Nα-(tert-Butyloxycarbonyl)peptide p-guanidinophenyl esters were synthesized by amidination of Nα-(tert-butyloxycarbonyl)peptide p-aminophenyl esters with 1-[N, N'-bis(benzyloxycarbonyl)amidino]pyrazole, followed by deprotection by catalytic hydrogenation, in good total yields. These synthetic esters were characterized as specific substrates for trypsin, and kinetic parameters for the trypsin-catalyzed hydrolysis are presented.