cycloaddition Reaction: Application in the Enantioselective Synthesis of Highly Substituted Carbocycles

    PubMed Central

    Trost, Barry M.; Silverman, Steven M.; Stambuli, James P.

    2011-01-01

    A protocol for the enantioselective [3+2] cycloaddition of trimethylenemethane with electron-deficient olefins has been developed. The synthesis of novel phosphoramidite ligands was critical in this effort, and the preparation and reactivity of these ligands is detailed. The evolution of the ligand design, commencing with acyclic amine-derived phosphoramidites and leading to cyclic pyrrolidine and azetidine structures is discussed. The conditions developed to effect an asymmetric TMM reaction using 2-trimethylsilylmethyl allyl acetate were shown to be tolerant of a wide variety of alkene acceptors, providing the desired methylenecyclopentanes with high levels of enantioselectivity. The donor scope was also explored and substituted systems were tolerated, including one bearing a nitrile moiety. These donors were reactive with unsaturated acylpyrroles, giving the product cyclopentane rings bearing three stereocenters in high enantioselectivity and complete diastereoselectivity. PMID:21936576

  2. Asymmetric total synthesis of (-)-lingzhiol via a Rh-catalysed [3+2] cycloaddition.

    PubMed

    Long, Rong; Huang, Jun; Shao, Wenbin; Liu, Song; Lan, Yu; Gong, Jianxian; Yang, Zhen

    2014-01-01

    The development of efficient reactions for the one-pot construction of bicyclic ring systems bearing two quaternary carbon centres at their bridgehead positions represents a significant challenge to synthetic chemistry. The development of new methods capable of overcoming this challenge is highly desirable, because this motif can be found in a wide range of natural products with significant biological activities. Herein, we report an efficient [3+2] cycloaddition reaction between an enal and an alleno rhodium species, which was generated in situ from the corresponding enynol via a retro metal-propargylation reaction, to give [3.3.0] and [3.4.0] bicyclic systems bearing two quaternary atoms at their bridgehead positions. The developed chemistry has been successfully applied to the asymmetric total synthesis of natural product (-)-lingzhiol (4) for the first time in 17 steps. PMID:25483390

  3. Haloperidol metabolite II prodrug: asymmetric synthesis and biological evaluation on rat C6 glioma cells.

    PubMed

    Sozio, Piera; Fiorito, Jole; Di Giacomo, Viviana; Di Stefano, Antonio; Marinelli, Lisa; Cacciatore, Ivana; Cataldi, Amelia; Pacella, Stephanie; Turkez, Hasan; Parenti, Carmela; Rescifina, Antonio; Marrazzo, Agostino

    2015-01-27

    In a previous work we reported the antiproliferative effects of (±)-MRJF4, a novel haloperidol metabolite II (HP-mII) (a sigma-1 antagonist and sigma-2 agonist) prodrug, obtained through conjugation to 4-phenylbutyric acid (PhBA) [a histone deacetylase inhibitor (HDACi)] via an ester bond. As a continuation of this work, here we report the asymmetric synthesis of compounds (R)-(+)-MRJF4 and (S)-(-)-MRJF4 and the evaluation of their biological activity on rat C6 glioma cells, derived from glioblastoma multiforme (GBM), which is the most common and deadliest central nervous system (CNS) invasive malignancy. Favourable physicochemical properties, high permeability in the parallel artificial membrane permeability assay (PAMPA), good enzymatic and chemical stability, in vivo anticancer activity, associated with the capacity to reduce cell viability and to increase cell death by apoptosis, render compound (R)-(+)-MRJF4 a promising candidate for the development of a useful therapeutic for gliomas therapy. PMID:25461306

  4. Enzymatic- and iridium-catalyzed asymmetric synthesis of a benzothiazepinylphosphonate bile acid transporter inhibitor.

    PubMed

    Cowan, David J; Collins, Jon L; Mitchell, Mark B; Ray, John A; Sutton, Peter W; Sarjeant, Amy A; Boros, Eric E

    2013-12-20

    A synthesis of the benzothiazepine phosphonic acid 3, employing both enzymatic and transition metal catalysis, is described. The quaternary chiral center of 3 was obtained by resolution of ethyl (2-ethyl)norleucinate (4) with porcine liver esterase (PLE) immobilized on Sepabeads. The resulting (R)-amino acid (5) was converted in two steps to aminosulfate 7, which was used for construction of the benzothiazepine ring. Benzophenone 15, prepared in four steps from trimethylhydroquinone 11, enabled sequential incorporation of phosphorus (Arbuzov chemistry) and sulfur (Pd(0)-catalyzed thiol coupling) leading to mercaptan intermediate 18. S-Alkylation of 18 with aminosulfate 7 followed by cyclodehydration afforded dihydrobenzothiazepine 20. Iridium-catalyzed asymmetric hydrogenation of 20 with the complex of [Ir(COD)2BArF] (26) and Taniaphos ligand P afforded the (3R,5R)-tetrahydrobenzothiazepine 30 following flash chromatography. Oxidation of 30 to sulfone 31 and phosphonate hydrolysis completed the synthesis of 3 in 12 steps and 13% overall yield. PMID:24256447

  5. Chiral relay in NHC-mediated asymmetric ?-lactam synthesis I; substituent effects in NHCs derived from (1 R,2 R)-cyclohexane-1,2-diamine

    Microsoft Academic Search

    Nicolas Duguet; Adele Donaldson; Stuart M. Leckie; James Douglas; Peter Shapland; Thomas B. Brown; Gwydion Churchill; Alexandra M. Z. Slawin; Andrew D. Smith

    2010-01-01

    The synthesis of a range of C2-symmetric imidazolinium salts from (1R,2R)-cyclohexane-1,2-diamine, and an evaluation of the reactivity and asymmetric induction of the derived NHCs as catalysts for the asymmetric synthesis of ?-lactams, is reported. In this series, optimal enantioselectivity (up to 70% ee) is observed using N-benzyl or N-1-naphthylmethyl-substituted NHCs, consistent with a chiral relay effect operating to dictate the

  6. An advance on exploring N-tert-butanesulfinyl imines in asymmetric synthesis of chiral amines.

    PubMed

    Lin, Guo-Qiang; Xu, Ming-Hua; Zhong, Yu-Wu; Sun, Xing-Wen

    2008-07-01

    Although catalytic asymmetric synthesis has undergone tremendous growth in the last 30 years, chiral auxiliary-aided asymmetric synthesis continues to attract considerable attention. Chiral N- tert-butanesulfinamide, as pioneered by Ellman and co-workers, is undoubtedly one of the most efficient auxiliaries developed to date; it allows the preparation, through simple conversion, of a diverse range of enantiopure amines, which are ubiquitous in natural products and biologically active molecules. Following on from our studies of the SmI(2)-mediated asymmetric syntheses of alpha,gamma-substituted gamma-butyrolactones, we found that simple homocoupling of chiral N- tert-butanesulfinyl imines in the presence of SmI(2) produced enantiopure vicinal C2-symmetric diamines in high yield. In addition, C2-unsymmetric chiral diamines are readily prepared through SmI(2)-mediated cross-couplings of N- tert-butanesulfinyl imines and nitrones; these transformations represented the first successful examples of asymmetric cross-coupling between two different imine species. Subsequently, we discovered another useful reaction induced by SmI(2), the efficient cross-coupling of N- tert-butanesulfinyl imines and aldehydes, which provides ready access to enantiopure anti-1,2-amino alcohols. The synthetic applicability of this reaction was demonstrated through its use in the facile total syntheses of (3R,4S)-statine, d- erythro-sphinganine, (+)-CP-99,994, and (+)-L-733,060. The Zn/In-mediated allylation of chiral N- tert-butanesulfinyl imines yields homoallylic amines. After pondering the reaction mechanism, we developed optimal reaction conditions for reversing the stereogenic outcome, thereby allowing the preparation of enantiopure homoallylic amines of either handedness from single enantiomers of the (R)- or (S)-sulfinyl imine. When a benzoyl-substituted allyl bromide is used for allylation, the reaction proceeds smoothly to give 2-vinyl-substituted anti-1,2-amino alcohols in high yields and diastereoselectivities, another simple method for preparing enantiopure amino alcohols. We employed these reactions in the syntheses of enantiopure allylglycine, 3-allyl-isoindolinones, and (-)-cytoxazone. Further studies led to the discovery that the allylations of N- tert-butanesulfinyl aldimines can be performed in water. The reactions described in this Account are among the simplest and most efficient synthetic methods available for preparing enantio-enriched diamines, amino alcohols, homoallylic amines, and other amine derivatives. These reactions are additionally attractive because of the ready availability of the starting materials, the simplicity of the reaction conditions, and the high degree of stereochemical control. Their applications in the total syntheses of several biologically interesting molecules illustrate the versatility of these transformations; we hope that they will stimulate the development of new synthetic methods. PMID:18533688

  7. Fully Reagent-Controlled Asymmetric Synthesis of (?)-Spongidepsin via the Zr-Catalyzed Asymmetric Carboalumination of Alkenes (ZACA Reaction)

    PubMed Central

    Zhu, Gangguo; Negishi, Ei-ichi

    2013-01-01

    The ZACA reaction has been shown to proceed satisfactorily with internally OH-substituted 1-alkenes, provided that the OH group is unprotected and non-allylic. This reaction was used for reagent-controlled asymmetric construction of 3. Allylic alcohol was converted to 2 in 7 steps via iterative ZACA processes and simple chromatography. (?)-Spongidepsin (1) was synthesized by using 2 and 3 through application of the esterification–amidation–ring closing metathesis protocol previously reported. PMID:17583343

  8. Asymmetric Total Synthesis of (?)-Plicatic Acid via a Highly Enantioselective and Diastereoselective Nucleophilic Epoxidation of Acyclic Trisubstitued Olefins

    PubMed Central

    Sun, Bing-Feng; Hong, Ran; Kang, Yan-Biao; Deng, Li

    2009-01-01

    The first total synthesis of (?)-plicatic acid has been achieved by a concise and enantioselective route. In this synthesis, a conceptually new strategy featuring an asymmetric epoxidation-intramolecular epoxy-ring-opening Friedel-Crafts reaction sequence was developed for the stereoselective construction of the 2,7’-cyclolignane skeleton bearing contiguous quaternary-quaternary-tertiary stereocenters. The implementation of this strategy was enabled by the development of a modified protocol for the Seebach epoxidation with TADOOH, which affords an unprecedented, highly enantioselective and diastereoselective epoxidation with a range of ?-carbonyl-?-substituted acrylates 3. PMID:19601599

  9. ?-Allyl-?-aryl ?-Amino Esters in the Asymmetric Synthesis of Acyclic and Cyclic Amino Acid Derivatives by Alkene Metathesis

    PubMed Central

    2015-01-01

    Allylating agents were explored for the asymmetric synthesis of ?-allyl-?-aryl ?-amino acids by tandem N-alkylation/?-allylation. Cross-metathesis of the tandem product was developed to provide allylic diversity not afforded in the parent reaction; the synthesis of homotyrosine and homoglutamate analogues was completed. Cyclic ?-amino acid derivatives could be accessed by ring-closing metathesis presenting a viable strategy to higher ring homologue of enantioenriched ?-substituted proline. The eight-membered proline analogue was successfully converted to the pyrrolizidine natural product backbone. PMID:24828423

  10. Asymmetric aza-Mannich reactions of sulfinimines: scope and application to the total synthesis of a bromopyrrole alkaloid.

    PubMed

    Lanter, James C; Chen, Hongfeng; Zhang, Xuqing; Sui, Zhihua

    2005-12-22

    [reaction: see text] An asymmetric intermolecular aza variant of the Mannich reaction is reported utilizing chiral sulfinimine anions as the nucleophile and N-sulfonyl aldimines as the electrophilic component. A wide range of nucleophiles and electrophiles are tolerated by the reaction conditions, delivering the condensation products in good to excellent yield with a high degree of stereocontrol. Application of this methodology to the total synthesis of a natural product is reported. PMID:16354096

  11. De novo asymmetric synthesis of oligo-rhamno di- and tri-saccharides related to the anthrax tetrasaccharide.

    PubMed

    Wang, Hua-Yu Leo; Guo, Haibing; O'Doherty, George A

    2013-04-22

    An asymmetric synthesis of the di- and trisaccharide portion of the naturally occurring anthrax tetrasaccharide from acetylfuran has been developed. The construction of the di- and trisaccharide subunits is based upon our previously disclosed route to anthrax tetrasaccharide. The approach uses iterative diastereoselective palladium-catalyzed glycosylations, Luche reductions, diastereoselective dihydroxylations, and regioselective protections for the assembly of the rhamno- di- and tri-saccharide. The route was also modified for the preparation of the mixed D-/L-disaccharide analogue. PMID:23794755

  12. De novo asymmetric synthesis of oligo-rhamno di- and tri-saccharides related to the anthrax tetrasaccharide

    PubMed Central

    Wang, Hua-Yu Leo; Guo, Haibing; O’Doherty, George A.

    2013-01-01

    An asymmetric synthesis of the di- and trisaccharide portion of the naturally occurring anthrax tetrasaccharide from acetylfuran has been developed. The construction of the di- and trisaccharide subunits is based upon our previously disclosed route to anthrax tetrasaccharide. The approach uses iterative diastereoselective palladium-catalyzed glycosylations, Luche reductions, diastereoselective dihydroxylations, and regioselective protections for the assembly of the rhamno- di- and tri-saccharide. The route was also modified for the preparation of the mixed D-/L-disaccharide analogue. PMID:23794755

  13. The synthesis and applications of a biaryl-based asymmetric phosphine ligand

    E-print Network

    Hirai, Satoko

    2005-01-01

    The asymmetric biaryl backbone of a dialkylbiphenyl phosphine ligand was developed, synthesized, and resolved. The application of the chiral phosphine ligand to the asymmetric Suzuki-Miyaura cross-coupling reaction was ...

  14. Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

    PubMed Central

    Omedes-Pujol, Marta

    2010-01-01

    Summary Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding reactions carried out in dichloromethane. A mechanistic study has been undertaken, comparing the catalytic activity of VO(salen)NCS in propylene carbonate and dichloromethane. Reactions in both solvents obey overall second-order kinetics, the rate of reaction being dependent on the concentration of both the aldehyde and trimethylsilyl cyanide. The order with respect to VO(salen)NCS was determined and found to decrease from 1.2 in dichloromethane to 1.0 in propylene carbonate, indicating that in propylene carbonate, VO(salen)NCS is present only as a mononuclear species, whereas in dichloromethane dinuclear species are present which have previously been shown to be responsible for most of the catalytic activity. Evidence from 51V NMR spectroscopy suggested that propylene carbonate coordinates to VO(salen)NCS, blocking the free coordination site, thus inhibiting its Lewis acidity and accounting for the reduction in catalytic activity. This explanation was further supported by a Hammett analysis study, which indicated that Lewis base catalysis made a much greater contribution to the overall catalytic activity of VO(salen)NCS in propylene carbonate than in dichloromethane. PMID:21085513

  15. Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate.

    PubMed

    North, Michael; Omedes-Pujol, Marta

    2010-01-01

    Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding reactions carried out in dichloromethane. A mechanistic study has been undertaken, comparing the catalytic activity of VO(salen)NCS in propylene carbonate and dichloromethane. Reactions in both solvents obey overall second-order kinetics, the rate of reaction being dependent on the concentration of both the aldehyde and trimethylsilyl cyanide. The order with respect to VO(salen)NCS was determined and found to decrease from 1.2 in dichloromethane to 1.0 in propylene carbonate, indicating that in propylene carbonate, VO(salen)NCS is present only as a mononuclear species, whereas in dichloromethane dinuclear species are present which have previously been shown to be responsible for most of the catalytic activity. Evidence from ?¹V NMR spectroscopy suggested that propylene carbonate coordinates to VO(salen)NCS, blocking the free coordination site, thus inhibiting its Lewis acidity and accounting for the reduction in catalytic activity. This explanation was further supported by a Hammett analysis study, which indicated that Lewis base catalysis made a much greater contribution to the overall catalytic activity of VO(salen)NCS in propylene carbonate than in dichloromethane. PMID:21085513

  16. Asymmetric Synthesis of Spirocyclic 2-Benzopyrans for Positron Emission Tomography of ?1 Receptors in the Brain

    PubMed Central

    Holl, Katharina; Schepmann, Dirk; Fischer, Steffen; Ludwig, Friedrich-Alexander; Hiller, Achim; Donat, Cornelius K.; Deuther-Conrad, Winnie; Brust, Peter; Wünsch, Bernhard

    2014-01-01

    Sharpless asymmetric dihydroxylation of styrene derivative 6 afforded chiral triols (R)-7 and (S)-7, which were cyclized with tosyl chloride in the presence of Bu2SnO to provide 2-benzopyrans (R)-4 and (S)-4 with high regioselectivity. The additional hydroxy moiety in the 4-position was exploited for the introduction of various substituents. Williamson ether synthesis and replacement of the Boc protective group with a benzyl moiety led to potent ?1 ligands with high ?1/?2-selectivity. With exception of the ethoxy derivative 16, the (R)-configured enantiomers represent eutomers with eudismic ratios of up to 29 for the ester (R)-18. The methyl ether (R)-15 represents the most potent ?1 ligand of this series of compounds, with a Ki value of 1.2 nM and an eudismic ratio of 7. Tosylate (R)-21 was used as precursor for the radiosynthesis of [18F]-(R)-20, which was available by nucleophilic substitution with K[18F]F K222 carbonate complex. The radiochemical yield of [18F]-(R)-20 was 18%–20%, the radiochemical purity greater than 97% and the specific radioactivity 175–300 GBq/µmol. Although radiometabolites were detected in plasma, urine and liver samples, radiometabolites were not found in brain samples. After 30 min, the uptake of the radiotracer in the brain was 3.4% of injected dose per gram of tissue and could be reduced by coadministration of the ?1 antagonist haloperidol. [18F]-(R)-20 was able to label those regions of the brain, which were reported to have high density of ?1 receptors. PMID:24451404

  17. Asymmetric synthesis and biological evaluation of natural or bioinspired cytotoxic c2-symmetrical lipids with two terminal chiral alkynylcarbinol pharmacophores.

    PubMed

    Listunov, Dymytrii; Fabing, Isabelle; Saffon-Merceron, Nathalie; Gaspard, Hafida; Volovenko, Yulian; Maraval, Valérie; Chauvin, Remi; Génisson, Yves

    2015-06-01

    Bidirectional syntheses of C2-symmetrical lipids embedding two terminal alkynylcarbinol pharmacophores are reported. Naturally occurring chiral alkenylalkynylcarbinol units were generated using Pu's procedure for enantioselective addition of terminal alkynes to aldehydes, allowing the first asymmetric synthesis of (3R,4E,16E,18R)-icosa-4,16-diene-1,19-diyne-3,18-diol, isolated from Callyspongia pseudoreticulata. Two synthetic analogues embedding the recently uncovered (S)-dialkynylcarbinol pharmacophore were secured using Carreira's procedure adapted to ynal substrates. The dramatic effect of the carbinol configuration on cytotoxicity was confirmed with submicromolar IC50 values against HCT116 cells. PMID:25961794

  18. A Fully Synthetic and Biochemically Validated Phosphatidyl Inositol-3-Phosphate Hapten via Asymmetric Synthesis and Native Chemical Ligation

    PubMed Central

    Chandler, Brent D.; Burkhardt, Anne L.; Foley, Klaudia; Cullis, Courtney; Driscoll, Denise; D’Amore, Natalie Roy; Miller, Scott J.

    2014-01-01

    We report the synthesis and biochemical validation of a phosphatidyl inositol-3 phosphate (PI3P) immunogen. The inositol stereochemistry was secured through peptide-catalyzed asymmetric phosphorylation catalysis, and the subsequent incorporation of a cysteine residue was achieved by native chemical ligation (NCL). Conjugation of the PI3P hapten to maleimide activated keyhole limpet hemocyanin (KLH) provided a PI3P immunogen, which was successfully used to generate selective PI3P antibodies. The incorporation of a sulfhydryl nucleophile into a phosphoinositide hapten demonstrates a general strategy to reliably access phosphoinositide immunogens. PMID:24344932

  19. Synthesis of (-)-?9-trans-Tetrahydrocannabinol - Stereocontrol via Mo-catalyzed Asymmetric Allylic Alkylation Reaction

    PubMed Central

    Trost, Barry M.; Dogra, Kalindi

    2008-01-01

    ?9-THC is synthesized in enantiomericaly pure form, where all of the stereochemistry is derived from the molybdenum catalyzed asymmetric alkylation reaction of the extremely sterically congested bis-ortho substituted cinnamyl carbonate in high regio- and enantioselectivity. PMID:17266321

  20. Synthesis of chiral sulfoximine-based thioureas and their application in asymmetric organocatalysis

    PubMed Central

    Frings, Marcus; Thomé, Isabelle

    2012-01-01

    Summary For the first time, chiral sulfoximine derivatives have been applied as asymmetric organocatalysts. In combination with a thiourea-type backbone the sulfonimidoyl moiety leads to organocatalysts showing good reactivity in the catalytic desymmetrization of a cyclic meso-anhydride and moderate enantioselectivity in the catalytic asymmetric Biginelli reaction. Straightforward synthetic routes provide the newly designed thiourea-sulfoximine catalysts in high overall yields without affecting the stereohomogeneity of the sulfur-containing core fragment. PMID:23019479

  1. Asymmetric reactions in continuous flow

    PubMed Central

    Mak, Xiao Yin; Laurino, Paola

    2009-01-01

    Summary An overview of asymmetric synthesis in continuous flow and microreactors is presented in this review. Applications of homogeneous and heterogeneous asymmetric catalysis as well as biocatalysis in flow are discussed. PMID:19478913

  2. Synthesis and PKC binding of a new class of a-ring diversifiable bryostatin analogues utilizing a double asymmetric hydrogenation and cross-coupling strategy.

    PubMed

    Wender, Paul A; Horan, Joshua C

    2006-09-28

    The design, asymmetric synthesis, and biological evaluation of a new class of bryostatin analogues based on a pseudosymmetric spacer domain are described. An aryl bromide diversification site is incorporated allowing access to systematically varied analogues. The new analogues all exhibit potent, nanomolar affinity to PKC. PMID:16986955

  3. ?-Ketophosphonates as ester surrogates: isothiourea-catalyzed asymmetric diester and lactone synthesis.

    PubMed

    Smith, Siobhan R; Leckie, Stuart M; Holmes, Reuben; Douglas, James; Fallan, Charlene; Shapland, Peter; Pryde, David; Slawin, Alexandra M Z; Smith, Andrew D

    2014-05-01

    Isothiourea HBTM-2.1 catalyzes the asymmetric Michael addition/lactonization of aryl- and alkenylacetic acids using ?-keto-?,?-unsaturated phosphonates as ?,?-unsaturated ester surrogates, giving access to a diverse range of stereodefined lactones or enantioenriched functionalized diesters upon ring-opening. PMID:24734989

  4. Asymmetric Synthesis of ?-Branched Amines via Rh(III)-Catalyzed C–H Bond Functionalization

    PubMed Central

    2015-01-01

    The first asymmetric intermolecular addition of non-acidic C–H bonds to imines is reported. The use of the activating N-perfluorobutanesulfinyl imine substituent is essential for achieving sufficient reactivity and provides outstanding diastereoselectivity (>98:2 dr). Straightforward removal of the sulfinyl group with HCl yields the highly enantiomerically enriched amine hydrochlorides. PMID:24901217

  5. Asymmetric synthesis of quaternary ?-fluoro-?-keto-amines via detrifluoroacetylative Mannich reactions.

    PubMed

    Xie, Chen; Dai, Yanling; Mei, Haibo; Han, Jianlin; Soloshonok, Vadim A; Pan, Yi

    2015-05-19

    Efficient asymmetric detrifluoroacetylative Mannich addition reactions between 2-fluoro-1,3-di-ketones/hydrates and chiral N-sulfinyl-imines via C-C bond cleavage were reported, which afforded C-F quaternary ?-fluoro-?-keto-amines with excellent yields and high diastereoselectivity. PMID:25947253

  6. Synthesis of colloidal Janus nanoparticles by asymmetric capping of mesoporous silica with phenylsilsesquioxane.

    PubMed

    Ujiie, Hiroto; Shimojima, Atsushi; Kuroda, Kazuyuki

    2015-02-21

    Colloidal mesoporous silica nanoparticles asymmetrically capped with non-porous phenylsilsesquioxane have been prepared by adding phenyltriethoxysilane to an aqueous dispersion of mesostructured silica-surfactant composite nanoparticles. The integration of colloidal stability, mesoporosity and the Janus structure is quite promising for materials design applicable in various fields, including catalysis, biomedicine and coatings. PMID:25605540

  7. Palladium-Catalyzed Asymmetric Alkylation in the Synthesis of Cyclopentanoid and Cycloheptanoid Core Structures Bearing All-

    E-print Network

    Stoltz, Brian M.

    , iodoethane, acrylonitrile, methyl vinyl ketone, and acrolein were distilled prior to use. Purified water for the Synthesis of Ligands L3 and L4 SI 8 Procedures for Synthesis of Enantioenriched Vinylogous Esters 7 SI 10 using Enantioselective Decarboxylative Alkylation Reactions Synthetic Studies on Vinylogous Esters 8/7a

  8. Asymmetric Synthesis of 1,3-Butadienyl-2-carbinols by the Homoallenylboration of Aldehydes with a Chiral Phosphoric Acid Catalyst.

    PubMed

    Huang, Yiyong; Yang, Xing; Lv, Zongchao; Cai, Chen; Kai, Cheng; Pei, Yong; Feng, Yu

    2015-06-15

    Asymmetric C(sp)?C(sp(2) ) bond formation to give enantiomerically enriched 1,3-butadienyl-2-carbinols occurred through a homoallenylboration reaction between a 2,3-dienylboronic ester and aldehydes under the catalysis of a chiral phosphoric acid (CPA). A diverse range of enantiomerically enriched butadiene-substituted secondary alcohols with aryl, heterocyclic, and aliphatic substituents were synthesized in very high yield with high enantioselectivity. Preliminary density functional theory (DFT) calculations suggest that the reaction proceeds via a cyclic six-membered chairlike transition state with essential hydrogen-bond activation in the allene reagent. The catalytic reaction was amenable to the gram-scale synthesis of a chiral alkyl butadienyl adduct, which was converted into an interesting optically pure compound bearing a benzo-fused spirocyclic cyclopentenone framework. PMID:25939725

  9. Asymmetric synthesis of a CBI-based cyclic N-acyl O-amino phenol duocarmycin prodrug.

    PubMed

    Uematsu, Mika; Boger, Dale L

    2014-10-17

    A short, asymmetric synthesis of a cyclic N-acyl O-amino phenol duocarmycin prodrug subject to reductive activation based on the simplified 1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (CBI) DNA alkylation subunit is described. A key element of the approach entailed treatment of iodo-epoxide 7, prepared by N-alkylation of 6 with (S)-glycidal 3-nosylate, with EtMgBr at room temperature to directly provide the optically pure alcohol 8 in 78% yield (99% ee) derived from an effective metal-halogen exchange and subsequent regioselective intramolecular 6-endo-tet cyclization. Following O-debenzylation, introduction of a protected N-methylhydroxamic acid, direct trannannular spirocyclization, and subsequent stereoelectronically controlled acid-catalyzed cleavage of the resulting cyclopropane (HCl), further improvements in a unique intramolecular cyclization with N-O bond formation originally introduced for formation of the reductively labile prodrug functionality are detailed. PMID:25247380

  10. Enantiopure narrow bite-angle P-OP ligands: synthesis and catalytic performance in asymmetric hydroformylations and hydrogenations.

    PubMed

    Fernández-Pérez, Héctor; Benet-Buchholz, Jordi; Vidal-Ferran, Anton

    2014-11-17

    Herein is reported the preparation of a set of narrow bite-angle P-OP ligands the backbone of which contains a stereogenic carbon atom. The synthesis was based on a Corey-Bakshi-Shibata (CBS)-catalyzed asymmetric reduction of phosphomides. The structure of the resulting 1,1-P-OP ligands, which was selectively tuned through adequate combination of the configuration of the stereogenic carbon atom, its substituent, and the phosphite fragment, proved crucial for providing a rigid environment around the metal center, as evidenced by X-ray crystallography. These new ligands enabled very good catalytic properties in the Rh-mediated enantioselective hydrogenation and hydroformylation of challenging and model substrates (up to 99?%?ee). Whereas for asymmetric hydrogenation the optimal P-OP ligand depended on the substrate, for hydroformylation, a single ligand was the highest-performing one for almost all studied substrates: it contains an R-configured stereogenic carbon atom between the two phosphorus ligating groups, and an S-configured 3,3'-diphenyl-substituted biaryl unit. PMID:25335770

  11. Total synthesis of gobiusxanthin stereoisomers and their application to determination of absolute configurations of natural products: revision of reported absolute configuration of epigobiusxanthin.

    PubMed

    Yamano, Yumiko; Ematsu, Kotaro; Kurimoto, Hiromasa; Maoka, Takashi; Wada, Akimori

    2015-01-01

    (3R)-Gobiusxanthin stereoisomers (1a-d) were synthesized by stereoselective Wittig reaction of the (3R)-C15-acetylenic tri-n-butylphosphonium salt 7 with C25-apocarotenal stereoisomers 5a,b and 14a,b bearing four kinds of 3,6-dihydroxy-?-end groups. The validity of the reported stereochemistry of gobiusxanthin was demonstrated by the fact that the reported spectral data of natural gobiusxanthin were in agreement with those of synthetic (3R,3'S,6'R)-gobiusxanthin (1a). On the other hand, the reported CD spectral data of natural epigobiusxanthin, which has been assigned as (3R,3'R,6'R)-isomer (3'-epigobiusxanthin), were identical with those of synthetic (3R,3'S,6'S)-isomer 1d (6'-epigobiusxanthin) rather than those of the corresponding synthetic 3'-epi-isomer 1b. It was found that the stereochemistry at C3-position has little effect on the shape of their CD spectra. Thus, in order to reinforce the validity of the absolute configurations at C3-position of natural specimens, (3S,3'S,6'R)- and (3S,3'S,6'S)-stereoisomers 1e and 1f were also synthesized and a HPLC analytical method for four stereoisomers was established by using a column carrying a chiral stationary phase. The HPLC analysis has proven that the stereochemistry of the natural epigobiusxanthin is 3R,3'S,6'S. PMID:25561412

  12. Total Synthesis of Gobiusxanthin Stereoisomers and Their Application to Determination of Absolute Configurations of Natural Products: Revision of Reported Absolute Configuration of Epigobiusxanthin

    PubMed Central

    Yamano, Yumiko; Ematsu, Kotaro; Kurimoto, Hiromasa; Maoka, Takashi; Wada, Akimori

    2014-01-01

    (3R)-Gobiusxanthin stereoisomers (1a–d) were synthesized by stereoselective Wittig reaction of the (3R)-C15-acetylenic tri-n-butylphosphonium salt 7 with C25-apocarotenal stereoisomers 5a,b and 14a,b bearing four kinds of 3,6-dihydroxy-?-end groups. The validity of the reported stereochemistry of gobiusxanthin was demonstrated by the fact that the reported spectral data of natural gobiusxanthin were in agreement with those of synthetic (3R,3'S,6'R)-gobiusxanthin (1a). On the other hand, the reported CD spectral data of natural epigobiusxanthin, which has been assigned as (3R,3'R,6'R)-isomer (3'-epigobiusxanthin), were identical with those of synthetic (3R,3'S,6'S)-isomer 1d (6'-epigobiusxanthin) rather than those of the corresponding synthetic 3'-epi-isomer 1b. It was found that the stereochemistry at C3-position has little effect on the shape of their CD spectra. Thus, in order to reinforce the validity of the absolute configurations at C3-position of natural specimens, (3S,3'S,6'R)- and (3S,3'S,6'S)-stereoisomers 1e and 1f were also synthesized and a HPLC analytical method for four stereoisomers was established by using a column carrying a chiral stationary phase. The HPLC analysis has proven that the stereochemistry of the natural epigobiusxanthin is 3R,3'S,6'S. PMID:25561412

  13. Synthesis of several cleistrioside and cleistetroside natural products via a divergent de novo asymmetric approach.

    PubMed

    Wu, Bulan; Li, Miaosheng; O'Doherty, George A

    2010-12-01

    The de novo asymmetric syntheses of several partially acylated dodecanyl tri- and tetra-rhamnoside natural products (cleistriosides-5 and 6 and cleistetrosides-2 to 7) have been achieved (19-24 steps). The divergent route requires the use of three or less protecting groups. The asymmetry was derived via Noyori reduction of an acylfuran. The rhamno-stereochemistry was installed by a diastereoselective palladium-catalyzed glycosylation, ketone reduction and dihydroxylation. PMID:21038879

  14. Synthesis of Several Cleistrioside and Cleistetroside Natural Products via a Divergent De Novo Asymmetric Approach

    PubMed Central

    Wu, Bulan; Li, Miaosheng; O’Doherty, George A.

    2010-01-01

    The de novo asymmetric syntheses of several partially acylated dodecanyl tri- and tetra-rhamnoside natural products (cleistriosides-5 & 6 and cleistetrosides-2 to 7) have been achieved (19 to 24 steps). The divergent route requires the use of three or less protecting groups. The asymmetry was derived via Noyori reduction of an acylfuran. The rhamno-stereochemistry was installed by a diastereoselective palladium-catalyzed glycosylation, ketone reduction and dihydroxylation. PMID:21038879

  15. Asymmetric Synthesis of Medium-Sized Rings by Intramolecular Au(I)-Catalyzed Cyclopropanation

    PubMed Central

    Watson, Iain D. G.; Ritter, Stefanie; Toste, F. Dean

    2009-01-01

    An efficient method for the asymmetric gold(I)-catalyzed preparation of medium sized rings has been developed. The method provides 7- to 9-membered rings in excellent yield. High enantioselectivities can be achieved for 7- and 8-membered ring products employing chiral gold(I) complexes. The results provide insight into the mechanism, showing the fluxional nature of gold(I)-stabilized vinyl carbenoid intermediates. PMID:19161306

  16. Efficient synthesis of carbazolespirooxindole skeletons via asymmetric Diels-Alder reaction of 3-vinylindoles and methyleneindolinones.

    PubMed

    Zheng, Haifeng; He, Peng; Liu, Yangbin; Zhang, Yulong; Liu, Xiaohua; Lin, Lili; Feng, Xiaoming

    2014-08-14

    A highly efficient catalytic asymmetric Diels-Alder reaction between 3-vinylindoles and methyleneindolinones has been achieved using chiral N,N'-dioxide-Ni(II) complexes as the catalysts. A wide variety of substrates were readily tolerated, generating exclusively the corresponding exo-carbazolespirooxindole derivatives in excellent yields with high enantiomeric excesses (up to 98% yield, >99?:?1 d.r., and 98% ee) under mild reaction conditions. PMID:24967917

  17. Synthesis, photo- and electroluminescence properties of asymmetrical alternating copoly( p-phenylenevinylene) derivatives

    NASA Astrophysics Data System (ADS)

    Tan, Songting; Zou, Yingping; Zhu, Weiguo; Jiang, Changyun

    2006-06-01

    A series of asymmetrical alternating copoly( p-phenylenevinylene) derivatives (PPVs), poly(2-methoxy-5-alkoxy)-1,4-(phenylene vinylene)-alt-1,4-(phenylene vinylene), have been successfully synthesized via the Wittig polycondensation reaction as potential electroluminescent (EL) materials. These copolymers contain two components, one is phenylene vinylene with asymmetrical flexible side chain to improve the solubility of the copolymer in common solvents and to suppress its crystallization; the other is a rigid phenylene vinylene moiety to improve the luminescent quantum efficiency and the thermal stability. The photoluminescent (PL) properties and thermal behavior of these copolymers have been investigated in detail. The results showed that the PL intensity increased but the thermal stability decreased with increasing side chain length. A double-layer device of ITO/PEDOT-PSS/Polymer 3/Ba/Al showed a greenish yellow emission peaking at 548 nm with a turn-on voltage as low as 6.2 V. A maximum brightness of 534 cd/m 2 was obtained at a driving voltage of 10 V.

  18. Enzymatic Desymmetrising Redox Reactions for the Asymmetric Synthesis of Biaryl Atropisomers

    PubMed Central

    Staniland, Samantha; Yuan, Bo; Giménez-Agulló, Nelson; Marcelli, Tommaso; Willies, Simon C; Grainger, Damian M; Turner, Nicholas J; Clayden, Jonathan

    2014-01-01

    Atropisomeric biaryls carrying ortho-hydroxymethyl and formyl groups were made enantioselectively by desymmetrisation of dialdehyde or diol substrates. The oxidation of the symmetrical diol substrates was achieved using a variant of galactose oxidase (GOase), and the reduction of the dialdehydes using a panel of ketoreductases. Either M or P enantiomers of the products could be formed, with absolute configurations assigned by time-dependent DFT calculations of circular dichroism spectra. The differing selectivities observed with different biaryl structures offer an insight into the detailed structure of the active site of the GOase enzyme. PMID:25156181

  19. Catalytic, asymmetric, and stereodivergent synthesis of non-symmetric ?,?-diaryl-?-amino acids.

    PubMed

    Molinaro, Carmela; Scott, Jeremy P; Shevlin, Michael; Wise, Christopher; Ménard, Alain; Gibb, Andrew; Junker, Ellyn M; Lieberman, David

    2015-01-21

    We report a concise, enantio- and diastereoselective route to novel nonsymmetrically substituted N-protected ?,?-diaryl-?-amino acids and esters, through the asymmetric hydrogenation of tetrasubstituted olefins, some of the most challenging examples in the field. Stereoselective generation of an E- or Z-enol tosylate, when combined with stereoretentive Suzuki-Miyaura cross-coupling and enantioselective hydrogenation catalyzed by (NBD)2RhBF4 and a Josiphos ligand, allows for full control over the two vicinal stereogenic centers. High yields and excellent enantioselectivities (up to 99% ee) were obtained for a variety of N-acetyl, N-methoxycarbonyl, and N-Boc ?,?-diaryldehydroamino acids, containing a diverse and previously unreported series of heterocyclic and aryl substituted groups (24 examples) and allowing access to all four stereoisomers of these valuable building blocks. PMID:25523503

  20. Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate.

    PubMed

    Laurenson, James A B; Parkinson, John A; Percy, Jonathan M; Rinaudo, Giuseppe; Roig, Ricard

    2013-01-01

    Esters of crotonic acid were brominated on a multigramme scale using a free radical procedure. A phase transfer catalysed fluorination transformed these species to the 4-fluorobut-2E-enoates reproducibly and at scale (48-53%, ca. 300 mmol). Asymmetric dihydroxylation reactions were then used to transform the butenoate, ultimately into all four diastereoisomers of a versatile fluorinated C4 building block at high enantiomeric-enrichment. The (DHQ)2AQN and (DHQD)2AQN ligands described by Sharpless were the most effective. The development and optimisation of a new and facile method for the determination of ee is also described; (19)F{(1)H} spectra recorded in d-chloroform/diisopropyl tartrate showed distinct baseline separated signals for different enantiomers. PMID:24367430

  1. Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

    PubMed Central

    Laurenson, James A B; Parkinson, John A; Rinaudo, Giuseppe; Roig, Ricard

    2013-01-01

    Summary Esters of crotonic acid were brominated on a multigramme scale using a free radical procedure. A phase transfer catalysed fluorination transformed these species to the 4-fluorobut-2E-enoates reproducibly and at scale (48–53%, ca. 300 mmol). Asymmetric dihydroxylation reactions were then used to transform the butenoate, ultimately into all four diastereoisomers of a versatile fluorinated C4 building block at high enantiomeric-enrichment. The (DHQ)2AQN and (DHQD)2AQN ligands described by Sharpless were the most effective. The development and optimisation of a new and facile method for the determination of ee is also described; 19F{1H} spectra recorded in d-chloroform/diisopropyl tartrate showed distinct baseline separated signals for different enantiomers. PMID:24367430

  2. The synthesis and characterization of new iron coordination complexes utilizing an asymmetric coordinating chelate ligand

    SciTech Connect

    Watkins, B.E.; Satcher, J.H.

    1995-07-01

    A binuclear, unsymmetric coordinating ligand that is an effective metal chelator has been designed and synthesized. The new ligand has been shown to react readily with iron(II)/(III) forming a variety of coordination complexes. The binuclear complexes are of significant interest since they represent proof-of-principle for the development of coordinatively asymmetric, binuclear metal chelate compounds. Although this structural type of chelator now appears to be common in biological systems, it has not been previously described for inorganic coordination chemistry. The isolation of oxidation products will be helpful in establishing reaction mechanism(s) of these complexes with molecular oxygen. It is expected that this ligand and derivatives of it will play an important role in the development of bioinorganic complexes that aim to mimic enzyme active sites that function by substrate interaction at only one metal site of a multimetal active site.

  3. Diastereoselective Synthesis of 1-Deoxygalactonojirimycin, 1-Deoxyaltronojirimycin, and N-Boc-(2S,3S)-3-Hydroxypipecolic Acid via Proline Catalyzed ?-Aminoxylation of Aldehydes.

    PubMed

    Chacko, Shibin; Ramapanicker, Ramesh

    2015-05-01

    An efficient synthesis of deoxygalactonojirimycin and deoxyaltronojirimycin through the use of proline catalyzed asymmetric ?-aminoxylation of a higher homologue of Garner's aldehyde, derived from l-aspartic acid, is reported. The method is also used for a highly diastereoselective synthesis of the N-Boc derivative of (2S,3S)-3-hydroxypipecolic acid. The configuration of the proline catalyst used for the asymmetric aminoxylation step ultimately controls the absolute configuration of three adjacent stereogenic centers in the final products. PMID:25860296

  4. Asymmetric Synthesis of Functionalized Dihydro- and Tetrahydropyrans via an Organocatalytic Domino Michael–Hemiacetalization Reaction

    PubMed Central

    Urbanietz, Gregor; Atodiresei, Iuliana; Enders, Dieter

    2014-01-01

    Starting from ?-hydroxymethyl nitroalkenes and various 1,3-dicarbonyl compounds, a one-pot organocatalyzed diastereo- and enantioselective synthesis of polyfunctionalized dihydro- and tetrahydropyran derivatives via a domino Michael-hemiacetalization sequence is reported. The title compounds bearing a variety of functional groups can be synthesized in this way in good yields (59–91%) and with moderate to excellent diastereoselectivities (26–98% de) and enantioselectivities (71–99% ee). PMID:25284900

  5. De novo asymmetric synthesis of cladospolide B-D: structural reassignment of cladospolide D via the synthesis of its enantiomer.

