Kinetically Controlled Peptide Synthesis Mediated by Papain Using the Carbamoylmethyl Ester as an Acyl Donor

Abstract

A series of dipeptides were synthesized generally in good yields with carbamoylmethyl (Cam) esters as acyl donors in the presence of a cysteine protease, papain, immobilized on Celite. Several segment condensations were also achieved generally in high yields without danger of racemization and formation of the secondary-hydrolysis product. Moreover, partial sequences of some bioactive peptides were prepared through segment condensations, and aimed-at peptides were obtained generally in high yields without the racemization of C-terminal residues of the carboxyl components. Thus, the superiority of the Cam ester in the kinetically controlled peptide synthesis was once again ascertained in couplings mediated by the cysteine protease as in those catalyzed by the serine proteases reported earlier.