The Stereochemistry of Rings A and B in 6-Substituted Δ4-3-Oxosteroids: A Study of H1 Allylic Spin-Spin Coupling in Systems with Defined Geometry

The preparation of some 6-substituted A4-3-oxosteroids is described. As previously announced, the stereochemistry at the 6-position, which is of importance in connection with biological activity, may be deduced from examination of the N.M.R. signal due to the vinylic proton at C4 which appears as a singlet ( W H= 1.5 - 1.8 c/s)in the 6ß-substituted series and as a doublet (J = 1.6 - 1.8 c/s) in the 6a-substituted series. The general dependence of the allylic coupling constants on stereochemistry is examined and an empirical angular relation shown to exist, with the coupling constant at a maximum when the angle subtended between the allylic and vinylic protons is 90° and at a minimum when it is 0 or 180°. Theoretical implications are briefly considered.