Synthesis of Indolizidines (-)-195B, (-)-223AB and (-)-239AB: (2S,5R)-1- [(Benzyloxy)carbonyl]-2-methoxycarbonyl-5-(4-pentenyl)pyrrolidine as a Versatile Chiral Building Block.

Abstract The total syntheses of three levogyre 3,5-disubstituted indolizidines, (−)-195B, (−)-223AB and (−)-239AB are described. The employed strategy is based on the utilization of the common enantiopure trans 2,5-disubstituted pyrrolidine 3 , which is assembled by addition of pent-4-enylcopper to N-acyl iminium ion derived from (S)-proline.