Conformational effects in 20-oxosteroids

Abstract

The relative stabilities of C-17 epimers of twenty-five 20-oxopregnanes have been determined by measuring the compositions of mixtures resulting from base-catalysed equilibrations. The compounds involved included a variety of steroids in which functionality in ring B, C, or D was varied. In most cases, the equilibrium mixture contained 75–82% of 17β-isomer. The exceptions were 16β-methylprogesterone (100% 17α), 12α-hydroxyprogesterone (100% 17β), pregn-11-ene-3,20-dione (49·5% 17β), pregn-9(11)-ene-3,12,30-trione (46% 17β), and 11-oxoprogesterone (71·5% 17β).