Unitat de Recerca en Síntesi Asimètrica (URSA-PCB), Parc Científic de Barcelona, and Departament de Química Orgànica, Universitat de Barcelona, c/Josep Samitier, 1-5, 08028-Barcelona, Spain.
[reaction: see text] Deoxymannojirimycin (2) and swainsonine (4) have been synthesized from each enantiomer of the same bicyclic carbamate precursor 7. The key intermediate was prepared by a simple and efficient three-step synthesis involving RCM of the diene 8, which in turn is easily accessible in any configuration from enantiomerically enriched 2,3-epoxy-4-penten-1-ol 9.