Short stereoselective synthesis of alpha-substituted gamma-lactams.

A concise, stereoselective synthesis of alpha-substituted gamma-lactams is reported. gamma-Lactam scaffolds 2 and 3, possessing an Evans' chiral auxiliary and two types of N substituents, were successfully alkylated with different electrophiles to give alpha-substituted gamma-lactams with reasonable diastereoselectivities. The use of a masked carboxymethyl function off the lactam nitrogen provided a convergent means to alpha-substituted gamma-lactam dipeptide isosteres.