The Asymmetric Addition of the Sn(II) Enolates of Thioesters to α-Iminoesters. A Convenient Synthesis of Optically Active cis-Substituted β-Lactams.

Abstract
The asymmetric addition of the Sn(II) enolates derived from thioesters to α-iminoesters having the chiral auxiliary on the nitrogen atom proceeds smoothly to afford syn-β-aminoacid derivatives, which are in turn converted to optically active cis-substituted β-lactams.