Dehydrooligopeptides. XX. Unusual Peptide Bond Cleavage of Dehydrotripeptide Esters Containing α-Dehydroamino Acid Residue at P2 by Using Papain

Article abstract of DOI:10.1246/bcsj.70.1427

Enzymatic ester hydrolysis and coupling of various N- protected Δ² - dehydrotripeptide methyl esters (Boc-AA-ΔAA-AA-OMe) (4) by using protease papain in Mcllvaine buffer are mainly described. The substrates (4) used were prepared by one-pot coupling of N-carboxy-α-dehydroamino acid anhydride (ΔAA·NCA) with N- and C-component L-α-amino acids (AA). Even in the enzymatic reaction of 4 containing an unusual ΔAA residue, the normal ester hydrolysis took place to give Boc-AA-ΔAA-AA-OH (6) and, in certain cases, the interesting unusual peptide bond cleavage at P₂ of 6 occured further to give the unexpected N-(1,2-dioxoalkyl)-AA-OH. Besides examining in detail the differences between the enzymatic actions to the structures of 4, we also studied the mechanisms of the ester and peptide bond hydrolyses. As the results, the reverse enzymatic coupling of 4 with H-AA-ΔVal-OMe was first achieved to give dehydropentapeptide containing two ΔAA residues.