Synthesis of 13α-steroids. A new route to 16-substituted 13α-androstanes

Abstract

1,4-Addition of MeMgl on D-homo-18-norandrost-13(17a)-en-17-one (3) yields stereospecifically D-homo-13α-androstan-17-one (4). Ring-D contraction leads to a compound having a 13α-androstane skeleton: the Favorskii rearrangement of bromo ketone (9) yields 13α-androstane-16α- and 16β-carboxylic acids (8) and (14). Ketone (4) is oxidized by Tl^III to (8). The transformation of these carboxylic acids into methyl ketones, alcohols, and, finally, 13α-androstan-16-one is described.