Direct asymmetric synthesis of beta-amino ketones from sulfinimines (N-sulfinylimines). Synthesis of (-)-indolizidine 209B.

N-Sulfinyl beta-amino ketones, prepared directly from the potassium enolates of methyl ketones and enantiopure sulfinimines, are transformed in one pot to protected amino ketones, which are valuable chiral building blocks for the assembly of piperidines. The utility of this methodology is illustrated in a concise asymmetric synthesis of (-)-indolizidine 209B. [reaction: see text]