Total Synthesis of ( + )-Swainsonine, (–)- Swainsonine, ( + )-8-epi-Swainsonine and ( + )- Dideoxy-Imino-Lyxitol by an Organocatalyzed Aldolization/Reductive Amination Sequence

A tactical combination of either (S)- or (R)-proline catalyzed aldol reaction followed by intramolecular reductive amination enabled the synthesis of a chiral pyrrolidine derivative with 3 contiguous stereocenters in only 2 synthetic steps, starting from achiral precursors. This product, obtainable in both enantiomeric forms, was further exploited as a common intermediate in total syntheses of the biologically active iminosugars: ( + )-swainsonine, (–)-swainsonine, ( + )-8-epi-swainsonine, and ( + )-dideoxy-imino-lyxitol