Premium
An NMR study of A‐ring conformation in some 4‐en‐3‐one steroids
Author(s) -
Marat Kirk,
Templeton J. F.,
Kumar V. P. Sashi
Publication year - 1987
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260250107
Subject(s) - chemistry , ring (chemistry) , degree of unsaturation , ring flip , substitution (logic) , cyclohexane conformation , stereochemistry , crystallography , ring size , carbon 13 nmr , molecule , hydrogen bond , organic chemistry , computer science , programming language
NMR spectral data are given for the A‐ring in ten 4‐en‐3‐one steroids, and the strategy of the spectral analysis is described. The data are interpreted in terms of an equilibrium between normal and inverted half‐chair conformations, with the normal conformation predominant in all cases except when 2β‐acetoxy substitution forces inversion. Substitution at the 17α position has no measurable effect upon the A‐ring conformation while 6α and 19‐nor substitution have only a small effect. Unsaturation at the C‐5 position results in a flattened A‐ring. The results obtained from NMR are compared with those obtained by x‐ray crystallography. The A‐ring conformation shows far less variation in solution than it does in the solid.