    PubMed

    Xing, Yalan; O'Doherty, George A

    2009-03-01

    The enantioselective synthesis of cladospolide B, C, and (ent)-cladospolide D has been achieved in 11-15 steps from 1-nonyne. The route relies upon an alkyne zipper reaction to relay an ynone and dienoate functional groups across a nine carbon fragment, which enables a highly enantioselective Noyori ynone reduction and a diastereo- and regioselective Sharpless dihydroxylation of a dienoate. In addition to being a flexible approach to three members of the cladospolide natural products, this route for the first time correctly established the structure for cladospolide D. PMID:19193044

  6. Asymmetric noncovalent synthesis of self-assembled one-dimensional stacks by a chiral supramolecular auxiliary approach.

    PubMed

    George, Subi J; de Bruijn, Robin; Tomovi?, Željko; Van Averbeke, Bernard; Beljonne, David; Lazzaroni, Roberto; Schenning, Albertus P H J; Meijer, E W

    2012-10-24

    Stereoselective noncovalent synthesis of one-dimensional helical self-assembled stacks of achiral oligo(p-phenylenevinylene) ureidotriazine (AOPV3) monomers is obtained by a chiral supramolecular auxiliary approach. The racemic mixture of helical stacks of achiral AOPV3 molecules is converted into homochiral helical stacks, as shown by both spectroscopic measurements and molecular modeling simulations. The conversion is promoted by an orthogonal two-point ion-pair interaction with the chiral auxiliary dibenzoyl tartaric acid (D- or L-TA) molecules, which biases the angle population distribution and thereby the stack helicity. The induced preferred helicity is maintained by the OPV stacks even after the removal of the chiral auxiliary by extraction with ethylenediamine (EDA), due to the kinetic stability of the OPV stacks at room temperature. Spectroscopic probing of the helical self-assembly and the racemization process of these ?-conjugated OPV chromophores shed further light into the mechanistic pathways of this chiral asymmetric noncovalent synthesis and the kinetic stability of the stacks produced. The racemization of the stacks follows first-order kinetics and no switch in mechanism is observed as a result of a temperature change; therefore, a racemization via disassembly assembly is proposed. Remarkably, the preferred helicity of the stacks of achiral AOPV3 can be retained almost completely after a heating-cooling cycle where the stacks first partially depolymerize and then polymerize again with the still existing stacks being the seeds for self-assembly of achiral AOPV3. Only after a fully dissociated state is obtained at high temperatures, the optical activity of the supramolecular stack self-assembled at room temperature is lost. PMID:23030496

  7. Asymmetric synthesis from terminal alkenes by diboration/cross-coupling cascades

    PubMed Central

    Mlynarski, Scott N.; Schuster, Christopher H.; Morken, James P.

    2013-01-01

    Amongst prospective starting materials for organic synthesis, terminal (monosubstituted) alkenes are ideal. In the form of ?-olefins, they are manufactured on enormous scale and they are the core product features from many organic chemical reactions. While their latent reactivity can easily enable hydrocarbon chain extension, alkenes also have the attractive feature of being stable in the presence of many acids, bases, oxidants and reductants. In spite of these impressive attributes, relatively few catalytic enantioselective transformations have been developed that transform aliphatic ?-olefins in >90% ee and, with the exception of site-controlled isotactic polymerization of ?-olefins,1 none of these processes result in chain-extending C-C bond formation to the terminal carbon.2, 3, 4, 5, 6 Herein, we describe a strategy that directly addresses this gap in synthetic methodology and present a single-flask catalytic enantioselective conversion of terminal alkenes into a range of chiral products. These reactions are enabled by an unusual neighboring group participation effect that accelerates Pd-catalyzed cross-coupling of 1,2-bis(boronates) relative to nonfunctionalized alkyl boronate analogs. In tandem with enantioselective diboration, this reactivity feature connects abundant alkene starting materials to a diverse array of chiral products. Importantly with respect to synthesis utility, the tandem diboration/cross-coupling reaction (DCC reaction) generally provides products in high yield and high selectivity (>95:5 enantiomer ratio), employs low loadings (1–2 mol %) of commercially available catalysts and reagents, it offers an expansive substrate scope, and can address a broad range of alcohol and amine synthesis targets, many of which cannot be easily addressed with current technology. PMID:24352229

  8. Enantioselective Synthesis of ?-Arylamines via Chiral Phosphoric Acid-Catalyzed Asymmetric Reductive Amination.

    PubMed

    Kim, Kyung-Hee; Lee, Chun-Young; Cheon, Cheol-Hong

    2015-06-19

    A new method for the synthesis of chiral ?-aryl amines via chiral phosphoric acid-catalyzed enantioselective reductive amination of benzyl methyl ketone derivatives with Hantzsch ester was developed. Various chiral ?-aryl amines were obtained in high yields and with good to high enantioselectivities. This transformation is applicable to gram-scale reactions, and the catalyst loading can be reduced to 1 mol % without sacrificing any catalytic efficacy. Furthermore, the resulting ?-aryl amine was successfully converted into a tetrahydroisoquinoline compound without any loss of enantioselectivity. PMID:26000470

  9. Stereoselective Synthesis of ?-Hydroxy Enamines, Amino Cyclopropanes and 1,3-Amino Alcohols via Asymmetric Catalysis

    PubMed Central

    Valenta, Petr; Carroll, Patrick J.; Walsh, Patrick J.

    2010-01-01

    Tandem methods for the catalytic asymmetric preparation of enantioenriched ?-hydroxy (E)-enamines and cyclopropylamines are presented. The diastereoselective hydrogenation of enantioenriched (E)-trisubstituted hydroxy enamines to generate 1,2-disubstituted 1,3-amino alcohols is also outlined. These methods are initiated by highly regioselective hydroboration of N-tosyl substituted ynamides with diethylborane to generate ?-amino alkenyl boranes. In situ boron to zinc transmetalation generates ?-amino alkenyl zinc reagents. These functionalized vinylzinc intermediates were subsequently added to aldehydes in the presence of catalyst derived from an enantioenriched amino alcohol (morpholino isoborneol, MIB). The catalyst promotes highly enantioselective C–C bond-formation to provide ?-hydroxy enamines in good isolated yields (68–86%) with 54–98% enantioselectivity. The intermediate zinc ?-alkoxy enamines can be subjected to a tandem cyclopropanation to afford amino cyclopropyl carbinols with three continuous stereocenters in a one-pot procedure with good yields (72–82%), enantioselectivities of 76–94% and diastereomeric ratios >20:1. Diastereoselective hydrogenation of isolated enantioenriched ?-hydroxy enamines over Pd/C furnished syn-1,2-disubstituted-1,3-amino alcohols with high yields (82–90%) and moderate to excellent diastereoselectivities. These methods were used in an efficient preparation of the enantioenriched precursor to PRC200-SS derivatives, which are potent serotonin-norepinephrine-dopamine reuptake inhibitors. PMID:20853837

  10. Synthesis, Annealing and Performance of Pd-Au Asymmetric Composite Membranes for Hydrogen Purification

    SciTech Connect

    Ma, Yi Hua [Worcester Polytechnic Institute; Chen, Chao-Huang [Worcester Polytechnic Institute; Catalano, Jacopo [Worcester Polytechnic Institute; Guazzone, Federico [Worcester Polytechnic Institute; Payzant, E Andrew [ORNL

    2013-01-01

    Composite asymmetric Pd-Au membranes, based on porous Inconel and Hastelloy tubular supports, were prepared by means of electroless deposition and galvanic displacement techniques and tested, before and after Au deposition, in pure H2 atmosphere. The final membranes, with Au average bulk composition up to 16.7 wt%, were 9 15 m thick and showed, for the entire duration of characterization, H2/He ideal selectivity in excess of 900. The annealing of the as-prepared membranes was conducted through the coating and diffusion mechanism in He and H2 atmospheres at 500 C. The annealing conditions were chosen after non-isothermal and isothermal HT-XRD studies on coupons synthetized with similar preparation methods. After the formation of the Pd-Au layer, the membranes showed steady flux and a stable Au gradient on the membrane top layer. Comparisons between permeance for Pd/Au and pure Pd membranes indicated that the membranes with an Au average bulk composition of 4.5 and 5.4 wt% had an enhancement, up to 20%, of the H2 permeability in the temperature range 250 450 C with respect to pure Pd membranes. On the other hand, the membrane having the highest Au composition, 16.7 wt%, even though characterized by a lower H2 permeability (77% of pure Pd) had a rather high surface Au composition (approximately 46 wt%), which might provide good H2S poisoning tolerance.

  11. Convergent approach to pumiliotoxin alkaloids. Asymmetric total synthesis of (+)-pumiliotoxins A, B, and 225F.

    PubMed

    Aoyagi, Sakae; Hirashima, Shintaro; Saito, Kosuke; Kibayashi, Chihiro

    2002-08-01

    A versatile convergent approach for preparing the pumiliotoxin alkaloids has been developed employing Pd(0)-catalyzed cross-coupling reactions between homoallylic organozincs and vinyl iodides. The (Z)-iodoalkylidene indolizidine 34, which served as a common key intermediate, was synthesized through highly stereoselective addition of the chiral silylallene 19 to (S)-acetylpyrrolidine followed by a palladium-catalyzed intramolecular carbonylation[bond]cyclization sequence. This synthetic process allowed the first total synthesis of (+)-pumiliotoxin 225F. The intermediate (Z)-iodoalkylidene indolizidine 34 obtained was converted to a homoallylzinc chloride derivative and subjected to homoallyl-vinyl cross-coupling with the (E)-vinyl iodide 42 using Pd(PPh(3))(4) catalyst to give the cross-coupled product 47 with a 1,5-diene side chain. Subsequent deprotection provided (+)-pumiliotoxin A. On the other hand, the (Z)-iodoalkylidene indolizidine 34 was transformed into the homoallyl-tert-butyl zinc derivative, which underwent palladium-catalyzed cross-coupling with the (E)-vinyl iodide 50 and subsequent deprotection to afford (+)-pumiliotoxin B. PMID:12153249

  12. Asymmetric chemoenzymatic synthesis of miconazole and econazole enantiomers. The importance of chirality in their biological evaluation.

    PubMed

    Mangas-Sánchez, Juan; Busto, Eduardo; Gotor-Fernández, Vicente; Malpartida, Francisco; Gotor, Vicente

    2011-04-01

    A simple and novel chemoenzymatic route has been applied for the first time in the synthesis of miconazole and econazole single enantiomers. Lipases and oxidoreductases have been tested in stereoselective processes; the best results were attained with oxidoreductases for the introduction of chirality in an adequate intermediate. The behaviors of a series of ketones and racemic alcohols in bioreductions and acetylation procedures, respectively, have been investigated; the best results were found with alcohol dehydrogenases A and T, which allowed the production of (R)-2-chloro-1-(2,4-dichlorophenyl)ethanol in enantiopure form under very mild reaction conditions. Final chemical modifications have been performed in order to isolate the target fungicides miconazole and econazole both as racemates and as single enantiomers. Biological evaluation of the racemates and single enantiomers has shown remarkable differences against the growth of several microorganisms; while (R)-miconazole seemed to account for most of the biological activity of racemic miconazole on all the strains tested, both enantiomers of econazole showed considerable biological activities. In this manner, (R)-econazole showed higher values against Candida krusei , while higher values were observed for (S)-econazole against Cryptococcus neoformans, Penicillium chrysogenum, and Aspergillus niger. PMID:21384803

  13. Total synthesis of junionone, a natural monoterpenoid from Juniperus communis L., and determination of the absolute configuration of the naturally occurring enantiomer by ROA spectroscopy.

    PubMed

    Lovchik, Martin A; Fráter, Georg; Goeke, Andreas; Hug, Werner

    2008-01-01

    Recently, we reported a novel access to 2,2-diethyl-3-[(E/Z)-prop-1-en-1-yl]cyclobutanone by an intramolecular nucleophilic substitution with allylic rearrangement (S(N)i') of (E)-6-chloro-3,3-diethylhept-4-en-2-one. The ring closure reaction was found to proceed with selective syn-displacement of the leaving group. This method was now applied to the total synthesis of junionone, an olfactorily interesting cyclobutane monoterpenoid isolated from Juniperus communis, L. S(N)i' Ring closure of the ketone enolate of (E)-3,3-dimethyl-5-[(2R,3R)-3-methyloxiran-2-yl]pent-4-en-2-one (R,R)-(E)-4' proceeded only after the epoxide moiety had been activated by Lewis acid and led to the junionone precursors (3R)- and (3S)-3-[(1E,3R)-3-hydroxybut-1-en-1-yl]-2,2-dimethylcyclobutanone (S/R,R)-(E)-3. The ratio of syn- and anti-conformers in the transitory molecular arrangement was found to depend on the nature of the Lewis acid. The absolute configuration of both the synthetic as well as the natural junionone, isolated from juniper berry oil, was determined by Raman Optical Activity (ROA) spectroscopy. Our experiments led to a novel synthetic route to both (+)- and (-)-junionone, the first determination of the absolute configuration of natural junionone, and to the development of a practical ROA procedure for measuring milligram quantities of volatile liquids. PMID:18205115

  14. Asymmetric synthesis of novel (1H-benzo[d]imidazol -2-ylthio)- and (di-n-butylamino-2-ylthio)acetamides.

    PubMed

    ?aczkowski, Krzysztof Z

    2013-01-01

    Asymmetric synthesis of novel (1H-benzo[d]imidazol-2-ylthio)- and (di-n-butylamino)acetamides is described. The o-nitrobenzyl oxime ethers were reduced with borane in the presence of oxazaborolidenes derived from norephedrine or diphenylvalinol and diphenylphosphinic amide was reduced with modified sodium tetrahydroborate catalyzed with beta-ketoiminato cobalt(II) complex to the corresponding amines with high yields and moderate enantiomeric excess. Reaction of amines with 2-chloroacetyl chloride and next with thiobenzimidazole or n-dibutylamine gave corresponding products with high yields. PMID:23614279

  15. An efficient approach to Aspidosperma alkaloids via [4 + 2] cycloadditions of aminosiloxydienes: stereocontrolled total synthesis of (+/-)-tabersonine. Gram-scale catalytic asymmetric syntheses of (+)-tabersonine and (+)-16-methoxytabersonine. Asymmetric syntheses of (+)-aspidospermidine and (-)-quebrachamine.

    PubMed

    Kozmin, Sergey A; Iwama, Tetsuo; Huang, Yong; Rawal, Viresh H

    2002-05-01

    Described is a concise, highly stereocontrolled strategy to the Aspidosperma family of indole alkaloids, one that is readily adapted to the asymmetric synthesis of these compounds. The strategy is demonstrated by the total synthesis of (+/-)-tabersonine (rac-1), proceeding through a 12-step sequence. The basis for this approach was provided by a highly regio- and stereoselective [4 + 2] cycloaddition of 2-ethylacrolein with 1-amino-3-siloxydiene developed in our laboratory. Subsequent elaboration of the initial adduct into the hexahydroquinoline DE ring system was accomplished efficiently by a ring-closing olefin metathesis reaction. A novel ortho nitrophenylation of an enol silyl ether with (o-nitrophenyl)phenyliodonium fluoride was developed to achieve an efficient, regioselective introduction of the requisite indole moiety. The final high-yielding conversion of the ABDE tetracycle into pentacyclic target rac-1 relied on intramolecular indole alkylation and regioselective C-carbomethoxylation. Our approach differs strategically from previous routes and contains built-in flexibility necessary to access many other members of the Aspidosperma family of indole alkaloids. The versatility of the synthetic strategy was illustrated through the asymmetric syntheses of the following Aspidosperma alkaloids: (+)-aspidospermidine, (-)-quebrachamine, (-)-dehydroquebrachamine, (+)-tabersonine, and (+)-16-methoxytabersonine. Of these, (+)-tabersonine and (+)-16-methoxytabersonine were synthesized in greater than 1-g quantities and in enantiomerically enriched form ( approximately 95% ee). The pivotal asymmetry-introducing step was a catalyzed enantioselective Diels-Alder reaction, which proceeded to afford the cycloadducts in up to 95% ee. Significantly, the synthetic sequence was easy to execute and required only four purifications over the 12-step synthetic route. PMID:11971711

  16. New chiral phosphinephosphinite ligands: Application to stereoselective synthesis of a key intermediate of 1{beta}-methyl carbapenems by Rh(I)-catalyzed asymmetric hydroformylation

    SciTech Connect

    Saito, Takao; Yoshida, Akifumi; Matsumura, Kazuhiko [Takasago International Corp., Kanagawa (Japan)] [and others

    1995-12-31

    Transition metal catalyzed asymmetric hydroformylation is an attractive and highly useful homologation process for organic synthesis. Recently, the authors reported that the Rh(I) complexes of phosphinephosphite BINAPHOS are highly efficient catalysts for enantioselective hydroformylation of a variety of olefins. This time, the authors have designed and synthesized new chiral phosphinephosphinite ligands having binaphthyl backbone, (R)-2-diarylphosphino-2{prime}-diarylphosphinoxy-1,1{prime}-binaphthy1 (hereafter abbreviated (R)-BIPNITE). The Rh(I) complexes of these ligands are effective catalysts for the asymmetric hydroformylation of 4-vinylazetidin-2-one to give the corresponding oxo-aldehyde 3{beta} as the major product in very high diastereoselectivities and in good regioselectivities. Interestingly, modifications of the aryl substituents in phosphine and phosphinite moieties afforded higher selectivities. Aldehyde 3{beta} was easily oxidized with NaClO{sub 2} to 4, a key intermediate of 1{beta}-methyl carbapenems. Thus, the present method provides a new practical route to a versatile key intermediate for the synthesis of carbapenem antibiotics.

  17. Theoretical study of the asymmetric phase-transfer mediated epoxidation of chalcone catalyzed by chiral crown ethers derived from monosaccharides

    Microsoft Academic Search

    Attila Makó; Dóra K. Menyhárd; Péter Bakó; György Keglevich; László Toke

    2008-01-01

    The synthesis of a novel, optically active crown ether derived from ?-d-altropyranoside is described. A significantly different asymmetric induction was generated by the ?-d-glucopyranoside-, ?-d-mannopyranoside- and ?-d-altropyranoside-based chiral crown catalysts in the epoxidation of trans-chalcone with tert-butyl hydroperoxide under phase-transfer catalytic conditions. It was shown that absolute configuration of the crown-ring fused carbon atoms of the monosaccharides has a great

  18. Scalable Synthesis of the Potent HIV Inhibitor BMS-986001 by Non-Enzymatic Dynamic Kinetic Asymmetric Transformation (DYKAT).

    PubMed

    Ortiz, Adrian; Benkovics, Tamas; Beutner, Gregory L; Shi, Zhongping; Bultman, Michael; Nye, Jeffrey; Sfouggatakis, Chris; Kronenthal, David R

    2015-06-01

    Described herein is the synthesis of BMS-986001 by employing two novel organocatalytic transformations: 1)?a highly selective pyranose to furanose ring tautomerization to access an advanced intermediate, and 2)?an unprecedented small-molecule-mediated dynamic kinetic resolution to access a variety of enantiopure pyranones, one of which served as a versatile building block for the multigram, stereoselective, and chromatography-free synthesis of BMS-986001. The synthesis required five chemical transformations and resulted in a 44?% overall yield. PMID:25925234

  19. Diastereoselective Allylation of "N"-"Tert"-Butanesulfinyl Imines: An Asymmetric Synthesis Experiment for the Undergraduate Organic Laboratory

    ERIC Educational Resources Information Center

    Chen, Xiao-Yang; Sun, Li-Sen; Gao, Xiang; Sun, Xing-Wen

    2015-01-01

    An asymmetric synthetic experiment that encompasses both diastereoselectivity and enantioselectivity is described. In this experiment, Zn-mediated allylation of an ("R")-"N"-"tert"-butanesulfinyl imine is first performed to obtain either diastereomer using two different solvent systems, followed by oxidation of the…

  20. Highly enantioselective synthesis of 1,3-mercapto alcohols from ?,?-unsaturated ketones: asymmetric bifunctional group exchange reaction

    Microsoft Academic Search

    Hiroaki Shiraki; Kiyoharu Nishide; Manabu Node

    2000-01-01

    Optically active 1,3-mercapto alcohols were synthesized from ?,?-unsaturated ketones using a chiral reagent B and dimethylaluminum chloride in two steps. The transformation involved a tandem Michael addition–MPV reduction and a base-catalyzed elimination. The two newly created chiral carbons in trans-chalcone derivatives were enantioselectively controlled to a high degree. Using the above transformation, an asymmetric bifunctional group exchange reaction between the

  1. Stereoselective synthesis of ( R )-3-quinuclidinol through asymmetric reduction of 3-quinuclidinone with 3-quinuclidinone reductase of Rhodotorula rubra

    Microsoft Academic Search

    Atsuko Uzura; Fumiki Nomoto; Akiko Sakoda; Yukifumi Nishimoto; Michihiko Kataoka; Sakayu Shimizu

    2009-01-01

    A novel nicotinamide adenine dinucleotide phosphate-dependent carbonyl reductase, 3-quinuclidinone reductase, was isolated\\u000a from Rhodotorula rubra JCM3782. The enzyme catalyzes the asymmetric reduction of 3-quinuclidinone to (R)-3-quinuclidinol. The gene encoding the enzyme was also cloned and sequenced. A 819-bp nucleotide fragment was confirmed\\u000a to be the gene encoding the 3-quinuclidinone reductase by agreement of the internal amino acid sequences of the

  2. Stereoselective synthesis of multisubstituted alkenes via ring opening reactions of cyclopropenes. Enantioselective copper catalysed asymmetric reduction of alkenylheteroarenes. 

    E-print Network

    Wang, Yi

    2010-01-01

    A catalytic organometallic addition-ring opening sequence of cyclopropenes that enables the efficient and highly stereoselective synthesis of multisubstituted alkenes has been developed. A possible mechanism of organoaluminium ...

  3. A Double Asymmetric Hydrogenation Strategy for the Reduction of 1,1-Diaryl Olefins Applied to an Improved Synthesis of CuIPhEt, a C2-Symmetric N-Heterocyclic Carbenoid

    PubMed Central

    Spahn, Elizabeth; Albright, Abigail; Shevlin, Michael; Pauli, Larissa; Pfaltz, Andreas; Gawley, Robert E.

    2013-01-01

    A library of iridium and rhodium phosphine catalysts have been screened for the double asymmetric hydrogenation of 2,6-di-(1-phenylethenyl)-4-methyl aniline to produce the C2-symmetric aniline precursor of the N-heterocyclic carbenoid CuIPhEt. The best catalyst produced the desired enantiomer in 98.6% selectivity. This rare example of a highly selective hydrogenation of a 1,1-diaryl olefin enables a 4 step asymmetric synthesis of the C2-symmetric phenylethyl imidazolium ion (IPhEt) from p-toluidine and phenylacetylene, and its conversion to the hydrosilylation catalyst CuIPhEt. PMID:23383707

  4. A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase Transfer Catalysts. Synthesis of Catalyst Libraries and Evaluation of Catalyst Activity

    PubMed Central

    Denmark, Scott E.; Gould, Nathan D.; Wolf, Larry M.

    2011-01-01

    Despite over three decades of research into asymmetric phase transfer catalysis (APTC), a fundamental understanding of the factors that affect the rate and stereoselectivity of this important process are still obscure. This paper describes the initial stages of a long-term program aimed at elucidating the physical organic foundations of APTC employing a chemoinformatic analysis of the alkylation of a protected glycine imine with a libraries of enantiomerically enriched quaternary ammonium ions. The synthesis of the quaternary ammonium ions follows a diversity oriented approach wherein the tandem inter[4+2]/intra[3+2] cycloaddition of nitroalkenes serves as the key transformation. A two part synthetic strategy comprised of: (1) preparation of enantioenriched scaffolds and (2) development of parallel synthesis procedures is described. The strategy allows for the facile introduction of four variable groups in the vicinity of a stereogenic quaternary ammonium ion. The quaternary ammonium ions exhibited a wide range of activity and to a lesser degree enantioselectivity. Catalyst activity and selectivity are rationalized in a qualitative way based on the effective positive potential of the ammonium ion. PMID:21446721

  5. Synthesis, structures, electrochemistry and catalytic activities of copper(II) and palladium(II) complexes with asymmetric tetraazacycloannulenes

    Microsoft Academic Search

    E. H. Kim; D. I. Kim; H. S. Lee; H. G. Na; J. C. Byun; J. H. Choi; Y. C. Park

    2007-01-01

    Copper(II) and palladium(II) complexes with 15-membered asymmetric 5,9-dihydro-2,4,10,12-tetramethyl-1,5,9,13-monobenzotetraazacyclo[15]tetradecine have been synthesized and characterized. The electrochemical behaviors of the complexes showed a reduction and two one-electron irreversible oxidation waves in given potential ranges due to the metal ion and macrocycle ring, respectively. The electrocatalytic reduction of dioxygen on glassy carbon electrodes electropolymerized by such 15-membered and 14-membered tetraazaannulene complexes occurred at

  6. Calcium-catalyzed asymmetric synthesis of 3-tetrasubstituted oxindoles: efficient construction of adjacent quaternary and tertiary chiral centers.

    PubMed

    Shimizu, Shota; Tsubogo, Tetsu; Xu, Pengyu; Kobayashi, Sh?

    2015-04-17

    Chiral Ca-catalyzed asymmetric addition reactions of 3-substituted oxindoles with N-Boc-imines afford 3-tetrasubstituted oxindole derivatives bearing adjacent quaternary and tertiary chiral centers, which are key structures for biological activities. Ubiquitous and nontoxic Ca catalysts (1-10 mol %) work well in this reaction, and high yields (up to 99%) and selectivities (up to >99% ee) of the products with wide substrate scope have been attained. The structures of the chiral Ca catalysts and intermediary Ca enolates are also discussed. PMID:25849712

  7. The synthesis of chiral ?-aryl-?,?-unsaturated amino alcohols via a Pd-catalyzed asymmetric allylic amination.

    PubMed

    Quan, Mao; Butt, Nicholas; Shen, Jiefeng; Shen, Kaiji; Liu, Delong; Zhang, Wanbin

    2013-11-14

    Chiral ?-aryl-?,?-unsaturated amino alcohols were synthesized via a Pd-catalyzed asymmetric allylic amination of 4-aryl-1,3-dioxolan-2-one using planar chiral 1,2-disubstituted ferrocene-based phosphinooxazolines as ligands. Under the optimized reaction conditions, a series of substrates were examined and the products were obtained in good to excellent yields (up to 92%) and enantioselectivities (up to 98% ee) under mild reaction conditions. The desired products were determined to be of (R)-configuration and could subsequently be transformed into compounds with interesting biological activity using simple transformations. PMID:24077558

  8. Synthesis and Application of New Ligands Derived from N-Heterocyclic Carbenes, Phosphines and Phosphites for Asymmetric Hydrogenations

    E-print Network

    Khumsubdee, Sakunchai

    2013-11-05

    (R)-baclofen,102-104 (S)-pregabalin,105-107 and (S)-vigabatrin.108-110 Not only interacts with GABA receptors, some ?-amino acid derivatives, such as statine, also act as an inhibitor of aspartic acid protease which is an important part... selectively interact with receptors modulated by GABA, including baclofen,111-113 pregabalin,114 vigabatrin,109 the experimental therapeutics in Figure 2.2, and tubulysins. Consequently, asymmetric syntheses of these fragments have been a focus of attention...

  9. Asymmetric Ion-Pairing Catalysis

    PubMed Central

    Brak, Katrien

    2014-01-01

    Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction. PMID:23192886

  10. Chiral fullerenes from asymmetric catalysis.

    PubMed

    Maroto, Enrique E; Izquierdo, Marta; Reboredo, Silvia; Marco-Martínez, Juan; Filippone, Salvatore; Martín, Nazario

    2014-08-19

    Fullerenes are among the most studied molecules during the last three decades, and therefore, a huge number of chemical reactions have been tested on these new carbon allotropes. However, the aim of most of the reactions carried out on fullerenes has been to afford chemically modified fullerenes that are soluble in organic solvents or even water in the search for different mechanical, optical, or electronic properties. Therefore, although a lot of effort has been devoted to the chemical functionalization of these molecular allotropes of carbon, important aspects in the chemistry of fullerenes have not been properly addressed. In particular, the synthesis of chiral fullerenes at will in an efficient manner using asymmetric catalysis has not been previously addressed in fullerene science. Thus, despite the fact that the chirality of fullerenes has always been considered a fundamental issue, the lack of a general stereoselective synthetic methodology has restricted the use of enantiopure fullerene derivatives, which have usually been obtained only after highly expensive HPLC isolation on specific chiral columns or prepared from a pool of chiral starting materials. In this Account, we describe the first stereodivergent catalytic enantioselective syntheses in fullerene science, which have allowed the highly efficient synthesis of enantiomerically pure derivatives with total control of the stereochemical result using metallic catalysts and/or organocatalysts under very mild conditions. Density functional theory calculations strongly support the experimental findings for the assignment of the absolute configuration of the new stereocenters, which has also been ascertained by application of the sector rule and single-crystal X-ray diffraction. The use of the curved double bond of fullerene cages as a two-?-electron component in a variety of stereoselective cycloaddition reactions represents a challenging goal considering that, in contrast to most of the substituted olefins used in these reactions, pristine fullerene is a noncoordinating dipolarophile. The aforementioned features make the study of stereoselective 1,3-dipolar cycloadditions onto fullerenes a unique scenario to shed light onto important mechanistic aspects. On the other hand, the availability of achiral starting materials as well as the use of nonexpensive asymmetric catalysts should provide access to chiral fullerenes and their further application in a variety of different fields. In this regard, in addition to biomedical applications, chiral fullerenes are of interest in less-studied areas such as materials science, organic electronics, and nanoscience, where control of the order and morphology at the nanometer scale are critical issues for achieving better device efficiencies. PMID:25080165

  11. Asymmetric synthesis of allylic sulfonic acids: enantio- and regioselective iridium-catalyzed allylations of Na2SO3.

    PubMed

    Liu, Wei; Zhao, Xiao-ming; Zhang, Hong-bo; Zhang, Liang; Zhao, Ming-zhu

    2014-12-15

    An enantioselective allylation reaction of allylic carbonates with sodium sulfite (Na2 SO3 ) catalyzed by Ir complex was accomplished, providing allylic sulfonic acids in good to excellent yields with a high level of enantio- and regioselectivities. (R)-2-Phenyl-2-sulfoacetic acid, a key intermediate for the synthesis of Cefsulodin and Sulbenicillin, was synthesized as well. PMID:25367779

  12. Acylation, Diastereoselective Alkylation, and Cleavage of an Oxazolidinone Chiral Auxiliary: A Multistep Asymmetric Synthesis Experiment for Advanced Undergraduates

    ERIC Educational Resources Information Center

    Smith, Thomas E.; Richardson, David P.; Truran, George A.; Belecki, Katherine; Onishi, Megumi

    2008-01-01

    An introduction to the concepts and experimental techniques of diastereoselective synthesis using a chiral auxiliary is described. The 4-benzyl-2-oxazolidinone chiral auxiliary developed by Evans is acylated with propionic anhydride under mild conditions using DMAP as an acyl transfer catalyst. Deprotonation with NaN(TMS)[subscript 2] at -78…

  13. Synthesis of ortho-phenyl substituted MeO-BIPHEP ligand and its application in Rh-catalyzed asymmetric hydrogenation

    E-print Network

    Zhang, Xumu

    Synthesis of ortho-phenyl substituted MeO-BIPHEP ligand and its application in Rh--A new BIPHEP-type ligand with phenyl groups at the 3,30 -positions, o-Ph-MeO-BIPHEP 3 was prepared of a-dehydroamino acid derivatives. The strong influence of o-phenyl groups of the ligand

  14. Asymmetric Synthesis of the C1-C6 Portion of the Psymberin Using an Evans Chiral Auxiliary

    PubMed Central

    Pal, Ashutosh; Peng, Zhenghong; Schuber, Paul T.; Bhanu Prasad, Basvoju A.; Bornmann, William G.

    2014-01-01

    The C1-C6 region of the potent cytotoxic agent psymberin has been synthesized. The key transformations of the synthesis are an auxiliary-controlled addition of a Sn(II)-glycolate enolate to an aldehyde to yield the anti aldol product and transforming the primary alcohol into a terminal olefin utilizing organoselenium chemistry. PMID:25110364

  15. An organocatalytic Mannich/denitration reaction for the asymmetric synthesis of 3-ethylacetate-substitued 3-amino-2-oxindoles: formal synthesis of AG-041R.

    PubMed

    Zhao, Kun; Shu, Tao; Jia, Jiaqi; Raabe, Gerhard; Enders, Dieter

    2015-03-01

    The highly enantioselective organocatalytic addition of ethyl nitroacetate to isatin-derived N-Boc ketimines (Boc = tert-butoxycarbonyl), followed by the removal of the nitro group, is described. The scalable reaction sequence leads to the title compounds as important intermediates of pyrroloindoline alkaloids and related drugs in excellent yields and enantioselectivities. The synthesis of the hexahydrofurano[2,3-b]indole skeleton, the spirocarbamate oxindole unit, and the formal synthesis of AG-041R have been carried out to demonstrate the synthetic utility of this protocol. PMID:25630891

  16. Stereoselective synthesis of (R)-3-quinuclidinol through asymmetric reduction of 3-quinuclidinone with 3-quinuclidinone reductase of Rhodotorula rubra.

    PubMed

    Uzura, Atsuko; Nomoto, Fumiki; Sakoda, Akiko; Nishimoto, Yukifumi; Kataoka, Michihiko; Shimizu, Sakayu

    2009-06-01

    A novel nicotinamide adenine dinucleotide phosphate-dependent carbonyl reductase, 3-quinuclidinone reductase, was isolated from Rhodotorula rubra JCM3782. The enzyme catalyzes the asymmetric reduction of 3-quinuclidinone to (R)-3-quinuclidinol. The gene encoding the enzyme was also cloned and sequenced. A 819-bp nucleotide fragment was confirmed to be the gene encoding the 3-quinuclidinone reductase by agreement of the internal amino acid sequences of the purified enzyme. The gene encodes a total of 272 amino acid residues, and the deduced amino acid sequence shows similarity to those of several short-chain dehydrogenase/reductase family proteins. An expression vector, pWKLQ, which contains the full length 3-quinuclidinone reductase gene was constructed. Using Escherichia coli cells coexpressing the 3-quinuclidinone reductase and glucose dehydrogenase (cofactor regeneration enzyme) genes, 618 mM 3-quinuclidinone was almost stiochiometrically converted to (R)-3-quinuclidinol with an >99.9% enantiomeric excess within 21 h of reaction. PMID:19234697

  17. Studies on an (S)-2-Amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic Acid (AMPA) Receptor Antagonist IKM-159: Asymmetric Synthesis, Neuroactivity, and Structural Characterization

    PubMed Central

    Juknait?, Lina; Sugamata, Yutaro; Tokiwa, Kazuya; Ishikawa, Yuichi; Takamizawa, Satoshi; Eng, Andrew; Sakai, Ryuichi; Pickering, Darryl S.; Frydenvang, Karla; Swanson, Geoffrey T.; Kastrup, Jette S.; Oikawa, Masato

    2015-01-01

    IKM-159 was developed and identified as a member of a new class of heterotricyclic glutamate analogues that act as AMPA receptor-selective antagonists. However, it was not known which enantiomer of IKM-159 was responsible for its pharmacological activities. Here, we report in vivo and in vitro neuronal activities of both enantiomers of IKM-159 prepared by enantioselective asymmetric synthesis. By employment of (R)-2-amino-2-(4-methoxyphenyl)ethanol as a chiral auxiliary, (2R)-IKM-159 and the (2S)-counterpart were successfully synthesized in 0.70% and 1.5% yields, respectively, over a total of 18 steps. Both behavioral and electrophysiological assays showed that the biological activity observed for the racemic mixture was reproduced only with (2R)-IKM-159, whereas the (2S)-counterpart was inactive in both assays. Racemic IKM-159 was crystallized with the ligand-binding domain of GluA2, and the structure revealed a complex containing (2R)-IKM-159 at the glutamate binding site. (2R)-IKM-159 locks the GluA2 in an open form, consistent with a pharmacological action as competitive antagonist of AMPA receptors. PMID:23432124

  18. Asymmetric one-pot synthesis of 1,3-oxazolidines and 1,3-oxazinanes via hemiaminal intermediates.

    PubMed

    Nimmagadda, Sri Krishna; Zhang, Zuhui; Antilla, Jon C

    2014-08-15

    A highly efficient method for the enantioselective one-pot synthesis of 1,3-oxazolidines and 1,3-oxazinanes has been reported. The reaction proceeds via the formation of hemiaminal intermediates obtained by the enantioselective addition of respective alcohols to imines catalyzed by a chiral magnesium phosphate catalyst, followed by intramolecular cyclization under mildly basic conditions. A wide range of substrates have been converted to the respective chiral heterocyclic products in high yields and with excellent enantioselectivities using this one-pot procedure. PMID:25075467

  19. Asymmetric Synthesis and Evaluation of Danshensu-Cysteine Conjugates as Novel Potential Anti-Apoptotic Drug Candidates

    PubMed Central

    Pan, Li-Long; Wang, Jie; Jia, Yao-Ling; Zheng, Hong-Ming; Wang, Yang; Zhu, Yi-Zhun

    2014-01-01

    We have previously reported that the danshensu-cysteine conjugate N-((R)-3-benzylthio-1-methoxy-1-oxo-2-propanyl)-2-acetoxy-3-(3,4-diacetoxyphenyl) propanamide (DSC) is a potent anti-oxidative and anti-apoptotic agent. Herein, we further design and asymmetrically synthesize two diastereoisomers of DSC and explore their potential bioactivities. Our results show that DSC and its two diastereoisomers exert similar protective effects in hydrogen peroxide (H2O2)-induced cellular injury in SH-SY5Y cells, as evidenced by the increase of cell viability, superoxide dismutase (SOD), and reduced glutathione (GSH) activity, and glutathione peroxidase (GPx) expression, and the decrease of cellular morphological changes and nuclear condensation, lactate dehydrogenase (LDH) release, and malondialdehyde (MDA) production. In H2O2-stimulated human umbilical vein endothelial cells (HUVEC), DSC concentration-dependently attenuates H2O2-induced cell death, LDH release, mitochondrial membrane potential collapse, and modulates the expression of apoptosis-related proteins (Bcl-2, Bax, caspase-3, and caspase-9). Our results provide strong evidence that DSC and its two diastereoisomers have similar anti-oxidative activity and that DSC exerts significant vascular-protective effects, at least in part, through inhibition of apoptosis and modulation of endogenous antioxidant enzymes. PMID:25551606

  20. 1: Mass asymmetric fission barriers for {sup 98}Mo; 2: Synthesis and characterization of actinide-specific chelating agents

    SciTech Connect

    Veeck, A.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; [Lawrence Livermore National Lab., CA (United States). Glenn T. Seaborg Inst. for Transactinium Science; [Lawrence Berkeley National Lab., CA (United States). Nuclear Science Div.

    1996-08-01

    Excitation functions have been measured for complex fragment emission from the compound nucleus {sup 98}Mo, produced by the reaction of {sup 86}Kr with {sup 12}C. Mass asymmetric fission barriers have been obtained by fitting the excitation functions with a transition state formalism. The extracted barriers are {approximately} 5.7 MeV higher, on average, than the calculations of the Rotating Finite Range Model (RFRM). These data clearly show an isospin dependence of the conditional barriers when compared with the extracted barriers from {sup 90}Mo and {sup 94}Mo. Eleven different liquid/liquid extractants were synthesized based upon the chelating moieties 3,2-HOPO and 3,4-HOPO; additionally, two liquid/liquid extractants based upon the 1,2-HOPO chelating moiety were obtained for extraction studies. The Pu(IV) extractions, quite surprisingly, yielded results that were very different from the Fe(III) extractions. The first trend remained the same: the 1,2-HOPOs were the best extractants, followed closely by the 3,2-HOPOs, followed by the 3,4-HOPOs; but in these Pu(IV) extractions the 3,4-HOPOs performed much better than in the Fe(III) extractions. 129 refs.

  1. Enhanced asymmetric induction for the copolymerization of CO2 and cyclohexene oxide with unsymmetric enantiopure salenCo(III) complexes: synthesis of crystalline CO2-based polycarbonate.

    PubMed

    Wu, Guang-Peng; Ren, Wei-Min; Luo, Yi; Li, Bo; Zhang, Wen-Zhen; Lu, Xiao-Bing

    2012-03-28

    Enantiopure metal-complex catalyzed asymmetric alternating copolymerization of CO(2) and meso-epoxides is a powerful synthetic strategy for preparing optically active polycarbonates with main-chain chirality. The previous studies regarding chiral zinc catalysts provided amorphous polycarbonates with moderate enantioselectivity, and thus, developing highly stereoregular catalysts for this enantioselective polymerization is highly desirable. Herein, we report the synthesis of highly isotactic poly(cyclohexene carbonate)s from meso-cyclohexene oxide using dissymmetrical enantiopure salenCo(III) complexes in conjunction with bis(triphenylphosphine)iminium chloride (PPNCl) as catalyst. The presence of a chiral induction agent such as (S)-propylene oxide or (S)-2-methyltetrahydrofuran significantly improved the enantioselectivity regarding (S,S)-salenCo(III) catalyst systems. Up to 98:2 of RR:SS was observed in the resultant polycarbonates obtained from the catalyst system based on (S,S)-salenCo(III) complex 4d bearing an adamantyl group on the phenolate ortho position, in the presence of (S)-2-methyltetrahydrofuran. Primary ONIOM (DFT:UFF) calculations, which were performed to investigate the effect of the competitive coordination of (S)-induction agent versus cyclohexene oxide to Co(III) center on enantioselectivity, suggest that the (S)-C-O bond in cyclohexene oxide is more favorable for cleavage, due to the interaction between oxygen atom of (S)-induction agent and (S)-C-H of the coordinated cyclohexene oxide. The highly isotactic poly(cyclohexene carbonate) is a typical semicrystalline polymer, possessing a melting point of 216 °C and a decomposition temperature of 310 °C. PMID:22385473

  2. Discovery of aromatic components with excellent fragrance properties and biological activities: ?-ionols with antimelanogenetic effects and their asymmetric syntheses.

