Determination of absolute configuration (AC) is one of the most challenging features in the structure elucidation of chiral natural products, especially those with complex structures. With revolutionary advancements in the area of quantum chemical calculations of chiroptical spectroscopy over the pa...

Elucidation of the correct stereochemistry of the metabolite is essential for the mechanistic study of bioactive compounds. Isoflavan-4-ol has the same chiropical chromophore as THD, the biosynthetic precursor of the potent phytoestrogen S-equol. Interested in the correct absolute configuration of isoflavan-4-ol stereoisomers and to compare the available ...

Horeau's method furnishes the correct absolute configuration for those sesquiterpene lactones where one methylene group is adjacent to the asymmetric carbon bearing the hydroxyl group. In 6-hydroxylated pseudoguaianolides a high optical yield can be empir...

Xestenone is a marine norditerpenoid found in the northeastern Pacific sponge Xestospongia vanilla. The relative configuration of C-3 and C-7 in xestenone was determined by NOESY spectral analysis. However the relative configuration of C-12 and the absolute configuration of this compound were ...

The absolute configuration of the guaiane-type sesquiterpene lactone 8-epiisolippidiol-3-O-?-D-glucopyranoside, isolated from plants of the genus Crepis, and the predominant solution-state conformation in CD3OD were determined by comparison of experimental and calculated VCD spectra. It has been found that the reported stereostructure ...

The basic parameters describing the internal structure of rotating convfiurations are calculated on the basis of Einstein's gravitation theory. The influence of rotation on the absolute gravitational mass defect is determined. (auth)

The absolute stereochemistry of the chiral dihydrodiols formed from ortho- and meta-dichlorobenzene were determined. Both diols were found to be enantiomerically pure with 1S,2S absolute configuration. Toluene-grown cells of Pseudomonas putida F1 and Pseu...

Strictamine (4), strictalamine (6), and nor-C-fluorocurarine (8) have been isolated from Rhazya stricta. X-ray structure determination and chemical correlation establish the structures and absolute configurations of 4, 6, and also, by extension, of the Picralima bases, especially with respect to the configurations ...

The absolute configuration of trans-cyclooctene has been determined and the levorotatory enantiomer is assigned the (R)-configuration. (1S.2S)(+)-1,2-Dimethoxycyclooctane was synthesized from (2R:3R)-(+)-tartaric acid and its rotation was shown to be iden...

secretion obtained from larvae of the European cabbage butterfly, Pieris rapae.4 This finding was somewhat. In addition, the assignment of the absolute configuration of pinoresinol isolated from Pieris rapae represents

Three new cannabichromanone derivatives were isolated from high potency cannabis, along with the known cannabichromanone. Full spectroscopic data, including the use of electronic circular dichroism and Mosher ester analysis to determine the absolute configuration of these compounds, are reported. All isolates were tested for ...

In an attempt to determine the cause of repeated fish kills in an estuarine aquaculture facility in Maryland, a toxin was isolated from Karlodinium veneficum with hemolytic, cytotoxic, and ichthyotoxic properties, which was referred to as karlotoxin-2 (KmTx2). The structure of KmTx2 was elucidated by means of detailed 1D and 2D NMR spectra including 2D INADEQUATE. The relative ...

Sotolon (1) and maple furanone (2) are naturally occurring chiral furanones. These 5-substituted-2(5H)-furanones are industrially significant aroma compounds due to their characteristic organoleptic properties and extraordinarily low odor thresholds. Each enantiomer of 1 and 2 was successfully obtained by preparative enantioselective supercritical fluid chromatography. The ...

Neutron diffraction has been used to monitor the absolute stereochemistry of an enzymatic reaction. (-)(2S)malic-3-d acid was prepared by the action of fumarase on fumaric acid in D/sub 2/O. After a large number of cations were screened, it was found that (+)(R)..cap alpha..-phenylethylamine forms the large crystals necessary for a neutron diffraction analysis. The subsequent ...

Prigogine's Principle of Minimum Entropy Production'', as well as the complementary maximum entropy production principle were examined from a more basic point of view. Two theorems are provided: absolute maximum entropy configurations can be considered to timedevelop from absolute maximum entropy ...

[reaction: see text] Chiral bidentate silyl reagents have been developed for the GC analysis of aliphatic 1,3- and 1,4-diols. These reagents react with the diols to cyclic siloxanes, which allow the determination of their enantiomeric composition even in complex mixtures. The absolute configuration of 4,6-nonadecanediol 7, occurring in ...

A new method was developed to assign the absolute configuration of molecules using kinetic resolution catalysts. Secondary alcohols were acylated in the presence of Birman's S-HBTM and R-HBTM catalysts, and the fast-reacting catalyst was identified by NMR analysis of the reaction mixture. A mnemonic was developed to assign ...

Published data on the synthesis, absolute configurations and biological properties of chiral hydroxy phosphonates are generalised and described systematically. Examples of asymmetric synthesis of hydroxy phosphonates by the phospho-aldol reaction, reduction of keto phosphonates, chemo-enzymatic approach, and so on are discussed. Methods for ...

