Imidazolidine derivatives and their use

Imidazolidine derivative represented by the general formula (I) and medicines containing them as the active ingredient, representative examples include chymase inhibitor AND PREVENTIVE OR REMEDY FOR DISEASES CIRCULATORY OR CARDIAC CAUSED BY ABNORMAL PALPITATIONS INDUCED Angiotensin II WHERE AYB each represents an aromatic hydrocarbon group which may be substituted by one or more substituents selected from halogen, alkyl, alkoxy, alkylenedioxy, phenoxy, nitro, cyano, phenyl, alkanoylamino, carboxyl BE esterified alkyl or alkenyl, carboxyalkyl BE esterified alkyl or alkenyl, carboxyalkyloxy BE OALQUENILO alkyl esterified, N-alkylpiperazinyl alkoxycarbonyl, N-alkylpiperazinyl-CARBONIALQUILO, N-morpholinocarbonyl ALQUILOPIPERAZINIL-carbonylalkyloxy Y; X represents oxygen or sulfur.