Acid-catalysed reactions of 1α,2α-epoxy-1β-methyl- and 1α-hydroxy-1β-methyl-5α-steroids

Abstract

The reaction of 1α,2α-epoxy-1β-methyl-5α-androstane-3β,17β-diol diacetate (4) with boron trifluoride–ether leads to both the A-nor derivative (5) and the 2α-hydroxy-1-methylene compound (6). The epoxide (4) on treatment with acetic anhydride–acetic acid and toluene-p-sulphonic acid gives, depending upon temperature, the 1α,2β-diacetoxy-compound (11) or the 2β-acetoxy-1-methylene compound (12), while with formic acid gives the 2-formate (13) of the 1α,2β-diol. The reaction of 1α,2α-epoxy-1β-methyl-5α-androstane-3α,17β-diol diacetate (14) with boron trifluoride affords the A-noraldehyde (15) and the 1-methylene derivative (16). 1β-Methyl-5α-androstane-1α,3β,17β-triol 3,17-diacetate (19) with toluene-p-sulphonic acid is simply acetylated to give (20) and dehydrated to give (21).