Concise and divergent total synthesis of swainsonine, 7-alkyl swainsonines, and 2,8a-diepilentiginosine via a chiral heterocyclic enaminoester intermediate

The concise and divergent total syntheses of (−)-swainsonine, (−)-7-alkyl swainsonines, and (−)-2,8a-diepilentiginosine from a common chiral heterocyclic enaminoester intermediate in five-step sequences are presented. The highly efficient annulation reaction of the chiral heterocyclic enaminoester with various α,β-unsaturated carboxylates, and a straightforward carboxy inversion constituted the key features of the synthetic pathway. This work provides an example for divergent synthesis of different natural and unnatural polyhydroxylated indolizidines from a readily available platform.