Dehydrooligopeptides. XVIII. Enzymatic Hydrolysis and Coupling of Dehydrodipeptide Esters Containing α-Dehydroamino Acid Residue by Using Papain

The enzymatic hydrolysis of N-protected dehydrodipeptide methyl esters (2) (Protect-ΔAA-AA-OMe) was first achieved, despite the requisite of the only neutral and large proteinic L-α-amino acid (AA) in the case using papain. Furthermore, the reverse enzymatic coupling of the C-component 2 with N-component α-amino acid anilides or dehydrodipeptide esters containing dehydrovaline (ΔVal) residue was also successful. Consequently, the present study suggests that the proteolytic enzyme papain is able to become a very useful tool for peptide synthesis by a coupling of the C-component dehydropeptide with N-component α-amino acid, peptide, or dehydropeptide.