Asymmetric Syntheses of 1-Deoxy-6,8a-di-<i>epi</i>-castanospermine and 1-Deoxy-6-<i>epi</i>-castanospermine

Abstract

Asymmetric syntheses of both 1-deoxy-6,8a-di-<i>epi</i>-castanospermine and 1-deoxy-6-<i>epi</i>-castanospermine, polyhydroxylated indolizidine alkaloids that act as selective glycosidase inhibitors, have been accomplished in seven steps. The key feature of our unique syntheses includes the stereoselective introduction of the C-3 and C-4 hydroxyl groups utilizing the aza-Claisen rearrangement-induced ring expansion of 1-acyl-2-alkoxyvinyl pyrrolidine and a substrate-controlled stereoselective transannulation of the resulting azoninone intermediate