Several kinds of modified chymotrypsin were prepared with water-soluble acylating reagents, and their characteristics after hydrolyzing with unmodified chymotrypsin in aqueous-N,N'-dimethylformamide (DMF) media were compared. It was found that chymotrypsin (Csin), of which a 20% amino group was modified with a benzyloxycarbonyl group (Z(20)Csin), had more favorable characteristics than unmodified chymotrypsin with regard to hydrolytic activity in an aqueous DMF media. We also investigated the Z(20)Csin-catalyzed peptide synthesis in two different solution systems. In the one-layer system containing water and DMF, Z(20)Csin catalyzed the peptide bond formation in a higher yield than that by unmodifide chymotrypsin and enabled a synthetic reaction in even an 80% (v/v) DMF media, in which the hydrolytic reaction could not be carried out. Z(20)Csin catalyzed the condensation between some N-acyl amino acids or peptide derivatives and amino acids in 90% ethylacetate, 90% hexane or 50% benzene. This latter method employs a two-layer system, and the modified enzyme may be able to reduce the number of synthetic steps when preparing acyl peptides.

In order to increase the applications of the water-soluble active ester method, water-soluble acylating reagents, [p-(benzyloxycarbonyloxy)phenyl]dimethylsulfonium methyl sulfate, [p-(t-butoxycarbonyloxy)phenyl]dimethylsulfonium methyl sulfate and [p-(9-fluorenylmethyloxycarbonyloxy)phenyl]dimethylsulfonium methyl sulfate, were synthesized from of p-hydroxyphenyldimethylsulfonium methyl sulfate. These compounds had high solubility (more than 30%) in water and were found to act as excellent water-soluble acylating reagents for the synthesis of N-benzyloxycarbonyl, N-t-butoxycarbonyl, N-9-fluorenylmethyloxycarbonyl amino acid derivatives in aqueous solution. They converted dipeptides to N-acyl-dipeptides in aqueous media as well as amino acids. In addition, they were found to be efficient reagents for protecting the side chains of lysine, ornithine, and cysteine.

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ChemInform Abstract The title compound (III) is a useful reagent for the protection of amino acids, e.g. (IV). The marked advantage of using the water soluble (III) is the easy removal of unreacted reagent from the reaction mixture.