Brønsted Acid Catalyzed Peptide Synthesis through Azlactone Rings

Brønsted acid catalyzed azlactone ring opening by amino acids leading to the synthesis of dipeptides is presented. Eleven compounds were synthesized in good to excellent isolated yields. Catalyst loading revealed that 5.0 mol % of (+/-)-CSA as an organocatalyst, under room temperature for 24 h, was suitable to promote this transformation.