Direct and highly stereoselective synthesis of quinolizidine iminosugars promoted by l-proline-Et3N.

A mild and effective method for the synthesis of polyhydroxylated quinolizidine iminosugars is described. The Mannich-type reaction of iminosugar C-glycosides with aldehyde in the presence of l-proline-Et3N provides polyhydroxylated quinolizidine iminosugars, and desired products as the potential glucosidase inhibitors were obtained in good to excellent yields with excellent stereoselectivity.