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Rotational strengths calculated on the basis of quantum-mechanically obtained minimum energy geometries were used to determine the absolute configurations of axially chiral 3-aryl-4(3H)-quinazolinones from the sign of the observed Cotton effects (CEs). For the spectral data, CNDO/S calculations were used; for the geometries, ab initio (RHF/6-31G) and semiempirical (AM1) theories were used. Oscillator and rotational strengths of all excited states down to 200 nm were compared to experimental absorption and circular dichroism (CD) data. It was found that the sign of the 1Lb Cotton effects obtained for the enantiomers of methaqualone and derivatives of 3-aryl-2-alkylthio-4(3H)-quinazolinones can be correlated unambiguously with the absolute configuration. Furthermore, the sign of the Cotton effect of the π-π* transition of the thiocarbonyl chromophore of 3-aryl-2-mercapto-4(3H)-quinazolinones is suitable for a successful stereochemical correlation. Chirality 10:253–261, 1998. © 1998 Wiley-Liss, Inc. 相似文献
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Assessing the reactivity of optical antipodes is of central importance in drug research. Using the model of 2-methoxy-2-phenylacetic acid-4-nitrophenylester (MPE), the rate of hydrolysis in the presence of β-cyclodextrin (CD), hydroxyethyl- and hydroxypropyl-β-CD, as well as methyl-β-CD is studied photometrically and by means of HPLC (Chiralcel-OD-R-column). Both β-CD and hydroxyalkylated-β-CD catalyze (?)-(R)-enantiomers to a larger extent than (+)-(S)-enantiomers, resulting in an enrichment of the latter. Methyl-β-CD stabilizes the ester trifold, thus abolishing chiral discrimination. © 1995 Wiley-Liss, Inc. 相似文献
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P. Ascherson A. Bastian Beyrich E. du Bois-Reymond C. Bolle Borchardt Curtius Ewald Garcke R. Hartmann A. W. Hofmann L. Kny C. Koch Kronecker Lepsins P. Magnus v. Martens Mommsen W. Peters Pringsheim Roth W. Siemens Virchow Weber M. Websky L. Wittmack Zeller 《Plant Systematics and Evolution》1877,27(8):287-287
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