    PubMed

    Komaki, Ryoichi; Ikawa, Takashi; Saito, Kozumo; Hattori, Kazuyo; Ishikawa, Natsuyo; Fukawa, Hidemichi; Egi, Masahiro; Akai, Shuji

    2013-01-01

    Both enantiomers of dihydro-?-ionol and ?-ionol, contained in the aromatic components of Osmanthus flower and of Hakuto peach, were obtained with high optical purity by lipase-catalyzed kinetic resolution of the racemates. It was found that all these enantiomers had different characteristic favorable scents and high antimelanogenetic effects. The absolute configuration and the enantiomer ratios of dihydro-?-ionol in the aromatic components of Osmanthus flower and of Hakuto peach were determined. The asymmetric synthesis of (R)-dihydro-?-ionol, one of the most valuable raw materials for fragrance and flavor, was performed from inexpensive ?-ionone via lipase-catalyzed dynamic kinetic resolution followed by reduction. PMID:23449199

  3. Chiral Amines as Nucleophilic Catalysts in Asymmetric

    E-print Network

    Johnson, Jeff S.

    Synthesis Biocatalysis #12;Outline · kinetic resolution of alcohols/amines · C-acylation (quaternary centersChiral Amines as Nucleophilic Catalysts in Asymmetric Synthesis Stephen Greszler University R O N Ph O N N O S S tBu #12;Mechanisms of Organocatalysis by Amines Acyl Ammonium Catalysis 1

  4. Ligand-enabled multiple absolute stereocontrol in metal-catalysed cycloaddition for construction of contiguous all-carbon quaternary stereocentres

    NASA Astrophysics Data System (ADS)

    Ohmatsu, Kohsuke; Imagawa, Naomichi; Ooi, Takashi

    2014-01-01

    The development of a general catalytic method for the direct and stereoselective construction of contiguous all-carbon quaternary stereocentres remains a formidable challenge in chemical synthesis. Here, we report a highly enantio- and diastereoselective [3+2] annulation reaction of 5-vinyloxazolidinones and activated trisubstituted alkenes catalysed by a palladium complex bearing a newly devised phosphine ligand with a chiral ammonium salt component, which enables the single-step construction of three contiguous stereocentres, including vicinal all-carbon quaternary stereocentres, in a five-membered heterocyclic framework. This stereoselective cycloaddition protocol relies on the remarkable ability of the chiral ligand to rigorously control the absolute stereochemistry of each chiral centre associated with the multiple bond-forming events, and provides a reliable catalytic process for the asymmetric synthesis of densely functionalized pyrrolidines.

  5. Synthesis of (3S,3?S)- and meso-Stereoisomers of Alloxanthin and Determination of Absolute Configuration of Alloxanthin Isolated from Aquatic Animals

    PubMed Central

    Yamano, Yumiko; Maoka, Takashi; Wada, Akimori

    2014-01-01

    In order to determine the absolute configuration of naturally occurring alloxanthin, a HPLC analytical method for three stereoisomers 1a–c was established by using a chiral column. Two authentic samples, (3S,3?S)- and meso-stereoisomers 1b and 1c, were chemically synthesized according to the method previously developed for (3R,3?R)-alloxanthin (1a). Application of this method to various alloxanthin specimens of aquatic animals demonstrated that those isolated from shellfishes, tunicates, and crucian carp are identical with (3R,3?R)-stereoisomer 1a, and unexpectedly those from lake shrimp, catfish, biwa goby, and biwa trout are mixtures of three stereoisomers of 1a–c. PMID:24862182

  6. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K. (Pleasanton, CA); Snyderman, Neal J. (Berkeley, CA); Rowland, Mark S. (Alamo, CA)

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  7. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K. (Pleasanton, CA); Snyderman, Neal J. (Berkeley, CA); Rowland, Mark S. (Alamo, CA)

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  8. Mechanistic insight into NOYORI asymmetric hydrogenations.

    PubMed

    Kitamura, Masato; Nakatsuka, Hiroshi

    2011-01-21

    The BINAP-Ru-catalyzed asymmetric hydrogenations have contributed fundamentally to "molecular catalyst chemistry", as well as the "chemical industry", in terms of the production of important chiral compounds such as pharmaceuticals, agrochemicals, flavors, fragrances, and health supplements since 1986 when the great breakthrough was made through an efficient asymmetric synthesis of tetrahydroisoquinolines. This highlight overviews mechanistic models proposed in the Noyori hydrogenation of olefins and ketones. PMID:20676440

  9. Strength by joining methods: combining synthesis with NMR, IR, and vibrational circular dichroism spectroscopy for the determination of the relative configuration in hemicalide.

    PubMed

    De Gussem, Ewoud; Herrebout, Wouter; Specklin, Simon; Meyer, Christophe; Cossy, Janine; Bultinck, Patrick

    2014-12-22

    The relative configuration of a key subunit of hemicalide, a recently isolated, highly bioactive marine natural product having potent antiproliferative activity against a panel of human cancer cell lines, was assigned by combining stereocontrolled synthesis of model substrates with NMR, IR, and vibrational circular dichroism (VCD) spectroscopy. The assignment of the absolute configuration of asymmetric carbon center C42 in two structurally complex epimeric substructures containing six stereocenters by VCD analysis illustrates the power and reliability of combining methods. PMID:25346258

  10. BF 3·Et 2O catalyzed diastereoselective nucleophilic reactions of 3-silyloxypiperidine N, O-acetal with silyl enol ether and application to the asymmetric synthesis of (+)-febrifugine

    Microsoft Academic Search

    Ru-Cheng Liu; Wei Huang; Jing-Yi Ma; Bang-Guo Wei; Guo-Qiang Lin

    2009-01-01

    The asymmetric BF3·Et2O catalyzed nucleophilic reactions of 3-silyloxypiperidine N,O-acetal 10 with silyl enol ethers derived from ketones are described. (+)-Febrifugine 1, an antimalarial alkaloid, was successfully synthesized based on this nucleophilic substitution. In addition, N,O-acetal 10 was synthesized from l-benzyl glutamate in 11 steps.

  11. Asymmetric construction of quaternary carbon centers by sequential conjugate addition of lithium amide and in situ alkylation: utility in the synthesis of (-)-aspidospermidine.

    PubMed

    Suzuki, Mayuko; Kawamoto, Yoshito; Sakai, Takeo; Yamamoto, Yasutomo; Tomioka, Kiyoshi

    2009-02-01

    Chiral diether ligand-controlled asymmetric conjugate addition of a lithium amide to cyclopentenecarboxylate and subsequent in situ alkylation gave a chiral cyclopentane derivative bearing a quaternary carbon with high enantio- and diastereoselectivity. The cyclopentane derivative was converted successfully to (-)-aspidospermidine. PMID:19115978

  12. Design, synthesis, and X-ray crystallographic analysis of a novel class of HIV-1 protease inhibitors.

    PubMed

    Ganguly, Ashit K; Alluri, Sesha S; Caroccia, Danielle; Biswas, Dipshikha; Wang, Chih-Hung; Kang, Eunhee; Zhang, Yong; McPhail, Andrew T; Carroll, Steven S; Burlein, Christine; Munshi, Vandna; Orth, Peter; Strickland, Corey

    2011-10-27

    In the present paper, design, synthesis, X-ray crystallographic analysis, and HIV-1 protease inhibitory activities of a novel class of compounds are disclosed. Compounds 28-30, 32, 35, and 40 were synthesized and found to be inhibitors of the HIV-1 protease. The crucial step in their synthesis involved an unusual endo radical cyclization process. Absolute stereochemistry of the three asymmetric centers in the above compounds have been established to be (4S,2'R,3'S) for optimal potency. X-ray crystallographic analysis has been used to determine the binding mode of the inhibitors to the HIV-1 protease. PMID:21916489

  13. Gold-catalyzed asymmetric allylic substitution of free alcohols: an enantioselective approach to chiral chromans with quaternary stereocenters for the synthesis of vitamin E and analogues.

    PubMed

    Uria, Uxue; Vila, Carlos; Lin, Ming-Yuan; Rueping, Magnus

    2014-10-20

    The enantioselective synthesis of ?- and ?-tocopherol (the most biologically active members of vitamin?E family) and analogues has been accomplished employing a new enantioselective gold catalyzed intramolecular allylic alkylation reaction followed by an olefin cross-metathesis as key steps. The methodology proved to be applicable to different olefins highlighting its potential for the synthesis of diverse libraries. PMID:25201099

  14. Asymmetric Hydrogenation of Itaconic Acid and Enol Acetate Derivatives with

    E-print Network

    Zhang, Xumu

    .; Kitamura, M.; Noyori, R. In Catalytic Asymmetric Synthesis; Ojima. I., Ed.; Wiley-VCH: Weinheim, Germany- moto, H., Eds.; Springer: Berlin, Germany, 1999; p 121. (c) Ohkuma, T.; Noyori, R. In Comprehensi

  15. An absolute Johnson noise thermometer

    E-print Network

    Callegaro, Luca; Pisani, Marco; Pollarolo, Alessio

    2009-01-01

    We developed an absolute Johnson noise thermometer (JNT), an instrument to measure the thermodynamic temperature of a sensing resistor, with traceability to voltage, resistance and frequency quantities. The temperature is measured in energy units, and can be converted to SI units (kelvin) with the accepted value of the Boltzmann constant kb; or, conversely, it can be employed to perform measurements at the triple point of water, and obtain a determination of kb. The thermometer is composed of a correlation spectrum analyzer an a calibrated noise source, both constructed around commercial mixed-signal boards. The calibrator generates a pseudorandom noise, by digital synthesis and amplitude scaling with inductive voltage dividers; the signal spectrum is a frequency comb covering the measurement bandwidth. JNT measurements at room temperature are compatible with those of a standard platinum resistance thermometer within the combined uncertainty of 60 ppm. A path towards future improvements of JNT accuracy is als...

  16. Eosinophil count - absolute

    MedlinePLUS

    ... you have certain allergic diseases, infections, and other medical conditions. ... to show up as orange-red granules. The technician then counts how ... white blood cell count to give the absolute eosinophil count.

  17. Ru-TsDPEN with formic acid/Hunig's base for asymmetric transfer hydrogenation, a practical synthesis of optically enriched N-propyl pantolactam.

    PubMed

    Zhang, Ji; Blazecka, Peter G; Bruendl, Michelle M; Huang, Yun

    2009-02-01

    The Noyori-Ikariya catalysts, Ru-TsDPEN 1 or 2, in combination with HCOOH/Hunig's base (5:2) have been successfully utilized for catalytic asymmetric transfer hydrogenation of alpha-ketopantolactam, and optically enriched N-substituted pantolactam was prepared (S/C = 500, up to 95% ee and 99% conversion in HCOOH/Hunig's base condition). More than 2 kg of this key intermediate 9 has been synthesized efficiently with excellent chemical yield and chiral purity. PMID:19105680

  18. Asymmetric organocatalyzed Michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde and the three one-pot sequential synthesis of (-)-horsfiline and (-)-coerulescine.

    PubMed

    Mukaiyama, Takasuke; Ogata, Kento; Sato, Itaru; Hayashi, Yujiro

    2014-10-13

    (-)-Horsfiline and (-)-coerulescine were synthesized through three one-pot operations in 33 and 46% overall yield, respectively. Key to the success was the efficient use of a diarylprolinol silyl ether to catalyze the asymmetric Michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde. This allowed the all-carbon quaternary, spirocyclic carbon stereocenter to be constructed in good yield with excellent enantioselectivity. PMID:25155110

  19. Terminating Catalytic Asymmetric Heck Cyclizations by Stereoselective Intramolecular Capture of ?3-Allylpalladium Intermediates: Total Synthesis of (?)-Spirotryprostatin B and Three Stereoisomers

    PubMed Central

    Overman, Larry E.; Rosen, Mark D.

    2010-01-01

    A catalytic intramolecular Heck reaction, followed by capture of the resulting ?3-allylpalladium intermediate by a tethered diketopiperazine, is the central step in a concise synthetic route to (?)-spirotryprostatin B and three stereoisomers. This study demonstrates that an acyclic, chiral ?3-allylpalladium fragment generated in a catalytic asymmetric Heck cyclization can be trapped by even a weakly nucleophilic diketopiperazine more rapidly than it undergoes diastereomeric equilibration. PMID:20725641

  20. Synthesis of asymmetrical bispyridinium compounds bearing cyano-moiety and evaluation of their reactivation activity against tabun and paraoxon-inhibited acetylcholinesterase

    Microsoft Academic Search

    Kamil Musilek; Ondrej Holas; Kamil Kuca; Daniel Jun; Vlastimil Dohnal; Martin Dolezal

    2006-01-01

    Three asymmetrical AChE reactivators with cyano-moiety and propane linker were synthesized using modification of currently known synthetic pathways. Their potency to reactivate AChE inhibited by nerve agent tabun and insecticide paraoxon was tested in vitro and compared to pralidoxime, HI-6, obidoxime, K027, and K048. According to the results, three compounds seem to be promising against paraoxon-inhibited AChE. Better results were

  1. A one-pot combination of amine and heterocyclic carbene catalysis: direct asymmetric synthesis of ?-hydroxy and ?-malonate esters from ?,?-unsaturated aldehydes

    Microsoft Academic Search

    Gui-Ling Zhao; Armando Córdova

    2007-01-01

    The one-pot combination of amine and heterocyclic carbene catalysis (AHCC) enabled the synthesis of ?-hydroxy, ?-malonate and ?-amino esters from ?,?-unsaturated aldehydes with high enantioselectivity (91–97% ee).

  2. Improved synthesis and application of planar-chiral nucleophilic catalysts in asymmetric reactions and copper-catalyzed enantioselective N-H insertion reactions

    E-print Network

    Lee, Elaine C

    2007-01-01

    The development of an improved synthesis of nucleophilic planar-chiral catalysts is described in Chapter 1. This route is amenable to scale-up and preparative chiral HPLC is unnecessary to resolve the racemic catalysts. ...

  3. Absolute and relative blindsight.

    PubMed

    Balsdon, Tarryn; Azzopardi, Paul

    2015-03-01

    The concept of relative blindsight, referring to a difference in conscious awareness between conditions otherwise matched for performance, was introduced by Lau and Passingham (2006) as a way of identifying the neural correlates of consciousness (NCC) in fMRI experiments. By analogy, absolute blindsight refers to a difference between performance and awareness regardless of whether it is possible to match performance across conditions. Here, we address the question of whether relative and absolute blindsight in normal observers can be accounted for by response bias. In our replication of Lau and Passingham's experiment, the relative blindsight effect was abolished when performance was assessed by means of a bias-free 2AFC task or when the criterion for awareness was varied. Furthermore, there was no evidence of either relative or absolute blindsight when both performance and awareness were assessed with bias-free measures derived from confidence ratings using signal detection theory. This suggests that both relative and absolute blindsight in normal observers amount to no more than variations in response bias in the assessment of performance and awareness. Consideration of the properties of psychometric functions reveals a number of ways in which relative and absolute blindsight could arise trivially and elucidates a basis for the distinction between Type 1 and Type 2 blindsight. PMID:25305691

  4. Absolute neutrino mass scale

    NASA Astrophysics Data System (ADS)

    Capelli, Silvia; Di Bari, Pasquale

    2013-04-01

    Neutrino oscillation experiments firmly established non-vanishing neutrino masses, a result that can be regarded as a strong motivation to extend the Standard Model. In spite of being the lightest massive particles, neutrinos likely represent an important bridge to new physics at very high energies and offer new opportunities to address some of the current cosmological puzzles, such as the matter-antimatter asymmetry of the Universe and Dark Matter. In this context, the determination of the absolute neutrino mass scale is a key issue within modern High Energy Physics. The talks in this parallel session well describe the current exciting experimental activity aiming to determining the absolute neutrino mass scale and offer an overview of a few models beyond the Standard Model that have been proposed in order to explain the neutrino masses giving a prediction for the absolute neutrino mass scale and solving the cosmological puzzles.

  5. Asymmetric Schiff Base (N 2 O 3 ) Complexes as Ligands Towards Mn(II), Fe(III) and Co(II), Synthesis and Characterization

    Microsoft Academic Search

    Saied M. E. Khalil; Adel. A. Emara

    2002-01-01

    Heterobi- and tri-nuclear complexes [LMM'Cl] and [(LM) 2 M'](M=Ni or Cu and M'=Mn, Fe or Co) have been synthesised. The heteronuclear complexes were prepared by stepwise reactions using two mononuclear Ni(II) and Cu(II) complexes of the general formula [HLM]·1\\/2H 2 O, as ligands towards the metal ions, Mn(II), Fe(III) and Co(II). The asymmetrical pentadentate (N 2 O 3 ) Schiff-base

  6. Tunable synthesis of hierarchical NiCo2O4 nanosheets-decorated Cu/CuOx nanowires architectures for asymmetric electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Kuang, Min; Zhang, Yu Xin; Li, Tong Tao; Li, Kai Feng; Zhang, Sheng Mao; Li, Gang; Zhang, Wei

    2015-06-01

    We demonstrate a facile and tunable preparative strategy of porous NiCo2O4 nanosheets-decorated Cu-based nanowires hybrids as high-performance supercapacitor electrodes. A fast faradic reaction has been realized by inducing elementary copper core in the composite, which assists in high electric conductivity of the cell and creates intimate channels for fast charge collection and electron transfer. As a result, this hybrid composite electrode displays high specific capacitance (578 F g-1 at current density of 1.0 A g-1) and rate capability (80.1% capacitance retention from 1 A g-1 to 10 A g-1). Additionally, asymmetric device is constructed from NiCo2O4/Cu-based NWs and activated graphene (AG) with an operation potential from 0 to 1.4 V. The asymmetric device exhibits an energy density of 12.6 Wh kg-1 at a power density of 344 W kg-1 and excellent long-term cycling stability (only 1.8% loss of its initial capacitance after 10,000 cycles). These attractive findings suggest that such unique NiCo2O4/Cu-based NWs hybrid architecture is promising for electrochemical applications as efficient electrode material.

  7. Studies in asymmetric ?-lactone synthesis: extensions of the chiral nucleophile catalyzed aldol-lactonization (NCAL) reaction and new transformations of chlorinated ?-lactones 

    E-print Network

    Tennyson, Reginald L.

    2001-01-01

    -lactones were accomplished to further extend the utility of these products. In addition, 4-(trichloromethyl)-2-oxetanone was transformed into a variety of amino acid precursors. The first synthesis of the natural amino acid, 2-amino-5-methyl-6-hydroxyhex-4...

  8. Asymmetric Amplification and Autocatalysis

    E-print Network

    Stoltz, Brian M.

    asymmetric epoxidation. #12;Models for Asymmetric Nonlinear Effects Noyori's Model: H. Kagan J. Am. Chem. Soc) Reactant Product (R) Kagan's ML2 Model: Catalytic Cycle KHomo KHetero Catalytic Cycle 1/2 1/2 R. Noyori J

  9. Symmetric Cryptography Asymmetric Cryptography

    E-print Network

    Ramkumar, Mahalingam

    Outline Symmetric Cryptography Asymmetric Cryptography Key Management Network Security Cryptography Symmetric Cryptography Asymmetric Cryptography Key Management Network Security 1 Symmetric Cryptography Symmetric Cryptography Overview Block Cipher Modes Multiple Encryption Hash Functions Message Authentication

  10. Symmetric Cryptography Asymmetric Cryptography

    E-print Network

    Ramkumar, Mahalingam

    Outline Trust Symmetric Cryptography Asymmetric Cryptography Key Management Network Security Cryptography - A Review Mahalingam Ramkumar Mississippi State University, MS September 22, 2006 Ramkumar Review #12;Outline Trust Symmetric Cryptography Asymmetric Cryptography Key Management Network Security 1

  11. Asymmetric dark matter

    SciTech Connect

    Kumar, Jason [Department of Physics and Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)

    2014-06-24

    We review the theoretical framework underlying models of asymmetric dark matter, describe astrophysical constraints which arise from observations of neutron stars, and discuss the prospects for detecting asymmetric dark matter.

  12. Simplified design of microwave filters with asymmetric transfer functions

    Microsoft Academic Search

    S. Bila; D. Baillargeat; S. Verdeyme; F. Seyfert; L. Baratchart; C. Zanchi; J. Sombrin

    2003-01-01

    This paper presents the design of a microwave bandpass filter having an asymmetric transfer function and a symmetric geometry. The purpose is to demonstrate that an efficient synthesis can provide simpler solutions for the hardware implementation. An example of a 6th order dual mode filter in circular waveguide technology is presented. Considering the desired topology, the initial synthesis from the

  13. About the measurement of absolute isotropic surface stress of crystals

    NASA Astrophysics Data System (ADS)

    Müller, P.; Kern, R.

    1994-01-01

    Some recent publications report measurements of the curvature of thin asymmetric sheets and deduce the difference of surface stress ( s1 - s2) of both its faces 1 and 2 using a simple formula due to Stoney. An exact formulation gives a relation where ( s1 + s2) enters also. It is shown here how, for thin sheets, ( s1 - s2) and ( s1 + s2) can be measured and therefore the absolute surface stresses s1 and s2. For thicker sheets, only ( s1 - s2) can be measured. Two experimental methods for measuring the absolute surface stresses are proposed.

  14. Palladium-catalyzed asymmetric synthesis of axially chiral (allenylmethyl)silanes and chirality transfer to stereogenic carbon centers in S(E)' reactions.

    PubMed

    Ogasawara, Masamichi; Ueyama, Kazuhito; Nagano, Takashi; Mizuhata, Yoshiyuki; Hayashi, Tamio

    2003-01-23

    [reaction: see text] Novel stereoselective reactions of 4-substituted-1-trimethylsilyl-2,3-butadienes ((allenylmethyl)silanes) were developed. The axially chiral (allenylmethyl)silanes were prepared from (3-bromopenta-2,4-dienyl)trimethylsilane by a Pd-catalyzed asymmetric reaction with soft nucleophiles with up to 88% enantioselectivity. The (allenylmethyl)silanes reacted with acetals in the presence of a TiCl(4) promoter to give 1,3-diene derivatives via an S(E)' pathway. The 1,3-dienyl products have (E)-geometry exclusively and up to 88%( )()chirality transfer from the axially chiral allenes to the centrally chiral 1,3-dienes was observed in the S(E)' reaction. PMID:12529144

  15. Asymmetric Ultrasonic Pulse Radiation Using Electromagnetic-Induction Transducer and PZT(Pb(Zr-Ti)O3) Transducer with Wave Synthesis Method

    NASA Astrophysics Data System (ADS)

    Endoh, Nobuyuki; Yamamoto, Koji

    1993-05-01

    In medical applications, especially in urology, we use a fragmentation calculus technique with shock waves. This technique is very profitable because of no abdominal surgery for a human being. Large negative sound amplitude pulses, however, can cause problems such as internal hemorrhage or pain in the human body. The final goal of this study is to develop a means to project an intense positive unipolar pulse without negative sound pressure. We improved a composite transducer consisting of an electromagnetic-induction-type (EMI) transducer and PZT (Pb(Zr-Ti)O3) transducers. An EMI transducer consisting of a metal coil and vibration membrane can project intense sound pulses into water. In order to suppress its negative sound pressure, we project a compensation pulse with PZT transducers using an inverse filtering method. An asymmetric pulse whose P+ to P- amplitude ratio was very high was projected in water.

  16. Controlled synthesis, asymmetrical transport behavior and luminescence properties of lanthanide doped ZnO mushroom-like 3D hierarchical structures

    NASA Astrophysics Data System (ADS)

    Yue, Dan; Lu, Wei; Jin, Lin; Li, Chunyang; Luo, Wen; Wang, Mengnan; Wang, Zhenling; Hao, Jianhua

    2014-10-01

    Lanthanide doped ZnO mushroom-like 3D hierarchical structures have been fabricated by polyol-mediated method and characterized by various microstructural and optical techniques. The results indicate that the as-prepared ZnO:Ln3+ (Ln = Tb, Eu) samples have a hexagonal phase structure and possess a mushroom-like 3D hierarchical morphology. The length of the whole mushroom from stipe bottom to pileus top is about 1.0 ?m, and the diameters of pileus and stipe are about 0.8 ?m and 0.4 ?m, respectively. It is found that the flow of N2 is the key parameter for the formation of the novel ZnO structure and the addition of (NH4)2HPO4 has a prominent effect on the phase structure and the growth of mushroom-like morphology. The potential mechanism of forming this morphology is proposed. The pileus of the formed mushroom is assembled by several radial ZnO:Ln3+ nanorods, whereas the stipe is composed of over layered ZnO:Ln3+ nanosheets. Moreover, asymmetrical I-V characteristic curves of ZnO:Ln3+ mushrooms indicate that the texture composition of the 3D hierarchical morphology might lead to the asymmetrical transport behavior of electrical conductivity. Lanthanide doped ZnO samples can exhibit red or green emission under the excitation of UV light.Lanthanide doped ZnO mushroom-like 3D hierarchical structures have been fabricated by polyol-mediated method and characterized by various microstructural and optical techniques. The results indicate that the as-prepared ZnO:Ln3+ (Ln = Tb, Eu) samples have a hexagonal phase structure and possess a mushroom-like 3D hierarchical morphology. The length of the whole mushroom from stipe bottom to pileus top is about 1.0 ?m, and the diameters of pileus and stipe are about 0.8 ?m and 0.4 ?m, respectively. It is found that the flow of N2 is the key parameter for the formation of the novel ZnO structure and the addition of (NH4)2HPO4 has a prominent effect on the phase structure and the growth of mushroom-like morphology. The potential mechanism of forming this morphology is proposed. The pileus of the formed mushroom is assembled by several radial ZnO:Ln3+ nanorods, whereas the stipe is composed of over layered ZnO:Ln3+ nanosheets. Moreover, asymmetrical I-V characteristic curves of ZnO:Ln3+ mushrooms indicate that the texture composition of the 3D hierarchical morphology might lead to the asymmetrical transport behavior of electrical conductivity. Lanthanide doped ZnO samples can exhibit red or green emission under the excitation of UV light. Electronic supplementary information (ESI) available: STEM-SEI image and EDS elemental mapping of an individual ZnO: Eu3+ mushroom. See DOI: 10.1039/c4nr04359f

  17. The Direct Catalytic Asymmetric Aldol Reaction

    PubMed Central

    Brindle, Cheyenne S.

    2013-01-01

    Asymmetric aldol reactions are a powerful method for the construction of carbon-carbon bonds in an enantioselective fashion. Historically this reaction has been performed in a stoichiometric fashion to control the various aspects of chemo-, diastereo-, regio- and enantioselectivity, however, a more atom economical approach would unite high selectivity with the use of only a catalytic amount of a chiral promoter. This critical review documents the development of direct catalytic asymmetric aldol methodologies, including organocatalytic and metal-based strategies. New methods have improved the reactivity, selectivity and substrate scope of the direct aldol reaction and enabled the synthesis of complex molecular targets PMID:20419212

  18. Bifunctional Asymmetric Catalysis

    PubMed Central

    PAULL, DANIEL H.; ABRAHAM, CIBY J.; SCERBA, MICHAEL T.; ALDEN-DANFORTH, ETHAN; LECTKA, THOMAS

    2008-01-01

    CONSPECTUS In the field of catalytic, asymmetric synthesis, there is a growing emphasis on multifunctional systems, in which multiple parts of a catalyst or multiple catalysts work together to promote a specific reaction. These efforts, in part, are result-driven, and they are also part of a movement toward emulating the efficiency and selectivity of nature’s catalysts, enzymes. In this Account, we illustrate the importance of bifunctional catalytic methods, focusing on the cooperative action of Lewis acidic and Lewis basic catalysts by the simultaneous activation of both electrophilic and nucleophilic reaction partners. For our part, we have contributed three separate bifunctional methods that combine achiral Lewis acids with chiral cinchona alkaloid nucleophiles, for example, benzoylquinine (BQ), to catalyze highly enantioselective cycloaddition reactions between ketene enolates and various electrophiles. Each method requires a distinct Lewis acid to coordinate and activate the electrophile, which in turn increases the reaction rates and yields, without any detectable influence on the outstanding enantioselectivities inherent to these reactions. To place our results in perspective, many important contributions to this emerging field are highlighted and our own reports are chronicled. PMID:18402470

  19. Biomimetic asymmetric synthesis of (R)-GTRI-02 and (3S,4R)-3,4-dihydroxy-3,4-dihydronaphthalen-1(2H)-ones.

    PubMed

    Husain, Syed Masood; Schätzle, Michael A; Röhr, Caroline; Lüdeke, Steffen; Müller, Michael

    2012-07-20

    The NADPH-dependent tetrahydroxynaphthalene reductase (T4HNR) from Magnaporthe grisea was used for the biomimetic synthesis of (R)-GTRI-02 by stereoselective reduction of 1-(3,6,8-trihydroxy-1-methylnaphthalen-2-yl)ethanone. This also led to the isolation of a (3S,4R)-cis-ketodiol formed by T4HNR-catalyzed reduction of the corresponding hydroxynaphthoquinone. Flaviolin and lawsone also reduced to corresponding cis-ketodiols in good yields. PMID:22738326

  20. New Method to Estimate Missing Data by Using the Asymmetrical Winsorized Mean in a Time Series

    Microsoft Academic Search

    A. M. H. Al-Khazaleh

    2009-01-01

    In this paper we consider the problem of missing data in a time series analysis. We propose asymmetrical r ?= s winsorized mean to handle the problem of missing data. Beside that we suggested the Neyman allo- cation method to choose the values of r and s in asymmetric winsorized mean. We used the a absolute mean error and mean

  1. Absolute beam brightness detector.

    PubMed

    Dudnikov, Vadim

    2012-02-01

    In generally accepted emittance measurement, main attention is concentrated on emittance areas ?(x), ?(y) occupied by desired part of ion beam in transverse phase space and shape of these areas. The absolute beam phase density (brightness) as usually is not measured directly and the average beam brightness B is calculated from a beam intensity I and the transverse emittances. In the ion source and low energy beam transport (LEBT) optimization, it is important to preserve the beam brightness because some aberration of ion optic and beam instabilities can decrease the brightness of the central part of ion beam significantly. For these brightness measurements, it is convenient to use an absolute beam brightness detector with the brightness determination from one short considered in this article. PMID:22380223

  2. Absolute beam brightness detector

    SciTech Connect

    Dudnikov, Vadim [Muons, Inc., Batavia, Illinois 60510 (United States)

    2012-02-15

    In generally accepted emittance measurement, main attention is concentrated on emittance areas {epsilon}{sub x}, {epsilon}{sub y} occupied by desired part of ion beam in transverse phase space and shape of these areas. The absolute beam phase density (brightness) as usually is not measured directly and the average beam brightness B is calculated from a beam intensity I and the transverse emittances. In the ion source and low energy beam transport (LEBT) optimization, it is important to preserve the beam brightness because some aberration of ion optic and beam instabilities can decrease the brightness of the central part of ion beam significantly. For these brightness measurements, it is convenient to use an absolute beam brightness detector with the brightness determination from one short considered in this article.

  3. New phosphine-diamine and phosphine-amino-alcohol tridentate ligands for ruthenium catalysed enantioselective hydrogenation of ketones and a concise lactone synthesis enabled by asymmetric reduction of cyano-ketones.

    PubMed

    Fuentes, José A; Phillips, Scott D; Clarke, Matthew L

    2012-01-01

    Enantioselective hydrogenation of ketones is a key reaction in organic chemistry. In the past, we have attempted to deal with some unsolved challenges in this arena by introducing chiral tridentate phosphine-diamine/Ru catalysts. New catalysts and new applications are presented here, including the synthesis of phosphine-amino-alcohol P,N,OH ligands derived from (R,S)-1-amino-2-indanol, (S,S)-1-amino-2-indanol and a new chiral P,N,N ligand derived from (R,R)-1,2-diphenylethylenediamine. Ruthenium pre-catalysts of type [RuCl2(L)(DMSO)] were isolated and then examined in the hydrogenation of ketones. While the new P,N,OH ligand based catalysts are poor, the new P,N,N system gives up to 98% e.e. on substrates that do not react at all with most catalysts. A preliminary attempt at realising a new delta lactone synthesis by organocatalytic Michael addition between acetophenone and acrylonitrile, followed by asymmetric hydrogenation of the nitrile functionalised ketone is challenging in part due to the Michael addition chemistry, but also since Noyori pressure hydrogenation catalysts gave massively reduced reactivity relative to their performance for other acetophenone derivatives. The Ru phosphine-diamine system allowed quantitative conversion and around 50% e.e. The product can be converted into a delta lactone by treatment with KOH with complete retention of enantiomeric excess. This approach potentially offers access to this class of chiral molecules in three steps from the extremely cheap building blocks acrylonitrile and methyl-ketones; we encourage researchers to improve on our efforts in this potentially useful but currently flawed process. PMID:23216944

  4. New phosphine-diamine and phosphine-amino-alcohol tridentate ligands for ruthenium catalysed enantioselective hydrogenation of ketones and a concise lactone synthesis enabled by asymmetric reduction of cyano-ketones

    PubMed Central

    2012-01-01

    Enantioselective hydrogenation of ketones is a key reaction in organic chemistry. In the past, we have attempted to deal with some unsolved challenges in this arena by introducing chiral tridentate phosphine-diamine/Ru catalysts. New catalysts and new applications are presented here, including the synthesis of phosphine-amino-alcohol P,N,OH ligands derived from (R,S)-1-amino-2-indanol, (S,S)-1-amino-2-indanol and a new chiral P,N,N ligand derived from (R,R)-1,2-diphenylethylenediamine. Ruthenium pre-catalysts of type [RuCl2(L)(DMSO)] were isolated and then examined in the hydrogenation of ketones. While the new P,N,OH ligand based catalysts are poor, the new P,N,N system gives up to 98% e.e. on substrates that do not react at all with most catalysts. A preliminary attempt at realising a new delta lactone synthesis by organocatalytic Michael addition between acetophenone and acrylonitrile, followed by asymmetric hydrogenation of the nitrile functionalised ketone is challenging in part due to the Michael addition chemistry, but also since Noyori pressure hydrogenation catalysts gave massively reduced reactivity relative to their performance for other acetophenone derivatives. The Ru phosphine-diamine system allowed quantitative conversion and around 50% e.e. The product can be converted into a delta lactone by treatment with KOH with complete retention of enantiomeric excess. This approach potentially offers access to this class of chiral molecules in three steps from the extremely cheap building blocks acrylonitrile and methyl-ketones; we encourage researchers to improve on our efforts in this potentially useful but currently flawed process. PMID:23216944

  5. Absolute configuration of helminthogermacrene

    Microsoft Academic Search

    Adewale Martins Adio; Claudia Paul; Hailemichael Tesso; Petra Kloth; Wilfried A König

    2004-01-01

    The absolute configuration of the sesquiterpene hydrocarbon helminthogermacrene is established. Helminthogermacrene is an (E,Z)-configurational isomer of germacrene A and thus undergoes similar transformations forming elemenes via Cope rearrangement and yielding bicyclic systems via acid catalyzed reactions. The reaction products are investigated using enantioselective GC and extensive NMR measurements (1H–; 1H1H-COSY; HSQC; HMBC and NOE-experiments). In addition, NMR data of related

  6. Multiplexed absolute quantification in

    E-print Network

    Cai, Long

    Multiplexed absolute quantification in proteomics using artificial QCAT proteins of concatenated and construction of an artificial gene encoding a concatenation of tryptic peptides (QCAT protein) from several,688.78 T3 T11 T20 T14 T8 T18 T6 T5 T10 T7 T17 T16 T15T4 T13 T19 T25 T22 T21 QCAT protein 405.2 T1 386.25 1

  7. Measurement of the absolute branching fraction of the Ds+- meson

    E-print Network

    The Belle collaboration

    2007-01-30

    The Ds+- -> K+-K-+pi+- absolute branching fraction is measured using e+e- -> Ds*+- Ds1-+(2536) events collected by the Belle detector at the KEKB e+e- asymmetric energy collider. Using the ratio of yields when either the Ds1 or Ds* is fully reconstructed, we find Br(Ds+- -> K+-K-+pi+-)= (4.0+-0.4(stat)+-0.4(sys))%.

  8. Total Synthesis of Fostriecin: Via a Regio- and Stereoselective Polyene Hydration, Oxidation and Hydroboration Sequence

    PubMed Central

    Gao, Dong; O’Doherty, George A.

    2010-01-01

    A total synthesis of the fostriecin has been achieved in 24 steps from enyne 11. The lactone moiety was installed by a Leighton allylation and Grubbs ring-closing metathesis (RCM) reaction. The highly reactive Z,Z,E-triene moiety was installed via a late stage Suzuki-Miyaura cross coupling of a remarkably stable Z-vinyl boronate. The relative and absolute stereocenters of the C-8,9,11 triol were generated with a regio- and stereoselective asymmetric hydration/oxidation sequence. PMID:20687585

  9. Improved synthesis of structural analogues of (?)-epicatechin gallate for modulation of staphylococcal ?-lactam resistance?

    PubMed Central

    Anderson, James C.; Grounds, Helen; Reeves, Suzanna; Taylor, Peter W.

    2014-01-01

    The high-yielding synthesis of enantiomerically pure epicatechin gallate analogues where the A and/or B-ring hydroxylation is reduced or altered has been achieved by optimising routes to the catechin stereochemistry. The B-ring analogues were synthesised by using an electrophilic ring closure onto an enantiomerically enriched epoxide as a key step. The A and B-ring hydroxyl-deleted analogues were synthesised through a Mitsunobu cyclisation. For the B-ring analogues, the anti- (catechin) stereochemistry was converted to the syn- (epicatechin) stereochemistry by a known oxidation/reduction protocol. Absolute stereochemistry was derived from either a Sharpless epoxidation or asymmetric dihydroxylation. PMID:24876661

  10. Widely applicable synthesis of enantiomerically pure tertiary alkyl-containing 1-alkanols by zirconium-catalyzed asymmetric carboalumination of alkenes and palladium- or copper-catalyzed cross-coupling.

    PubMed

    Xu, Shiqing; Lee, Ching-Tien; Wang, Guangwei; Negishi, Ei-ichi

    2013-08-01

    A highly enantioselective and widely applicable method for the synthesis of various chiral 2-alkyl-1-alkanols, especially those of feeble chirality, has been developed. It consists of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and palladium- or copper-catalyzed cross-coupling. By virtue of the high selectivity factor (E) associated with iodine, either (S)- or (R)-enantiomer of 3-iodo-2-alkyl-1-alkanols (1), prepared by ZACA reaction of allyl alcohol, can be readily purified to the level of ?99% ee by lipase-catalyzed acetylation. A variety of chiral tertiary alkyl-containing alcohols, including those that have been otherwise difficult to prepare, can now be synthesized in high enantiomeric purity by Pd- or Cu-catalyzed cross-coupling of (S)-1 or (R)-2 for introduction of various primary, secondary, and tertiary carbon groups with retention of all carbon skeletal features. These chiral tertiary alkyl-containing alcohols can be further converted into the corresponding acids with full retention of the stereochemistry. The synthetic utility of this method has been demonstrated in the highly enantioselective (?99% ee) and efficient syntheses of (R)-2-methyl-1-butanol and (R)- and (S)-arundic acids. PMID:23670801

  11. Asymmetric synthesis of pochonin?E and F, revision of their proposed structure, and their conversion to potent Hsp90 inhibitors.

    PubMed

    Karthikeyan, Ganesan; Zambaldo, Claudio; Barluenga, Sofia; Zoete, Vincent; Karplus, Martin; Winssinger, Nicolas

    2012-07-16

    A concise and modular synthesis of pochonin?E and F, and their epimers at C-6 established the correct stereochemistry of these two natural products. Several members of the pochonin family have been shown to bind the heat shock protein?90 (Hsp90), which has been the focus of intense drug discovery efforts. Pochonin?E and F as well as their epimers were derivatized into the corresponding pochoximes and further modified at the C-6 position. Molecular dynamics simulations, docking studies, and Hsp90 affinity measurements were performed to evaluate the impact of these modifications. PMID:22696415

  12. Studies in asymmetric ?-lactone synthesis: extensions of the chiral nucleophile catalyzed aldol-lactonization (NCAL) reaction and new transformations of chlorinated ?-lactones

    E-print Network

    Tennyson, Reginald L.

    2001-01-01

    . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . 45 3. 5. 4. Organotin Addition 46 3. 5. 5. Hydride Addition. . . . . 47 Sg2' . . 48 3. 6. 1. Cuprate Addition. . . 48 3. 7. Dyotropic Rearrangements. 3. 7. 1. 7-Lactone Synthesis 49 49 Miscellaneous 4. 1. Decarboxylation 4. 1. 1, Thermal... condensation reaction between lithium ynolates, aldehydes and ketones. For example, they showed that the reaction of ynolate 6 with 5-keto ester 8 gives the bicyclic P-lactone 10, which underwent acid-catalyzed decarboxylation to give cyclohexene 11 in 74...

