15β-hydroxysteroids (Part V). Steroids of the human perinatal period: The synthesis of 3β, 15β, 17α-trihydroxy-5-pregnen-20-one from 15β, 17α-dihydroxy-4-pregnen-3,20-dione

A simple three-step synthetic method is reported on the conversion of delta 4-3-ketosteroids to the corresponding 3 beta-hydroxy-delta 5-steroid analogues. 17 alpha-Hydroxy-4-pregnen-3,20-dione (10a) was used as a model to develop a method for the synthesis of 3 beta, 17 alpha-dihydroxy-5-pregnen-20-one (16). The major problem being the synthesis of 3,17 alpha-diacetoxy-3,5-pregnadien-20-one (14) was solved by acetylating using a mixture of acetic anhydride and perchloric acid. The conversion of 15 beta, 17 alpha-dihydroxy-4-pregnen-3, 20-dione (8), product of Penicillium citrinum fermentation, to the desired 3 beta,15 beta,17 alpha-trihydroxy-5-pregnen-20-one (1), is described using a modification of this method. Reaction of 8 with acetic anhydride and perchloric acid in ethyl acetate gave 3,15 beta,17 alpha-triacetoxy-3,5-pregnadien-20-one (17) which on reduction with sodium borohydride gave 5-pregnen-3 beta,15 beta,17 alpha, 20(S + R)-tetrols (18a and 18b); however, reduction of 17 with a mixture of sodium borohydride and potassium bicarbonate gave after basic hydrolysis with methanolic sodium hydroxide the desired product 3 beta,15 beta,17 alpha-trihydroxy-5-pregnen-20-one (1) in good yield (54%).