A chiral hexahydroindolizine as key intermediate in the synthesis of tri- and tetrahydroxyindolizidines

The highly stereoselective functionalization of hexahydro-3-oxo-indolizine 6 has been examined. The bishydroxylated product can be transformed successfully into the trihydroxyindolizidine 11 in 57% overall yield. In addition, a simple elimination process to give the α,β-unsaturated lactam 13 and a second highly stereoselective bishydroxylation can be used to synthesise the tetrahydroxyindolizidine 19 in 30% overall yield.