18-Norpregna-8,11,13-trienes: reaction of 16α,17α-epoxypregn-8-en-11-ones with Lewis acids

Abstract

Treatment of 3β-acetoxy-16α,17α-epoxy-5α-pregn-8-ene-7,11,20-trione (6) with acetic anhydride gave 3β,17α-diacetoxy-5α-pregna-8,14-diene-7,11,20-trione (10) and 3β,16α-diacetoxy-11-hydroxy-17β-methyl-18-nor-5α,17α-pregna-8,11,13-triene-7,20-dione (8). Two competing mechanisms for the reaction are proposed. Similar attempts to aromatise 3β-acetoxy-16α,17α-epoxy-5α-pregn-8-ene-11,20-dione (4) were unsuccessful.