  13. Two 2D Cd(II) coordination polymers based on asymmetrical Schiff-base ligand: Synthesis, crystal structures and luminescent properties

    NASA Astrophysics Data System (ADS)

    Dang, Dong-Bin; Li, Meng-Meng; Bai, Yan; Zhou, Rui-Min

    2013-02-01

    Two new two-dimensional coordination polymers [Cd3L2(SCN)6]n (1) and [CdLI2]n (2) have been synthesized and characterized by IR spectroscopy, elemental analysis, TG technique, XRPD and complete single crystal structure analysis, where L is 4-(pyridine-2-yl)methyleneamino-1,2,4-trizaole. Asymmetrical Schiff-base ligand L with five- and six-membered N-containing heterocyclic rings acts as a tridentate bridging ligand to bind two Cd(II) centers through one terminal Ntriazolyl and one pyridylimine chelate unit in 1 and 2. For polymer 1, tridentate bridging ligands link Cd-(1,3-?-SCN-) 1D inorganic chains to form a 2D layer network. The existence of Csbnd H⋯? and ?sbnd ? stacking interactions between 2D hybrid layers further gives rise to a 3D supramolecular network. In comparison with 1, polymer 2 shows a 2D layer network containing hexanuclear macrometallacyclic units. The 2D layers are staggered together through the combination of Csbnd H⋯? and ?sbnd ? stacking interactions and forming a 3D supramolecular structure. The luminescent properties of the polymers 1 and 2 were investigated in the solid state at room temperature.

  14. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the mirror is slightly tilted. Hence, one can determine the amount and direction of tilt from the coordinates of the target image on the viewing plane.

  15. Spontaneous resolution, asymmetric catalysis, and fluorescence properties of ?- and ?-[cu(tzmp)]N enantiomers from in situ [2 + 3] cycloaddition synthesis.

    PubMed

    Tang, Yun-Zhi; Xiong, Jian-Bo; Gao, Ji-Xing; Tan, Yu-Hui; Xu, Qing; Wen, He-Rui

    2015-06-01

    Although a number of acentric or chiral tetrazole complexes were synthesized from Sharpless reaction, there are no spontaneous resolution Cu(I)-tetrazole compounds from in situ [2 + 3] cycloaddition synthesis that have been reported before. The first enantiomers ?- and ?- of metal tetrazole compound [Cu(Tzmp)]n (1) (HTzmp = 3-tetrazolemethylpyridine) were obtained and isolated from in situ [2 + 3] cycloaddition reactions of a flexible organic nitrile (3-cyanomethylpyridine) with sodium azide in the presence of CuCl2 as the Lewis acid. ?-1 and ?-1 feature a homochiral helical coordination polymeric system and {4(4).6(2)} two-dimensional framework. The photoluminescence study suggests 1 exhibits strong green fluorescence in solid state with maximal emission peaks around 535 nm. Remarkably, the ?- and ?- of [Cu(Tzmp)]n (1) catalyzes the enantioselective Henry reaction with high yield (more than 96%) and certain enantioselectivity (up to 69%). PMID:25970815

  16. NOVA: Absolute Zero

    NSDL National Science Digital Library

    On a hot day, some might wish they could get the temperature down a bit. They might not wish it to be as cold as, say absolute zero, but there are many scientists who are interested in doing just that. For those who are curious, absolute zero clocks in at around minus 460 degrees Fahrenheit. This engaging website is meant to serve as a complementary resource to the two-part series that recently aired on NOVA on this engaging topic. Visitors can start by watching a short preview of the program, and then continuing on to look over some of the special interactive features on the site. All told, there are ten different features, including "A Sense of Scale", "How Low Can You Go?", and "Milestones in Cold Research". The "Milestones in Cold Research" is a great place to start, as it's an interactive timeline that chronicles the "netherworld of extraordinarily low temperatures" as investigated by everyone from Galileo to current researchers. Of course, there are also more playful features here, such as "The Ice Trade", which asks users to dispatch ships loaded with natural ice to Florida, Brazil, and India.

  17. Measurement of the absolute \

    SciTech Connect

    Aunion, Jose Luis Alcaraz; /Barcelona, IFAE

    2010-07-01

    This thesis presents the measurement of the charged current quasi-elastic (CCQE) neutrino-nucleon cross section at neutrino energies around 1 GeV. This measurement has two main physical motivations. On one hand, the neutrino-nucleon interactions at few GeV is a region where existing old data are sparse and with low statistics. The current measurement populates low energy regions with higher statistics and precision than previous experiments. On the other hand, the CCQE interaction is the most useful interaction in neutrino oscillation experiments. The CCQE channel is used to measure the initial and final neutrino fluxes in order to determine the neutrino fraction that disappeared. The neutrino oscillation experiments work at low neutrino energies, so precise measurement of CCQE interactions are essential for flux measurements. The main goal of this thesis is to measure the CCQE absolute neutrino cross section from the SciBooNE data. The SciBar Booster Neutrino Experiment (SciBooNE) is a neutrino and anti-neutrino scattering off experiment. The neutrino energy spectrum works at energies around 1 GeV. SciBooNE was running from June 8th 2007 to August 18th 2008. In that period, the experiment collected a total of 2.65 x 10{sup 20} protons on target (POT). This thesis has used full data collection in neutrino mode 0.99 x 10{sup 20} POT. A CCQE selection cut has been performed, achieving around 70% pure CCQE sample. A fit method has been exclusively developed to determine the absolute CCQE cross section, presenting results in a neutrino energy range from 0.2 to 2 GeV. The results are compatible with the NEUT predictions. The SciBooNE measurement has been compared with both Carbon (MiniBoonE) and deuterium (ANL and BNL) target experiments, showing a good agreement in both cases.

  18. Prediction of Multi-Target Networks of Neuroprotective Compounds with Entropy Indices and Synthesis, Assay, and Theoretical Study of New Asymmetric 1,2-Rasagiline Carbamates

    PubMed Central

    Romero Durán, Francisco J.; Alonso, Nerea; Caamaño, Olga; García-Mera, Xerardo; Yañez, Matilde; Prado-Prado, Francisco J.; González-Díaz, Humberto

    2014-01-01

    In a multi-target complex network, the links (Lij) represent the interactions between the drug (di) and the target (tj), characterized by different experimental measures (Ki, Km, IC50, etc.) obtained in pharmacological assays under diverse boundary conditions (cj). In this work, we handle Shannon entropy measures for developing a model encompassing a multi-target network of neuroprotective/neurotoxic compounds reported in the CHEMBL database. The model predicts correctly >8300 experimental outcomes with Accuracy, Specificity, and Sensitivity above 80%–90% on training and external validation series. Indeed, the model can calculate different outcomes for >30 experimental measures in >400 different experimental protocolsin relation with >150 molecular and cellular targets on 11 different organisms (including human). Hereafter, we reported by the first time the synthesis, characterization, and experimental assays of a new series of chiral 1,2-rasagiline carbamate derivatives not reported in previous works. The experimental tests included: (1) assay in absence of neurotoxic agents; (2) in the presence of glutamate; and (3) in the presence of H2O2. Lastly, we used the new Assessing Links with Moving Averages (ALMA)-entropy model to predict possible outcomes for the new compounds in a high number of pharmacological tests not carried out experimentally. PMID:25255029

  19. Relative versus absolute quantitation in disease glycomics.

    PubMed

    Moh, Edward S X; Thaysen-Andersen, Morten; Packer, Nicolle H

    2015-04-01

    The glycome of a diagnostic biological material such as blood, urine, saliva, tissue, or cell cultures comprises of a vast array of structurally distinct glycans attached to the protein complement. Aberrant glycan structures and distributions result from changes in specific glycosyltransferase activities and have different biological significance, making proper quantitation of glycans highly important. In this review, common HPLC/CE and LC-MS/MS-based methods for glycomics, their advantages and disadvantages, will be discussed with respect to the main quantitative strategies. With the increasing interest in absolute quantitation for glycomics, we discuss absolute and relative glycome quantitation and how it affects the resulting conclusions drawn from glycomics studies. We argue that while absolute quantitation of glycomes may be attractive for some areas of clinical glycomics, relative quantitation of glycans remains the most informative and time/cost-effective method to obtain biological insight into the regulation of the cellular glycosylation machinery and the synthesis of the resultant glycan structures in most research questions due to the enzymatic relatedness of the biosynthesized glycans. Recent developments in multiplexing of glycomes by the introduction of stable isotopic labeling of glycans show promise for providing another level of information to the existing benefits of relative quantitation. PMID:25684231

  20. Synthesis and assignment of absolute configuration of (-)-oleocanthal: a potent, naturally occurring non-steroidal anti-inflammatory and anti-oxidant agent derived from extra virgin olive oils.

    PubMed

    Smith, Amos B; Han, Qiang; Breslin, Paul A S; Beauchamp, Gary K

    2005-10-27

    [structure: see text] Effective total syntheses and the assignment of absolute configurations of both the (+)- and (-)-enantiomers of oleocanthal 1 (a.k.a. deacetoxy ligstroside aglycon), the latter derived from extra virgin olive oils and known to be responsible for the back of the throat irritant properties of olive oils, have been achieved. The absolute and relative stereochemistry of the naturally occurring enantiomer (-)-1 proved to be 3S,4E. Both syntheses begin with d-(-)-ribose, proceed in 12 steps, and are achieved with an overall yield of 7%. Both enantiomers proved to be non-steroidal anti-inflammatory and anti-oxidant agents. PMID:16235961

  1. Absolute neutrino mass measurements

    SciTech Connect

    Wolf, Joachim [Karlsruhe Institute of Technology (KIT), IEKP, Postfach 3640, 76021 Karlsruhe (Germany)

    2011-10-06

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.

  2. Catalytic Asymmetric Dihydroxylation by Gold Colloids Functionalized with Self-Assembled Monolayers

    E-print Network

    Mrksich, Milan

    Catalytic Asymmetric Dihydroxylation by Gold Colloids Functionalized with Self-Assembled Monolayers of methyl- terminated monolayers on gold colloids is similar to that for alkanethiolates assembled and synthesis of functional nanoparticles based on the assembly of terminally substituted alkanethiols

  3. Fast Parallel Absolute Irreducibility Testing

    Microsoft Academic Search

    Erich Kaltofen

    1985-01-01

    e present a fast parallel deterministic algorithm for testing multivariate integral polyno- - c mials for absolute irreducibility, that is irreducibility over the complex numbers. More pre isely, we establish that the set of absolutely irreducible integral polynomials belongs to the e i complexity class NC of Boolean circuits of polynomial size and logarithmic depth. Therefor t also belongs to

  4. Chiral Proline-Based Ligands for Iridium-Catalyzed Asymmetric Hydrogenation

    E-print Network

    Amrhein, Valentin

    Chiral Proline-Based Ligands for Iridium-Catalyzed Asymmetric Hydrogenation Inauguraldissertation. Parts of this work have been previously published: ,,Proline-Based P,O Ligands/Iridium Complexes in Iridium-Catalyzed Asymmetric Hydrogenation: New Catalysts, Substrates and Applications in Total Synthesis

  5. Asymmetric rearrangement of racemic epoxides catalyzed by chiral Brønsted acids.

    PubMed

    Zhuang, Minyang; Du, Haifeng

    2013-03-01

    This paper describes a chiral Brønsted acid catalyzed asymmetric 1,2-rearrangement of racemic epoxides via a hydrogen-shift process for the synthesis of chiral aldehydes, and, followed by a reduction, a variety of optically active alcohols can be furnished in moderate yields with up to 50% ee. Especially, a facile one-pot synthesis of chiral alcohols directly from simple alkenes by a sequential epoxidation, rearrangement, and reduction has also been realized. PMID:23361172

  6. Asymmetric Dark Matter Stars

    E-print Network

    Kouvaris, Chris

    2015-01-01

    We study the possibility of asymmetric dark matter with self-interactions forming compact stable objects. We solve the Tolman-Oppenheimer-Volkoff equation and find the mass-radius relation of such "dark stars", their density profile and their Chandrasekhar mass limit. We consider fermionic asymmetric dark matter with Yukawa-type self-interactions appropriate for solving the well known problems of the collisionless dark matter paradigm. We find that in several cases the relativistic effects are significant.

  7. Copper-Catalyzed Intermolecular Asymmetric Propargylic Dearomatization of Indoles.

    PubMed

    Shao, Wen; Li, He; Liu, Chuan; Liu, Chen-Jiang; You, Shu-Li

    2015-06-22

    The first copper-catalyzed intermolecular dearomatization of indoles by an asymmetric propargylic substitution reaction was developed. This method provides a highly efficient synthesis of versatile furoindoline and pyrroloindoline derivatives containing a quaternary carbon stereogenic center and a terminal alkyne moiety with up to 86?% yield and 98?% ee. PMID:25968474

  8. Asymmetric MRI Magnet Design Using a Hybrid Numerical Method

    Microsoft Academic Search

    Huawei Zhao; Stuart Crozier; David M. Doddrell

    1999-01-01

    This paper describes a hybrid numerical method for the design of asymmetric magnetic resonance imaging magnet systems. The problem is formulated as a field synthesis and the desired current density on the surface of a cylinder is first calculated by solving a Fredholm equation of the first kind. Nonlinear optimization methods are then invoked to fit practical magnet coils to

  9. Cold asymmetrical fermion superfluids

    SciTech Connect

    Caldas, Heron

    2003-12-19

    The recent experimental advances in cold atomic traps have induced a great amount of interest in fields from condensed matter to particle physics, including approaches and prospects from the theoretical point of view. In this work we investigate the general properties and the ground state of an asymmetrical dilute gas of cold fermionic atoms, formed by two particle species having different densities. We have show in a recent paper, that a mixed phase composed of normal and superfluid components is the energetically favored ground state of such a cold fermionic system. Here we extend the analysis and verify that in fact, the mixed phase is the preferred ground state of an asymmetrical superfluid in various situations. We predict that the mixed phase can serve as a way of detecting superfluidity and estimating the magnitude of the gap parameter in asymmetrical fermionic systems.

  10. Constructions of Sparse Asymmetric Connectors Constructions of Sparse Asymmetric

    E-print Network

    Jäger, Gerold

    Constructions of Sparse Asymmetric Connectors Constructions of Sparse Asymmetric Connectors Gerold;Constructions of Sparse Asymmetric Connectors Overview 1 Connector Problem Formulation Modeling as an undirected graph Connectors 2 Preliminaries Hall's Theorem Connector condition Structure of an efficient (n, N, 2

  11. Asymmetric trade and agglomeration

    Microsoft Academic Search

    Kristian BEHRENS

    2003-01-01

    We extend the quadratic utility approach by Ottaviano et al. [19] and by Behrens [1] to the range of intermediate values of transport costs in or- der to investigate how asymmetric trade affects the regional distribution of economic activities. Asymmetry in trade is an endogenous result of price competition and transport costs: depending on both the spatial distribution of firms

  12. ASYMMETRIC ENCRYPTION Recommended Book

    E-print Network

    Bellare, Mihir

    ASYMMETRIC ENCRYPTION 1 / 60 #12;Recommended Book Steven Levy. Crypto. Penguin books. 2001. A non over private and authenticated channels. 3 / 60 #12;Public Key Encryption · Alice has a secret key, . . .) can use Alice's public key to send her an encrypted message which only she can decrypt. Think

  13. Asymmetric Synaptic Depression in

    Microsoft Academic Search

    Mircea I. Chelaru; Valentin Dragoi

    Synaptic depression is essential for controlling the balance be- tween excitation and inhibition in cortical networks. Several studies have shown that the depression of intracortical synapses is asymmetric, that is, inhibitory synapses depress less than excit- atory ones. Whether this asymmetry has any impact on cortical function is unknown. Here we show that the differential depression of intracortical synapses provides

  14. Absolute flux scale for radioastronomy

    SciTech Connect

    Ivanov, V.P.; Stankevich, K.S.

    1986-07-01

    The authors propose and provide support for a new absolute flux scale for radio astronomy, which is not encumbered with the inadequacies of the previous scales. In constructing it the method of relative spectra was used (a powerful tool for choosing reference spectra). A review is given of previous flux scales. The authors compare the AIS scale with the scale they propose. Both scales are based on absolute measurements by the ''artificial moon'' method, and they are practically coincident in the range from 0.96 to 6 GHz. At frequencies above 6 GHz, 0.96 GHz, the AIS scale is overestimated because of incorrect extrapolation of the spectra of the primary and secondary standards. The major results which have emerged from this review of absolute scales in radio astronomy are summarized.

  15. Catalytic Asymmetric Arylation of ?-Aryl-?-diazoacetates with Aniline Derivatives.

    PubMed

    Xu, Bin; Li, Mao-Lin; Zuo, Xiao-Dong; Zhu, Shou-Fei; Zhou, Qi-Lin

    2015-07-15

    The asymmetric arylation of diazo compounds with aniline derivatives cooperatively catalyzed by an achiral dirhodium complex and a chiral spiro phosphoric acid is reported. The reaction provides a new method for the facile synthesis of ?-diarylacetates, versatile building blocks with a diaryl tertiary chiral center, in good yields (up to 95%) with high enantioselectivities (up to 97% ee). Preliminary mechanistic studies suggest that the arylation reaction proceeds via a stepwise process, in which the enantioselectivity is controlled by a chiral spiro phosphoric acid-promoted proton shift in a zwitterionic intermediate. This work represents the first asymmetric intermolecular C(sp(2))-H bond insertion reaction with arenes. PMID:26121223

  16. Classical Mechanics without Absolute Space

    E-print Network

    D. Lynden-Bell; J. Katz

    1995-10-01

    A relative mechanics with no absolute space is shown to be equivalent to Newtonian mechanics applied in a universe of zero net angular momentum. Closed spaces in General Relativity have no angular momentum and shrivel to one point as the mass-energy contained tends to zero, so obeying Mach's principle on the origin of inertia.

  17. Absolute luminosity measurements at LHCb

    E-print Network

    Hopchev, Plamen

    2011-01-01

    Absolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC running at a centre-of-mass energy of 7 TeV. In addition to the classic ``van der Meer'' scan method a novel technique has been developed which makes use of direct imaging of the individual beams using both proton-gas and proton-proton interactions. The beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. We describe both methods and compare the two results. In addition, we present the techniques used to transport the absolute luminosity measurement ...

  18. On the synthesis of fixed order stabilizing controllers 

    E-print Network

    Kang, Sin Cheon

    2007-04-25

    In this dissertation, we consider two problems concerning the synthesis of fixed order controllers for Single Input, Single Output systems. The first problem deals with the synthesis of absolutely stabilizing fixed order ...

  19. Multipartite asymmetric quantum cloning

    SciTech Connect

    Iblisdir, S.; Gisin, N. [GAP-Optique, University of Geneva, 20 rue de l'Ecole-de-Medecine, CH-1211 (Switzerland); Acin, A. [ICFO-Institut de Ciencies Fotoniques, Jordi Girona 29, 08034 Barcelona (Spain); Cerf, N.J. [QUIC, Ecole Polytechnique, CP 165, Universite Libre de Bruxelles, 1050 Brussels (Belgium); Filip, R. [Department of Optics, Palacky University, 17. listopadu 50, 77200 Olomouc (Czech Republic); Fiurasek, J. [QUIC, Ecole Polytechnique, CP 165, Universite Libre de Bruxelles, 1050 Brussels (Belgium); Department of Optics, Palacky University, 17. listopadu 50, 77200 Olomouc (Czech Republic)

    2005-10-15

    We investigate the optimal distribution of quantum information over multipartite systems in asymmetric settings. We introduce cloning transformations that take N identical replicas of a pure state in any dimension as input and yield a collection of clones with nonidentical fidelities. As an example, if the clones are partitioned into a set of M{sub A} clones with fidelity F{sup A} and another set of M{sub B} clones with fidelity F{sup B}, the trade-off between these fidelities is analyzed, and particular cases of optimal N{yields}M{sub A}+M{sub B} cloning machines are exhibited. We also present an optimal 1{yields}1+1+1 cloning machine, which is an example of a tripartite fully asymmetric cloner. Finally, it is shown how these cloning machines can be optically realized.

  20. Asymmetric dipolar ring

    DOEpatents

    Prosandeev, Sergey A. (Fayetteville, AR); Ponomareva, Inna V. (Tampa, FL); Kornev, Igor A. (Ill-de-France, FR); Bellaiche, Laurent M. (Fayetteville, AR)

    2010-11-16

    A device having a dipolar ring surrounding an interior region that is disposed asymmetrically on the ring. The dipolar ring generates a toroidal moment switchable between at least two stable states by a homogeneous field applied to the dipolar ring in the plane of the ring. The ring may be made of ferroelectric or magnetic material. In the former case, the homogeneous field is an electric field and in the latter case, the homogeneous field is a magnetic field.

  1. Asymmetric block copolymers for supramolecular templating of inorganic nanospace materials.

    PubMed

    Bastakoti, Bishnu Prasad; Li, Yunqi; Kimura, Tatsuo; Yamauchi, Yusuke

    2015-05-01

    This review focuses on polymeric micelles consisting of asymmetric block copolymers as designed templates for several inorganic nanospace materials with a wide variety of compositions. The presence of chemically distinct domains of asymmetric triblock and diblock copolymers provide self-assemblies with more diverse morphological and functional features than those constructed by EOn POm EOn type symmetric triblock copolymers, thereby affording well-designed nanospace materials. This strategy can produce unprecedented nanospace materials, which are very difficult to prepare through other conventional organic templating approaches. Here, the recent development on the synthesis of inorganic nanospace materials are mainly focused on, such as hollow spheres, tubes, and porous oxides, using asymmetric triblock copolymers. PMID:25533589

  2. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  3. Chlorine, an atom economical auxiliary for asymmetric aldol reactions.

    PubMed

    Halperin, Shira D; Britton, Robert

    2013-02-13

    An auxiliary strategy has been developed for asymmetric reactions of aldehydes in which the auxiliary itself is not chiral, but a single chlorine atom introduced via organocatalytic ?-chlorination. The stereodirecting influence of the chlorine atom is then exploited prior to its removal by radical reduction. This strategy is demonstrated in the synthesis of several aldols (92-99% ee) and the natural products (+)-dihydroyashabushiketol and (+)-solistatin. PMID:23370443

  4. Astronomy Ranking Task: Apparent and Absolute Magnitude

    E-print Network

    Farritor, Shane

    Astronomy Ranking Task: Apparent and Absolute Magnitude Exercise #3 Description: The figure below shows five stars (A - E) as they appear in the night sky from Earth. The absolute magnitude number: ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ D. Ranking Instructions: Rank the absolute magnitude number (from greatest to least) of each star (A

  5. What is wrong with absolute individual fitness?

    E-print Network

    Wilson, David. S.

    What is wrong with absolute individual fitness? David Sloan Wilson Departments of Biology is that fit- ness is a relative concept. It does not matter how well an organism survives and reproduces, only arguments are framed in terms of absolute individual fitness. The absolute fitness criterion (AFC) can

  6. Absolute convergence implies convergence Willard Miller

    E-print Network

    Olver, Peter

    Absolute convergence implies convergence Willard Miller November 13, 2007 Definition 1 The series k=1 Ak is absolutely convergent if the series k=1 |Ak| converges. Thus the p-series for p = 2 k=1 1 k2 is absolutely convergent, as is the alternating series k=1 (-1)k-1 k2 . However

  7. Asymmetric photoredox transition-metal catalysis activated by visible light

    NASA Astrophysics Data System (ADS)

    Huo, Haohua; Shen, Xiaodong; Wang, Chuanyong; Zhang, Lilu; Röse, Philipp; Chen, Liang-An; Harms, Klaus; Marsch, Michael; Hilt, Gerhard; Meggers, Eric

    2014-11-01

    Asymmetric catalysis is seen as one of the most economical strategies to satisfy the growing demand for enantiomerically pure small molecules in the fine chemical and pharmaceutical industries. And visible light has been recognized as an environmentally friendly and sustainable form of energy for triggering chemical transformations and catalytic chemical processes. For these reasons, visible-light-driven catalytic asymmetric chemistry is a subject of enormous current interest. Photoredox catalysis provides the opportunity to generate highly reactive radical ion intermediates with often unusual or unconventional reactivities under surprisingly mild reaction conditions. In such systems, photoactivated sensitizers initiate a single electron transfer from (or to) a closed-shell organic molecule to produce radical cations or radical anions whose reactivities are then exploited for interesting or unusual chemical transformations. However, the high reactivity of photoexcited substrates, intermediate radical ions or radicals, and the low activation barriers for follow-up reactions provide significant hurdles for the development of efficient catalytic photochemical processes that work under stereochemical control and provide chiral molecules in an asymmetric fashion. Here we report a highly efficient asymmetric catalyst that uses visible light for the necessary molecular activation, thereby combining asymmetric catalysis and photocatalysis. We show that a chiral iridium complex can serve as a sensitizer for photoredox catalysis and at the same time provide very effective asymmetric induction for the enantioselective alkylation of 2-acyl imidazoles. This new asymmetric photoredox catalyst, in which the metal centre simultaneously serves as the exclusive source of chirality, the catalytically active Lewis acid centre, and the photoredox centre, offers new opportunities for the `green' synthesis of non-racemic chiral molecules.

  8. Asymmetrically Modified Nucleosomes

    PubMed Central

    Voigt, Philipp; LeRoy, Gary; Drury, William J.; Zee, Barry M.; Son, Jinsook; Beck, David; Young, Nicolas L.; Garcia, Benjamin A.; Reinberg, Danny

    2012-01-01

    SUMMARY Mononucleosomes, the basic building blocks of chromatin, contain two copies of each core histone. The associated posttranslational modifications regulate essential chromatin-dependent processes, yet whether each histone copy is identically modified in vivo is unclear. We demonstrate that nucleosomes in embryonic stem cells, fibroblasts, and cancer cells exist in both symmetrically and asymmetrically modified populations for histone H3 lysine 27 di/trimethylation (H3K27me2/3) and H4K20me1. To explore implications of nucleosomal asymmetry, we analyzed co-occurrence of histone marks and obtained direct physical evidence for bivalent nucleosomes carrying H3K4me3 or H3K36me3 along with H3K27me3, albeit on opposite H3 tails. Bivalency at target genes was resolved upon differentiation of ES cells. Polycomb Repressive Complex 2-mediated methylation of H3K27 was inhibited when nucleosomes contain symmetrically, but not asymmetrically, placed H3K4me3 or H3K36me3. These findings uncover a potential mechanism for the incorporation of bivalent features into nucleosomes and demonstrate how asymmetry might set the stage to diversify functional nucleosome states. PMID:23021224

  9. Optimal Asymmetric Quantum Cloning

    E-print Network

    Alastair Kay; Ravishankar Ramanathan; Dagomir Kaszlikowski

    2012-08-28

    While the no-cloning theorem, which forbids the perfect copying of quantum states, is well-known as one of the defining features of quantum mechanics, the question of how well the theory allows a state to be cloned is yet to be completely solved. In this paper, rigorous solutions to the problem of M to N asymmetric cloning of qudits are obtained in a number of interesting cases. The central result is the solution to the 1 to N universal asymmetric qudit cloning problem for which the exact trade-off in the fidelities of the clones for every N and d is derived. Analogous results are proven for qubits when M=N-1. We also consider state-dependent 1 to N qubit cloning, providing a general parametrization in terms of a Heisenberg star Hamiltonian. In all instances, we determine the feasibility of implementing the cloning economically, i.e., without an ancilla, and determine the dimension of the ancilla when an economic implementation is not possible.

  10. Circular asymmetric Helmholtz resonators

    PubMed

    Selamet; Ji

    2000-05-01

    A three-dimensional (3D) analytical approach is developed to account for the nonplanar wave propagation in the cavity and neck of "piston-driven" circular asymmetric Helmholtz resonators. The present 3D analytical results are compared with (1) the numerical predictions from the boundary element method (BEM) to evaluate the analytical approach; and (2) the one-dimensional (1D) solution to examine the effect of nonplanar waves at area discontinuity between the neck and the cavity. In order to improve the 1D solution, the end correction is also determined by using the 3D analytical approach. The effect of neck offset on the resonance frequency of circular asymmetric Helmholtz resonators is investigated. Predictions of resonance frequency and transmission loss from the present 3D and corrected 1D analytical approaches are, respectively, identical and close to the BEM results, while the corrected 1D approach provides a better accuracy compared to the 1D solutions with Ingard's correction. Finally, the boundary element method is employed to determine the wave attenuation performance of the "pipe-mounted" Helmholtz resonators to examine the effect of multidimensional waves in the vicinity of the main duct and neck junction. PMID:10830358

  11. Preparation of asymmetric porous materials

    DOEpatents

    Coker, Eric N. (Albuquerque, NM)

    2012-08-07

    A method for preparing an asymmetric porous material by depositing a porous material film on a flexible substrate, and applying an anisotropic stress to the porous media on the flexible substrate, where the anisotropic stress results from a stress such as an applied mechanical force, a thermal gradient, and an applied voltage, to form an asymmetric porous material.

  12. Asymmetric competition between plant species

    Microsoft Academic Search

    J. Connolly; P. Wayne

    1996-01-01

    Despite extensive interest in the role of plant size in competition, few formal attempts have been made to quantify the magnitude of asymmetric competition, particularly for interactions between members of different species. This paper introduces the concept of asymmetric interspecific competition at the population livel (i.e. mean plant performance) in mixtures of species. It proposes an index of interspecific competitive

  13. Asymmetric alkynylation of seven-membered cyclic imines by combining chiral phosphoric acids and Ag(I) catalysts: synthesis of 11-substituted-10,11-dihydrodibenzo[b,f][1,4]oxazepine derivatives.

    PubMed

    Ren, Yuan-Yuan; Wang, You-Qing; Liu, Shuang

    2014-12-01

    Asymmetric alkynylation of seven-membered cyclic imine dibenzo[b,f][1,4]oxazepines is successfully achieved by combining chiral phosphoric acid and Ag(I) catalysts. Various arylacetylenes, conjugated enynes, and terminal 1,3-diynes are good substrates for this reaction, and aliphatic hexyne is also a suitable donor at elevated temperature. Optimization of this approach has provided a facile method to synthesize optically active 11-substituted-10,11-dihydrodibenzo[b,f][1,4]oxazepine derivatives containing a carbon-carbon triple bond with 63-99% ee. Subsequent transformations of the carbon-carbon triple bond for the heterocyclic products have been disclosed. PMID:25375832

  14. Absolute and Comparative Performance Feedback 1 Running Head: ABSOLUTE AND COMPARATIVE PERFORMANCE FEEDBACK

    E-print Network

    Absolute and Comparative Performance Feedback 1 Running Head: ABSOLUTE AND COMPARATIVE PERFORMANCE FEEDBACK Objective Standards Matter Too Much: The Use and Abuse of Absolute and Comparative Performance Feedback in Absolute and Comparative Judgments and Decisions Don A. Moore Carnegie Mellon University

  15. Stereodivergent Synthesis of Chiral Fullerenes by [3 + 2] Cycloadditions to C60

    PubMed Central

    2013-01-01

    A wide range of new dipoles and catalysts have been used in 1,3-dipolar cycloadditions of N-metalated azomethine ylides onto C60 yielding a full stereodivergent synthesis of pyrrolidino[60]fullerenes with complete diastereoselectivities and very high enantioselectivities. The use of less-explored chiral ?-iminoamides as starting 1,3-dipoles leads to an interesting double asymmetric induction resulting in a matching/mismatching effect depending upon the absolute configuration of the stereocenter in the starting ?-iminoamide. An enantioselective process was also found in the retrocycloaddition reaction as revealed by mass spectrometry analysis on quasi-enantiomeric pyrrolidino[60]fullerenes. Theoretical DFT calculations are in very good agreement with the experimental data. On the basis of this agreement, a plausible reaction mechanism is proposed. PMID:24359021

  16. Error analysis of a new asymmetric Abel-inversion method

    SciTech Connect

    Park, Hyeon K.

    1990-06-01

    Propagation of the various errors in a new asymmetric Abel-inversion method is investigated. In order to provide a meaningful error analysis of the inversion process, both the effects of geometrical factors and measuremental errors are studied. The dominant source of uncertainty in the determination of local electron density is due to the spline fitting of the interferometric measurements with uneven spacings. The propagation of these errors is highly spatially localized and heavily damped in this inversion method. The absolute range of error in the local electron density is {plus minus}1.5 {times} 10{sup 12} cm{sup {minus}3}. 4 refs., 3 figs.

  17. Asymmetric Twin Dark Matter

    E-print Network

    Farina, Marco

    2015-01-01

    We study a natural implementation of Asymmetric Dark Matter in Twin Higgs models. The mirroring of the Standard Model strong sector suggests that a twin baryon with mass around 5 GeV is a natural dark matter candidate once a twin baryon number asymmetry comparable to the SM asymmetry is generated. We explore twin baryon dark matter in two different scenarios, one with minimal content in the twin sector and one with a complete copy of the SM, including a light twin photon. The essential requirements for successful thermal history are presented, and in doing so we address some of the cosmological issues common to many Twin Higgs models. The required interactions we introduce predict signatures at direct detection experiments and at the LHC.

  18. Minimal Asymmetric Dark Matter

    E-print Network

    Boucenna, Sofiane M; Nardi, Enrico

    2015-01-01

    In the early Universe, any particle carrying a conserved quantum number and in chemical equilibrium with the thermal bath will unavoidably inherit a particle-antiparticle asymmetry. A new particle of this type, if stable, would represent a candidate for asymmetric dark matter (DM) with an asymmetry directly related to the baryon asymmetry. We study this possibility for a minimal DM sector constituted by just one (generic) $SU(2)_L$ multiplet $\\chi$ carrying hypercharge, assuming that at temperatures above the electroweak phase transition an effective operator enforces chemical equilibrium between $\\chi$ and the Higgs boson. We argue that limits from DM direct detection searches severely constrain this scenario, ruling out the possibility of scalar multiplets, and leaving as the only possibilities fermion DM with hypercharge $y = 1/2$ and $y = 1$ with a mass in the few TeV range.

  19. Enantioselective synthesis of 12-amino alkylidenecyclopentenone prostaglandins.

    PubMed

    Roulland, Emmanuel; Monneret, Claude; Florent, Jean-Claude; Bennejean, Caroline; Renard, Pierre; Léonce, Stéphane

    2002-06-28

    An enantioselective synthesis of new 12-amino alkylidenecyclopentenone prostaglandins is reported. The key step of the synthesis involved a [3.3] sigmatropic rearrangement of an asymmetric allylic cyanate to elaborate an asymmetric 5-amino-1,6-diene which was further transformed into cyclopentenone by successive ring-closing metathesis reaction catalyzed by the Grubbs reagent and one-pot oxidation. A palladium-catalyzed cross-coupling reaction on a 5-iodo-1,5-diene allowed the synthesis of prostanoids with variable Rw side chains. These new compounds exhibit high cytotoxic activities. PMID:12076134

  20. Apparatus for absolute pressure measurement

    NASA Technical Reports Server (NTRS)

    Hecht, R. (inventor)

    1969-01-01

    An absolute pressure sensor (e.g., the diaphragm of a capacitance manometer) was subjected to a superimposed potential to effectively reduce the mechanical stiffness of the sensor. This substantially increases the sensitivity of the sensor and is particularly useful in vacuum gauges. An oscillating component of the superimposed potential induced vibrations of the sensor. The phase of these vibrations with respect to that of the oscillating component was monitored, and served to initiate an automatic adjustment of the static component of the superimposed potential, so as to bring the sensor into resonance at the frequency of the oscillating component. This establishes a selected sensitivity for the sensor, since a definite relationship exists between resonant frequency and sensitivity.

  1. Synthesis and Suzuki-Miyaura Cross-Coupling of Enantioenriched Secondary Potassium ?-Trifluoroboratoamides: Catalytic, Asymmetric Conjugate Addition of Bisboronic Acid and Tetrakis(dimethylamino)diboron to ?,?-Unsaturated Carbonyl Compounds

    PubMed Central

    Wisniewski, Steven R.; Hosseini-Sarvari, Mona

    2014-01-01

    Enantioenriched potassium ?-trifluoroboratoamides have been synthesized via an asymmetric, copper-catalyzed 1,4-addition of tetrahydroxydiboron (BBA) and tetrakis(dimethylamino)diboron to ?,?-unsaturated amides. These dibora reagents provide access to the desired organotrifluoroborates using effective and atom economical sources of boron. The copper-catalyzed ?-boration is extended to ?,?-unsaturated ketones and esters. Desired potassium organotrifluoroborates are synthesized with yields up to 92% and enantiomeric ratios up to 98:2. The enantioenriched potassium ?-trifluoroboratoamides are successfully cross-coupled with an array of aryl and heteroaryl chlorides in high yield with complete stereochemical fidelity as the transmetalation proceeds through an SE2 mechanism via an open transition state. PMID:24741373

  2. Asymmetric hydroformylation of Z-enamides and enol esters with rhodium-bisdiazaphos catalysts.

    PubMed

    Abrams, M Leigh; Foarta, Floriana; Landis, Clark R

    2014-10-15

    Asymmetric hydroformylation (AHF) of Z-enamides and Z-enol esters provides chiral, alpha-functionalized aldehydes with high selectivity and atom economy. Rh-bisdiazaphospholane catalysts enable hydroformylation of these challenging disubstituted substrates under mild reaction conditions and low catalyst loadings. The synthesis of a protected analog of l-DOPA demonstrates the utility of AHF for enantioselective, atom-efficient synthesis of peptide precursors. PMID:25241657

  3. Extremal asymmetric universal cloning machines

    E-print Network

    Mingming Jiang; Sixia Yu

    2012-02-08

    The trade-offs among various output fidelities of asymmetric universal cloning machines are investigated. First we find out all the attainable optimal output fidelities for the 1 to 3 asymmetric universal cloning machine and it turns out that there are two kinds of extremal asymmetric cloning machines which have to cooperate in order to achieve some of the optimal output fidelities. Second we construct a family of extremal cloning machines that includes the universal symmetric cloning machine as well as an asymmetric 1 to $1+N$ cloning machine for qudits with two different output fidelities such that the optimal trade-off between the measurement disturbance and state estimation is attained in the limit of infinite $N$.

  4. Extremal asymmetric universal cloning machines

    E-print Network

    Jiang, Mingming

    2012-01-01

    The trade-offs among various output fidelities of asymmetric universal cloning machines are investigated. First we find out all the attainable optimal output fidelities for the 1 to 3 asymmetric universal cloning machine and it turns out that there are two kinds of extremal asymmetric cloning machines which have to cooperate in order to achieve some of the optimal output fidelities. Second we construct a family of extremal cloning machines that includes the universal symmetric cloning machine as well as an asymmetric 1 to $1+N$ cloning machine for qudits with two different output fidelities such that the optimal trade-off between the measurement disturbance and state estimation is attained in the limit of infinite $N$.

  5. Asymmetric decompositions of abelian groups

    Microsoft Academic Search

    T. O. Banach; I. V. Protasov

    1999-01-01

    A subsetA of an Abelian groupG is said to be asymmetric ifg+S?A for any elementg?G and any infinite symmetric subsetS?G (S=?S). The minimal cardinality of a decomposition of the groupG into asymmetric sets is denoted by ?(G). for any Abelian groupG, the cardinal number ?(G is expressed via the following cardinal invariants: the free rank, the 2-rank, and the cardinality

  6. Asymmetric Bessel modes.

    PubMed

    Kotlyar, V V; Kovalev, A A; Soifer, V A

    2014-04-15

    We propose a new, three-parameter family of diffraction-free asymmetric elegant Bessel modes (aB-modes) with an integer and fractional orbital angular momentum (OAM). The aB-modes are described by the nth-order Bessel function of the first kind with complex argument. The asymmetry degree of the nonparaxial aB-mode is shown to depend on a real parameter c?0: when c=0, the aB-mode is identical to a conventional radially symmetric Bessel mode; with increasing c, the aB-mode starts to acquire a crescent form, getting stretched along the vertical axis and shifted along the horizontal axis for c?1. On the horizontal axis, the aB-modes have a denumerable number of isolated intensity zeros that generate optical vortices with a unit topological charge of opposite sign on opposite sides of 0. At different values of the parameter c, the intensity zeros change their location on the horizontal axis, thus changing the beam's OAM. An isolated intensity zero on the optical axis generates an optical vortex with topological charge n. The OAM per photon of an aB-mode depends near-linearly on c, being equal to ?(n+cI1(2c)/I0(2c)), where ? is the Planck constant and In(x) is a modified Bessel function. PMID:24979002

  7. Asymmetric Gepner Models (Revisited)

    E-print Network

    Gato-Rivera, B

    2010-01-01

    We reconsider a class of heterotic string theories studied in 1989, based on tensor products of N=2 minimal models with asymmetric simple current invariants. We extend this analysis from (2,2) and (1,2) spectra to (0,2) spectra with SO(10) broken to the Standard Model. In the latter case the spectrum must contain fractionally charged particles. We find that in nearly all cases at least some of them are massless. However, we identify a large subclass where the fractional charges are at worst half-integer, and often vector-like. The number of families is very often reduced in comparison to the 1989 results, but there are no new tensor combinations yielding three families. All tensor combinations turn out to fall into two classes: those where the number of families is always divisible by three, and those where it is never divisible by three. We find an empirical rule to determine the class, which appears to extend beyond minimal N=2 tensor products. We observe that distributions of physical quantities such as th...

  8. A Facile Stereoselective Total Synthesis of (R)-Rugulactone

    PubMed Central

    Reddy, B. Narasimha; Singh, R. P.

