To obtain a new compound useful for a medicine effective in treatment of various diseases such as hypertension and cardiac disease caused by chymotrypsin-like protease, and a biochemical reagent.

This new compound is 2,2-dimethyl-3-(N-4-cyanobenzoy)amino-5- phenylpentanoic anhydride of the formula. The compound of the formula is obtained by reacting 2,2-dimethyl-3-amino-5-phenylpentanoic acid with 4- cyanobenzoyl chloride in the presence of pyridine in dimethylformamide to provide (A) 2,2-dimethyl-3-(N-4-cyanobenzoyl)amino-5-phenyl-pentanoic acid, and further reacting the components A with each other in the presence of triethylamine in methylene chloride by using bromo-tris-pyrrolidino-phosphonium hexafluorophosphate. When using the compound as a medicine, the clinical daily dose by an oral administration is preferably 10-100 mg/adult expressed in terms of an active ingredient.