Abstract Chromogenic substrates of the following types were synthesized: X-Phenylalanine p-nitroanilides, where X= acetyl, hydroxyacetyl, methoxyethoxyacetyl, and 3-carboxy-2- propenoyl,(glycyl) n-phenylalanine p-nitroanilides and 3-carboxypropanoyl (glycyl) n- phenylalanine p-nitroanilides, where n= 1, 2, 3,(glycyl) n-tyrosine p-nitroanilides and 3- carboxypropanoyl (glycyl) n-tyrosine p-nitroanilides, where n= 0, 1, 2, and also ...