    2014-01-01

    An efficient and novel synthesis of (R)-rugulactone has been achieved employing Sharpless asymmetric epoxidation of allyl alcohols followed by selective hydride reduction of epoxy alcohols and olefin cross metathesis reactions. PMID:24971179

  9. A facile stereoselective total synthesis of (R)-rugulactone.

    PubMed

    Reddy, B Narasimha; Singh, R P

    2014-01-01

    An efficient and novel synthesis of (R)-rugulactone has been achieved employing Sharpless asymmetric epoxidation of allyl alcohols followed by selective hydride reduction of epoxy alcohols and olefin cross metathesis reactions. PMID:24971179

  10. Catalytic Asymmetric Peroxidation of ?,?-Unsaturated Nitroalkenes by a Bifunctional Organic Catalyst

    PubMed Central

    2015-01-01

    A new enantioselective peroxidation of ?,?-unsaturated nitroalkenes was realized with an easily accessible acid–base bifunctional organic catalyst derived from cinchona alkaloids. This reaction provides unprecedented easy access to optically active chiral peroxides, as illustrated by the asymmetric synthesis of ?-peroxy nitro compounds. PMID:24730647

  11. Formation of asymmetric one-sided metal-tipped semiconductor nanocrystal dots and rods

    Microsoft Academic Search

    Taleb Mokari; Claudia G. Sztrum; Asaf Salant; Eran Rabani; Uri Banin

    2005-01-01

    Multicomponent nanoparticles represent a new approach for creating smart materials, requiring the development of the growth of different material types on one particle. Here, we report the synthesis of asymmetric metal-semiconductor heterostructures where gold is grown on one side of CdSe nanocrystal quantum rods and dots, creating nanostructures offering intrinsic asymmetry for diverse device functionalities such as diode elements, along

  12. 49 CFR 236.709 - Block, absolute.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...Transportation 4 2010-10-01 2010-10-01 false Block, absolute. 236.709 Section 236.709 Transportation...DEVICES, AND APPLIANCES Definitions § 236.709 Block, absolute. A block in which no train is permitted to enter while it...

  13. 49 CFR 236.709 - Block, absolute.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...Transportation 4 2011-10-01 2011-10-01 false Block, absolute. 236.709 Section 236.709 Transportation...DEVICES, AND APPLIANCES Definitions § 236.709 Block, absolute. A block in which no train is permitted to enter while it...

  14. Astronomy Ranking Task: Apparent and Absolute Magnitude

    E-print Network

    Farritor, Shane

    Astronomy Ranking Task: Apparent and Absolute Magnitude Exercise #4 Description: The table below provides partial magnitude and distance information for five stars (A - E). Star Name Apparent Magnitude Absolute Magnitude Distance from Earth (parsecs) A -1 3 B 5 1 C 0 10 D 1 10,000 E 3 3 A. Ranking

  15. Absolute Income, Relative Income, and Happiness

    ERIC Educational Resources Information Center

    Ball, Richard; Chernova, Kateryna

    2008-01-01

    This paper uses data from the World Values Survey to investigate how an individual's self-reported happiness is related to (i) the level of her income in absolute terms, and (ii) the level of her income relative to other people in her country. The main findings are that (i) both absolute and relative income are positively and significantly…

  16. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  17. Introducing the Mean Absolute Deviation "Effect" Size

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2015-01-01

    This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

  18. Quantum nonequilibrium equalities with absolute irreversibility

    E-print Network

    Ken Funo; Yûto Murashita; Masahito Ueda

    2015-03-30

    We derive quantum nonequilibrium equalities in absolutely irreversible processes. Here by absolute irreversibility we mean that in the backward process the density matrix does not return to the subspace spanned by those eigenvectors that have nonzero weight in the initial density matrix. Since the initial state of a memory and the postmeasurement state of the system are usually restricted to a subspace, absolute irreversibility occurs during the measurement and feedback processes. An additional entropy produced in absolute irreversible processes needs to be taken into account to derive nonequilibrium equalities. We discuss a model of a feedback control on a qubit system to illustrate the obtained equalities. By introducing $N$ heat baths each composed of a qubit and letting them interact with the system, we show how the entropy reduction via feedback control can be converted into work. An explicit form of extractable work in the presence of absolute irreversibility is given.

  19. Symmetric and asymmetric charge transport in interacting asymmetric quantum impurities

    NASA Astrophysics Data System (ADS)

    Roy, Dibyendu

    2010-02-01

    We study steady-state charge transfer across an interacting resonance-level model connected asymmetrically to two leads. For a linear energy dispersion relation of the leads, we calculate current-voltage characteristics of the model exactly employing the scattering Bethe ansatz of Mehta-Andrei and find symmetric transport showing the absence of diode effect. Next we study a lattice version of this model with a nonlinear dispersion for the leads using the Lippmann-Schwinger scattering theory. We find that the inclusion of nonlinearity in the leads’ dispersion causes rectification for asymmetric junctions but does not rectify for asymmetric interactions and perfect junctions. The model in the latter case can be mapped into a model of a single noninteracting electron in higher dimensions.

  20. There is Neither Classical Bug with a Superluminal Shadow Nor Quantum Absolute Collapse Nor (Subquantum) Superluminal Hidden Variable

    Microsoft Academic Search

    Vladan Pankovic; Milan Predojevic; Miodrag Krmar; Milan Radovanovic

    2005-01-01

    In this work we analyse critically Griffiths's example of the classical superluminal motion of a bug shadow. Griffiths considers that this example is conceptually very close to quantum nonlocality or superluminality,i.e. quantum breaking of the famous Bell inequality. Or, generally, he suggests implicitly an absolute asymmetric duality (subluminality vs. superluminality) principle in any fundamental physical theory.It, he hopes, can be

  1. Synthesis and crystal structure of new dicopper(II) complexes having asymmetric N,N'-bis(substituted)oxamides with DNA/protein binding ability: In vitro anticancer activity and molecular docking studies.

    PubMed

    Zheng, Kang; Zhu, Ling; Li, Yan-Tuan; Wu, Zhi-Yong; Yan, Cui-Wei

    2015-08-01

    Two new dicopper(II) complexes bridged by asymmetric N,N'-bis(substituted)oxamide ligands: N-(5-chloro-2-hydroxyphenyl)-N'-[2-(dimethylamino)ethyl]oxamide (H3chdoxd) and N-hydroxypropyl-N'-(2-carboxylatophenyl)oxamide (H3oxbpa), and end-capped with 2,2'-bipyridine (bpy), namely [Cu2(ClO4)(chdoxd)(CH3OH)(bpy)]·H2O (1) and [Cu2(pic)(oxbpa)(CH3OH)(bpy)]·0.5CH3OH (2) (pic denotes picrate anion), have been synthesized and characterized by elemental analysis, molar conductivity measurement, IR and electronic spectral studies, and single-crystal X-ray diffraction. The X-ray diffraction analysis revealed that both the copper(II) ions bridged by the cis-oxamido ligands in dicopper(II) complexes 1 and 2 are all in square-pyramidal environments with the corresponding Cu?Cu separations of 5.194(3) and 5.1714(8)Å, respectively. In the crystals of the two complexes, there are abundant hydrogen bonds and ?-? stacking interactions contributing to the supramolecular structure. The reactivities toward herring sperm DNA (HS-DNA) and bovine serum albumin (BSA) of the two complexes are studied both theoretically and experimentally, indicating that both the two complexes can interact with the DNA in the mode of intercalation, and effectively bind to BSA via the favored binding sites Trp134 for the complex 1 and Trp213 for the complex 2. Interestingly, the in vitro anticancer activities of the two complexes against the selected tumor cell lines are consistent with their DNA/BSA-binding affinities following the order of 1>2. The effects of coordinated counterions in the two complexes on DNA/BSA-binding ability and in vitro anticancer activity are preliminarily discussed. PMID:26057022

  2. Asymmetric distances for binary embeddings.

    PubMed

    Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana

    2014-01-01

    In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes that binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances that are applicable to a wide variety of embedding techniques including locality sensitive hashing (LSH), locality sensitive binary codes (LSBC), spectral hashing (SH), PCA embedding (PCAE), PCAE with random rotations (PCAE-RR), and PCAE with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques. PMID:24231864

  3. Asymmetric Distances for Binary Embeddings.

    PubMed

    Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana

    2013-05-21

    In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes which binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances which are applicable to a wide variety of embedding techniques including Locality Sensitive Hashing (LSH), Locality Sensitive Binary Codes (LSBC), Spectral Hashing (SH), PCA Embedding (PCAE), PCA Embedding with random rotations (PCAE-RR), and PCA Embedding with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques. PMID:23712997

  4. Asymmetric retinal growth in the adult teleost green sunfish (Lepomis cyanellus).

    PubMed

    Cameron, D A

    1995-01-01

    Previous studies on fish retina have suggested that a curved, non-fused embryonic fissure is associated with, and perhaps caused by, asymmetric growth along the retina's marginal germinal zone (where neurons and Müller glia are added appositionally throughout life). In this report retinal growth was measured directly in adult green sunfish (Lepomis cyanellus), which has a curved, non-fused embryonic fissure. Growth was asymmetric in both small and large fish: ventral and nasal retina grew more than temporal and dorsal retina. This asymmetry was due to different net rates of cellular addition, rather than differential passive expansion. The absolute rates of retinal growth in the centroperipheral direction were roughly exponential functions of fish size--smaller fish grow faster than large fish--but the area of new retina added per unit time did not vary with fish size. Visual implications of asymmetric retinal growth are evaluated. PMID:7718505

  5. Asymmetric counterpropagating fronts without flow

    NASA Astrophysics Data System (ADS)

    Andrade-Silva, I.; Clerc, M. G.; Odent, V.

    2015-06-01

    Out-of-equilibrium systems exhibit domain walls between different states. These walls, depending on the type of connected states, can display rich spatiotemporal dynamics. In this Rapid Communication, we investigate the asymmetrical counterpropagation of fronts in an in-plane-switching cell filled with a nematic liquid crystal. Experimentally, we characterize the different front shapes and propagation speeds. These fronts present dissimilar elastic deformations that are responsible for their asymmetric speeds. Theoretically, using a phenomenological model, we describe the observed dynamics with fair agreement.

  6. Novel optoelectronic systems for use in absolute position sensing applications

    NASA Astrophysics Data System (ADS)

    Griffiths, Roger Phillip

    This thesis describes the development of two novel optoelectronic systems which have been designed for use in absolute position sensing applications. Chapter 1 provides an introduction to the work and reviews the wide variety of optical techniques which are presently available for position measurement. The second chapter provides a synopsis of a new type of optical position sensor designed for medium range sensing applications. This novel system uses optical feedback to a semiconductor laser to measure position. Unlike other proposed feedback sensing systems, this arrangement monitors the frequencies of RF beat modes generated within the laser diode to produce a position measurement capable of micron scale accuracy. The system operates using low optical powers and may be configured to operate as a non-contact, contact or fibre-addressed sensor. Chapter 4 examines the stability of the sensor. In particular, it assesses how the sensor is affected by variations in key operating parameters, such as bias current and feedback strength. Meanwhile, chapter 5 describes a number of signal processing systems which may be used to interface with the RF signal generated by the optical system to provide a real-time output of a suitable form. In addition to examining the experimental operation of the sensor, a thorough theoretical analysis of the operation of the system is presented in chapters 3 and 6. Both steady-state and dynamic approaches are used to analyse the behaviour of the optical system. These allow accurate predictions of the sensor performance to be generated, both for general operation and for stability analysis. Finally chapter 7 describes a separate novel optical position sensor, which provides absolute position measurement with accuracies of 0.004% of measurement range. This sensor utilises reflection from a novel dual track grating, which consists of a pseudo-random binary sequence written in parallel with a periodic asymmetric pattern.

  7. Stochastic Frontiers and Asymmetric Information Models

    E-print Network

    Boyer, Edmond

    Stochastic Frontiers and Asymmetric Information Models Philippe Gagnepain Departamento de Economía and production stochastic frontiers; asymmetric information; technical inefficiency; effort; regulation; test or conferences. Under a slightly different title, this paper has been presented at The ASSET Conference

  8. Nonequilibrium equalities in absolutely irreversible processes

    NASA Astrophysics Data System (ADS)

    Murashita, Yuto; Funo, Ken; Ueda, Masahito

    2015-03-01

    Nonequilibrium equalities have attracted considerable attention in the context of statistical mechanics and information thermodynamics. Integral nonequilibrium equalities reveal an ensemble property of the entropy production ? as = 1 . Although nonequilibrium equalities apply to rather general nonequilibrium situations, they break down in absolutely irreversible processes, where the forward-path probability vanishes and the entropy production diverges. We identify the mathematical origins of this inapplicability as the singularity of probability measure. As a result, we generalize conventional integral nonequilibrium equalities to absolutely irreversible processes as = 1 -?S , where ?S is the probability of the singular part defined based on Lebesgue's decomposition theorem. The acquired equality contains two physical quantities related to irreversibility: ? characterizing ordinary irreversibility and ?S describing absolute irreversibility. An inequality derived from the obtained equality demonstrates the absolute irreversibility leads to the fundamental lower bound on the entropy production. We demonstrate the validity of the obtained equality for a simple model.

  9. New absolute magnitude calibrations for detached binaries

    E-print Network

    S. Bilir; T. Ak; E. Soydugan; F. Soydugan; E. Yaz; N. Filiz Ak; Z. Eker; O. Demircan; M. Helvaci

    2008-06-07

    Lutz-Kelker bias corrected absolute magnitude calibrations for the detached binary systems with main-sequence components are presented. The absolute magnitudes of the calibrator stars were derived at intrinsic colours of Johnson-Cousins and 2MASS (Two Micron All Sky Survey) photometric systems. As for the calibrator stars, 44 detached binaries were selected from the Hipparcos catalogue, which have relative observed parallax errors smaller than 15% ($\\sigma_{\\pi}/\\pi\\leq0.15$). The calibration equations which provide the corrected absolute magnitude for optical and near-infrared pass bands are valid for wide ranges of colours and absolute magnitudes: $-0.18magnitude calibrations of this study can be used as a convenient statistical tool to estimate the true distances of detached binaries out of Hipparcos' distance limit.

  10. Magnifying absolute instruments for optically homogeneous regions

    SciTech Connect

    Tyc, Tomas [Institute of Theoretical Physics and Astrophysics, Masaryk University, Kotlarska 2, CZ-61 137 Brno (Czech Republic)

    2011-09-15

    We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.

  11. Absolute intensity measurements in the vacuum ultraviolet

    NASA Astrophysics Data System (ADS)

    Samson, James A. R.

    1986-01-01

    The basic principles governing the construction and use of absolute detectors are discussed. The absolute detector must be constructed to insure collection of all ions and to insure that no secondary ionization occurs. The fundamental standard for the absolute detection of VUV radiation and X-rays is based on the ionizing properties of the radiation. The principle of the ionization chamber is described; the wavelength range of the ion chamber is from Xe threshold at 102.2 nm to the double ionization threshold of He at 15.7 nm. The use of Geiger or proportional counters as an absolute standard for wavelengths less than 30 nm and less than 10 nm in the soft X-ray region is examined. Various types of transfer standards such as thermocouples, photodiodes, and photocathodes, and the procedures for calibrating a detector are considered.

  12. Absolute and relative quantification of RNA modifications via biosynthetic isotopomers

    PubMed Central

    Kellner, Stefanie; Ochel, Antonia; Thüring, Kathrin; Spenkuch, Felix; Neumann, Jennifer; Sharma, Sunny; Entian, Karl-Dieter; Schneider, Dirk; Helm, Mark

    2014-01-01

    In the resurging field of RNA modifications, quantification is a bottleneck blocking many exciting avenues. With currently over 150 known nucleoside alterations, detection and quantification methods must encompass multiple modifications for a comprehensive profile. LC–MS/MS approaches offer a perspective for comprehensive parallel quantification of all the various modifications found in total RNA of a given organism. By feeding 13C-glucose as sole carbon source, we have generated a stable isotope-labeled internal standard (SIL-IS) for bacterial RNA, which facilitates relative comparison of all modifications. While conventional SIL-IS approaches require the chemical synthesis of single modifications in weighable quantities, this SIL-IS consists of a nucleoside mixture covering all detectable RNA modifications of Escherichia coli, yet in small and initially unknown quantities. For absolute in addition to relative quantification, those quantities were determined by a combination of external calibration and sample spiking of the biosynthetic SIL-IS. For each nucleoside, we thus obtained a very robust relative response factor, which permits direct conversion of the MS signal to absolute amounts of substance. The application of the validated SIL-IS allowed highly precise quantification with standard deviations <2% during a 12-week period, and a linear dynamic range that was extended by two orders of magnitude. PMID:25129236

  13. A Cryogenic Radiometer for Absolute Radiometric Measurements

    Microsoft Academic Search

    J E Martin; N P Fox; P J Key

    1985-01-01

    The adoption in 1979 of a new definition of the candela, which permitted a detector-based approach to the realization of the unit, has emphasized the importance of high-accuracy absolute radiation detectors. This paper describes a new electrical-substitution absolute radiometer operating at 5 K, based on a standard commercial helium cryostat, which has been developed at NPL for optical radiant-power measurements.

  14. The absolute magnitudes of Type IA supernovae

    Microsoft Academic Search

    M. M. Phillips

    1993-01-01

    Absolute magnitudes in the B, V, and I bands are derived for nine well-observed Type Ia supernovae, using host galaxy distances estimated via the surface brightness fluctuations or Tully-Fisher methods. These data indicate that there is a significant intrinsic dispersion in the absolute magnitudes at maximum light of Type Ia supernovae, amounting to +\\/- 0.8 mag in B, +\\/- 0.6

  15. Absolute plate motions and regional subduction evolution

    NASA Astrophysics Data System (ADS)

    Chertova, M. V.; Spakman, W.; van den Berg, A. P.; van Hinsbergen, D. J. J.

    2014-10-01

    investigate the influence of absolute plate motion on regional 3-D evolution of subduction using numerical thermomechanical modeling. Building on our previous work, we explore the potential impact of four different absolute plate motion frames on subduction evolution in the western Mediterranean region during the last 35 My. One frame is data-based and derived from the global moving hotspot reference frame (GMHRF) of Doubrovine et al. (2012) and three are invented frames: a motion frame in which the African plate motion is twice that in the GMHRF, and two frames in which either the African plate or the Iberian continent is assumed fixed to the mantle. The relative Africa-Iberia convergence is the same in all frames. All motion frames result in distinctly different 3-D subduction evolution showing a critical dependence of slab morphology evolution on absolute plate motion. We attribute this to slab dragging through the mantle forced by the absolute motion of the subducting plate, which causes additional viscous resistance affecting subduction evolution. We observed a strong correlation between increase in northward Africa motion and decrease in the speed of westward slab rollback along the African margin. We relate this to increased mantle resistance against slab dragging providing new insight into propagation and dynamics of subduction transform edge propagator (STEP) faults. Our results demonstrate a large sensitivity of 3-D slab evolution to the absolute motion of the subducting plate, which inversely suggests that detailed modeling of natural subduction may provide novel constraints on absolute plate motions.

  16. Rational development of iron catalysts for asymmetric transfer hydrogenation.

    PubMed

    Sues, Peter E; Demmans, Karl Z; Morris, Robert H

    2014-06-01

    The asymmetric reduction of ketones and imines by transfer of hydrogen from isopropanol as the solvent catalyzed by metal complexes is a very useful method for preparing valuable enantioenriched alcohols and amines. Described here is the development of three generations of progressively more active iron catalysts for this transformation. Key features of this process of discovery involved the realization that one carbonyl ligand was needed (as in hydrogenases), the synthesis of modular ligands templated by iron, the elucidation of the mechanisms of catalyst activation and action, as well as the rational synthesis of precursors that lead directly and easily to the species in the catalytic cycle. The discovery that iron, an abundant element that is essential to life, can form catalysts of these hydrogenation reactions is a contribution to green chemistry. PMID:24763699

  17. Asymmetric Wholesale Pricing: Theory and Evidence

    Microsoft Academic Search

    Sourav Ray; Haipeng Chen; Mark Bergen; Daniel Levy

    2005-01-01

    Asymmetric pricing is the phenomenon where prices rise more readily than they fall. We articulate, and provide empirical support for, a theory of asymmetric pricing in wholesale prices. In particular, we show how wholesale prices may be asymmetric in the small but symmetric in the large, when retailers face costs of price adjustments. Such retailers will not adjust prices for

  18. Control of asymmetric cell division.

    PubMed

    Roubinet, Chantal; Cabernard, Clemens

    2014-12-01

    Asymmetric cell division (ACD) is a mechanism to generate cellular diversity and used by prokaryotes and eukaryotes alike. Stem cells in particular rely on ACD to self-renew the stem cell while simultaneously generating a differentiating sibling. It is well established that the differential partitioning of cell fate determinants in the form of RNA and proteins between sibling cells induces changes in cell behavior and fate. Recently, insight into molecular mechanisms has been gained that could explain how centrosomes and centrosome-associated structures such as histones, chromosomes or the primary cilium, segregate asymmetrically. Similarly, many cell types also generate physical asymmetry in the form of sibling cell size differences. Emerging data suggests that spindle-induced cleavage furrow positioning through regulated spindle placement and spindle geometry is insufficient to explain all occurrence of cell-size asymmetry. Instead, asymmetric membrane extension based on asymmetric Myosin localization and cortical remodeling could be a driving force for the generation of physical asymmetry. PMID:25264944

  19. LG tools for asymmetric wargaming

    Microsoft Academic Search

    Boris Stilman; Alex Yakhnis; Vladimir Yakhnis

    2002-01-01

    Asymmetric operations represent conflict where one of the sides would apply military power to influence the political and civil environment, to facilitate diplomacy, and to interrupt specified illegal activities. This is a special type of conflict where the participants do not initiate full-scale war. Instead, the sides may be engaged in a limited open conflict or one or several sides

  20. Constructions of Sparse Asymmetric Connectors

    E-print Network

    Jäger, Gerold

    Constructions of Sparse Asymmetric Connectors Gerold J¨ager Christian-Albrechts-University of Kiel) 2 #12;I O L (depth k - 1) · We denote above construction as an (n, N, k)- connector. · In literature with |X| n. Then n vertex disjoint edges exist, iff |(S)| |S| for all S X with |S| n 4 #12;Connector

  1. Constructions of Sparse Asymmetric Connectors

    E-print Network

    Jäger, Gerold

    Constructions of Sparse Asymmetric Connectors Gerold J¨ager University of Kiel Germany December simultaneously. · We denote above construction as an (n, N, k)- connector. · In literature, the problem only consider the case k = 2. 2 #12;Connector condition From Hall's theorem we obtain: Proposition 1

  2. Asymmetric Caching: Improved Network Deduplication

    E-print Network

    Sivakumar, Raghupathy

    on Smartphones: Ideal vs. Reality " , MobiSys 2012 Mobile Introduction 2 C1 C 2 C3 Rabin Fingerprinting H1 H2 H3Asymmetric Caching: Improved Network Deduplication for Mobile Devices Shruti Sanadhya,1 Raghupathy of Technology, Atlanta, GA, USA 2HP Labs, Palo Alto, CA, USA 3Xerox PARC, Palo Alto, CA, USA 1 #12;· Network

  3. Total synthesis of (+)-madangamine D.

    PubMed

    Ballette, Roberto; Pérez, Maria; Proto, Stefano; Amat, Mercedes; Bosch, Joan

    2014-06-10

    Madangamines are a group of bioactive marine sponge alkaloids, embodying an unprecedented diazapentacyclic skeletal type. The enantioselective total synthesis of madangamine?D has been accomplished, and represents the first total synthesis of an alkaloid of the madangamine group. It involves the stereoselective construction of the diazatricyclic ABC core using a phenylglycinol-derived lactam as the starting enantiomeric scaffold and the subsequent assembly of the peripheral macrocyclic rings. The synthesis provides, for the first time, a pure sample of madangamine?D and confirms the absolute configuration of this alkaloid family. PMID:24798407

  4. Asymmetric Dimethylarginine, Endothelial Dysfunction and Renal Disease

    PubMed Central

    Aldámiz-Echevarría, Luis; Andrade, Fernando

    2012-01-01

    l-Arginine (Arg) is oxidized to l-citrulline and nitric oxide (NO) by the action of endothelial nitric oxide synthase (NOS). In contrast, protein-incorporated Arg residues can be methylated with subsequent proteolysis giving rise to methylarginine compounds, such as asymmetric dimethylarginine (ADMA) that competes with Arg for binding to NOS. Most ADMA is degraded by dimethylarginine dimethyaminohydrolase (DDAH), distributed widely throughout the body and regulates ADMA levels and, therefore, NO synthesis. In recent years, several studies have suggested that increased ADMA levels are a marker of atherosclerotic change, and can be used to assess cardiovascular risk, consistent with ADMA being predominantly absorbed by endothelial cells. NO is an important messenger molecule involved in numerous biological processes, and its activity is essential to understand both pathogenic and therapeutic mechanisms in kidney disease and renal transplantation. NO production is reduced in renal patients because of their elevated ADMA levels with associated reduced DDAH activity. These factors contribute to endothelial dysfunction, oxidative stress and the progression of renal damage, but there are treatments that may effectively reduce ADMA levels in patients with kidney disease. Available data on ADMA levels in controls and renal patients, both in adults and children, also are summarized in this review. PMID:23109853

  5. A study of electric-field-induced second-harmonic generation in asymmetrical Gaussian potential quantum wells

    NASA Astrophysics Data System (ADS)

    Zhai, Wangjian

    2014-12-01

    Electric-field-induced second-harmonic generation in asymmetrical Gaussian potential quantum wells is investigated using the effective mass approximation employing the compact density matrix method and the iterative approach. Our results show that the absolute value, the real part and the imaginary part of second-harmonic generation are greatly affected by the height of the Gaussian potential quantum wells, the range of the Gaussian confinement potential and the applied electric field. The relationship between the absolute value and the imaginary part of second-harmonic generation together with the relationship between the absolute value and the real part of second-harmonic generation is studied. It is found that no matter how the height of the Gaussian potential quantum wells, the range of the Gaussian confinement potential and the applied electric field vary, the resonant peaks of the absolute value of second-harmonic generation do not originate from the imaginary part but from the real part.

  6. Error analysis of a new asymmetric Abel-inversion method

    SciTech Connect

    Park, H.K. (Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (USA))

    1990-10-01

    Propagation of the various errors in a new asymmetric Abel-inversion method (Hyeon K. Park, Plasma Phys. Controlled Fusion {bold 31}, 2035 (1989)) is investigated. In order to provide a meaningful error analysis of the inversion process, both the effects of geometrical factors and measuremental errors are studied. The dominant source of uncertainty in the determination of local electron density is due to the spline fitting of the interferometric measurements with uneven spacings. The propagation of these errors is highly spatially localized and heavily damped in this inversion method. The absolute range of error in the local electron density is {plus minus}1.5{times}10{sup 12} cm{sup {minus}3}.

  7. Quantitative standards for absolute linguistic universals.

    PubMed

    Piantadosi, Steven T; Gibson, Edward

    2014-01-01

    Absolute linguistic universals are often justified by cross-linguistic analysis: If all observed languages exhibit a property, the property is taken to be a likely universal, perhaps specified in the cognitive or linguistic systems of language learners and users. In many cases, these patterns are then taken to motivate linguistic theory. Here, we show that cross-linguistic analysis will very rarely be able to statistically justify absolute, inviolable patterns in language. We formalize two statistical methods--frequentist and Bayesian--and show that in both it is possible to find strict linguistic universals, but that the numbers of independent languages necessary to do so is generally unachievable. This suggests that methods other than typological statistics are necessary to establish absolute properties of human language, and thus that many of the purported universals in linguistics have not received sufficient empirical justification. PMID:24117660

  8. Absolute calibration in vivo measurement systems

    SciTech Connect

    Kruchten, D.A.; Hickman, D.P.

    1991-02-01

    Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.

  9. Asymmetric Divisions, Aggresomes and Apoptosis

    PubMed Central

    Singhvi, Aakanksha; Garriga, Gian

    2010-01-01

    Asymmetric cell division (ACD) is a fundamental process used to generate cell diversity during metazoan development and occurs when a cell divides to generate daughter cells that adopt distinct fates(Horvitz and Herskowitz, 1992; Knoblich, 2001). Stem cell division is also a type of ACD and provides a source of new cells during development and in adult animals. Some ACDs produce a daughter cell that dies. The logic of why a cell divides to generate a dying daughter remains elusive. Recently it was shown that denatured proteins are segregated asymmetrically during cell division, We review recent data that provides interesting insights into how apoptosis is regulated during ACD and speculate on potential connections between ACD-induced cell death and partitioning of denatured proteins. We discuss potential mechanisms for this link and what it may imply for development and disease in metazoans. PMID:19091567

  10. Asymmetric divisions, aggresomes and apoptosis.

    PubMed

    Singhvi, Aakanksha; Garriga, Gian

    2009-01-01

    Asymmetric cell division (ACD) is a fundamental process used to generate cell diversity during metazoan development that occurs when a cell divides to generate daughter cells adopting distinct fates. Stem cell divisions, for example, are a type of ACD and provide a source of new cells during development and in adult animals. Some ACDs produce a daughter cell that dies. In many cases, the reason why a cell divides to generate a dying daughter remains elusive. It was shown recently that denatured proteins are segregated asymmetrically during cell division. Here, we review data that provide interesting insights into how apoptosis is regulated during ACD and speculate on potential connections between ACD-induced cell death and partitioning of denatured proteins. PMID:19091567

  11. New absolute measurements of the solar spectrum

    NASA Astrophysics Data System (ADS)

    Burlov-Vasiljev, K. A.; Gurtovenko, E. A.; Matvejev, Yu. B.

    1995-03-01

    During 1986-1989 at the high-altitude station on the Peak Terskol, Caucasus (h = 3000 m) absolute measurements of the solar disk-center intensity were performed. The observations were carried out with the specialized solar telescope (D = 23 cm, F = 3 m) and grating spectrometer (F = 2 m, grating 140 x 150 mm, 600 grooves mm-1). The ribbon tungsten lamps used for absolute calibration were calibrated to the USSR standard of spectral intensity and were also compared with the irradiance standard of the PMO/WRC (Davos, Switzerland), with the lamps used in the Alma-Ata Observatory (Kazakhstan) and in Simferopol University for absolute measurements of stellar spectra. Methods and apparatus were improving step by step during 1985-1988. Special care was paid to the study of all possible sources of errors, in particular to the method of correction for atmospheric extinction, to polarization properties of optical elements of the apparatus, and to establishing the most reliable absolute calibration system. Finally, the observations performed during 1989 utilized only the refined methods and apparatus. As a result, the absolute integrals of the solar disk-centre intensity for 1-nm wide spectral bands in the range 310-685 nm are available. We estimate the total error is 2.5% at 310 nm and 2.1% at 680 nm. The absolute irradiance for 5-nm wide spectral bands is also obtained. We compare our results with results by Neckel and Labs (1984), with the irradiance filter measurements performed in PMO/WRC and calibration of the Sun's spectral irradiance to the stellar irradiance standard Vega by Lockwood (1992). Our results show a systematic difference with data by Neckel and Labs in the near-ultraviolet. The results by Neckel and Labs are probably underestimated in this spectral range by 8%.

  12. Asymmetric Auxin Response Precedes Asymmetric Growth and Differentiation of asymmetric leaf1 and asymmetric leaf2 Arabidopsis Leaves

    Microsoft Academic Search

    Jessie M. Zgurski; Rita Sharma; Dee A. Bolokoski; Elizabeth A. Schultz

    2004-01-01

    We have analyzed the development of leaf shape and vascular pattern in leaves mutant for ASYMMETRIC LEAVES1 (AS1 )o r AS2 and compared the timing of developmental landmarks to cellular response to auxin, as measured by expression of the DR5:b-glucuronidase (GUS) transgene and to cell division, as measured by expression of the cycB1:GUS transgene. We found that the earliest visible

  13. Dividend Policy under Asymmetric Information

    Microsoft Academic Search

    Merton H. Miller; Kevin Rock

    1985-01-01

    ABSTRACT We extend the standard finance model of the firm's dividend\\/investment\\/financing decisions by allowing the firm's managers,to know,more than outside investors about the true state of the firm's current earnings. The extension endogenizes the dividend (and financing) announcement,effects amply documented,in recent research. But once trading of shares is admitted to the model along with asymmetric information, the familiar Fisherian criterion

  14. Absolute Stability And Hyperstability In Hilbert Space

    NASA Technical Reports Server (NTRS)

    Wen, John Ting-Yung

    1989-01-01

    Theorems on stabilities of feedback control systems proved. Paper presents recent developments regarding theorems of absolute stability and hyperstability of feedforward-and-feedback control system. Theorems applied in analysis of nonlinear, adaptive, and robust control. Extended to provide sufficient conditions for stability in system including nonlinear feedback subsystem and linear time-invariant (LTI) feedforward subsystem, state space of which is Hilbert space, and input and output spaces having finite numbers of dimensions. (In case of absolute stability, feedback subsystem memoryless and possibly time varying. For hyperstability, feedback system dynamical system.)

  15. Absolute measurement of hyperspectral and angular reflection.

    PubMed

    Hwang, Jisoo

    2014-09-20

    A new instrument for absolute measurement of hyperspectral and angular reflection is presented. The instrument determines absolute values of angular reflection quantities in a wavelength range from 380 to 780 nm with a 3 nm spectral resolution by using a white source and a CCD-based spectroradiometer. Through uncertainty evaluation, the measurement uncertainty is determined as 1.4%-2.9% (k=2) for white diffuse material of Spectralon. The gonioreflectometric determination and an integrating-sphere-based reflection measurement traceable to KRISS spectral reflectance scale are compared by determining hemispherical reflectance, which results in agreement in their uncertainties. PMID:25322100

  16. Beyond Repetiton: Karl Kraus's "Absolute Satire"

    E-print Network

    Linden, Ari

    2013-10-01

    KU ScholarWorks | http://kuscholarworks.ku.edu Beyond Repetition: Karl Kraus’s “Absolute Satire” by Ari Linden KU ScholarWorks is a service provided by the KU Libraries’ Office of Scholarly Communication & Copyright. This is the published version... of the article, made available with the permission of the publisher. The original published version can be found at the link below. Ari Linden. (2013). Beyond Repetition: Kark Kraus’s “Absolute Satire.” German Studies Review 36(3):515-536. Published version...

  17. Asymmetric Wettability Directs Leidenfrost Droplets

    SciTech Connect

    Agapov, Rebecca L [ORNL] [ORNL; Boreyko, Jonathan B [ORNL] [ORNL; Briggs, Dayrl P [ORNL] [ORNL; Srijanto, Bernadeta R [ORNL] [ORNL; Retterer, Scott T [ORNL] [ORNL; Collier, Pat [ORNL] [ORNL; Lavrik, Nickolay V [ORNL] [ORNL

    2014-01-01

    Leidenfrost phenomena on nano- and microstructured surfaces are of great importance for increasing control over heat transfer in high power density systems utilizing boiling phenomena. They also provide an elegant means to direct droplet motion in a variety of recently emerging fluidic systems. Here, we report the fabrication and characterization of tilted nanopillar arrays (TNPAs) that exhibit directional Leidenfrost water droplets under dynamic conditions, namely on impact with Weber numbers 40 at T 325 C. The batch fabrication of the TNPAs was achieved by glancing-angle anisotropic reactive ion etching of a thermally dewet platinum mask, with mean pillar diameters of 100 nm and heights of 200-500 nm. In contrast to previously implemented macro- and microscopic Leidenfrost ratchets, our TNPAs induce no preferential directional movement of Leidenfrost droplets under conditions approaching steady-state film boiling, suggesting that the observed droplet directionality is not a result of asymmetric vapor flow. Using high-speed imaging, phase diagrams were constructed for the boiling behavior upon impact for droplets falling onto TNPAs, straight nanopillar arrays, and smooth silicon surfaces. The asymmetric impact and directional trajectory of droplets was exclusive to the TNPAs for impacts corresponding to the transition boiling regime, revealing that asymmetric wettability upon impact is the mechanism for the droplet directionality.

  18. Analytical study of the origin and behavior of asymmetric vortices

    NASA Technical Reports Server (NTRS)

    Tobak, Murray; Degani, David; Zilliac, Gregory G.

    1990-01-01

    An hypothesis advanced originally to explain computational observations is supported by theoretical considerations: The asymmetric mean flow observed on bodies of revolution at moderate to high angles of attack is the result of a convective instability of an originally symmetric flow to a time-invariant space-fixed disturbance. Additionally, the time-dependent fluctuations characteristic of the flow at higher angles of attack (up to 90 deg) are the result of an absolute instability of an originally steady flow to a small temporal disturbance of finite duration. Within a common domain, the instability mechanisms may coexist. The experimentally confirmed existence of bistable states, wherein the side-force variation with nose roll angle approaches a square-wave distribution, is attributed to the dominant influence of a pair of trailing vortices from the ogival forebody. Their existence is made possible by the appearance of foci of separation in the skin-friction line pattern beyond a critical angle of attack. The extreme sensitivity of the asymmetric flow orientation to nose geometry, demonstrated experimentally, is attributed to the presence of an indeterminate phase in the family of possible solutions for the three-dimensional wave system.

  19. Pacific trench motions controlled by the asymmetric plate configuration

    NASA Astrophysics Data System (ADS)

    Nagel, T. J.; Ryan, W. B. F.; Malinverno, A.; Buck, W. R.

    2009-04-01

    We present a novel explanation for absolute trench-normal motions of slabs surrounding the Pacific. Rapid retreat on the eastern side and slow advance in the west can result from the large-scale asymmetric plate configuration. We use simple fluid dynamics to explain the mechanical workings of the idea and the results of a simple finite difference scheme to estimate the effect on trench motion velocities. The idea is based on two key assumptions. First, we follow the concept of large-scale horizontal counter flow in the asthenosphere driven by accretion into lithosphere and plate motion. Second, we assume that horizontally wide slabs without large slab windows drift passively in the mantle flow field and do not retreat as a result of flow around the slab. If the asthenosphere transfers flow related horizontal shear stress into deeper levels of the mantle, an asymmetry in the plate configuration leads to different net pressure forces on the oceanward side of the two slabs and thus controls the retreat behavior. In an ocean with an asymmetric ridge position, the slab of the smaller plate should retreat faster than the slab of the larger plate, which may even advance. Our model explains the counterintuitive negative correlation between slab age and retreat velocity observed in the Pacific as well as the topographic asymmetry observed across the Pacific Rise.

  20. Parallel methods for absolute irreducibility testing

    Microsoft Academic Search

    Fatima K. Abu Salem; Laurence Tianruo Yang

    2008-01-01

    A heuristic algorithm for testing absolute irreducibility of multivariate polynomials over arbitrary elds using Newton Polytopes was proposed in (8). A preliminary implementa- tion by S. Gao and A. Lauder (2003) established a wide range of families of low degree and sparse polynomials for which the algorithm works ecien tly and with a high success rate. In this paper, we

  1. Absolute configuration of remisporines A & B.

    PubMed

    Sherer, Edward C; Cheeseman, James R; Williamson, R Thomas

    2015-04-14

    The absolute configuration of remisporine B was determined based on a comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Density functional theory (DFT) was used to calculate the ECD spectra varying the parameter controlling the number of calculated electronic transitions. Mapping the reaction surface provided support for the proposed Diels-Alder dimerization of remisporine A to form remisporine B. PMID:25735997

  2. TURING'S "ORACLE": FROM ABSOLUTE TO RELATIVE

    E-print Network

    Feferman, Solomon

    TURING'S "ORACLE": FROM ABSOLUTE TO RELATIVE COMPUTABILITY--AND BACK Solomon Feferman Logic Seminar} is not r.e. (xyT(z, x, y)) #12;2. Relative Effective Computability · `Oracle' computability (Turing 1939). A is effectively computable from B if it is computable by a machine which may call on an "oracle" for B. · Write f

  3. Astronomy Ranking Task: Apparent and Absolute Magnitude

    E-print Network

    Farritor, Shane

    Astronomy Ranking Task: Apparent and Absolute Magnitude Exercise #2 Description: The figure below magnitude. Ranking Order: Greatest 1 _______ 2 _______ 3 _______ 4 _______ 5 _______ Least Or, the apparent magnitude number would be the same for each star. ______ (indicate with check mark). Carefully explain your

  4. Absolute photoionization cross sections of atomic oxygen

    NASA Astrophysics Data System (ADS)

    Berkowitz, J.

    1997-02-01

    Conflicting calibrations of the absolute photoionization cross sections of atomic oxygen in the vacuum and extreme ultraviolet are tested by a sum-rule analysis. It is shown that the scaling factor obtained by Samson and Pareek results in much closer adherence to three sum rules.

  5. Absolute rate theories of epigenetic stability

    Microsoft Academic Search

    Aleksandra M. Walczak; José N. Onuchic; Peter G. Wolynes

    2005-01-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape and the transmission factor

  6. Absolute Points for Multiple Assignment Problems

    ERIC Educational Resources Information Center

    Adlakha, V.; Kowalski, K.

    2006-01-01

    An algorithm is presented to solve multiple assignment problems in which a cost is incurred only when an assignment is made at a given cell. The proposed method recursively searches for single/group absolute points to identify cells that must be loaded in any optimal solution. Unlike other methods, the first solution is the optimal solution. The…

  7. Increasing Capacity: Practice Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Dodds, Pennie; Donkin, Christopher; Brown, Scott D.; Heathcote, Andrew

    2011-01-01

    In most of the long history of the study of absolute identification--since Miller's (1956) seminal article--a severe limit on performance has been observed, and this limit has resisted improvement even by extensive practice. In a startling result, Rouder, Morey, Cowan, and Pfaltz (2004) found substantially improved performance with practice in the…

  8. The homological degree and Hopf's absolute degree

    NASA Astrophysics Data System (ADS)

    Sklyarenko, Evgenii G.

    2008-12-01

    A cohomological degree theory is constructed for continuous maps of topological manifolds, including manifolds with boundaries, with emphasis on the non-orientable case. Some applications are given, among which the most substantial is an extremely simple definition of Hopf's absolute degree (which coincides with the geometric degree). Bibliography: 29 titles.

  9. A concise enantioselective synthesis of (+)-febrifugine

    Microsoft Academic Search

    Lourdusamy Emmanuvel; Dayanand A. Kamble; Arumugam Sudalai

    2009-01-01

    A short enantioselective synthesis of (+)-febrifugine, a potent antimalarial alkaloid, has been described based on the regioselective asymmetric dihydroxylation of a 1,4-dienic ester as the key step. The strategy also involves chemoselective [3,3]-sigmatropic rearrangement of 1,5-hexadiene-3-ol and intramolecular lactamization of azidolactone for the construction of piperidine core.

