Acid-catalysed cleavage of some 3-substituted 5α,6α-epoxy-7-norandrostan-17-ones

Abstract

Crystallographic and spectroscopic studies show that treatment of 3β-acetoxy-5α,6α-epoxy-7-norandrostan-17-one with HBr in glacial acetic acid gives 3β-acetoxy-6-bromo and 3β,6-dibromo-7-norandrost-5-en-17-one and 5β-bromo-3α,6α-epoxy-7-norandrostan-17-one. Cleavage of the epoxide with periodic acid gives the 5β,6α-diol. The corresponding 3β-methanesuIphonate gave 3β,6β-dibromo-5β-methyl-7,19-dinorandrost-9-en-17-one and 1-methyl-7-norestra-1,3,5(10)-trien-17-one. The formation of these products is rationalized in terms of the various modes of collapse of a C-5 carbocation.