Steroids and steroidases. VIII. Further data on the preferred conformations of the cycloheptane rings of A-homosteroidketones

Abstract

The data presented substantiate the conclusions reported previously (1) regarding the applicability of the Hendrickson (2, 3) cycloheptane-based conformational analytical procedure to A-homosteroid-ketones of the 5α- and 5β- androstane and estrane series. For such cycloheptanone derivatives (with no bulky substituents at C-1 to C-5 of ring A) the twist chair conformations with the carbonyl group in the axis of adjacent position appear to be 1–2 kcal mole−1 lower in strain energy than predicted from the direct Hendrickson analysis and of these two favored conformers, the former may well be marginally preferred in many cases.