  10. Synthesis of proposed aglycone of mandelalide A.

    PubMed

    Reddy, Karla Mahender; Yamini, Vanipenta; Singarapu, Kiran K; Ghosh, Subhash

    2014-05-16

    A highly convergent synthesis of the proposed mandelalide A aglycone is reported. The cornerstones of the synthetic strategy include the following: E-selective intramolecular Heck cyclization, Masamune-Roush olefination, Stork-Zhao-Wittig olefination, modified Prins cyclization; Sharpless asymmetric dihydroxylation followed by Williamson-type etherification, Julia-Kocienski olefination, Brown crotylation, and Brown allylation reactions. PMID:24738830

  11. Total synthesis of (-)-?-kainic acid via chirality transfer through Ireland-Claisen rearrangement.

    PubMed

    Kesava Reddy, Naredla; Chandrasekhar, Srivari

    2013-04-01

    The total synthesis of (-)-?-Kainic acid is accomplished using a linear strategy involving Noyori asymmetric reduction and chirality transfer through Ireland-Claisen rearrangement as key steps. PMID:23470056

  12. Harnessing nonlinear rubber swelling for bulk synthesis of anisotropic hybrid nanoparticles

    E-print Network

    Ding, Tao; Smoukov, Stoyan. K.; Baumberg, Jeremy J.

    2014-08-27

    Asymmetric hybrid nanoparticles are at the forefront of colloidal chemistry as building blocks for novel structures and applications, as well as for exploring fundamental ways of breaking symmetry in physical systems. Current methods of synthesis...

  13. A convenient synthesis of cis and trans 4-tert-butoxycarbonyl-substituted cyclohexylglycine.

    PubMed

    Venkatraman, Srikanth; Njoroge, F George; Girijavallabhan, Viyyoor; McPhail, Andrew T

    2002-04-19

    A novel synthesis of cis and trans substituted 4-tert-butoxycarbonyl cyclohexylglycines via asymmetric aminohydroxylation of vinyl styrene followed by reduction of the aromatic ring and subsequent oxidation is reported. PMID:11950318

  14. Highly regio- and enantioselective synthesis of ?,?-unsaturated amido esters by catalytic hydrogenation of conjugated enamides.

    PubMed

    Gao, Min; Meng, Jing-jing; Lv, Hui; Zhang, Xumu

    2015-02-01

    An efficient and highly regio- and enantioselective catalytic asymmetric hydrogenation of ?,?-dienamido esters to ?,?-unsaturated amido esters has been achieved using Rh/TangPhos as the catalyst. A series of ?,?-unsaturated amido acids were furnished in excellent yields with up to 99% ee. This effective methodology was applied in the asymmetric synthesis of key intermediate of Ramipril, an ACE inhibitor. PMID:25511130

  15. Symmetric and Asymmetric Encryption GUSTAVUS J. SIMMONS

    E-print Network

    Lee, Ruby B.

    Symmetric and Asymmetric Encryption GUSTAVUS J. SIMMONS Sandm Laboratories, Albuquerque, New Mexico;306 · Gustavus J. Simmons CONTENTS INTRODUCTION 1 CLASSICAL CRYPTOGRAPHY 2 READER'S GUIDE 3 THE COMMUNICATIONS

  16. Symmetric mortality and asymmetric suicide cycles.

    PubMed

    Wu, Wen-Chieh; Cheng, Hui-Pei

    2010-06-01

    In this investigation, tests were performed to determine whether mortality cycles are asymmetric. Results from an asymmetry test of U.S. time-series data from 1951 to 2005 provide no evidence that all-cause mortality or mortality caused by disease causes asymmetric cycles. However, the rate of fatalities from suicide exhibits the pattern of an asymmetric cycle. The evidence for asymmetric suicide cycles is statistically significant for men and working-age groups but not for women and non-working-age groups. PMID:20378221

  17. Recent Developments in the Catalytic, Asymmetric Construction of Pyrroloindolines Bearing All-Carbon Quaternary Stereocenters

    PubMed Central

    Repka, Lindsay M.; Reisman, Sarah E.

    2014-01-01

    Pyrroloindoline alkaloids constitute a large family of natural products that has inspired the development of an impressive array of new reactions to prepare the key heterocyclic motif. This synopsis will address catalytic, asymmetric reactions developed to synthesize pyrroloindolines bearing C3a all-carbon quaternary stereocenters. The methods described herein include both transition metal-catalyzed and organocatalyzed reactions that have been demonstrated suitable for the synthesis of the pyrroloindoline framework. PMID:24295135

  18. LG tools for asymmetric wargaming

    NASA Astrophysics Data System (ADS)

    Stilman, Boris; Yakhnis, Alex; Yakhnis, Vladimir

    2002-07-01

    Asymmetric operations represent conflict where one of the sides would apply military power to influence the political and civil environment, to facilitate diplomacy, and to interrupt specified illegal activities. This is a special type of conflict where the participants do not initiate full-scale war. Instead, the sides may be engaged in a limited open conflict or one or several sides may covertly engage another side using unconventional or less conventional methods of engagement. They may include peace operations, combating terrorism, counterdrug operations, arms control, support of insurgencies or counterinsurgencies, show of force. An asymmetric conflict can be represented as several concurrent interlinked games of various kinds: military, transportation, economic, political, etc. Thus, various actions of peace violators, terrorists, drug traffickers, etc., can be expressed via moves in different interlinked games. LG tools allow us to fully capture the specificity of asymmetric conflicts employing the major LG concept of hypergame. Hypergame allows modeling concurrent interlinked processes taking place in geographically remote locations at different levels of resolution and time scale. For example, it allows us to model an antiterrorist operation taking place simultaneously in a number of countries around the globe and involving wide range of entities from individuals to combat units to governments. Additionally, LG allows us to model all sides of the conflict at their level of sophistication. Intelligent stakeholders are represented by means of LG generated intelligent strategies. TO generate those strategies, in addition to its own mathematical intelligence, the LG algorithm may incorporate the intelligence of the top-level experts in the respective problem domains. LG models the individual differences between intelligent stakeholders. The LG tools make it possible to incorporate most of the known traits of a stakeholder, i.e., real personalities involved in the conflict with their specific individual style.

  19. Asymmetric low back loading in asymmetric lifting movements is not prevented by pelvic twist

    Microsoft Academic Search

    Idsart Kingma; Jaap H van Dieën; Michiel de Looze; Huub M Toussaint; Patricia Dolan; Chris T. M Baten

    1998-01-01

    Asymmetric lifting is associated with an increased risk of low back disorders. Especially in lifting movements, characterized by a small amount of asymmetry, it is still the question if asymmetric lumbosacral torques occur, or if subjects try to avoid asymmetric back loading by twisting their pelvis with respect to the feet. An increase of the lifting speed or the box

  20. An Efficient Asymmetric Approach to Carbocyclic Nucleosides: Asymmetric

    E-print Network

    's6 palladium-catalyzed coupling of purine or pyrimidine bases with carbocyclic allylic carbonates to the same -allyl palladium intermediate for coupling to the nucleoside base. Our approach to the synthesis closure metathesis was accomplished in 97% yield by exposure of a dichloromethane solution of diene 7 to 1

  1. Asteroid absolute magnitudes and slope parameters

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    1991-01-01

    A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

  2. Absolute-magnitude distributions of supernovae

    SciTech Connect

    Richardson, Dean; Wright, John [Department of Physics, Xavier University of Louisiana, New Orleans, LA 70125 (United States); Jenkins III, Robert L. [Applied Physics Department, Richard Stockton College, Galloway, NJ 08205 (United States); Maddox, Larry, E-mail: drichar7@xula.edu [Department of Chemistry and Physics, Southeastern Louisiana University, Hammond, LA 70402 (United States)

    2014-05-01

    The absolute-magnitude distributions of seven supernova (SN) types are presented. The data used here were primarily taken from the Asiago Supernova Catalogue, but were supplemented with additional data. We accounted for both foreground and host-galaxy extinction. A bootstrap method is used to correct the samples for Malmquist bias. Separately, we generate volume-limited samples, restricted to events within 100 Mpc. We find that the superluminous events (M{sub B} < –21) make up only about 0.1% of all SNe in the bias-corrected sample. The subluminous events (M{sub B} > –15) make up about 3%. The normal Ia distribution was the brightest with a mean absolute blue magnitude of –19.25. The IIP distribution was the dimmest at –16.75.

  3. Absolute flux measurements in the rocket ultraviolet

    NASA Technical Reports Server (NTRS)

    Bohlin, R. C.; Frimout, D.; Lillie, C. F.

    1974-01-01

    A two-channel spectrometer was calibrated in the wavelength region 1200-3400 A and flown on an Aerobee rocket to observe the stars alpha Lyr, eta UMa, and zeta Oph. Standard tungsten lamps provided the absolute calibration down to 2250 A, and a photodiode calibrated by the National Bureau of Standards was the reference at shorter wavelengths. The molecular branching-ratio technique of relative calibration using the gases CO, NO, and N2 was a check on the absolute calibration. The flux from eta UMa agrees with the prediction of a hydrogen line blanketed model atmosphere within 10% between 1700 and 3400 A and within 4% over most of this wavelength region.

  4. Absolute quantification method for protein concentration.

    PubMed

    Li, Mingdong; Tan, Jiaojie; Tarlov, Michael J; Zachariah, Michael R

    2014-12-16

    A fast and accurate assay to determine the absolute concentration of proteins is described based on direct measurement of droplet entrapped oligomer formation in electrospray. Here we demonstrate the approach using electrospray differential mobility analysis (ES-DMA), which can distinguish monomers and dimers from higher order oligomers. A key feature of the method is that it allows determination of the absolute number concentration of proteins eliminating the need for protein-specific calibration. The method was demonstrated by measuring the concentration of a NIST Standard Reference Material 927e (bovine serum albumin), a high-purity immunoglobulin G 1?, and a formulated Rituximab. The method may be applied to any electrospray source, regardless of diagnostic tool (e.g., MS or ion-mobility, etc.), provided the electrospray is operated in a droplet-fission mode. PMID:25412350

  5. Absolute absorption spectroscopy based on molecule interferometry

    E-print Network

    Stefan Nimmrichter; Klaus Hornberger; Hendrik Ulbricht; Markus Arndt

    2008-11-07

    We propose a new method to measure the absolute photon absorption cross section of neutral molecules in a molecular beam. It is independent of our knowledge of the particle beam density, nor does it rely on photo-induced fragmentation or ionization. The method is based on resolving the recoil resulting from photon absorption by means of near-field matter-wave interference, and it thus applies even to very dilute beams with low optical densities. Our discussion includes the possibility of internal state conversion as well as fluorescence. We assess the influence of various experimental uncertainties and show that the measurement of absolute absorption cross sections is conceivable with high precision and using existing technologies.

  6. Absolute and relative dosimetry for ELIMED

    SciTech Connect

    Cirrone, G. A. P.; Schillaci, F.; Scuderi, V. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Institute of Physics Czech Academy of Science, ELI-Beamlines project, Na Slovance 2, Prague (Czech Republic)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Institute of Physics Czech Academy of Science, ELI-Beamlines project, Na Slovance 2, Prague (Czech Republic); Cuttone, G.; Candiano, G.; Musumarra, A.; Pisciotta, P.; Romano, F. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania (Italy); Carpinelli, M. [INFN Sezione di Cagliari, c/o Dipartimento di Fisica, Università di Cagliari, Cagliari (Italy)] [INFN Sezione di Cagliari, c/o Dipartimento di Fisica, Università di Cagliari, Cagliari (Italy); Leonora, E.; Randazzo, N. [INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy)] [INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy); Presti, D. Lo [INFN-Sezione di Catania, Via Santa Sofia 64, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy)] [INFN-Sezione di Catania, Via Santa Sofia 64, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy); Raffaele, L. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and INFN-Sezione di Catania, Via Santa Sofia 64, Catania (Italy); Tramontana, A. [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy)] [INFN, Laboratori Nazionali del Sud, Via Santa Sofia 62, Catania, Italy and Università di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, Catania (Italy); Cirio, R.; Sacchi, R.; Monaco, V. [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino, Italy and Università di Torino, Dipartimento di Fisica, Via P.Giuria, 1 10125 Torino (Italy)] [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino, Italy and Università di Torino, Dipartimento di Fisica, Via P.Giuria, 1 10125 Torino (Italy); Marchetto, F.; Giordanengo, S. [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino (Italy)] [INFN, Sezione di Torino, Via P.Giuria, 1 10125 Torino (Italy)

    2013-07-26

    The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

  7. Probing absolute spin polarization at the nanoscale.

    PubMed

    Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

    2014-12-10

    Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum. PMID:25423049

  8. An absolute measure for a key currency

    NASA Astrophysics Data System (ADS)

    Oya, Shunsuke; Aihara, Kazuyuki; Hirata, Yoshito

    It is generally considered that the US dollar and the euro are the key currencies in the world and in Europe, respectively. However, there is no absolute general measure for a key currency. Here, we investigate the 24-hour periodicity of foreign exchange markets using a recurrence plot, and define an absolute measure for a key currency based on the strength of the periodicity. Moreover, we analyze the time evolution of this measure. The results show that the credibility of the US dollar has not decreased significantly since the Lehman shock, when the Lehman Brothers bankrupted and influenced the economic markets, and has increased even relatively better than that of the euro and that of the Japanese yen.

  9. Relaxation towards negative absolute temperature states

    NASA Astrophysics Data System (ADS)

    Mandt, Stephan; Feiguin, Adrian; Manmana, Salvatore

    2014-03-01

    Motivated by the recent experimental observation of negative absolute temperature states with ultracold atoms in optical lattices, [Braun et al., Science 339 52 (2013)], we discuss the formation of these states. More specifically, we consider the relaxation after a sudden inversion of the external parabolic confining potential. First, previous numerical simulation results of a semiclassical Boltzmann equation for the case of fermions will be discussed, which show a surprisingly slow equilibration due to the diffusive rearrangement of the local kinetic energies in the inhomogeneous system. We then focus on the integrable system of one-dimensional hard-core bosons. Here, we provide convincing numerical evidence for the relaxation to a generalized Gibbs ensemble at negative absolute temperature, a notion we define in this context.

  10. Asymmetric Solar Polar Field Reversals

    NASA Astrophysics Data System (ADS)

    Svalgaard, Leif; Kamide, Yohsuke

    2013-01-01

    The solar polar fields reverse because magnetic flux from decaying sunspots moves toward the poles, with a preponderance of flux from the trailing spots. If there is a strong asymmetry, in the sense that most activity is in the northern hemisphere, then that excess flux will move toward the north pole and reverse that pole first. If there is more activity in the south later on, then that flux will help to reverse the south pole. In this way, two humps in the solar activity and a corresponding difference in the time of reversals develop (in the ideal case). Such a difference was originally noted in the very first observation of polar field reversal just after the maximum of the strongly asymmetric solar cycle 19, when the southern hemisphere was most active before sunspot maximum and the south pole duly reversed first, followed by the northern hemisphere more than a year later, when that hemisphere became most active. Solar cycles since then have had the opposite asymmetry, with the northern hemisphere being most active before solar maximum. We show that polar field reversals for these cycles have all happened in the north first, as expected. This is especially noteworthy for the present solar cycle 24. We suggest that the association of two or more peaks of solar activity when separated by hemispheres with correspondingly different times of polar field reversals is a general feature of the cycle, and that asymmetric polar field reversals are simply a consequence of the asymmetry of solar activity.

  11. Geometry-induced asymmetric diffusion

    E-print Network

    Robert S. Shaw; Norman Packard; Matthias Schröter; Harry L. Swinney

    2007-05-24

    Past work has shown that ions can pass through a membrane more readily in one direction than the other. We demonstrate here in a model and an experiment that for a mixture of small and large particles such asymmetric diffusion can arise solely from an asymmetry in the geometry of the pores of the membrane. Our deterministic simulation considers a two-dimensional gas of elastic disks of two sizes diffusing through a membrane, and our laboratory experiment examines the diffusion of glass beads of two sizes through a metal membrane. In both experiment and simulation, the membrane is permeable only to the smaller particles, and the asymmetric pores lead to an asymmetry in the diffusion rates of these particles. The presence of even a small percentage of large particles can clog a membrane, preventing passage of the small particles in one direction while permitting free flow of the small particles in the other direction. The purely geometric kinetic constraints may play a role in common biological contexts such as membrane ion channels.

  12. Blood Pressure Targets and Absolute Cardiovascular Risk.

    PubMed

    Odutayo, Ayodele; Rahimi, Kazem; Hsiao, Allan J; Emdin, Connor A

    2015-08-01

    In the Eighth Joint National Committee guideline on hypertension, the threshold for the initiation of blood pressure-lowering treatment for elderly adults (?60 years) without chronic kidney disease or diabetes mellitus was raised from 140/90 mm Hg to 150/90 mm Hg. However, the committee was not unanimous in this decision, particularly because a large proportion of adults ?60 years may be at high cardiovascular risk. On the basis of Eighth Joint National Committee guideline, we sought to determine the absolute 10-year risk of cardiovascular disease among these adults through analyzing the National Health and Nutrition Examination Survey (2005-2012). The primary outcome measure was the proportion of adults who were at ?20% predicted absolute cardiovascular risk and above goals for the Seventh Joint National Committee guideline but reclassified as at target under the Eighth Joint National Committee guideline (reclassified). The Framingham General Cardiovascular Disease Risk Score was used. From 2005 to 2012, the surveys included 12 963 adults aged 30 to 74 years with blood pressure measurements, of which 914 were reclassified based on the guideline. Among individuals reclassified as not in need of additional treatment, the proportion of adults 60 to 74 years without chronic kidney disease or diabetes mellitus at ?20% absolute risk was 44.8%. This corresponds to 0.8 million adults. The proportion at high cardiovascular risk remained sizable among adults who were not receiving blood pressure-lowering treatment. Taken together, a sizable proportion of reclassified adults 60 to 74 years without chronic kidney disease or diabetes mellitus was at ?20% absolute cardiovascular risk. PMID:26056340

  13. Absolute Flux Calibrated Spectrum of Vega

    Microsoft Academic Search

    L. Colina; R. Bohlin; F. Castelli

    An absolute flux calibrated reference spectrum of Vega, the primary calibration standard in the optical, is presented. The spectrum covers the entire 0.12 to 2.6 microns wavelength. The ultraviolet spectrum is based on IUE measurements. The optical and near-infrared up to 1.05 microns consists of Hayes (1985) average spectrum. A model spectrum normalized to Hayes (1985) Johnson V flux covers

  14. Absolute model ages from lunar crater morphology

    NASA Astrophysics Data System (ADS)

    Trang, David; Gillis-Davis, Jeffrey J.; Boyce, Joseph M.

    2015-04-01

    The degradation state of an impact crater is an indicator of its age. Previous workers have used crater degradation states to estimate ages of surfaces or geomorphological features; one example is the degree of freshness method developed by Pohn and Offield. Here we attempted to produce an empirical calibration that yields absolute model ages based upon the degree of freshness technique for craters ~8-20 km in diameter. To produce the calibration, we first selected 15 craters with degree of freshness values ranging from 2.5 to 6.3. Next, we used the Kaguya Terrain Camera data to measure crater density on the ejecta of these craters, from which absolute model age could be calculated. The resulting absolute model ages ranged from 0.9 to 4.0 Ga. We used two linear regressions to describe the relationship between the absolute model age and degree of freshness of the craters. We fitted each trend with two linear least-squares regressions, where the first regression represents craters with a degree of freshness from 0.0 to 4.9 and the second regression from 5.0 to 7.0. The 95% confidence belt shows that the calibrations are accurate to ±0.5 Ga to ±1.1 Ga for the fresh crater regression (5.0-7.0) and slightly more accurate, to ±0.3 Ga to ±0.1 Ga, for the degraded crater regression (0.0-4.9). However, the degraded crater regression is likely based upon craters with continuous ejecta that are crater saturated, thus implying that craters with a degree of freshness <5.0 is likely to be >3.8 Ga.

  15. Regressional models that describe oil absolute viscosity

    Microsoft Academic Search

    J. F. Toro-Vazquez; R. Infante-Guerrero

    1993-01-01

    Equations that describe the temperature dependence (298–338K) of absolute viscosity (?) of 21 oils and oil-liquid fat mixtures\\u000a were obtained based on two different approaches. Fitting each particular viscosity profile to a quadratic extension of the\\u000a Andrade equation provided the best predictive models (R2>0.96). However, the coefficients associated with temperature effect did not have a physical-chemical meaning. In contrast,\\u000a the

  16. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1982-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  17. The absolute bioavailability of caffeine in man

    Microsoft Academic Search

    J. Blanchard; S. J. A. Sawers

    1983-01-01

    The absolute bioavailability of orally administered caffeine was investigated in 10 healthy adult male volunteers, aged 18.8 to 30.0 years. The subjects were administered a 5 mg\\/kg dose of caffeine as either an aqueous oral solution or an intravenous infusion, on separate occasions about 1 week apart, in a randomized crossover fashion. Plasma samples were collected over the 24-h period

  18. Measurement of absolute gravity acceleration in Firenze

    NASA Astrophysics Data System (ADS)

    de Angelis, M.; Greco, F.; Pistorio, A.; Poli, N.; Prevedelli, M.; Saccorotti, G.; Sorrentino, F.; Tino, G. M.

    2011-01-01

    This paper reports the results from the accurate measurement of the acceleration of gravity g taken at two separate premises in the Polo Scientifico of the University of Firenze (Italy). In these laboratories, two separate experiments aiming at measuring the Newtonian constant and testing the Newtonian law at short distances are in progress. Both experiments require an independent knowledge on the local value of g. The only available datum, pertaining to the italian zero-order gravity network, was taken more than 20 years ago at a distance of more than 60 km from the study site. Gravity measurements were conducted using an FG5 absolute gravimeter, and accompanied by seismic recordings for evaluating the noise condition at the site. The absolute accelerations of gravity at the two laboratories are (980 492 160.6 ± 4.0) ?Gal and (980 492 048.3 ± 3.0) ?Gal for the European Laboratory for Non-Linear Spectroscopy (LENS) and Dipartimento di Fisica e Astronomia, respectively. Other than for the two referenced experiments, the data here presented will serve as a benchmark for any future study requiring an accurate knowledge of the absolute value of the acceleration of gravity in the study region.

  19. Negative absolute temperature for mobile particles

    NASA Astrophysics Data System (ADS)

    Braun, Simon; Ronzheimer, Philipp; Schreiber, Michael; Hodgman, Sean; Bloch, Immanuel; Schneider, Ulrich

    2013-05-01

    Absolute temperature is usually bound to be strictly positive. However, negative absolute temperature states, where the occupation probability of states increases with their energy, are possible in systems with an upper energy bound. So far, such states have only been demonstrated in localized spin systems with finite, discrete spectra. We realized a negative absolute temperature state for motional degrees of freedom with ultracold bosonic 39K atoms in an optical lattice, by implementing the attractive Bose-Hubbard Hamiltonian. This new state strikingly revealed itself by a quasimomentum distribution that is peaked at maximum kinetic energy. The measured kinetic energy distribution and the extracted negative temperature indicate that the ensemble is close to degeneracy, with coherence over several lattice sites. The state is as stable as a corresponding positive temperature state: The negative temperature stabilizes the system against mean-field collapse driven by negative pressure. Negative temperatures open up new parameter regimes for cold atoms, enabling fundamentally new many-body states. Additionally, they give rise to several counterintuitive effects such as heat engines with above unity efficiency.

  20. Asymmetric autocatalysis of pyrimidyl alkanol and its application to the study on the origin of homochirality.

    PubMed

    Soai, Kenso; Kawasaki, Tsuneomi; Matsumoto, Arimasa

    2014-12-16

    CONSPECTUS: Amplification of enantiomeric excess (ee) is a key feature for the chemical evolution of biological homochirality from the origin of chirality. We describe the amplification of ee in the asymmetric autocatalysis of 5-pyrimidyl alkanols in the reaction between diisopropylzinc (i-Pr2Zn) and pyrimidine-5-carbaldehydes. During the reaction, an extremely low ee (ca. 0.00005% ee) can be amplified to >99.5% ee, and therefore, the initial slightly major enantiomer is automultiplied by a factor of ca. 630000, while the initial slightly minor enantiomer is automultiplied by a factor of less than 1000. In addition, pyrimidyl alkanols with various substituents at the 2-position of the pyrimidine ring, 3-quinolyl alkanol, 5-carbamoyl-3-pyridyl alkanol, and large multifunctionalized pyrimidyl alkanols also act as highly efficient asymmetric autocatalysts in the addition of i-Pr2Zn to the corresponding aldehydes. The asymmetric autocatalysis of pyrimidyl alkanol can discriminate the chirality of various compounds. Chiral substances such as alcohols, amino acids, hydrocarbons, metal complexes, and heterogeneous chiral materials can act as chiral triggers for asymmetric autocatalysis to afford pyrimidyl alkanols with the corresponding absolute configuration of the initiator. This recognition ability of chiral compounds is extremely high, and chiral discrimination of a cryptochiral quaternary saturated hydrocarbon was established by applying asymmetric autocatalysis. By using the large amplification effect of the asymmetric autocatalysis, we can link various proposed origins of chirality with highly enantioenriched organic compounds in conjunction with asymmetric autocatalysis. Thus, a statistical fluctuation in ee of racemic compounds can be amplified to high ee by using asymmetric autocatalysis. Enantiomeric imbalance induced by irradiation of circularly polarized light can affect the enantioselectivity of asymmetric autocatalysis. The asymmetric autocatalysis was also triggered by the morphology of inorganic chiral crystals such as quartz, sodium chlorate, and cinnabar. Chiral organic crystals of achiral compounds also act as chiral initiators, and during the study of a crystal of cytosine, enantioselective chiral crystal phase transformation of the cytosine crystal was achieved by removal of the water of crystallization in an achiral monohydrate crystal. Enantioselective C-C bond formation was realized on the surfaces of achiral single crystals based on the oriented prochirality of achiral aldehydes. Furthermore, asymmetric autocatalysis of pyrimidyl alkanols is a highly sensitive reaction that can recognize and amplify the significantly small effect of a chiral compound arising solely from isotope substitution of hydrogen, carbon, and oxygen (D/H, (13)C/(12)C, and (18)O/(16)O). These examples show that asymmetric autocatalysis with an amplification of chirality is a powerful tool for correlating the origin of chirality with highly enantioenriched organic compounds. Asymmetric autocatalysis using two ?-amino alcohols reveals a reversal of enantioselectivity in the addition of i-Pr2Zn to aldehyde and is one approach toward understanding the mechanism of asymmetric dialkylzinc addition, where heteroaggregates act as the catalytic species. PMID:25511374

  1. Defect-free ultrahigh flux asymmetric membranes

    DOEpatents

    Pinnau, Ingo (Austin, TX); Koros, William J. (Austin, TX)

    1990-01-01

    Defect-free, ultrahigh flux integrally-skinned asymmetric membranes having extremely thin surface layers (<0.2 .mu.m) comprised of glassy polymers are disclosed. The membranes are formed by casting an appropriate drope followed by forced convective evaporation of solvent to obtain a dry phase separated asymmetrical structure. The structure is then washed in a precipitation liquid and dried.

  2. Multipartite asymmetric quantum cloning S. Iblisdir,1

    E-print Network

    Cerf, Nicolas

    Multipartite asymmetric quantum cloning S. Iblisdir,1 A. Acín,2 N. J. Cerf,3 R. Filip,4 J. Fiurásek in asymmetric settings. We introduce cloning transformations that take N identical replicas of a pure state in any dimension as input and yield a collection of clones with nonidentical fidelities. As an example

  3. Asymmetric stem cell division: Lessons from Drosophila

    Microsoft Academic Search

    Pao-Shu Wu; Boris Egger; Andrea H. Brand

    2008-01-01

    Asymmetric cell division is an important and conserved strategy in the generation of cellular diversity during animal development. Many of our insights into the underlying mechanisms of asymmetric cell division have been gained from Drosophila, including the establishment of polarity, orientation of mitotic spindles and segregation of cell fate determinants. Recent studies are also beginning to reveal the connection between

  4. Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

    PubMed Central

    Chauhan, Pankaj

    2012-01-01

    Summary Ball-milling and pestle and mortar grinding have emerged as powerful methods for the development of environmentally benign chemical transformations. Recently, the use of these mechanochemical techniques in asymmetric organocatalysis has increased. This review highlights the progress in asymmetric organocatalytic reactions assisted by mechanochemical techniques. PMID:23243475

  5. Asymmetric access price regulation in telecommunications markets

    Microsoft Academic Search

    Martin Peitz

    2005-01-01

    In liberalized telecommunications markets, the incumbent typically enjoys several advantages over any entrant. Regulation in such asymmetric markets stimulates competition in the short and the long term if retail prices are low and the entrant's profits are high so that entry is encouraged. I show that asymmetric access price regulation with a cost-based access price for the incumbent and an

  6. cybersecurity.pnnl.gov Asymmetric Resilient Cybersecurity

    E-print Network

    cybersecurity.pnnl.gov Asymmetric Resilient Cybersecurity Cyber attacks are persistent Cyber attack have disastrous consequences on the rest of the system. The Asymmetric Resilient Cybersecurity altering how cybersecurity is implemented today. These capabilities will be driven by and measured by real

  7. Absolute configuration assignment of a chiral molecule in the gas phase using foil-induced Coulomb explosion imaging

    NASA Astrophysics Data System (ADS)

    Herwig, Philipp; Zawatzky, Kerstin; Schwalm, Dirk; Grieser, Manfred; Heber, Oded; Jordon-Thaden, Brandon; Krantz, Claude; Novotný, Old?ich; Repnow, Roland; Schurig, Volker; Vager, Zeev; Wolf, Andreas; Trapp, Oliver; Kreckel, Holger

    2014-11-01

    Chiral molecules exist in two configurations that are nonsuperposable mirror images of one another. The underlying molecular structure is referred to as the absolute configuration. In chiral environments, the handedness of molecules influences their chemical characteristics dramatically, and therefore the determination of absolute configurations is of fundamental interest in organic chemistry and biology. Commonly applied techniques to assign absolute configuration are anomalous single-crystal x-ray diffraction and vibrational circular dichroism. However, these techniques become increasingly more challenging when applied to molecules that are made out of light atoms exclusively. Furthermore, there is no established method to determine the absolute handedness of gas-phase molecules that are not optically active. In this work, we apply the foil-induced Coulomb explosion imaging technique to determine directly the absolute configuration of the chiral molecule trans-2,3-dideuterooxirane (C2OD2H2) in the gas phase. The experiment leads to the definitive assignment of the (R ,R ) configuration to an enantio-selected dideuterooxirane sample with a statistical confidence of 5 ? . As the handedness of trans-2,3-dideuterooxirane is unambiguously linked by chemical synthesis to the stereochemical key reference glyceraldehyde, our results provide an independent verification of the absolute configuration of the stereochemical reference standard.

  8. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lu, Xuezeng; Xiang, Hongjun; Rondinelli, James; Materials Theory; Design Group Team

    2015-03-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the ``asymmetric multiferroic.'' In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  9. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lu, X. Z.; Xiang, H. J.

    2014-09-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the "asymmetric multiferroic." In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  10. A biomimetic asymmetric responsive single nanochannel.

    PubMed

    Hou, Xu; Yang, Fu; Li, Lin; Song, Yanlin; Jiang, Lei; Zhu, Daoben

    2010-08-25

    Artificial single nanochannels have emerged as possible candidates for mimicking the process of ionic transport in ion channels and boosting the development of bioinspired intelligent nanomachines for real-world applications, such as biosensors, molecular filtration, and nanofluidic devices. One challenge that remains is to make the artificial nanochannel "smart", with various functions like an organism in Nature. The components of ion channels are asymmetrically distributed between membrane surfaces, which are significant for the implementation of the complex biological function. Inspired by this natural asymmetrical design, here we develop a biomimetic asymmetric responsive single nanochannel system that displays the advanced feature of providing control over pH- and temperature-tunable asymmetric ionic transport properties through asymmetric modifications inside the single nanochannels, which could be considered as a primal platform for the simulation of different ionic transport processes as well as the enhancement of the functionality of ion channels. PMID:20677760

  11. CURRENT ORGANIC CHEMISTRY-ASYMMETRIC SYNTHESIS 1998. (R826113)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  12. CURRENT ORGANIC CHEMISTRY-ASYMMETRIC SYNTHESIS 2000. (R826113)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  13. CURRENT ORGANIC CHEMISTRY-ASYMMETRIC SYNTHESIS 1999. (R826113)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  14. Asymmetric Total Synthesis of Bacillariolide III, a Marine Oxylipin

    E-print Network

    Suh, Young-Ger

    , Seung-Mann Paek, Yong-Sil Lee, Seok-Ho Kim, Kwang-Ok Lee, and Young-Ger Suh*,,§ College of Pharmacy by Yamada and co- workers.5 College of Pharmacy, Seoul National University. § Center for Bioactive Hybrids

  15. De novo asymmetric synthesis of D- and L-swainsonine.

    PubMed

    Guo, Haibing; O'Doherty, George A

    2006-04-13

    [reaction: see text] The enantioselective syntheses of both enantiomers of the indolizidine natural product swainsonine have been achieved in 13 steps from furan. The indolizidine ring system is installed by a one-pot hydrogenolysis of both an azide and an O-Bn group along with an intramolecular reductive amination reaction. The asymmetry of swainsonine was introduced by Noyori reduction of an acylfuran. This route relies upon an Achmatowicz rearrangement, a diastereoselective palladium-catalyzed glycosylation, Luche reduction, and a dihydroxylation reaction. PMID:16597122

  16. Organocatalytic Asymmetric Assembly Reactions: Synthesis of Spirooxindoles via Organocascade Strategies

    E-print Network

    Barbas III, Carlos F.

    and the E3 ubiquitin ligase MDM2.4h NITD609 is a very promising drug candidate for the treatment of malaria ABSTRACT: Spirooxindoles have become a privileged skeleton given their broad and promising activities primary starting materials and then further subdivided according to the types of organocatalyst

  17. Clinical implementation of 4-dihydroxyborylphenylalanine synthesised by an asymmetric pathway.

    PubMed

    Kulvik, Martti; Vähätalo, Jyrki; Buchar, Evzen; Färkkilä, Markus; Järviluoma, Eija; Jääskeläinen, Juha; Kriz, Otomar; Laakso, Juha; Rasilainen, Merja; Ruokonen, Inkeri; Kallio, Merja

    2003-02-01

    Boron neutron capture therapy (BNCT) is an experimental therapeutic modality combining a boron pharmaceutical with neutron irradiation. 4-Dihydroxyborylphenylalanine (L-BPA) synthesised via the asymmetric pathway by Malan and Morin [Synlett. 167-168 (1996)] was developed to be the boron containing pharmaceutical in the first series of Finnish BNCT clinical trials. The final product was >98.5% chemically pure L-BPA with L-phenylalanine and L-tyrosine as the residual impurities. The solubility of L-BPA was enhanced by complex formation with fructose (BPA-F). The pH and osmolarity of the BPA-F preparation is in the physiological range. Careful attention was given to the pharmaceutical quality of the BPA-F preparations. Prior to starting clinical trials the acute toxicity of L-BPA was studied in male albino Sprague-Dawley rats. In accordance with earlier studies no adverse effects were observed. After completion of the development work L-BPA solution was administered to brain tumour patients in conjunction with clinical studies for development and testing of BPA-based BNCT. No clinically significant adverse events attributable to the L-BPA i.v. infusions were observed. We conclude that our synthesis development, complementary preclinical and clinical observations justify the safe use of L-BPA up to clinical phase III studies with L-BPA produced by the asymmetric pathway, originally presented by Malan and Morin in 1996. PMID:12594009

  18. Biomimetic total synthesis of (±)-doitunggarcinone A and (+)-garcibracteatone.

    PubMed

    Pepper, Henry P; Tulip, Stephen J; Nakano, Yuji; George, Jonathan H

    2014-03-21

    A full account of our oxidative radical cyclization approach to the synthesis of garcibracteatone and doitunggarcinone A is presented. This includes the first enantioselective synthesis of garcibracteatone, which allowed the absolute configuration of the natural compound to be determined. The first synthesis of doitunggarcinone A is also described, which confirms our reassignment of the relative configuration of this molecule. Novel syntheses of monoterpene fragments used to construct the target molecules are also reported. PMID:24575789

  19. Condensation on Slippery Asymmetric Bumps

    E-print Network

    Park, Kyoo-Chul; He, Neil; Aizenberg, Joanna

    2015-01-01

    Bumps are omnipresent from human skin to the geological structures on planets, which offer distinct advantages in numerous phenomena including structural color, drag reduction, and extreme wettability. Although the topographical parameters of bumps such as radius of curvature of convex regions significantly influence various phenomena including anti-reflective structures and contact time of impacting droplets, the effect of the detailed bump topography on growth and transport of condensates have not been clearly understood. Inspired by the millimetric bumps of the Namib Desert beetle, here we report the identified role of radius of curvature and width of bumps with homogeneous surface wettability in growth rate, coalescence and transport of water droplets. Further rational design of asymmetric convex topography and synergetic combination with slippery coating simultaneously enable self-transport, leading to unseen five-fold higher growth rate and an order of magnitude faster shedding time of droplets compared...

  20. Asymmetrically Coupled Directed Percolation Systems

    NASA Astrophysics Data System (ADS)

    Noh, Jae Dong; Park, Hyunggyu

    2005-04-01

    We introduce a dynamical model of coupled directed percolation systems with two particle species. The two species A and B are coupled asymmetrically in that A particles branch B particles, whereas B particles prey on A particles. This model may describe epidemic spreading controlled by reactive immunization agents. We study nonequilibrium phase transitions with attention focused on the multicritical point where both species undergo the absorbing phase transition simultaneously. In one dimension, we find that the inhibitory coupling from B to A is irrelevant and the model belongs to the unidirectionally coupled directed percolation class. On the contrary, a mean-field analysis predicts that the inhibitory coupling is relevant and a new universality appears with a variable dynamic exponent. Numerical simulations on small-world networks confirm our predictions.

  1. A wireless batch sealed absolute capacitive pressure sensor Orhan Akarb

    E-print Network

    Akin, Tayfun

    A wireless batch sealed absolute capacitive pressure sensor Orhan Akarb , Tayfun Akina,b,* , Khalil sensor; Sealed pressure sensor; Capacitive pressure sensor 1. Introduction Absolute pressure sensors- ricate absolute pressure sensors with sealed cavities that also allow easy lead transfer from inside

  2. Measuring absolute infrared spectral radiance with correlated visible photons

    E-print Network

    Sergienko, Alexander

    techniques have shown promise in two areas of radiometry: absolute measurement of detector quantum efficiency of measuring absolute spec- tral radiance without externally calibrated stan- dards, one employs the processMeasuring absolute infrared spectral radiance with correlated visible photons: technique

  3. A Conceptual Approach to Absolute Value Equations and Inequalities

    ERIC Educational Resources Information Center

    Ellis, Mark W.; Bryson, Janet L.

    2011-01-01

    The absolute value learning objective in high school mathematics requires students to solve far more complex absolute value equations and inequalities. When absolute value problems become more complex, students often do not have sufficient conceptual understanding to make any sense of what is happening mathematically. The authors suggest that the…

  4. Mixed Integer Linear Programming Method for Absolute Value Equations

    Microsoft Academic Search

    Longquan Yong

    2009-01-01

    We formulate the NP-hard absolute value equation as linear complementary problem when the singular values of A exceed one, and we proposed a mixed integer linear programming method to absolute value equation problem. The effectiveness of the method is demonstrated by its ability to solve random problems. Index Terms—absolute value equation; linear complementary problem; mixed integer linear programming. The basic

  5. Measurement of the Absolute Branching Fraction of D0 to K- pi+

    SciTech Connect

    Aubert, B.; Bona, M.; Boutigny, D.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prudent, X.; Tisserand, V.; Zghiche, A.; /Annecy, LAPP; Garra Tico, J.; Grauges, E.; /Barcelona U., ECM; Lopez, L.; Palano, A.; /Bari U.; Eigen, G.; Ofte, I.; Stugu, B.; Sun, L.; /Bergen U.; Abrams, G.S.; Battaglia, M.; Brown, D.N.; Button-Shafer, J.; /LBL, Berkeley

    2007-04-25

    The authors measure the absolute branching fraction for D{sup 0} {yields} K{sup -} {pi}{sup +} using partial reconstruction of {bar B}{sup 0} {yields} D*{sup +}X{ell}{sup -}{bar {nu}}{sub {ell}} decays, in which only the charged lepton and the pion from the decay D*{sup +} {yields} D{sup 0}{pi}{sup +} are used. Based on a data sample of 230 million B{bar B} pairs collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, they obtain {Beta}(D{sup 0} {yields} K{sup -}{pi}{sup +}) = (4.007 {+-} 0.037 {+-} 0.070)%, where the first error is statistical and the second error is systematic.

  6. Absolute Radiometric Calibration of EUNIS-06

    NASA Technical Reports Server (NTRS)

    Thomas, R. J.; Rabin, D. M.; Kent, B. J.; Paustian, W.

    2007-01-01

    The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a soundingrocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its Longwave bandpass of 300 - 370A. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been calibrated to an absolute accuracy of 7% (l-sigma) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to +- 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar E W spectrometer yet flown. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.

  7. A novel approach for absolute radar calibration

    NASA Astrophysics Data System (ADS)

    Merker, C.; Peters, G.; Clemens, M.; Lengfeld, K.; Ament, F.

