Chymase inhibitors are imperative for elucidation of the physiological functions of chymase and potentially useful therapeutic agents. Several chymase inhibitors such as sulfonyl fluoride derivatives [10] , Boc-Val-Pro-Phe-CO 2 Me [11] , Z-Ile-Glu-Pro-Phe-CO 2 Me, (F)-Phe-COGlu-Asp-ArgOMe [12] , N-(2-Naphthyl) carboxamido derivatives [13] , N- (2,2-dimethyl-3-(N-(4-cyanobenzoyl) amino) nonanoyl)-L-phenylalanine ethyl ester [14] , 3-benzylazetidine-2-one derivatives [15] , 1,3-diazetidine-2,4-dione derivatives [16] , methyllinderone derivatives [17] , chloromethyl ketone derivatives [18] , 1-oxacephem derivatives [19] , and 3-(phenylsulfonyl)-1-phenylimidazolidine-2,4-dione derivatives [20] have been reported previously. In general, chymase inhibitors readily decompose in plasma, thus the stability of the chymase inhibitors in human plasma has always been a matter of great concern. For a drug candidate, it is essential to enhance the stability of the active compound in human plasma. So, there is always a dire need to search for more stable inhibitors with high activity against human chymase.