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1H NMR and molecular mechanics studies of epimeric ethyl esters of 20(R, S)-hydroxy-23-norcholanoic acids

✍ Scribed by M. S. Maier; A. M. Seldes; E. G. Gros

Publisher: John Wiley and Sons
Year: 1991
Tongue: English
Weight: 380 KB
Volume: 29
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1260290208

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✦ Synopsis

Proton chemical shifts for the C-18, C-21, -CO,CH,CH, and -CO,CH,CH, protons of epimeric ethyl esters of 20(R,S)-hydroxy-23-norcholanoic acids were measured in deuteriochloroform and pyridine-d, . The observed solvent shifts due to specific OH-pyridine hydrogen-bonded complexes allowed the quantification of the epimeric mixtures by analysis of the pyridine-d, 'H NMR spectra. The main features of the pyridine-induced shifts are rationalized in terms of the preferred conformations for the 2OR-and ZOS-epimers, which are predicted by molecular mechanics calculations.

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