Stereoselective Approach to <i>cis</i>-2,3-Disubstituted Piperidines via Reduction of <i>N</i>‑Acyliminium Ion Intermediate: Enantioselective Synthesis of (+)-(2<i>S</i>,3<i>S</i>)‑CP-99,994

A very simple and efficient stereoselective approach to <i>cis</i>-2,3-disubstituted piperidines via the reduction of <i>N</i>-acyliminium ion intermediates is described. Application of this methodology is exemplified by the enantioselective total synthesis of (+)-(2<i>S</i>,3<i>S</i>)-CP-99,994