Asymmetric total synthesis of (+)-equilenin utilizing two types of cascadering expansion reactions of small ring systems

Enantioselective synthesis of (+)-equilenin 1 utilizing two types of cascad e ring expansion reactions of small ring systems is described. The first ke y step is an asymmetric epoxidation-ring expansion reaction of cyclopropyli dene derivatives to afford chiral cyclobutanones. We found that both the fr uctose-derived chiral ketone and the chiral (salen)Mn(III) complex were eff ective catalysts for the asymmetric induction. The second key step is the p alladium-promoted cascade ring expansion-intramolecular insertion reaction of the isopropenylcyclobutanol. Solvents were an important factor for the d iastereoselective formation of hydrindanes. By utilizing these methodologie s, the asymmetric total synthesis of (+)-equilenin 1 has been accomplished.