An Approach to Optically Active Pyrrolizidines by an Intramolecular Michael Reaction

Abstract

Treatment of a diastereomeric mixture (5:3) of the a-phenylsulfinylacetamide (3) with a catalytic amount of sodium ethoxide in ethanol at 0°C for 10 min gave the bicyclic lactams (4a) and (4b) in high total yield but with extensive racemization.The cyclization of the diastereomerically pure sulfoxide (3) followed by chromatographic separation of the resulting lactams (4a) and (4b) and desulfurization of each lactam gave (lS,8S)-(-)-and (lR.8R)-(+)-ethyl hexahydro-