Abstract: A prolylphenylalanylarginine derivative represented by the formula, ##STR1## wherein R.sub.1 represents hydrogen or benzoyl; R.sub.2 represents naphthyl or 6-bromo-2-naphthyl. The above compound is useful as an excellent substrate for various enzymes, such as trypsin, plasmin, kallikrein, urokinase, Clesterase and the like. Accordingly, the activity of enzymes can be measured by use of said compound as a substrate.

Abstract: A valylleucyllysine derivative represented by the formula, ##STR1## wherein R.sub.1 represents hydrogen or benzoyl and R.sub.2 represented naphthyl. The above compound is useful as an excellent substrate for various anzymes, such as, trypsin, plasmin, kallikrein, urokinase, Cl-esterase and the like. Accordingly, the activity of enzymes can be measured by use of said compound as a substrate.

Abstract: Amino- or guanidino-1,2,3,4-tetrahydro-1-naphthoic esters represented by the formula, ##STR1## wherein R.sub.1 is --NH.sub.2 or ##STR2## R.sub.3 is --H, --R.sub.4, --O--R.sub.4, --NHCOCH.sub.3, a halogen, --CN, ##STR3## --COOH, --COOR.sub.4, ##STR4## or --(CH.sub.2).sub.n --COOCH.sub.2 --CO--R.sub.5 ; R.sub.5 is --O--R.sub.4, --NH.sub.2 or ##STR5## n is 0, 1 or 2, and R.sub.4 is a lower alkyl, or pharmaceutically acceptable acid addition salts thereof. Owing to their inhibitory activity on proteolytic enzymes the said esters and acid addition salts thereof are useful in the therapy of diseases caused by such enzymes.

Abstract: Amino- or guanidino-phenylpropionic ester derivatives represented by the formula: ##STR1## wherein R is --NH.sub.2 or ##STR2## R.sup.1 is hydrogen or a lower alkyl group, and R.sup.2 is an unsubstituted or a lower-alkyl-, carboxyalkyl-, lower-alkoxy-, lower-alkoxycarbonyl- or halogen-substituted phenyl group or an unsubstituted or a halogen-substituted naphthyl group, and acid addition salts thereof are novel compounds exhibiting a specific enzyme-inhibitory activity to proteolytic enzymes and, therefore, they are useful as the therapeutic agent of diseases induced by abnormal activation of these enzymes. The above-mentioned compounds can be produced by subjecting a nitrocinnamic acid derivative represented by the formula: ##STR3## and a phenol derivative or a naphthol derivative represented by the formula:HO--R.sup.