Summary: A short, enantiospecific synthesis of (-)-swainsonine (1) from D-mannose has been achieved by a route involving, as a key step, a double cyclization of 4c. The synthesis takes advantage of new features of sodium borohydride for reducing conjugated esters and lactams.
![(3aR,9R,9aS,9bS)-2,2-dimethyloctahydro-[1,3]dioxolo[4,5-a]indolizin-9-yl methanesulfonate Structure](https://image.chemsrc.com/caspic/128/107690-78-8.png)
