An NMR study of A-ring conformation in some 4-en-3-one steroids

✍ Scribed by Kirk Marat; J. F. Templeton; V. P. Sashi Kumar

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 584 KB
• Volume: 25
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260250107

✦ Synopsis

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 ZP-acetoxy substitution forces inversion.

Substitution at the 17ry position has no measurable effect upon the

A-ring conformation while 6a 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. KEY WORDS N M R 4-en-3-one steroids Conformational analysis 'J(2a.28