Rearrangement of 4β,5β-methylenepregnanes: A simple approach to A-homopregnanes and 5β-methylpregnanes

Abstract

A-homopregnanes and 5β-methylpregnanes were prepared from the easily available 3β-hydroxy-20β-acetoxy-4β,5β-methylenepregnane by cationic and radical rearrangements respectively. The A-homopregnane was formed in a single step upon spontaneous rearrangement and elimination by treatment of the cyclopropyl alcohol with BF3·Et2O. The 5β-methylpregnane was obtained by cleavage of the hydrazone of the corresponding cyclopropylketone followed by rearrangement mediated by mercury(II) hydrides. ©ARKAT.