Asymmetric Synthesis of Quaternary α- and β-Amino Acids and β-Lactams via Proline-Catalyzed Mannich Reactions with Branched Aldehyde Donors

reaction: see text L-Proline-catalyzed direct asymmetric Mannich reactions of N-PMP protected alpha-imino ethyl glyoxylate with various alpha,alpha-disubstituted aldehydes affords quaternary beta-formyl alpha-amino acid derivatives with excellent yields and enantioselectivities. The Mannich products are further converted to the corresponding quaternary alpha- and beta-amino acids and beta-lactams.