The extremely low efficiency during the α-chymotrypsin-catalyzed coupling of an inherently poor amino acid substrate, e.g., alanine, using the methyl ester as an acyl donor was significantly improved using esters such as the 2,2,2-trifluoroethyl or carbamoylmethyl ester. The ameliorating effect of the latter ester was especially significant.
carbamoylmethyl (Cam) esters as acyldonors 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
Broadening of the substrate tolerance of α-chymotrypsin by using the carbamoylmethyl ester as an acyl donor in kinetically controlled peptide synthesis
In the kinetically controlled approach of peptide synthesis mediated by α-chymotrypsin, the broadening of the protease’s substrate tolerance is achieved by switching the acyldonor from the conventional methyl ester to the carbamoylmethyl ester. Thus, as a typical example, the extremely low coupling efficiency obtained by employing the methyl ester of an inherently poor amino acid substrate, Ala, is