A novel strategy for the enantioselective synthesis of the steroidal framework using cascade ring expansion reactions of small ring systems - Asymmetric total synthesis of (+)-equilenin

Enantioselective synthesis of (+)-equilenin (1) utilizing a novel strategy is described. The key steps are two cascade ring expansion reactions of sma ll ring systems; 1) chiral (salen)Mn-III complex-catalyzed cascade reaction of cyclopropylidene; 2) Pd-II-mediated cascade reaction of the cyclobutano l. (C) 1999 Elsevier Science Ltd. All rights reserved.