Diastereoselective access to nonracemic 2-cis-substituted and 2,6-cis-disubstituted piperidines.

Access to nonracemic amino ketones via a hydrozirconation/transmetalation/acylation sequence applied to Boc-protected 1-aminobut-3-enes is presented. This method was applied to the stereoselective synthesis of cyclic imines (or iminiums) which were diastereoselectively converted into 2-cis-substituted and 2,6-cis-disubstituted piperidines. The potential of this approach in the field of alkaloid synthesis was illustrated by the synthesis of (-)-coniine and (-)-indolizidine 209D. Furthermore, access to indolizidines bearing a quaternary center could also be envisioned through this strategy.