Enantioselective synthesis of (+)-equilenin 1 utilizing two types of cascade ringexpansion reactions of smallring systems is described. The first key step is an asymmetric epoxidation–ring expansion reaction of cyclopropylidene derivatives to afford chiral cyclobutanones. We found that both the fructose-derived chiral ketone and the chiral (salen)Mn(III) complex were effective catalysts for the asymmetric
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 ringexpansion reactions of small ring systems; 1) chiral (salen)MnIII complex-catalyzed cascade reaction of cyclopropylidene; 2) PdII-mediated cascade reaction of the cyclobutanol.