17-ALPHA-CONFIGURATED 20-METHYLPREGNANE DERIVATIVE

A mixture of 1a+1b (17α), obtained by C-17-epimerization of pregnenolone (1a) was converted into 3a+3b by Wittig-reaction. 3a+3b were acetylated to a mixture of 4a+4b, from which 4b was isolated by cristallization of 3a and following AgNO3-chromatography of the mother-liquors. Δ20(22) → Δ17-doublebond-isomerization occurs by hydrogenation (Pd/C) of 3a (17β) to give 5. Hydrogenation (Pt-catalyst) of 4b (17α) leads to 8b, which was converted into the 20-methylpregnane-derivatives 7b, 9b-13b. By comparison with the 17β epimers 1a-4a, 7a-13a a spectroscopic determination of the relative configuration on C-17 of 17-alkylsubstituted steroids was possible. © 1979.