    2015-02-01

    The theoretical framework of a novel approach for absolute radar calibration is presented and its potential analysed by means of synthetic data to lay out a solid basis for future practical application. The method presents the advantage of an absolute calibration with respect to the directly measured reflectivity, without needing a previously calibrated reference device. It requires a setup comprising three radars: two devices oriented towards each other, measuring reflectivity along the same horizontal beam and operating within a strongly attenuated frequency range (e.g. K or X band) and one vertical reflectivity and drop size distribution (DSD) profiler below this connecting line, which is to be calibrated. The absolute determination of the calibration factor is based on attenuation estimates. Using synthetic, smooth and geometrically idealised data calibration is found to perform best using homogeneous precipitation events with rain rates high enough to ensure a distinct attenuation signal (approx. 30 dBZ). Furthermore, the choice of the interval width (in measuring range gates) around the vertically pointing radar, needed for attenuation estimation, is found to have an impact on the calibration results. Further analysis is done by means of synthetic data with realistic, inhomogeneous precipitation fields taken from measurements. A calibration factor is calculated for each considered case using the presented method. Based on the distribution of the calculated calibration factors, the most probable value is determined by estimating the mode of a fitted shifted logarithmic normal distribution function. After filtering the data set with respect to rain rate and inhomogeneity and choosing an appropriate length of the considered attenuation path, the estimated uncertainty of the calibration factor is in the order of 1%. Considering stability and accuracy of the method, an interval of 8 range gates on both sides of the vertically pointing radar is most appropriate for calibration.

  8. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  9. Absolute calibration of the Auger fluorescence detectors

    SciTech Connect

    Bauleo, P.; Brack, J.; Garrard, L.; Harton, J.; Knapik, R.; Meyhandan, R.; Rovero, A.C.; /Buenos Aires, IAFE; Tamashiro, A.; Warner, D.

    2005-07-01

    Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the combined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.

  10. Characterization of the DARA solar absolute radiometer

    NASA Astrophysics Data System (ADS)

    Finsterle, W.; Suter, M.; Fehlmann, A.; Kopp, G.

    2011-12-01

    The Davos Absolute Radiometer (DARA) prototype is an Electrical Substitution Radiometer (ESR) which has been developed as a successor of the PMO6 type on future space missions and ground based TSI measurements. The DARA implements an improved thermal design of the cavity detector and heat sink assembly to minimize air-vacuum differences and to maximize thermal symmetry of measuring and compensating cavity. The DARA also employs an inverted viewing geometry to reduce internal stray light. We will report on the characterization and calibration experiments which were carried out at PMOD/WRC and LASP (TRF).

  11. Absolute Priority for a Vehicle in VANET

    NASA Astrophysics Data System (ADS)

    Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad

    In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.

  12. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    Thorpe, A.; Senftle, F.E.

    1959-01-01

    An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

  13. Absolute positions of SiO masers

    SciTech Connect

    Wright, M.C.H.; Carlstrom, J.E.; Plambeck, R.L.; Welch, W.J. (California Univ., Berkeley (USA))

    1990-04-01

    The absolute radio positions of the v = 1, J = 2-1 SiO masers toward nine stars have been measured with typical position uncertainties of + or - 0.15 arcsec. The stars include the IR source IRc2 in Orion and R Aqr. The maser positions are compared with astrometrically determined stellar positions. For six of the stars, the stellar and maser positions differ by less than 0.35 arcsec. For VY CMa, the optical position is displaced by 1.1 arcsec from the maser. 47 refs.

  14. Enantioselective Nucleophile-Catalyzed Synthesis of Tertiary Alkyl Fluorides via the ?-Fluorination of Ketenes: Synthetic and Mechanistic Studies

    E-print Network

    Lee, Sarah Yunmi

    The catalytic asymmetric synthesis of alkyl fluorides, particularly ?-fluorocarbonyl compounds, has been the focus of substantial effort in recent years. While significant progress has been described in the formation of ...

  15. Asymmetric Catalytic Cascade Reactions for Constructing Diverse Scaffolds and Complex Molecules.

    PubMed

    Wang, Yao; Lu, Hong; Xu, Peng-Fei

    2015-07-21

    With the increasing concerns about chemical pollution and sustainability of resources, among the significant challenges facing synthetic chemists are the development and application of elegant and efficient methods that enable the concise synthesis of natural products, drugs, and related compounds in a step-, atom- and redox-economic manner. One of the most effective ways to reach this goal is to implement reaction cascades that allow multiple bond-forming events to occur in a single vessel. This Account documents our progress on the rational design and strategic application of asymmetric catalytic cascade reactions in constructing diverse scaffolds and synthesizing complex chiral molecules. Our research is aimed at developing robust cascade reactions for the systematic synthesis of a range of interesting molecules that contain structural motifs prevalent in natural products, pharmaceuticals, and biological probes. The strategies employed to achieve this goal can be classified into three categories: bifunctional base/Brønsted acid catalysis, covalent aminocatalysis/N-heterocyclic carbene catalysis, and asymmetric organocatalytic relay cascades. By the use of rationally designed substrates with properly reactive sites, chiral oxindole, chroman, tetrahydroquinoline, tetrahydrothiophene, and cyclohexane scaffolds were successfully assembled under bifunctional base/Brønsted acid catalysis from simple and readily available substances such as imines and nitroolefins. We found that some of these reactions are highly efficient since catalyst loadings as low as 1 mol % can promote the multistep sequences affording complex architectures with high stereoselectivities and yields. Furthermore, one of the bifunctional base/Brønsted acid-catalyzed cascade reactions for the synthesis of chiral cyclohexanes has been used as a key step in the construction of the tetracyclic core of lycorine-type alkaloids and the formal synthesis of ?-lycorane. Guided by the principles of covalent aminocatalysis and N-heterocyclic carbene catalysis, we synthesized chiral piperidine, indole, and cyclobutane derivatives. The synthesis of chiral cyclobutanes and pyrroloindolones showed unprecedented reactivity of substrates and catalysts. The development of the strategy of asymmetric organocatalytic relay cascades has provided a useful tool for the controlled synthesis of specific diastereomers in complex molecules. This Account gives a panoramic view and the logic of our research on the design, development, and applications of asymmetric catalytic cascade reactions that will potentially provide useful insights into exploring new reactions. PMID:26099943

  16. Nonblocking operation of asymmetrical Clos networks

    SciTech Connect

    Liotopoulos, F.K.; Chalasani, S. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-31

    In this paper, we study the nonblocking operation of asymmetrical three-stage Clos networks. We consider a control algorithm for operating the asymmetrical Clos networks in the nonblocking mode. We derive sufficient conditions under which these networks are nonblocking for this control algorithm. Further, we provide results on the number of faults tolerated by the algorithm in the nonblocking mode of operation. We next design a different control algorithm for nonblocking operation of asymmetrical Clos networks. Using simulation results, the new control algorithm is shown to perform better than the previous one in terms of network utilization, blocking probability and fault-tolerance.

  17. Absolute Proper Motions of Southern Globular Clusters

    NASA Astrophysics Data System (ADS)

    Dinescu, D. I.; Girard, T. M.; van Altena, W. F.

    1996-05-01

    Our program involves the determination of absolute proper motions with respect to galaxies for a sample of globular clusters situated in the southern sky. The plates cover a 6(deg) x 6(deg) area and are taken with the 51-cm double astrograph at Cesco Observatory in El Leoncito, Argentina. We have developed special methods to deal with the modelling error of the plate transformation and we correct for magnitude equation using the cluster stars. This careful astrometric treatment leads to accuracies of from 0.5 to 1.0 mas/yr for the absolute proper motion of each cluster, depending primarily on the number of measurable cluster stars which in turn is related to the cluster's distance. Space velocities are then derived which, in association with metallicities, provide key information for the formation scenario of the Galaxy, i.e. accretion and/or dissipational collapse. Here we present results for NGC 1851, NGC 6752, NGC 6584, NGC 6362 and NGC 288.

  18. Absolute specular reflectance measurements in the infrared

    NASA Astrophysics Data System (ADS)

    Snail, Keith A.; Morrish, Arthur A.; Hanssen, Leonard

    1987-02-01

    The absolute reflectance of specular surfaces can be measured with a 'V-W' optical system invented by Strong. The most difficult systematic error to eliminate in a V-W measurement is drift of the beam spot on the detector surface with small angular shifts of the beam between the sample-in (W) and sample-out (V) positions. In the infrared, this problem is exacerbated by the nonuniformity and small size of available detectors. Previous researchers have minimized this error with integrating spheres (in the visible) and/or auxiliary optics which desensitize the system to sample tilt errors. In order to verify this sensitivity to beam drift, a set of angular response measurements were performed on a commercial, variable angle V-W accessory and then modeled with a CODE V raytrace. The absolute accuracy of the instrument was estimated by measuring the specular reflectance of silver from 2-20 microns and comparing it to a Hagens-Rubens model. Finally, a nonimaging concentrator and a gold integrating sphere are considered as ways to increase the effective area of the detector and thus further desensitize the optics to misalignment errors.

  19. Absolute configuration of 7-epi-sesquithujene.

    PubMed

    Khrimian, Ashot; Cossé, Allard A; Crook, Damon J

    2011-06-24

    7-epi-sesquithujene (1) is a bicyclic sesquiterpene isolated from phoebe oil, an essential oil of the Brazilian walnut tree, Phoebe porosa. It is also produced by stressed ash trees and has been shown to elicit strong electrophysiological responses on emerald ash borer, Agrilus planipennis, antennae. In the course of the development of a synthetic 7-epi-sesquithujene lure for field testing against the emerald ash borer, we found that the absolute configuration of this compound had not been determined. We isolated >95% pure 7-epi-sesquithujene from phoebe oil via successive fractionation and conventional and argentation (HPLC) chromatographies. The specific optical rotation of this compound matched that of a synthetic product of known configuration. We also synthesized two other stereoisomers of sesquithujene and developed a chiral GC method to separate all four. Based on the specific rotation, stereoselective syntheses, and chiral GC analyses, 7-epi-sesquithujene present in phoebe oil and white ash was found to have the 2S,6S,7R absolute configuration. PMID:21574561

  20. Swarm's Absolute Scalar Magnetometers Burst Mode Results

    NASA Astrophysics Data System (ADS)

    Coisson, P.; Vigneron, P.; Hulot, G.; Crespo Grau, R.; Brocco, L.; Lalanne, X.; Sirol, O.; Leger, J. M.; Jager, T.; Bertrand, F.; Boness, A.; Fratter, I.

    2014-12-01

    Each of the three Swarm satellites embarks an Absolute Scalar Magnetometer (ASM) to provide absolute scalar measurements of the magnetic field with high accuracy and stability. Nominal data acquisition of these ASMs is 1 Hz. But they can also run in a so-called "burst mode" and provide data at 250 Hz. During the commissioning phase of the mission, seven burst mode acquisition campaigns have been run simultaneously for all satellites, obtaining a total of ten days of burs-mode data. These campaigns allowed the identification of issues related to the operations of the piezo-electric motor and the heaters connected to the ASM, that do not impact the nominal 1 Hz scalar data. We analyze the burst mode data to identify high frequency geomagnetic signals, focusing the analysis in two regions: the low latitudes, where we seek signatures of ionospheric irregularities, and the high latitudes, to identify high frequency signals related to polar region currents. Since these campaigns have been conducted during the initial months of the mission, the three satellites where still close to each other, allowing to analyze the spatial coherency of the signals. Wavelet analysis have revealed 31 Hz signals appearing in the night-side in the equatorial region.

  1. Catalytic Asymmetric Construction of Vicinal Tetrasubstituted Stereocenters by the Mannich Reaction of Linear ?-Substituted Monothiomalonates with Isatin N-Boc Ketimines.

    PubMed

    Liu, Teng; Liu, Weiwei; Li, Xiaonian; Peng, Fangzhi; Shao, Zhihui

    2015-05-15

    A highly diastereo- and enantioselective method for the construction of vicinal tetrasubstituted stereocenters through the first catalytic asymmetric Mannich reaction of linear ?-substituted MTMs with isatin N-Boc ketimines has been developed. This protocol provides atom-economic synthesis of less accessible 3-aminooxindoles bearing vicinal tetrasubstituted stereocenters. Notably, it also constitutes the first example of stereoselective synthesis of ?-amino thioesters bearing vicinal tetrasubstituted stereocenters. PMID:25897636

  2. Total synthesis of sedum alkaloids via catalyst controlled aza-Cope rearrangement and hydroformylation with formaldehyde.

    PubMed

    Ren, Hong; Wulff, William D

    2013-01-18

    The catalytic asymmetric aminoallylation of chiral aldehydes is developed as a new method for the catalyst controlled synthesis of syn- and anti-1,3-aminoalcohols. This methodology is highlighted in the synthesis of the sedum alkaloids (+)-sedridine and (+)-allosedridine both of which have their final carbon incorporated during closure of the piperidine ring via a hydroformylation with formaldehyde. PMID:23259754

  3. Total Synthesis of Sedum Alkaloids via Catalyst Controlled aza-Cope Rearrangement and Hydroformylation with Formaldehyde

    PubMed Central

    Ren, Hong; Wulff, William D.

    2013-01-01

    The catalytic asymmetric aminoallylation of chiral aldehydes is developed as a new method for the catalyst controlled synthesis of syn- and anti-1,3-aminoalcohols. This methodology is highlighted in the synthesis of the sedum alkaloids (+)-sedridine and (+)-allosedridine both of which have their final carbon incorporated during closure of the piperidine ring via a hydroformylation with formaldehyde. PMID:23259754

  4. Use of Absolute and Comparative Performance Feedback in Absolute and Comparative Judgments and Decisions

    ERIC Educational Resources Information Center

    Moore, Don A.; Klein, William M. P.

    2008-01-01

    Which matters more--beliefs about absolute ability or ability relative to others? This study set out to compare the effects of such beliefs on satisfaction with performance, self-evaluations, and bets on future performance. In Experiment 1, undergraduate participants were told they had answered 20% correct, 80% correct, or were not given their…

  5. Total Synthesis of the Opioid Agonistic Indole Alkaloid, Mitragynine, as well as the First Total Synthesis of 9-Methoxygeissoschizol and 9-Methoxy-Nb-methylgeissoschizol

    PubMed Central

    Ma, Jun; Yin, Wenyuan; Zhou, Hao; Cook, James M.

    2008-01-01

    An enantiospecific method for the synthesis of 4-methoxytryptophan has been developed via a regiospecific Larock heteroannulation and employed for the first total synthesis of 9-methoxygeissoschizol, and 9-methoxy-Nb–methylgeissoschizol as well as the total synthesis of the opioid agonistic alkaloid, mitragynine. The asymmetric Pictet-Spengler reaction and a Ni(COD)2 mediated cyclization served as key steps. PMID:17685530

  6. Asymmetric wave propagation in planar chiral fibers

    E-print Network

    Shemuly, Dana

    We demonstrate the realization of a two-dimensional chiral optical waveguide with an infinite translational symmetry that exhibits asymmetric wave propagation. The low-symmetry geometry of the cross-section that lacks any ...

  7. Aqueous asymmetric cyclopropanation reactions in polymersome membranes.

    PubMed

    van Oers, Matthijs C M; Abdelmohsen, Loai K E A; Rutjes, Floris P J T; van Hest, Jan C M

    2014-04-21

    Copper-bis(oxazoline) complexes have been immobilised in the hydrophobic domain of a polymersome membrane to perform asymmetric cyclopropanation reactions in aqueous media with enhanced conversions and enantioselectivities. PMID:24457619

  8. Asymmetric Abelian Avalanches and Sandpiles Andrei Gabrielov

    E-print Network

    Gabrielov, Andrei

    Asymmetric Abelian Avalanches and Sandpiles Andrei Gabrielov Mathematical Sciences Institute consider two classes of threshold failure models, Abel- ian avalanches and sandpiles, with the redistribution matrices satisfying nat- ural conditions guaranteeing absence of infinite avalanches. We

  9. Symmetric and asymmetric hybridization in citrus spp.

    E-print Network

    Bona, Claudine M.

    2009-05-15

    it difficult to create large segregating populations for selection. Somatic hybridization by protoplast fusion circumvents sexual incompatibilities and is a powerful tool in genetic improvement. Symmetric and asymmetric hybdridization (gamma irradiation plus...

  10. Membrane-mimetic films of asymmetric phosphatidylcholine lipid bolaamphiphiles.

    PubMed

    Sun, Xue-Long; Biswas, Nilanjana; Kai, Toshitsugu; Dai, Zhifei; Dluhy, Richard A; Chaikof, Elliot L

    2006-01-31

    Membrane-spanning phospholipid bolaamphiphiles either alone or as a constituent of a multicomponent lipid membrane may prove to be facile building blocks for generating robust bioactive membrane-mimetic assemblies. We have previously reported the synthesis of asymmetric dialkyl phospholipid bolaamphiphiles that contain ester linked phosphatidylcholine and amine functionalities at opposite chain ends. In this report, we describe the synthesis of phospholipid bolaamphiphiles that are conjugated to biotin via the terminal amine with or without a poly(ethylene oxide) spacer arm of varying chain length. The behavior of biotinylated bolaamphiphiles as a self-assembled monolayer at an air-water interface was characterized by epi-fluorescence microscopy and revealed that domain structure and pi-A isotherms were substantially influenced by linker type and size. Substrate bound assemblies were produced by Langmuir-Blodgett deposition onto planar substrates coated with an avidin derivatized polyelectrolyte multilayer. Significantly, external reflectance infrared spectroscopy confirmed the fabrication of bolaamphiphile thin films that display extended stability in vitro. PMID:16430284

  11. The synthesis of a single enantiomer of a major ?-mycolic acid of M. tuberculosis

    Microsoft Academic Search

    Juma'a R. Al Dulayymi; Mark S. Baird; Evan Roberts

    2005-01-01

    We report a synthesis of a single enantiomer of a mycolic acid from Mycobacterium tuberculosis containing a di-cis-cyclopropane. The method can be simply varied to modify the chain lengths or the absolute stereochemistry of either cyclopropane.

  12. On the Construction of Asymmetric Quantum Codes

    NASA Astrophysics Data System (ADS)

    La Guardia, Giuliano G.

    2014-07-01

    Several families of good nonbinary asymmetric quantum codes are constructed in this paper. These new quantum codes are derived from the Calderbank-Shor-Steane (CSS) construction as well as the Hermitian construction applied respectively to two classical nested Bose-Chaudhuri-Hocquenghem (BCH) codes where one of them are additionally Euclidean (Hermitian) dual-containing. The asymmetric codes constructed here have parameters better than the ones available in the literature.

  13. Stem Cells and Asymmetric Cell Division

    Microsoft Academic Search

    Frank Hirth

    \\u000a Asymmetric stem cell division is a fundamental process used to generate cellular diversity and to provide a source of new\\u000a cells in developing and adult organisms. Asymmetric stem cell division leads to another stem cell via self-renewal, and a\\u000a second cell type which can be either a differentiating progenitor or a postmitotic cell. Experimental studies in model organisms\\u000a including the

  14. Modeling Asymmetric Rolling Process of Mg alloys

    SciTech Connect

    Cho, Jaehyung; Kim, Hyung-Wuk; Kang, Suk-Bong [Korea Institute of Materials Science, 66 Sangnam-dong, Changwon-city, Kyungnam, 641-010 (Korea, Republic of)

    2010-06-15

    Asymmetric deformation during rolling can arise in various ways: difference in the radii, speeds, frictions of the top and bottom rolls. Asymmetric warm rolling processes of magnesium alloys were modeled using a lagrangian incremental approach. A constitutive equation representing flow behaviors of AZ31 magnesium alloys during warm deformation was implemented to the modeling. Various roll speed ratios were introduced to investigate deformation behaviors of the magnesium alloys. Bending and texturing of the strips were examined.

  15. Asymmetric autocatalysis induced by meteoritic amino acids with hydrogen isotope chirality† †This article is part of a ChemComm ‘Catalysis in Organic Synthesis’ web-theme issue showcasing high quality research in organic chemistry. Please see our website (http://www.rsc.org/chemcomm/organicwebtheme2009) to access the other papers in this issue. ‡ ‡Electronic supplementary information (ESI) available: Procedures for the asymmetric autocatalysis in the presence of 1 and 2, the preparation of enantiomers of 1 and 2, and the determination of the enantiomeric purity of 1 and 2. See DOI: 10.1039/b908754k Click here for additional data file.

    PubMed Central

    Kawasaki, Tsuneomi; Shimizu, Masako; Nishiyama, Daisuke; Ito, Masateru; Ozawa, Hitomi

    2009-01-01

    Achiral meteoritic amino acids, glycine and ?-methylalanine, with hydrogen isotope (D/H) chirality, acted as the source of chirality in asymmetric autocatalysis with amplification of ee to afford highly enantioenriched 5-pyrimidyl alkanols. PMID:19597604

  16. Base Flow Asymmetry Effects on the Absolute Stability of Non-uniform Density Wakes

    NASA Astrophysics Data System (ADS)

    Emerson, Benjamin; Noble, David; Lieuwen, Tim

    2013-11-01

    This work investigates the hydrodynamic stability of bluff body wakes with non-uniform mean density. Such flows are common in bluff body combustors. The absolute/convective stability characteristics of the wake are important, because vortex shedding from the bluff body participates in such processes as mixing, flame blowoff, and combustion instability. Non-uniform density is a sensitive stability parameter for wake flows. Reduction of the wake density relative to the free stream density can stabilize the flow and suppress coherent vortex shedding. Practical bluff body combustors operate at a range of flame density ratios spanning this stability limit. Recent experimental bluff body combustor work by Tuttle et al. investigates wakes with asymmetry in the base flow density profiles. This motivates a hydrodynamic stability model for non-uniform density wakes that includes base flow asymmetry. The model developed in this study investigates the effects of asymmetric base flow velocity and density profiles. It begins with a parameterization of the base flow asymmetries. Results show that base flow asymmetry influences the absolute stability of the flow, and has a strong effect on the most amplified mode shape. The investigation concludes with a comparison to the vorticity equation. Here, we elucidate the physics of the model, and comment on the limitations of such a model.

  17. Experiments for the absolute neutrino mass measurement

    E-print Network

    Markus Steidl

    2009-06-02

    Experimental results and perspectives of different methods to measure the absolute mass scale of neutrinos are briefly reviewed. The mass sensitivities from cosmological observations, double beta decay searches and single beta decay spectroscopy differ in sensitivity and model dependance. Next generation experiments in the three fields reach the sensitivity for the lightest mass eigenstate of $m_1<0.2eV$, which will finally answer the question if neutrino mass eigenstates are degenerate. This sensitivity is also reached by the only model-independent approach of single beta decay (KATRIN experiment). For higher sensitivities on cost of model-dependance the neutrinoless double beta decay search and cosmological observation have to be applied. Here, in the next decade sensitivities are approached with the potential to test inverted hierarchy models.

  18. Swarm's Absolute Scalar Magnetometer metrological performances

    NASA Astrophysics Data System (ADS)

    Leger, J.; Fratter, I.; Bertrand, F.; Jager, T.; Morales, S.

    2012-12-01

    The Absolute Scalar Magnetometer (ASM) has been developed for the ESA Earth Observation Swarm mission, planned for launch in November 2012. As its Overhauser magnetometers forerunners flown on Oersted and Champ satellites, it will deliver high resolution scalar measurements for the in-flight calibration of the Vector Field Magnetometer manufactured by the Danish Technical University. Latest results of the ground tests carried out to fully characterize all parameters that may affect its accuracy, both at instrument and satellite level, will be presented. In addition to its baseline function, the ASM can be operated either at a much higher sampling rate (burst mode at 250 Hz) or in a dual mode where it also delivers vector field measurements as a by-product. The calibration procedure and the relevant vector performances will be discussed.

  19. Absolute radiometric calibration of the Thematic Mapper

    NASA Technical Reports Server (NTRS)

    Slater, P. N.; Biggar, S. F.; Holm, R. G.; Jackson, R. D.; Mao, Y.

    1986-01-01

    Calibration data for the solar reflective bands of the Landsat-5 TM obtained from five in-flight absolute radiometric calibrations from July 1984-November 1985 at White Sands, New Mexico are presented and analyzed. Ground reflectance and atmospheric data were utilized to predict the spectral radiance at the entrance pupil of the TM and the average number of digital counts in each TM band. The calibration of each of the TM solar reflective bands was calculated in terms of average digital counts/unit spectral radiance for each band. It is observed that for the 12 reflectance-based measurements the rms variation from the means as a percentage of the mean is + or - 1.9 percent; for the 11 measurements in the IR bands, it is + or - 3.4 percent; and the rms variation for all 23 measurements is + or - 2.8 percent.

  20. Absolutely Maximally Entangled Qudit Graph States

    E-print Network

    Wolfram Helwig

    2013-06-12

    Absolutely maximally entangled (AME) states are multipartite entangled states that are maximally entangled for any possible bipartition. In this paper, we study the description of AME states within the graph state formalism. The graphical representation provides an intuitive framework to visualize the entanglement in graph states, which makes them a natural candidate to describe AME states. We show two different methods of determining bipartite entanglement in graph states and use them to define various AME graph states. We further show that AME graph states exist for all number of parties, and that any AME graph states shared between an even number of parties can be used to describe quantum secret sharing schemes with a threshold or ramp access structure directly within the graph states formalism.

  1. Absolute image registration for geosynchronous satellites

    NASA Technical Reports Server (NTRS)

    Nankervis, R.; Koch, D.; Sielski, H.; Hall, D.

    1980-01-01

    A procedure for the absolute registration of earth images acquired by cameras on geosynchronous satellites is described. A conventional least squares process is used to estimate navigational parameters and camera pointing biases from observed minus computed landmark line and element numbers. These estimated parameters along with orbit and attitude dynamic models are used to register images, employing an automated grey-level correlation technique, inside the span represented by the landmark data. Experimental results obtained from processing the SMS-2 observation data base covering May 2, 1979 through May 20, 1979 show registration accuracies with a standard deviation of less than two pixels if the registration is within the landmark data span. It is also found that accurate registration can be expected for images obtained up to 48 hours outside of the landmark data span.

  2. Pd-catalyzed asymmetric allylic alkylation of pyrazol-5-ones with allylic alcohols: the role of the chiral phosphoric acid in C-O bond cleavage and stereocontrol.

    PubMed

    Tao, Zhong-Lin; Zhang, Wen-Quan; Chen, Dian-Feng; Adele, Arafate; Gong, Liu-Zhu

    2013-06-26

    The combination of a palladium complex with a chiral phosphoramidite ligand and a chiral phosphoric acid enables the first highly efficient asymmetric allylic alkylation of pyrazol-5-ones with allylic alcohols, affording multiply functionalized heterocyclic products in high yields with excellent enantioselectivities that would be of great potential in the synthesis of pharmaceutically interesting molecules. PMID:23734612

  3. Antifungal activity of tuberose absolute and some of its constituents.

    PubMed

    Nidiry, Eugene Sebastian J; Babu, C S Bujji

    2005-05-01

    The antifungal activity of the absolute of tuberose (Polianthes tuberosa ) and some of its constituents were evaluated against the mycelial growth of Colletotrichum gloeosporioides on potato-dextrose-agar medium. Tuberose absolute showed only mild activity at a concentration of 500 mg/L. However, three constituents present in the absolute, namely geraniol, indole and methyl anthranilate exhibited significant activity showing total inhibition of the mycelial growth at this concentration. PMID:16106389

  4. Absolute nuclear material assay using count distribution (LAMBDA) space

    SciTech Connect

    Prasad, Manoj K. (Pleasanton, CA); Snyderman, Neal J. (Berkeley, CA); Rowland, Mark S. (Alamo, CA)

    2012-06-05

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  5. Absolute luminosity measurements with the LHCb detector at the LHC

    Microsoft Academic Search

    R. Aaij; B. Adeva; M. Adinolfi; C. Adrover; A. Affolder; Z. Ajaltouni; J. Albrecht; F. Alessio; M. Alexander; G. Alkhazov; P. Alvarez Cartelle; A. A. Alves Jr; S. Amato; Y. Amhis; J. Anderson; R. B. Appleby; O. Aquines Gutierrez; F. Archilli; L. Arrabito; A. Artamonov; M. Artuso; E. Aslanides; G. Auriemma; S. Bachmann; J. J. Back; D. S. Bailey; V. Balagura; W. Baldini; R. J. Barlow; C. Barschel; S. Barsuk; W. Barter; A. Bates; C. Bauer; Th. Bauer; A. Bay; I. Bediaga; K. Belous; I. Belyaev; E. Ben-Haim; M. Benayoun; G. Bencivenni; S. Benson; J. Benton; R. Bernet; M van Beuzekom; A. Bien; S. Bifani; A. Bizzeti; P. M. Bjørnstad; T. Blake; F. Blanc; C. Blanks; J. Blouw; S. Blusk; A. Bobrov; V. Bocci; A. Bondar; N. Bondar; W. Bonivento; S. Borghi; A. Borgia; T. J. V. Bowcock; C. Bozzi; T. Brambach; J. van den Brand; J. Bressieux; D. Brett; S. Brisbane; M. Britsch; T. Britton; N. H. Brook; H. Brown; A. Büchler-Germann; I. Burducea; A. Bursche; J. Buytaert; S. Cadeddu; J. M. Caicedo Carvajal; O. Callot; M. Calvi; M. Calvo Gomez; A. Camboni; P. Campana; A. Carbone; G. Carboni; R. Cardinale; A. Cardini; L. Carson; K. Carvalho Akiba; G. Casse; M. Cattaneo; M. Charles; Ph. Charpentier; N. Chiapolini; K. Ciba; X. Cid Vidal; G. Ciezarek; P. E. L. Clarke; M. Clemencic; H. V. Cliff; J. Closier; C. Coca; V. Coco; J. Cogan; P. Collins; F. Constantin; G. Conti; A. Contu; A. Cook; M. Coombes; G A Cowan; R. Currie; B. D'Almagne; C. D'Ambrosio; P. David; I. De Bonis; S. De Capua; M. De Cian; F. De Lorenzi; J. M. De Miranda; L. De Paula; P. De Simone; D. Decamp; M. Deckenhoff; H. Degaudenzi; M. Deissenroth; L. Del Buono; C. Deplano; O. Deschamps; F. Dettori; J. Dickens; H. Dijkstra; P. Diniz Batista; S. Donleavy; F. Dordei; A. Dosil Suárez; D. Dossett; A. Dovbnya; F. Dupertuis; R. Dzhelyadin; C. Eames; S. Easo; U. Egede; V. Egorychev; S. Eidelman; D. van Eijk; F. Eisele; S. Eisenhardt; R. Ekelhof; L. Eklund; Ch. Elsasser; D. G. d'Enterria; D. Esperante Pereira; L. Estève; A. Falabella; E. Fanchini; C. Färber; G. Fardell; C. Farinelli; S. Farry; V. Fave; V. Fernandez Albor; M. Ferro-Luzzi; S. Filippov; C. Fitzpatrick; M. Fontana; F. Fontanelli; R. Forty; M. Frank; C. Frei; M. Frosini; S. Furcas; A. Gallas Torreira; D. Galli; M. Gandelman; P. Gandini; Y. Gao; J. C. Garnier; J. Garofoli; J. Garra Tico; L. Garrido; C. Gaspar; N. Gauvin; M. Gersabeck; T. Gershon; Ph. Ghez; V V Gligorov; C. Göbel; D. Golubkov; A. Golutvin; A. Gomes; H. Gordon; M. Grabalosa Gándara; R. Graciani Diaz; L. A. Granado Cardoso; E. Graugés; G. Graziani; A. Grecu; S. Gregson; B. Gui; E. Gushchin; Yu. Guz; T. Gys; G. Haefeli; C. Haen; S. C. Haines; T. Hampson; S. Hansmann-Menzemer; R. Harji; N. Harnew; J. Harrison; P. F. Harrison; J. He; V. Heijne; K. Hennessy; P. Henrard; J. A. Hernando Morata; E. van Herwijnen; E. Hicks; W. Hofmann; K. Holubyev; P. Hopchev; W. Hulsbergen; P. Hunt; T. Huse; R. S. Huston; D. Hutchcroft; D. Hynds; V. Iakovenko; P. Ilten; J. Imong; R. Jacobsson; A. Jaeger; M. Jahjah Hussein; E. Jans; F. Jansen; P. Jaton; B. Jean-Marie; F. Jing; M. John; D. Johnson; C. R. Jones; B. Jost; S. Kandybei; M. Karacson; T. M. Karbach; J. Keaveney; U. Kerzel; T. Ketel; A. Keune; B. Khanji; Y. M. Kim; M. Knecht; S. Koblitz; P. Koppenburg; A. Kozlinskiy; L. Kravchuk; K. Kreplin; M. Kreps; G. Krocker; P. Krokovny; F. Kruse; K. Kruzelecki; M. Kucharczyk; S. Kukulak; R. Kumar; T. Kvaratskheliya; V. N. La Thi; D. Lacarrere; G. Lafferty; A. Lai; D. Lambert; R. W. Lambert; E. Lanciotti; G. Lanfranchi; C. Langenbruch; T. Latham; R. Le Gac; J. van Leerdam; J.-P. Lees; R. Lefèvre; A. Leflat; J. Lefrançois; O. Leroy; T. Lesiak; L. Li; L. Li Gioi; M. Lieng; M. Liles; R. Lindner; C. Linn; B. Liu; G. Liu; J. H. Lopes; E. Lopez Asamar; N. Lopez-March; J. Luisier; F. Machefert; I. V. Machikhiliyan; F. Maciuc; O. Maev; J. Magnin; S. Malde; R. M. D. Mamunur; G Mancinelli; N. Mangiafave; U. Marconi; R. Märki; J. Marks; G. Martellotti; A. Martens; L. Martin; A. Martín Sánchez; D. Martinez Santos; A. Massafferri; R. Matev; Z. Mathe; C. Matteuzzi; M. Matveev; E. Maurice; B. Maynard; A. Mazurov; G. McGregor; R. McNulty; C. Mclean; M. Meissner; M. Merk; J. Merkel; R. Messi; S. Miglioranzi; D. A. Milanes; M.-N. Minard; S. Monteil; D. Moran; P. Morawski; I. Mous; F. Muheim; K. Müller; R. Muresan; B. Muryn; M. Musy; J. Mylroie-Smith; P. Naik; T. Nakada; R. Nandakumar; J. Nardulli; I. Nasteva; M Needham; N. Neufeld; C. Nguyen-Mau; M. Nicol; S. Nies; V. Niess; N. Nikitin; A. Oblakowska-Mucha; V. Obraztsov; S. Oggero; S. Ogilvy; O. Okhrimenko; R. Oldeman; M. Orlandea; J. M. Otalora Goicochea; P. Owen; B. Pal; J. Palacios; M. Palutan; J. Panman; A. Papanestis; M. Pappagallo; C J Parkinson; G. Passaleva; G. D. Patel; M. Patel; S. K. Paterson; G. N. Patrick; C Pavel-Nicorescu; A. Pazos Alvarez; A. Pellegrino; G. Penso

    2011-01-01

    Absolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of

  6. Advanced Optical Terrain Absolute Navigation for Pinpoint Lunar Landing

    Microsoft Academic Search

    Marco Mammarella; Marcos Avilés Rodrigálvarez; Andrea Pizzichini; Ana María Sánchez Montero

    \\u000a Pin-point landing can only be achieved developing precise Absolute Navigation systems. Craters, for their intrinsic properties,\\u000a are one of the most suitable and robust features identifiable in lunar landscape. The Optical Terrain Absolute Navigation\\u000a (OTAN) system provides absolute navigation features and is composed by two main parts: the off-line part, focused on the extraction\\u000a of the Landmark Database; the on-line

  7. Reconciling late Neogene Pacific absolute and relative plate motion changes

    Microsoft Academic Search

    Paul Wessel; Loren W. Kroenke

    2007-01-01

    New models of Pacific absolute plate motion relative to hot spots and models of relative plate motion involving the Pacific plate all agree there was a significant change in the late Neogene (Chron 3A, ?5.89 Ma), reflecting a more northerly absolute motion than previously determined. As Pacific absolute plate motion became slightly more northerly, left-stepping transform segments came under compression.

  8. Transition-Metal Catalyzed Synthesis of Aspergillide B: An Alkyne Addition Strategy

    PubMed Central

    Bartlett, Mark J.

    2012-01-01

    A catalytic enantioselective formal total synthesis of aspergillide B is reported. This linchpin synthesis was enabled by the development of new conditions for Zn-ProPhenol catalyzed asymmetric alkyne addition. This reaction was used in conjunction with ruthenium-catalyzed trans-hydrosilylation to affect the rapid construction of a late-stage synthetic intermediate of aspergillide B to complete a formal synthesis of aspergillide B in a highly efficient manner. PMID:22356535

  9. Asymmetric Epoxide Cyclisation Route to the F-pyran Fragment of the Altohyrtins and Key Aldol Studies

    Microsoft Academic Search

    James C. Anderson; Benjamin P. McDermott; Edward J. Griffin

    2000-01-01

    The evolution of an asymmetric synthesis of a differentially protected F-pyran ring of the altohyrtins is described, which relies on a key intramolecular cyclisation of a C43 hydroxyl group onto a C38–C39 epoxide. The C38–C39 epoxide stereochemistry was achieved through optimisation of substrate control. Key aldol studies towards coupling the F-pyran ring with an E-pyran ring precursor was investigated, but

  10. Asymmetric hydrogenation of alpha-chloro aromatic ketones catalyzed by eta6-arene/TsDPEN-ruthenium(II) complexes.

    PubMed

    Ohkuma, Takeshi; Tsutsumi, Kunihiko; Utsumi, Noriyuki; Arai, Noriyoshi; Noyori, Ryoji; Murata, Kunihiko

    2007-01-18

    Asymmetric hydrogenation of various alpha-chloro aromatic ketones with Ru(OTf)(TsDPEN)(eta6-arene) (TsDPEN = N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine) produces the chiral chlorohydrins in up to 98% ee. This reaction can be conducted even on a 206-g scale. The hydrogenation of an alpha-chloro ketone with a phenol moiety has been utilized for the synthesis of (R)-norphenylephrine without protection-deprotection operations. [reaction: see text]. PMID:17217278

  11. The asymmetric gait toenail unit sign.

    PubMed

    Zaias, Nardo; Rebell, Gerbert; Casal, German; Appel, Jason

    2012-01-01

    The aim of this investigation was to resolve a diagnostic problem and report toenail unit changes attributable to shoe friction that resemble onychomycosis, but that are fungus-negative, and identify common skeletal causes in patients with an asymmetric walking gait. X-ray and clinical feet inspections were performed to evaluate skeletal components that change normal foot biodynamics. Forty-nine patients, all dermatophyte-negative, were reviewed. All patients were those seen in our private practice who demonstrated skeletal and toenail unit abnormalities such as onycholysis, nail bed keratosis resembling distal subungual onychomycosis, nail plate surface abnormalities, distal toe skin keratosis, a diagnostic nail plate shape, as well as several skeletal abnormalities. The clinical abnormalities of the asymmetric gait syndrome include onycholysis, nail bed keratosis, nail plate surface abnormalities, and a diagnostic nail plate shape. By the patient's history, the skeletal findings that were present worsened with age and, in many patients, they were familial. Onychomycosis does not lead to an asymmetric gait nail problem, asymmetric gait toenail does not favor dermatophyte infection, and not all nail dystrophies are the result of an asymmetric walking gait. PMID:23008938

  12. Total synthesis of heronapyrrole C.

    PubMed

    Ding, Xiao-Bo; Furkert, Daniel P; Capon, Robert J; Brimble, Margaret A

    2014-01-17

    A flexible total synthesis of the 2-nitropyrrole-derived marine natural product, (+)-heronapyrrole C, is reported. The approach is based on regioselective access to key building blocks containing the rare 4-substituted 2-nitropyrrole motif. Sharpless asymmetric epoxidation and dihydroxylation and a Shi epoxidation were used to introduce the five stereogenic centers of the bis-THF-diol side chain. The N-benzoyloxymethyl (Boz) protecting group was crucial for functionalization of the 2-nitropyrrole moiety and enabling final deprotection under mild conditions. PMID:24351092

  13. Stereoselective synthesis of unsaturated ?-amino acids.

    PubMed

    Fanelli, Roberto; Jeanne-Julien, Louis; René, Adeline; Martinez, Jean; Cavelier, Florine

    2015-06-01

    Stereoselective synthesis of unsaturated ?-amino acids was performed by asymmetric alkylation. Two methods were investigated and their enantiomeric excess measured and compared. The first route consisted of an enantioselective approach induced by the Corey-Lygo catalyst under chiral phase transfer conditions while the second one involved the hydroxypinanone chiral auxiliary, both implicating Schiff bases as substrate. In all cases, the use of a prochiral Schiff base gave higher enantiomeric excess and yield in the final desired amino acid. PMID:25715756

  14. Synthesis, structure and reactivity of [15]-macrodilactones.

    PubMed

    Si, Debjani; Peczuh, Mark W

    2015-06-21

    A strategy for utilizing parameters such as the ring size, planar units and the connections between them, and the location of asymmetric centers has been applied to the design and synthesis of a new class of 15-membered macrocycles. The interplay between three planar units in combination with a hinge atom and a stereogenic center, introduces a planar chirality that defines the molecular topology of these [15]-macrodilactones. PMID:25994512

  15. Asymmetric Supernovae from Magnetocentrifugal Jets

    NASA Astrophysics Data System (ADS)

    Wheeler, J. Craig; Meier, David L.; Wilson, James R.

    2002-04-01

    Strong toroidal magnetic fields generated in stellar collapse can generate magnetocentrifugal jets in analogy to those found in simulations of black hole accretion. Magnetocentrifugal jets may explain why all core collapse supernovae are found to be substantially asymmetric and predominantly bipolar. We describe two phases: the initial LeBlanc-Wilson jet and a subsequent protopulsar or toroidal jet that propagates at about the core escape velocity. The prompt LeBlanc-Wilson jets will produce an excess of neutron-rich matter and hence cannot be the common origin of supernova explosions; similar but less severe problems arise with the protopulsar jet that may be alleviated by partial evacuation along the axis by rotation. The jets will produce bow shocks that tend to expel matter, including iron and silicon, into equatorial tori. This may help to account for observations of the element distribution in Cas A. A magnetic ``switch'' mechanism may apply in rare instances (when there is low density and large magnetic field), with subsequent increase in the speed and collimation of the toroidal jet. The conditions that turn the magnetic switch ``on'' would yield a jet that propagates rapidly and with small opening angle through the star, depositing relatively little momentum. The result could be enough infall to form a black hole. A third, highly relativistic jet from the rotating black hole could catch up to the protopulsar jet after it has emerged from the star. The interaction of these two jets plausibly could be the origin of the internal shocks thought to produce ?-ray bursts and could explain the presence of iron lines in the afterglow. Recent estimates that typical ?-ray burst energy is ~3×1050 ergs imply either a very low efficiency for conversion of rotation into jets by the Blandford-Znajek mechanism or a rather rapid turnoff of the jet process even though the black hole still rotates rapidly. Magnetars and ``hypernovae'' might arise in an intermediate parameter regime of energetic jets that yield larger magnetic fields and provide more energy than the routine case, but that are not so tightly collimated that they yield failed supernova.

