Synthesis of chromophoric dipeptides as substrates for papain

Chromophoric dipeptides (2) and (3) are found to be better substrates for papain in comparison to simpler substrates 1a or 1b. A synthetic strategy for obtaining α-NH(COOEt)-5-MTA-Et (1b), Ala-5-MTA-Et (2), Phe-5-MTA-Et (3) has been described.