Ikegami Shiro

Novel epimerizatton of steroidal allylic alcohols

Abstract Epimerization of 4-pregnene-3β,20α-diol into 4-pregnene-3β,20α-diol was achieved under the mild condition of an acidic medium at room temperature. This reaction was favorable for synthesis of 4-pregnene-3α,20α-diol in better yield, after chemical reduction of 20α-hydroxy-4-pregnen-3-one with metal hydrides, which resulted in predominant production of 4-pregnene-3β,20α-diol. The by-product which was formed more by raising the temperature was identified as 3,5-pregnadien-20α-ol. This method was also applicable for epimerization of other Δ 4 -3β-hydroxysteroids.