  16. Absolute spacetime: the twentieth century ether

    E-print Network

    Carl H. Brans

    1998-01-09

    All gauge theories need ``something fixed'' even as ``something changes.'' Underlying the implementation of these ideas all major physical theories make indispensable use of an elaborately designed spacetime model as the ``something fixed,'' i.e., absolute. This model must provide at least the following sequence of structures: point set, topological space, smooth manifold, geometric manifold, base for various bundles. The ``fine structure'' of spacetime inherent in this sequence is of course empirically unobservable directly, certainly when quantum mechanics is taken into account. This issue is at the basis of the difficulties in quantizing general relativity and has been approached in many different ways. Here we review an approach taking into account the non-Boolean properties of quantum logic when forming a spacetime model. Finally, we recall how the fundamental gauge of diffeomorphisms (the issue of general covariance vs coordinate conditions) raised deep conceptual problems for Einstein in his early development of general relativity. This is clearly illustrated in the notorious ``hole'' argument. This scenario, which does not seem to be widely known to practicing relativists, is nevertheless still interesting in terms of its impact for fundamental gauge issues.

  17. Redetermination and absolute configuration of berkeleydione

    PubMed Central

    Stierle, Andrea; Stierle, Donald; Decato, Daniel

    2015-01-01

    The crystal structure of the title compound, berkeleydione [systematic name; (5aS,7R,9S,11R,11aS)-methyl 9-hy­droxy-1,1,5,7,9,11a-hexa­methyl-14-methyl­idene-3,8,10-trioxo-1,3,4,5a,6,7,8,9,10,11,11a,12-dodeca­hydro-7,11-methano­cycloocta­[4,5]cyclo­hepta­[1,2-c]pyran-11-carboxyl­ate], C26H32O7, has been reported previously [Stierle et al. (2004 ?). Org. Lett. 6, 1049–1052]. However, the absolute configuration could not be determined from the data collected with Mo K? radiation and has now been determined by refinement of the Flack parameter with data collected using Cu K? radiation. It is in agreement with the previous circular dichroism assignment, and the crystal packing is similar to that described previously.

  18. An absolute clock of the cosmos?

    NASA Astrophysics Data System (ADS)

    Kotov, V. A.; Lyuty, V. M.

    2010-06-01

    In 1968-2005 different observers (mainly, one of the authors—V.M. Lyuty) performed numerous measurements of luminosity of the nucleus of the Seyfert galaxy NGC 4151. It is shown that ( a) luminosity of the object pulsated over 38 years with a period of 160.0106(7) min coinciding, within the error limits, with the well-known period P 0 = 160.0101(2) min of the enigmatic “solar” pulsations, and ( b) when registering oscillations of luminosity of NGC 4151 nucleus with the P 0 period, time moments of observations must be reduced to the earth instead of the sun, i.e., to the reference frame of the observer. The coherent P 0 oscillation is characterized, therefore, by invariability of both frequency and phase with respect to redshift z and the earth’s orbital motion, respectively. From these results it, thus, follows that the coherent P 0 oscillation seems to be of a true cosmological origin. The P 0 period itself might represent a course of the “cosmic clock” related to the existence of an absolute time of the Universe in Newton’s comprehension.

  19. Asymmetric soft-error resistant memory

    NASA Technical Reports Server (NTRS)

    Buehler, Martin G. (inventor); Perlman, Marvin (inventor)

    1991-01-01

    A memory system is provided, of the type that includes an error-correcting circuit that detects and corrects, that more efficiently utilizes the capacity of a memory formed of groups of binary cells whose states can be inadvertently switched by ionizing radiation. Each memory cell has an asymmetric geometry, so that ionizing radiation causes a significantly greater probability of errors in one state than in the opposite state (e.g., an erroneous switch from '1' to '0' is far more likely than a switch from '0' to'1'. An asymmetric error correcting coding circuit can be used with the asymmetric memory cells, which requires fewer bits than an efficient symmetric error correcting code.

  20. Pd and Mo Catalyzed Asymmetric Allylic Alkylation

    PubMed Central

    Trost, Barry M.

    2012-01-01

    The ability to control the alkylation of organic substrates becomes ever more powerful by using metal catalysts. Among the major benefits of metal catalysis is the possibility to perform such processes asymmetrically using only catalytic amounts of the chiral inducing agent which is a ligand to the metal of the catalyst. A unique aspect of asymmetric metal catalyzed processes is the fact that many mechanisms exist for stereoinduction. Furthermore, using the same catalyst system, many types of bonds including but not limited to C-C, C-N, C-O, C-S, C-P, and C-H can be formed asymmetrically. An overview of this process using palladium and molybdenum based metals being developed in my laboratories and how they influence strategy in synthesizing bioactive molecular targets is presented. PMID:22736934

  1. 4-Fluoro and 4-Hydroxy Pyrrolidine-thioxotetrahydropyrimidinones: Organocatalysts for Green Asymmetric Transformations in Brine.

    PubMed

    Kaplaneris, Nikolaos; Koutoulogenis, Giorgos; Raftopoulou, Marianna; Kokotos, Christoforos G

    2015-06-01

    The synthesis of both trans- and cis-diastereomers of pyrrolidinine-thioxotetrahydropyrimidinone bearing either a fluorine or a hydroxyl group was accomplished. The new compounds were tested for their catalytic properties in a variety of asymmetric organic transformations and compared with the first generation catalyst. It was found that the new catalysts could efficiently catalyze the reactions in brine, without the use of organic solvent, and by employing an almost stoichiometric amount of reagents. Thus, the products were isolated by simple extractions, avoiding the use of chromatography in excellent yields, diastereoselectivities, and enantioselectivities. PMID:25942500

  2. Easy To Synthesize, Robust Organo-osmium Asymmetric Transfer Hydrogenation Catalysts.

    PubMed

    Coverdale, James P C; Sanchez-Cano, Carlos; Clarkson, Guy J; Soni, Rina; Wills, Martin; Sadler, Peter J

    2015-05-26

    Asymmetric transfer hydrogenation (ATH) is an important process in organic synthesis for which the Noyori-type Ru(II) catalysts [(arene)Ru(Tsdiamine)] are now well established and widely used. We now demonstrate for the first time the catalytic activity of the osmium analogues. X-ray crystal structures of the 16-electron Os(II) catalysts are almost identical to those of Ru(II) . Intriguingly the precursor complex was isolated as a dichlorido complex with a monodentate amine ligand. The Os(II) catalysts are readily synthesised (within 1?h) and exhibit excellent enantioselectivity in ATH reactions of ketones. PMID:25853228

  3. Acoustical Power of Certain Sound Sources in Absolute Units

    Microsoft Academic Search

    Paul E. Sabine

    1923-01-01

    Acoustical power of certain sound sources in absolute units.-Having determined the threshold intensity (in absolute units) as a function of pitch for a particular observer (by Kranz' thermophone method) and the rate of dissipation of sound in the special sound chamber, the acoustic output of each of various sources in its fundamental or chief overtone, was computed from the observed

  4. Absolute external luminescence quantum efficiency of zinc oxide

    Microsoft Academic Search

    Mario Hauser; Alexander Hepting; Robert Hauschild; Huijuan Zhou; Johannes Fallert; Heinz Kalt; Claus Klingshirn

    2008-01-01

    We report on the measurement of the absolute external luminescence quantum efficiency of various ZnO samples using a miniature integrating sphere fitted into a cryostat. Even the absolute luminescence quantum efficiencies per spectral interval are directly accessible. Measurements have been carried out on high quality bulk samples and different commercially available ZnO powders from 8 K up to room temperature.

  5. New Silyl Ether Reagents for the Absolute Stereochemical Determination

    E-print Network

    Weibel, Douglas B.

    New Silyl Ether Reagents for the Absolute Stereochemical Determination of Secondary Alcohols R set of silyl ether reagents for determining the enantiomeric purity and absolute stereochemistry ether group allows for simple derivitiza- tion6 and convenient recovery of the original chiral compound

  6. Absolute Optical Calibrations Using a Simple Tungsten Bulb: Theory

    Microsoft Academic Search

    O. Harang; M. J. Kosch

    2003-01-01

    The absolute spectral intensity calibration of op- tical detectors has always been difficult. In the past, this was only possible using expensive sources, which had been cross-calibrated against national standards. We describe a simple theoretical approach to absolute optical calibrations using any ordinary Tungsten light bulb. A key element of the theory is transforming Tungsten into an equivalent black body

  7. ABSOLUTELY CONTINUOUS INVARIANT MEASURES AND SUPERSTABLE PERIODIC ORBITS

    E-print Network

    Thunberg, Hans

    ABSOLUTELY CONTINUOUS INVARIANT MEASURES AND SUPER­STABLE PERIODIC ORBITS: WEAK. Introduction This paper will be concerned with absolutely continuous invariant measures (ACIMs) and super­stable 1 can be approximated, in weak* sense, with measures supported on the super­stable periodic orbits

  8. Determination of Absolute Zero Using a Computer-Based Laboratory

    ERIC Educational Resources Information Center

    Amrani, D.

    2007-01-01

    We present a simple computer-based laboratory experiment for evaluating absolute zero in degrees Celsius, which can be performed in college and undergraduate physical sciences laboratory courses. With a computer, absolute zero apparatus can help demonstrators or students to observe the relationship between temperature and pressure and use…

  9. Investigation of the absolute instability of currents in oceanic gyres

    Microsoft Academic Search

    I. I. Karpatovich; G. K. Korotaev

    2004-01-01

    In the approximation of geometric optics, we study the absolute instability of currents in oceanic gyres. It is shown that absolute instability is observed in the case where the most unstable mode of wave motion is stationary. Our results qualitatively agree with the data of numerical experiments aimed at the simulation of the synoptic variability of large-scale oceanic gyres.

  10. Absolute Humidity and the Seasonality of Influenza (Invited)

    NASA Astrophysics Data System (ADS)

    Shaman, J. L.; Pitzer, V.; Viboud, C.; Grenfell, B.; Goldstein, E.; Lipsitch, M.

    2010-12-01

    Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent re-analysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here we show that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions. In addition, we show that variations of the basic and effective reproductive numbers for influenza, caused by seasonal changes in absolute humidity, are consistent with the general timing of pandemic influenza outbreaks observed for 2009 A/H1N1 in temperate regions. Indeed, absolute humidity conditions correctly identify the region of the United States vulnerable to a third, wintertime wave of pandemic influenza. These findings suggest that the timing of pandemic influenza outbreaks is controlled by a combination of absolute humidity conditions, levels of susceptibility and changes in population mixing and contact rates.

  11. Islamic Star Patterns in Absolute Geometry CRAIG S. KAPLAN

    E-print Network

    Washington at Seattle, University of

    Islamic Star Patterns in Absolute Geometry CRAIG S. KAPLAN University of Waterloo and DAVID H on the axioms of absolute geometry for exploring the design space of Islamic star patterns. Our approach makes-Euclidean geometry, symmetry, tessellations, tilings 1. INTRODUCTION The rise and spread of Islamic culture from

  12. Non-Hermitian model for asymmetric tunneling

    NASA Astrophysics Data System (ADS)

    Santos, Roberto B. B.; da Silva, Vinícius R.

    2014-11-01

    We present a simple non-Hermitian model to describe the phenomenon of asymmetric tunneling between two energy-degenerate sites coupled by a non-reciprocal interaction without dissipation. The system was described using a biorthogonal family of energy eigenvectors, the dynamics of the system was determined by the Schrödinger equation, and unitarity was effectively restored by proper normalization of the state vectors. The results show that the tunneling rates are indeed asymmetrical in this model, leading to an equilibrium that displays unequal occupation of the degenerate systems even in the absence of external interactions.

  13. Constructions of Codes Correcting Burst Asymmetric Errors

    Microsoft Academic Search

    Yuichi Saitoh; Hideki Imai

    1990-01-01

    A class of q-ary systematic codes correcting burst asymmetric errors is proposed. These codes have approximately b+logq(q–1)k+logq logq\\u000ak check symbols, where b is the maximal length of correctable burst asymmetric errors and k is the number of information symbols. The codes have less check symbols than ordinary burst-error-correcting codes if logq(q–1)k+logq logq\\u000akb. A decoding algorithm for the codes

  14. Asymmetric and unilateral hearing loss in children.

    PubMed

    Vila, Peter M; Lieu, Judith E C

    2015-07-01

    Asymmetric and unilateral hearing losses in children have traditionally been underappreciated, but health care practitioners are now beginning to understand their effect on development and the underlying pathophysiologic mechanisms. The common wisdom among medical and educational professionals has been that at least one normal-hearing or near-normal-hearing ear was sufficient for typical speech and language development in children. The objective of this review is to illustrate, to the non-otolaryngologist, the consequences of asymmetric and unilateral hearing loss in children on developmental and educational outcomes. Etiology, detection, and management are also discussed. Lastly, implications for further research are considered. PMID:26004144

  15. Testing the quasi-absolute method in photon activation analysis

    SciTech Connect

    Sun, Z. J. [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States); Wells, D. [Physics Department, South Dakota School of Mines and Technology, 501 E. Saint Joseph St. Rapid City, SD 57701 (United States); Starovoitova, V.; Segebade, C. [Idaho Accelerator Center, Idaho State University, 921 S. 8th Ave. Pocatello, ID 83209 (United States)

    2013-04-19

    In photon activation analysis (PAA), relative methods are widely used because of their accuracy and precision. Absolute methods, which are conducted without any assistance from calibration materials, are seldom applied for the difficulty in obtaining photon flux in measurements. This research is an attempt to perform a new absolute approach in PAA - quasi-absolute method - by retrieving photon flux in the sample through Monte Carlo simulation. With simulated photon flux and database of experimental cross sections, it is possible to calculate the concentration of target elements in the sample directly. The QA/QC procedures to solidify the research are discussed in detail. Our results show that the accuracy of the method for certain elements is close to a useful level in practice. Furthermore, the future results from the quasi-absolute method can also serve as a validation technique for experimental data on cross sections. The quasi-absolute method looks promising.

  16. Absolute Plate Velocities from Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Kreemer, Corné; Zheng, Lin; Gordon, Richard

    2015-04-01

    The orientation of seismic anisotropy inferred beneath plate interiors may provide a means to estimate the motions of the plate relative to the sub-asthenospheric mantle. Here we analyze two global sets of shear-wave splitting data, that of Kreemer [2009] and an updated and expanded data set, to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. We also explore the effect of using geologically current plate velocities (i.e., the MORVEL set of angular velocities [DeMets et al. 2010]) compared with geodetically current plate velocities (i.e., the GSRM v1.2 angular velocities [Kreemer et al. 2014]). We demonstrate that the errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. The SKS-MORVEL absolute plate angular velocities (based on the Kreemer [2009] data set) are determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11° Ma-1 (95% confidence limits) right-handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (?=19.2° ) differs insignificantly from that for continental lithosphere (?=21.6° ). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (?=7.4° ) than for continental lithosphere (?=14.7° ). Two of the slowest-moving plates, Antarctica (vRMS=4 mm a-1, ?=29° ) and Eurasia (vRMS=3 mm a-1, ?=33° ), have two of the largest within-plate dispersions, which may indicate that a plate must move faster than ˜5 mm a-1 to result in seismic anisotropy useful for estimating plate motion. We will investigate if these relationships still hold with the new expanded data set and with the alternative set of relative plate angular velocities. We have found systematic differences between the SKS orientations and our predicted plate motion azimuths underneath the Arabia plate, which suggests to us either plate-scale mantle flow process not directly associated with that plate's absolute motion or intrinsic lithospheric anisotropy. We will discuss more of such discrepancies underneath other plates using the enlarged data set.

  17. Formal total synthesis of aliskiren.

    PubMed

    Peters, Byron K; Liu, Jianguo; Margarita, Cristiana; Andersson, Pher G

    2015-05-01

    The efficient and selective formal total synthesis of aliskiren is described. Aliskiren, a renin inhibitor drug, has received considerable attention, primarily because it is the first of the renin inhibitor drugs to be approved by the FDA. Herein, the formal synthesis of aliskiren by iridium-catalyzed asymmetric hydrogenation of two allylic alcohol fragments is reported. Screening a number of N,P-ligated iridium catalysts yielded two catalysts that gave the highest enantioselectivity in the hydrogenation, which gave the saturated alcohols in 97 and 93?% ee. In only four steps after hydrogenation, the fragments were combined by using the Julia-Kocienski reaction to produce late-stage intermediate in an overall yield of 18?%. PMID:25783891

  18. Diastereoselective synthesis of P-chirogenic phosphoramidate prodrugs of nucleoside analogues (ProTides) via copper catalysed reaction.

    PubMed

    Pertusati, F; McGuigan, C

    2015-05-11

    The first copper-catalysed diastereoselective synthesis of P-chiral phosphoramidate prodrugs (ProTides) is reported. This procedure allows the synthesis of diastereomeric-enriched mixtures of ProTides. Application of this methodology to the asymmetric phosphorylation of purine and pyrimidine nucleoside analogues is presented. PMID:25867944

  19. Absolute determination of local tropospheric OH concentrations

    NASA Technical Reports Server (NTRS)

    Armerding, Wolfgang; Comes, Franz-Josef

    1994-01-01

    Long path absorption (LPA) according to Lambert Beer's law is a method to determine absolute concentrations of trace gases such as tropospheric OH. We have developed a LPA instrument which is based on a rapid tuning of the light source which is a frequency doubled dye laser. The laser is tuned across two or three OH absorption features around 308 nm with a scanning speed of 0.07 cm(exp -1)/microsecond and a repetition rate of 1.3 kHz. This high scanning speed greatly reduces the fluctuation of the light intensity caused by the atmosphere. To obtain the required high sensitivity the laser output power is additionally made constant and stabilized by an electro-optical modulator. The present sensitivity is of the order of a few times 10(exp 5) OH per cm(exp 3) for an acquisition time of a minute and an absorption path length of only 1200 meters so that a folding of the optical path in a multireflection cell was possible leading to a lateral dimension of the cell of a few meters. This allows local measurements to be made. Tropospheric measurements have been carried out in 1991 resulting in the determination of OH diurnal variation at specific days in late summer. Comparison with model calculations have been made. Interferences are mainly due to SO2 absorption. The problem of OH self generation in the multireflection cell is of minor extent. This could be shown by using different experimental methods. The minimum-maximum signal to noise ratio is about 8 x 10(exp -4) for a single scan. Due to the small size of the absorption cell the realization of an open air laboratory is possible in which by use of an additional UV light source or by additional fluxes of trace gases the chemistry can be changed under controlled conditions allowing kinetic studies of tropospheric photochemistry to be made in open air.

  20. Evaluation of the Absolute Regional Temperature Potential

    NASA Technical Reports Server (NTRS)

    Shindell, D. T.

    2012-01-01

    The Absolute Regional Temperature Potential (ARTP) is one of the few climate metrics that provides estimates of impacts at a sub-global scale. The ARTP presented here gives the time-dependent temperature response in four latitude bands (90-28degS, 28degS-28degN, 28-60degN and 60-90degN) as a function of emissions based on the forcing in those bands caused by the emissions. It is based on a large set of simulations performed with a single atmosphere-ocean climate model to derive regional forcing/response relationships. Here I evaluate the robustness of those relationships using the forcing/response portion of the ARTP to estimate regional temperature responses to the historic aerosol forcing in three independent climate models. These ARTP results are in good accord with the actual responses in those models. Nearly all ARTP estimates fall within +/-20%of the actual responses, though there are some exceptions for 90-28degS and the Arctic, and in the latter the ARTP may vary with forcing agent. However, for the tropics and the Northern Hemisphere mid-latitudes in particular, the +/-20% range appears to be roughly consistent with the 95% confidence interval. Land areas within these two bands respond 39-45% and 9-39% more than the latitude band as a whole. The ARTP, presented here in a slightly revised form, thus appears to provide a relatively robust estimate for the responses of large-scale latitude bands and land areas within those bands to inhomogeneous radiative forcing and thus potentially to emissions as well. Hence this metric could allow rapid evaluation of the effects of emissions policies at a finer scale than global metrics without requiring use of a full climate model.

  1. Terahertz Optical Asymmetric Demultiplexer Switch with a Symmetrical Switching Window

    E-print Network

    Haddadi, Hamed

    asymmetrical demultiplexer (TOAD) switch. This is achieved by saturating the semiconductor optical amplifier (SOA), located within the TOAD loop, from both directions. So that, both clockwise (CW) and counter], terahertz optical asymmetric demultiplexer (TOAD) [2], ultrafast nonlinear interferometer (UNI) [3

  2. Attitude Control of Asymmetric Satellites on Polar Near-Circular

    Microsoft Academic Search

    Wei Zhao; Weiwei Yang; Xiaoqian Chen; Yong Zhao

    2009-01-01

    In this paper, a general problem about the attitude dynamics and control of asymmetric satellites is discussed. Due to the asymmetric structure, the properties of such satellites are different from symmetric ones. Perturbation moments accumulate with time, and the attitude angles increase periodically with time. Furthermore, chaos could be happened. Traditional linear controller can not compensate enough for asymmetric satellite

  3. Secure Integration of Asymmetric and Symmetric Encryption Schemes

    E-print Network

    Pointcheval, David

    Secure Integration of Asymmetric and Symmetric Encryption Schemes Eiichiro FUJISAKI and Tatsuaki,okamotog@sucaba.isl.ntt.co.jp Abstract. This paper shows a generic and simple conversion from weak asymmetric and symmetric encryption, this conversion can be applied eÆciently to an asymmetric encryption scheme that provides a large enough coin

  4. The Hebrew University of Jerusalem Lecture 9 Asymmetric Cryptography

    E-print Network

    Porat, Ely

    The Hebrew University of Jerusalem Lecture 9 ­ Asymmetric Cryptography The Public Key Model Asymmetric Cryptography (also called Public­Key Cryptography) was a real breakthrough in cryptography. The major change between asymmetric cryptography and the `traditional' symmetric cryptography is that

  5. Observational Signatures of Asymmetric Magnetic Reconnection During Solar Eruptions

    E-print Network

    , flare/CME current sheets What happens during doubly asymmetric reconnection? Application: line-tied reconnection in flare/CME current sheets #12;NIMROD simulations of line-tied asymmetric reconnection with both asymmetric inflow and outflow #12;There is significant plasma flow across the X-line in both

  6. Asymmetrical Abel Inversion of MHD Generator Discharges

    Microsoft Academic Search

    J. M. Wetzer

    1983-01-01

    The method of Yasutomo et al. for asymmetrical Abel inversion is extended. The original solution consists of a radial part and a weight function, describing the degree of asymmetry. In this work, the radial part is generalized to an elliptical part by employing a coordinate transformation. A factor ¿ is introduced defining the ellipticity. The extended method is applied to

  7. Asymmetric Information and Financing with Convertibles

    Microsoft Academic Search

    Archishman Chakrabortyy; Bilge Y

    Asymmetric information regarding project prospects causes dilution, leading to adverse selection and ine-ciencies in the market for new investments. However, if the market obtains information about the flrm over time, issuing callable convertible securities with restrictive call provisions is optimal. Even when the market's information is noisy, such securities can be designed to make the payofi to new claimholders independent

  8. Asymmetric Information and Financing with Convertibles

    Microsoft Academic Search

    Archishman Chakraborty; Bilge Yilmaz

    2005-01-01

    Asymmetric information regarding project prospects causes dilution, leading to adverse selection and inefficiencies in the market for new investments. However, if the market obtains information about the firm over time, issuing callable convertible securities with restrictive call provisions is optimal. Even when the market's information is noisy, such securities can be designed to make the payoff to new claimholders independent

  9. Beam-beam issues in asymmetric colliders

    SciTech Connect

    Furman, M.A.

    1992-07-01

    We discuss generic beam-beam issues for proposed asymmetric e{sup +}- e{sup -} colliders. We illustrate the issues by choosing, as examples, the proposals by Cornell University (CESR-B), KEK, and SLAC/LBL/LLNL (PEP-II).

  10. Statics of a new asymmetrical parallel robot

    Microsoft Academic Search

    Mengli Wu; Dawei Zhang

    2008-01-01

    Amendment of virtual displacement is used for statics analysis of the sub-6 DOF asymmetrical PKM. The virtual displacement is in conjunction with the influence coefficients and generalized coordinates, so the generalized velocity and virtual displacement are unified. The spring is used and with parametric optimization, the static balancing for TAM is achieved.

  11. Attentional Control and Asymmetric Associative Priming

    ERIC Educational Resources Information Center

    Hutchison, Keith A.; Heap, Shelly J.; Neely, James H.; Thomas, Matthew A.

    2014-01-01

    Participants completed a battery of 3 attentional control (AC) tasks (OSPAN, antisaccade, and Stroop, as in Hutchison, 2007) and performed a lexical decision task with symmetrically associated (e.g., "sister-brother") and asymmetrically related primes and targets presented in both the forward (e.g., "atom-bomb") and backward…

  12. Asymmetric Wargaming: Toward A Game Theoretic Perspective

    Microsoft Academic Search

    G. M. Whittaker

    2000-01-01

    As we enter the 21st century the art and practice of warfare is radically changing. The US has emerged as the dominant conventional military power only to find its adversaries working their way out of the box. The Defense Advanced Research Agency Information Systems Office (DARPA\\/ISO) which is seeking new approaches to asymmetric threat modeling, analysis and prediction sponsored this

  13. Artificial surface with asymmetric reflection properties

    Microsoft Academic Search

    Kihun Chang; Jihwan Ahn; Young Joong Yoon

    2008-01-01

    An artificial surface with asymmetric reflection properties is presented. By covering a metal ground plane with periodic metal-dielectric composite textures, the electromagnetic reflection properties can be altered. By tuning the individual lattice of a periodic mushroom-type texture to vary the surface impedance, a surface with graded reflection phases as a function of position can be designed. Applying a linear gradient

  14. Asymmetric demand for energy: A cointegration approach

    NASA Astrophysics Data System (ADS)

    Maclean, Thomas Frank

    1997-12-01

    This paper uses time series data in a study of the demand for energy. One goal is to compare the results from the traditional autoregressive distributed lag (ADL) model to the error correction model (ECM) using cointegration. The second goal is to determine if the demand elasticity is asymmetric with respect to increasing and decreasing prices. This paper discusses three topics that are important to the use of time series data. The first topic is the presence and consequences unit roots which are common in time series data. The second topic is the identification of cointegrated variables and the third topic is a development of the ECM. This results in a model that can be used in either a single equation or multivariate system context and it will estimate both long run and short run elasticities. Asymmetry theory and its implications are studied along with an investigation into competing methods of creating the asymmetric variables. Simulations provided evidence that the use of dummy variables results in biased estimates and that the cumulative difference method of Wolffram/Houck gives valid estimates. The results of the empirical part of the paper show that the short run estimates of the ADL model are like those of the error correction model, but the cointegration method's long run estimates are better since they are known to be consistent and asymptotically unbiased. Tests for asymmetry do not support the theory of asymmetric long run price elasticities; however there is evidence to support the presence of asymmetric demand in the short run.

  15. Cascading failures on networks with asymmetric dependence

    NASA Astrophysics Data System (ADS)

    Li, Ming; Liu, Run-Ran; Jia, Chun-Xiao; Wang, Bing-Hong

    2014-12-01

    Networks with mutual dependence have been shown to be much more vulnerable to random failures and targeted attacks than those without. However, in real networks, the dependence between two nodes is not always mutual. Periphery nodes may depend on hub nodes, yet the converse is not necessarily true. Considering this asymmetric dependence, we propose a model of cascading dynamics of networks, where the dependence between nodes is determined by their degrees. We find that the asymmetric dependence makes networks more robust than the symmetric one, and the percolation transition point is not sensitive to the number of the asymmetric dependence nodes. Furthermore, scale-free networks with asymmetric dependence can still be very robust to random failures, rather than extremely fragile as the one with mutual dependence. We also develop an approach to analyse this model and obtain the exact solutions for the size of the giant component and the critical point. Both simulation and analytical results reveal the existence of the crossover between the first- and the second-order percolation transitions in our model.

  16. Scheduling data broadcast in asymmetric communication environments

    Microsoft Academic Search

    Nitin H. Vaidya; Sohail Hameed

    1999-01-01

    With the increasing popularity of portable wireless computers, mechanisms to efficiently transmit information to wireless clients are of significant interest. The environment under consideration is asymmetric in that the information server has much more bandwidth available, as compared to the clients. In such environments, often it is not possible (or not desirable) for the clients to send explicit requests to

  17. Mach bands change asymmetrically during solar eclipses.

    PubMed

    Ross, John; Diamond, Mark R; Badcock, David R

    2003-01-01

    Observations made during two partial eclipses of the Sun show that the Mach bands on shadows cast by the Sun disappear and reappear asymmetrically as an eclipse progresses. These changes can be explained as due to changes in the shape of the penumbras of shadows as the visible portion of the Sun forms crescents of different orientation. PMID:12892435

  18. Iron-catalyzed asymmetric hydrosilylation of ketones.

    PubMed

    Zuo, Ziqing; Zhang, Lei; Leng, Xuebing; Huang, Zheng

    2015-03-25

    A series of iron complexes of chiral iminopyridine-oxazoline (IPO) ligands have been synthesized. The most sterically hindered iron catalyst exhibits excellent activity (up to 99% yield) and high enantioselectivity (up to 93% ee) in asymmetric hydrosilylation of aryl ketones. PMID:25712676

  19. Constructions of Sparse Asymmetric Connectors Extended Abstract

    E-print Network

    Jäger, Gerold

    Constructions of Sparse Asymmetric Connectors Extended Abstract Andreas Baltz, Gerold J. For k = (log N + log2 n) Oru¸c [5] gave the presently best (n, N)-connector with O(N + n · log n) edges. For k = 2 we show by a probabilistic argument that an optimal (n, N)- connector has (N) edges, if n N 1

  20. Polarization of Drosophila Neuroblasts During Asymmetric Division

    E-print Network

    Prehoda, Ken

    asymmetric aPKC activity to the polarization of downstream factors. Polarized aPKC activity is created a complex system that orchestrates robust aPKC polarity, which in turn polarizes substrates by coupling the discovery of the first polarized components, neuroblasts have been an excellent model system

  1. Asymmetric Multiprocessing for High Performance Computing

    E-print Network

    Shinozuka, Masanobu

    Asymmetric Multiprocessing for High Performance Computing Stephen Jenks Electrical Engineering and Superscalar Since the 1960s But has become integrated Microprocessors High Clock Speed Great performance and Computer Science UC Irvine sjenks@uci.edu Source: NVIDIA #12;Overview and Motivation Conventional Parallel

  2. Stochastic Differential Games with Asymmetric Information

    SciTech Connect

    Cardaliaguet, Pierre, E-mail: Pierre.Cardaliaguet@univ-brest.fr; Rainer, Catherine [Universite de Brest, Laboratoire de Mathematique (UMR CNRS 6205) (France)], E-mail: Catherine.Rainer@univ-brest.fr

    2009-02-15

    We investigate a two-player zero-sum stochastic differential game in which the players have an asymmetric information on the random payoff. We prove that the game has a value and characterize this value in terms of dual viscosity solutions of some second order Hamilton-Jacobi equation.

  3. Government procurement and asymmetric rebate auctions

    Microsoft Academic Search

    In-Gyu Kim

    1997-01-01

    This paper characterizes a Nash equilibrium at an asymmetric rebate auction in which a government, seeking the most, favorable concessions from competing bidders, announces a fixed-price of an auctioned project and a price-preference policy prior to bidding competition.

  4. Asymmetric Information in Fads Models Paolo Guasoni

    E-print Network

    Guasoni, Paolo

    Asymmetric Information in Fads Models Paolo Guasoni Boston University and University of Pisa guasoni@bu.edu August 31, 2004 Abstract Fads models were introduced by Shiller (1984) and Summers (1986 the decomposition result to the problem of testing the presence of fads from market data. An application to the NYSE

  5. Designing asymmetric neural networks with associative memory

    SciTech Connect

    Zhao Hong [Department of Physics, Xiamen University, Xiamen 361005 (China)

    2004-12-01

    A strategy for designing asymmetric neural networks of associative memory with controllable degree of symmetry and controllable basins of attraction is presented. It is shown that the performance of the networks depends on the degree of the symmetry, and by adjusting the degree of the symmetry the spurious memories or unwanted attractors can be suppressed completely.

  6. Directional emission from asymmetric resonant cavities

    NASA Astrophysics Data System (ADS)

    Nöckel, Jens U.; Stone, A. Douglas; Chen, Gang; Grossman, Helene L.; Chang, Richard K.

    1996-10-01

    Asymmetric resonant cavities with highly noncircular but convex cross sections are predicted theoretically to have high- Q whispering gallery modes with highly anisotropic emission. We develop a ray dynamics model for the emission pattern and present numerical and experimental confirmation of the theory.

  7. Corporate investment and financing under asymmetric information

    Microsoft Academic Search

    Erwan Morellecy; Norman Schürhoff

    2011-01-01

    We develop a dynamic model of corporate investment and financing decisions in which corporate insiders have superior information about the firm's growth prospects. We show that firms with positive private information can credibly signal their type to outside investors using the timing of corporate actions and their debt-equity mix. Using this result, we show that asymmetric information induces firms with

  8. Dynamic Investment and Financing under Asymmetric Information

    Microsoft Academic Search

    Erwan Morellecy; Norman SCHURHOFF

    2009-01-01

    This paper develops a tractable real options framework to analyze the effects of asymmetric information on investment and financing decisions when firms require external funds to finance investment. Our analysis shows that corporate insiders can signal their private information to outside investors using the timing of investment and the firm's debt-equity mix. Several important contributions follow from this result. First,

  9. Asymmetric Sequence Divergence of Duplicate Genes

    Microsoft Academic Search

    Gavin C. Conant; Andreas Wagner

    2003-01-01

    Much like humans, gene duplicates may be created equal, but they do not stay that way for long. For four completely sequenced genomes we show that 20%-30% of duplicate gene pairs show asymmetric evolution in the amino acid sequence of their protein products. That is, one of the duplicates evolves much faster than the other. The greater this asymmetry, the

  10. A time-varying, analysis\\/synthesis auditory filterbank using the gammachirp

    Microsoft Academic Search

    Toshio Irino; Masashi Unoki

    1998-01-01

    A time-varying, analysis\\/synthesis auditory filterbank has been developed using a new implementation of the “gammachirp”, which has been shown to be an excellent function for the asymmetric, level-dependent auditory filter. The gammachirp filter is shown to be implemented through a combination of a gammatone filter and an IIR asymmetric compensation filter; which largely reduces the computational cost for time-varying filtering.

  11. Enantioselective synthesis of (-)-dihydrocodeine and formal synthesis of (-)-thebaine, (-)-codeine, and (-)-morphine from a deprotonated ?-aminonitrile.

    PubMed

    Geffe, Mario; Opatz, Till

    2014-10-17

    The ?-benzylation of a deprotonated bicyclic ?-aminonitrile, followed by Noyori's asymmetric transfer hydrogenation combined with the Grewe cyclization onto a symmetrical A-ring precursor, are the key steps of a short and high-yielding enantioselective synthesis of the morphinan (-)-dihydrocodeine. This compound can be converted to (-)-thebaine in high yield by known transformations, while (-)-codeine and (-)-morphine are available from an advanced intermediate. PMID:25271381

  12. Absolute Antenna Calibration at the US National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G. L.; Bilich, A. L.

    2012-12-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. Determination of antenna phase center behavior is known as "antenna calibration". Since 1994, NGS has computed relative antenna calibrations for more than 350 antennas. In recent years, the geodetic community has moved to absolute calibrations - the IGS adopted absolute antenna phase center calibrations in 2006 for use in their orbit and clock products, and NGS's CORS group began using absolute antenna calibration upon the release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD 83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and have been converted to absolute, it is considered best practice to independently measure phase center characteristics in an absolute sense. Consequently, NGS has developed and operates an absolute calibration system. These absolute antenna calibrations accommodate the demand for greater accuracy and for 2-dimensional (elevation and azimuth) parameterization. NGS will continue to provide calibration values via the NGS web site www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as well as the legacy ANTINFO format. The NGS absolute system is located in Corbin, Virginia, and uses field measurements and actual GNSS satellite signals to quantitatively determine the carrier phase advance/delay introduced by the antenna element. NGS is interested in providing calibrations for a wide variety of dual-frequency, geodetic-grade antennas, from types in use at IGS and CORS reference stations to rover antennas not normally seen in those networks. In this presentation, we describe the NGS absolute calibration facility, and discuss the observation models and strategy used to generate NGS absolute calibrations. We also demonstrate that NGS absolute phase center variation (PCV) patterns are consistent with published values determined by other absolute antenna calibration facilities.

  13. Ferroelectric bolometer measures RF absolute power at submillimeter wavelengths

    NASA Technical Reports Server (NTRS)

    Cohn, M.; Rodgers, J. D.

    1966-01-01

    Two ferroelectric bolometer sensing elements measure low rf absolute power at millimeter and submillimeter wavelengths. The sensing elements are mounted in sections of waveguide and connected in series in a standard temperature compensating bridge circuit.

  14. Temporal Dynamics of Microbial Rhodopsin Fluorescence Reports Absolute Membrane Voltage

    PubMed Central

    Hou, Jennifer H.; Venkatachalam, Veena; Cohen, Adam E.

    2014-01-01

    Plasma membrane voltage is a fundamentally important property of a living cell; its value is tightly coupled to membrane transport, the dynamics of transmembrane proteins, and to intercellular communication. Accurate measurement of the membrane voltage could elucidate subtle changes in cellular physiology, but existing genetically encoded fluorescent voltage reporters are better at reporting relative changes than absolute numbers. We developed an Archaerhodopsin-based fluorescent voltage sensor whose time-domain response to a stepwise change in illumination encodes the absolute membrane voltage. We validated this sensor in human embryonic kidney cells. Measurements were robust to variation in imaging parameters and in gene expression levels, and reported voltage with an absolute accuracy of 10 mV. With further improvements in membrane trafficking and signal amplitude, time-domain encoding of absolute voltage could be applied to investigate many important and previously intractable bioelectric phenomena. PMID:24507604

  15. Absolutely continuous spectrum of a Schroedinger operator on a tree

    SciTech Connect

    Kupin, S. [Universite Aix-Marseille, 39 rue Joliot-Curie, 13453 Marseille Cedex 13 (France)

    2008-11-15

    We give sufficient conditions for the presence of the absolutely continuous spectrum of a Schroedinger operator on a regular rooted tree without loops (also called regular Bethe lattice or Cayley tree)

  16. Absolutely continuous spectrum of a Schrödinger operator on a tree

    E-print Network

    S. Kupin

    2008-05-18

    We give sufficient conditions for the presence of the absolutely continuous spectrum of a Schr\\"odinger operator on a regular rooted tree without loops (also called regular Bethe lattice or Cayley tree).

  17. Comparative vs. Absolute Performance Assessment with Environmental Sustainability Metrics

    E-print Network

    High, Karen

    to another dilemma. This can be further explained as follows. For example, the environmental performanceComparative vs. Absolute Performance Assessment with Environmental Sustainability Metrics Xun Jin Different goals and potential audiences determine that two types of environmental performance assessments

  18. Chiral poly-rare earth metal complexes in asymmetric catalysis

    PubMed Central

    Shibasaki, Masakatsu

    2006-01-01

    Asymmetric catalysis is a powerful component of modern synthetic organic chemistry. To further broaden the scope and utility of asymmetric catalysis, new basic concepts for the design of asymmetric catalysts are crucial. Because most chemical reactions involve bond-formation between two substrates or moieties, high enantioselectivity and catalyst activity should be realized if an asymmetric catalyst can activate two reacting substrates simultaneously at defined positions. Thus, we proposed the concept of bifunctional asymmetric catalysis, which led us to the design of new asymmetric catalysts containing two functionalities (e.g. a Lewis acid and a Brønsted base or a Lewis acid and a Lewis base). These catalysts demonstrated broad reaction applicability with excellent substrate generality. Using our catalytic asymmetric reactions as keys steps, efficient total syntheses of pharmaceuticals and their biologically active lead natural products were achieved. PMID:25792774

  19. Enantiospecific total syntheses and assignment of absolute configuration of cannabinol-skeletal carbazole alkaloids murrayamines-o and -p.

    PubMed

    Dethe, Dattatraya H; Das, Saikat; Dherange, Balu D; Mahapatra, Samarpita

    2015-06-01

    First enantiospecific total syntheses of the cannabinol-skeletal carbazole alkaloids murrayamines-O and -P isolated from root barks of Murraya euchrestifoli, have been accomplished by highly diastereoselective, Lewis acid catalyzed coupling reactions of commercially available monoterpenes with carbazole derivative, which in addition to confirming the structure also established the absolute configuration of the natural products. Synthesis of both natural products and their enantiomers was achieved with high atom economy, in a protecting-group free manner and in six steps longest linear sequence from commercially available aniline derivative and verbenol. PMID:25891514

  20. Efficient absolute difference circuits in Virtex-5 FPGAs

    Microsoft Academic Search

    Stefania Perri; Paolo Zicari; Pasquale Corsonello

    2010-01-01

    This paper presents a novel architecture optimized for realizing efficient absolute difference circuits in Virtex-5 FPGA devices. The proposed structure efficiently uses the 6-input look-up-tables available within the chosen devices family to maximize speed performance and to minimize the amount of occupied resources. In comparison with the DSP- and the LUT-based absolute difference circuits automatically synthesized and mapped by the