Stereoselective Total Synthesis of (±)-Swainsonine Based on Endo Mode Cyclization

A new stereoselective total synthesis of (+/-)-swainsonine is described. Successive treatment of cis-3,4-epoxy-7-(p-toluenesulfonamido)-1-heptyne with dicobalt octacarbonyl, Lewis acid, and cerium(IV) ammonium nitrate effected stereoselective formation of the trans-2-ethynyl-3-hydroxypiperidine skeleton with retention of configuration at the propynyl center. The piperidine derivative thus prepared was converted into the title compound efficiently.