Unsaturated steroids. Part 9. Synthesis of some aromatic ring c steroids

Abstract

7α,11α,22α,23α-Tetrabromo-5α-ergost-8-en-3β-yl acetate (1) has been aromatised to 22α,23α-dibromo-12-methyl-18-nor-5α-ergosta-8,11,13-trien-3β-yl acetate (2) in solution by using an acidic catalyst. Stepwise removal of the side-chain from 12-methyl-18-nor-5α-ergosta-8,11,13,22-tetraen-3β-yl acetate (5) afforded successively the C-22 aldehyde (6), the C-20 ketone (8), and 3β-hydroxy-12-methyl-18-nor-5α-androsta-8,11,13-trien-17-one (18). Associated derivatives are described; certain reaction mechanisms have been clarified.