Solid phase synthesis of N-carboxy alkyl-containing peptides derived from enantiopure αketo-β-aminoacids

α-Keto-β-aminoacids 5a-c can be reductively aminated with the peptide sequence H2N-Leu-Val-Phe-Phe on a solid support to afford N-carboxy alkyl peptides 1a-c. The N-carboxy alkyl lysine derivative 7 was subsequently extended from the N-terminus with glutamine and histidine residues.