Synthetic studies of withanolides. Part 2. Synthesis of 4aβ,5β-epoxy-4a,5,6,7,8,8a-hexahydro-4β-hydroxy-8aβ-methylnaphthalen-1(4H)-one and related compounds

The title compound, a simple AB ring moiety of withaferin A, and its seven isomers, were synthesized via octahydro-4a-hydroxy-5-(phenylthio)-8a-methylnaphthalen-1(2H)-ones [(5a) and (5b)]. The key steps in the synthesis involve either 1,2-phenylthio-migration, or dehydration reactions of (5a) and (5b).