INTRAMOLECULAR DIELS-ALDER REACTION WITH FURAN DIENE. A NEW SYNTHESIS OF 11-KETO STEROIDS

Article abstract of DOI:10.1016/S0040-4039(00)88118-6

A novel D <*> BCD <*> ABCD route to 11-keto steroids is reported involving a high yield stereoselective intramolecular Diels-Alder reaction of furan-diene 5a in water as a key-step.The dienophilic side chain is readily introduced starting from 2 via a sequence involving alkylation with ethyl 4-iodo-3-ethoxycrotonate, reduction and acid hydrolysis.The reduced adduct 8a, obtained in 24 percent overall yield from 2-methyl-1,3-cyclopentanedione, is converted into (+/-)-adrenosterone (16) via base-opening to 9 and further transformation to 13, the dienediolate equivalent of which is a known intermediate in corticosteroid synthesis.