D-homoandrostanes. 4. The incubation of some D-homo-5 alpha-androstanes with Rhizopus nigricans.

Nine dioxygenated D-homoandrostanes were incubated with Rhizopus nigricans to investigate the effect of D-ring modification on microbiological hydroxylation. Structure determination of the products by NMR spectroscopy, and in certain cases independent synthesis of their oxidised products, showed that in contrast to 5 alpha-androstanes the majority of the compounds were hydroxylated in the "reverse" mode, and only D-homo-5 alpha-androstane-3,17-dione was hydroxylated in the "normal" mode to any extent. Stereospecific ring D-hydroxylation at C(17 alpha) was observed for both D-homo-5 alpha-androstane-3,6- and 3,7-diones.