An alternative route to 2α,3α-diols from 2,3-unsaturated 5α-steroids avoiding the use of osmium tetroxide

Abstract

A method for preparation of 2α,3α-dihydroxy-5α-steroids from 2,3-unsaturated 5α-steroids without the use of OsO4 is described. It involves the sequence of epoxidation, cleavage of the oxirane ring by HI, acetylation, oxidative replacement of iodine by hydroxyl and alkaline hydrolysis (I → VI) without purification of the intermediates. The presence of a 6-keto group does not decrease the yields. The yields are comparable with those obtained by osmylation and the method can find general use, particularly in the synthesis of brassinolide analogs.