Ring c aromatic steroids. Part 2. Rearrangement of 16α,17α-epoxy-and 17α-hydroxy-5,7-dienes

Abstract

Epoxide-opening in 3β-acetoxy-16α,17α-epoxypregna-5,7-dien-20-one (3) and its Δ^6,8(14)-isomer (7), as induced by boron trifluoride–acetic anhydride is accompanied by C-13 methyl migration. The product, 3β,16α-diacetoxy-17β-methyl-18-norpregna-5,7,13-trien-20-one (4) was converted in two steps into the c-aromatic steroid 3β,16α-diacetoxy-17β-methyl-18-norpregna-8,11,13-trien-20-one (6) as a mixture of C-5-epimers. A D-homo-product (17) resulted from acid-catalysed rearrangement of 3β,20ξ-diacetoxy-17α-hydroxypregna-5,7-diene (16).