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.
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
L-Amino-acid 4-methoxybenzylester hydrochlorides were synthesised by the interaction of 4-methoxybenzyl halides with amine or silver salts of the corresponding N-(2-nitrophenylthio)-L-amino-acids followed by removal of the N-protecting group. Direct esterification of the toluene-4-sulphonate of L-phenylalanine with 4-methoxybenzyl alcohol proceeded in rather low yield. Esters were cleaved with formic