Proline-catalyzed, asymmetric mannich reactions in the synthesis of a DPP-IV inhibitor.

[reaction: see text] A highly stereoselective L-proline-catalyzed, asymmetric direct Mannich reaction between a glyoxalate-derived imine and phenyl acetaldehyde was employed for the formation of a syn substituted beta-phenyl homoserine. This Mannich adduct was then readily elaborated to a functionalized beta-phenyl aspartic acid derivative through a series of mild and efficient transformations.