1. We report the trypsin-catalysed conversion, in high yield, of peptides to peptide hydrazides, t-butyloxycarbonylhydrazides and phenylhydrazides. The substitution is at the alpha-carboxy group. 2. We discuss the relative merits of carrying out the conversion either simultaneously with tryptic cleavage of the parent protein or after such cleavage. 3. We report analogous results with chymotrypsin, elastase and subtilisin. 4. We propose the use of such products in protein semi-synthesis and in the preparation of specific proteinase inhibitors.