Fully protected diastereoisomers of deoxyguanylyl (3' leads to 5') deoxyadenosine stereospecifically labelled on phosphorus with oxygen-18 have been synthesized by oxidation of phosphite triester intermediates in the presence of 18O-labelled water. The diastereoisomers have been chromatographically separated and their absolute configuration at phosphorus ...

The absolute configuration of small crystallizable molecules can be determined with anomalous X-ray diffraction as shown by Bijvoet in 1951. For the majority of compounds that can neither be crystallized nor easily be converted into crystallizable derivatives, stereocontrolled organic synthesis is still required to establish their ...

The absolute configuration of small crystallizable molecules can be determined with anomalous X-ray diffraction as shown by Bijvoet in 1951. For the majority of compounds that can neither be crystallized nor easily be converted into crystallizable derivatives, stereocontrolled organic synthesis is still required to establish their ...

Macropodumines B and C (1, 2) are fused pentacyclic alkaloids previously isolated from the Chinese medicinal plant Daphniphyllum macropodum. Macropodumine B (1) possesses an amazing structural feature of a cyclopentadienyl carbanion, stabilized as a zwitterion by an internal iminium cation, which was confirmed by X-ray diffraction analysis. On the basis of the X-ray geometry, the ...

on a 1% agarose gel. Cell transfection and laser scanning confocal microscopy HCT116 human colon images of modified SEP53 expression in the human colonic carcinoma cell line HCT116. Deletion

North America and is an economically important pest of hop, Humulus lupulus L. (Urticales: Cannabaceae californicus Mots. on hops, Humulus lupulus L., in Idaho. J. Entom. Soc. British Columbia 81:20�24. BOYER, F

Enantiomers of 4-(1,1,2-trimethylhexyl)phenol, a chiral isomer of the endocrine disrupting chemical nonylphenol, have been resolved and isolated by preparative chiral HPLC. The absolute configurations of the enantiomers were then determined by an X-ray crystallographic study of the (-)-camphanoyl derivative of the first eluted ...

... Title : DETERMINATION AND APPLICATION OF ABSOLUTE TRANSITION PROBABILITIES AND LIFETIMES OF ATOMS, MOLECULES, AND IONS ...

Axicon surfaces are widely used in nowadays optical engineering, requiring accurate metrology for these highly aspheric surfaces. In this contribution, we present a complete approach to determine the shape deviation of axicons in an absolute manner. The setup is an interferometric null configuration using a computer generated hologram ...

A novel acetogenin, asiminocin (1), was isolated by activity-directed fractionation from the stem bark of the paw paw tree, Asimina triloba. By spectral and chemical methods, 1 was identified as (30S)-hydroxy-4-deoxyasimicin. The absolute configuration of 1, along with those of previously reported acetogenins asimin, asiminacin, bullatin, (30S)-bullanin, ...

A new method was developed for the enantiomeric resolution of asymmetric derivatives of 3,7-dimethylenebicyclo(3.3.1)nonane by liquid chromatography on a chiral sorbent, i.e., silica gel impregnated with silver d-camphor-10-sulfonate. During transannular electrophilic cyclization and photocyclization the enantiomeric dienes, the absolute configurations of ...

The purpose of this research is to establish unambiguously the relationship of the configurations of 1,2,2triphenylethylamine and 1,2,2- triphenylethanol, and to establish the absolute configurations of these same compounds. The value of the specific rotation of completely resolved 1,2,2- triphenylethanol was ...

A study has been made of the 1H NMR spectra of peracetylated beta-glucopyranosides and alpha-arabinopyranosides obtained by reaction of D- and L-glucoses, and L- and D-arabinoses with either (R)- or (S)-2-octanols. The obtained and literature data show that 1H NMR spectra may be used to determine the absolute configuration of the ...

Six novel monoterpene chromane esters were isolated from the aerial parts of Peperomia obtusifolia (Piperaceae) using chiral chromatography. This is the first time that chiral chromane esters of this kind, ones with a tethered chiral terpene, have been isolated in nature. Due to their structural features, it is not currently possible to assess directly their absolute ...

A new spirotetronate-class polyketide, maklamicin (1), was isolated from the culture extract of an endophytic actinomycete of the genus Micromonospora. The structure and relative configuration of 1 were elucidated by interpretation of NMR and other spectroscopic data, and the absolute configuration was determined ...

The circular dichroism (CD) is an excellent method for determining the absolute stereochemistry of organic compounds. The CD spectra of four biphenyl compounds were determined by using CD spectrometer, and two pairs of symmetrical CD spectra were obtained. The absolute configuration of biphenyl ...

The configuration of leucettamol A (1), a known long-chain �two-headed� sphingolipid (dimeric sphingolipid) from the marine sponge Leucetta microrhaphis, was determined by conversion to an N,N�,O,O�-tetrabenzoyl derivative, measurement of the exciton coupled circular dichroism spectrum (ECCD) and quantitative analysis by deconvolution of superposed ...