INTRAMOLECULAR DIELS-ALDER REACTION WITH FURAN-DIENE. TOTAL SYNTHESIS OF (+/-)-11-KETOTESTOSTERONE AND (+/-)-ADRENOSTERONE.

Article abstract of DOI:10.1016/S0040-4020(01)82362-0

A novel D <*> BCD <*> ABCD route to 11-keto steroids is reported involving a high yield stereoselective intramolecular Diels-Alder reaction of furan-diene 12 in water as a key-step.The dienophilic side chain is readily introduced starting from 8 via a sequence involving alkylation with ethyl (E)-3-ethoxy-4-iodo-2-butenoate, reduction and acid hydrolysis.The reduced adduct 14 is further converted into (+/-)-adrenosterone (6) via 24, the dienediolate equivalent of which is a known intermediate in corticosteroid synthesis.