Substituted 1,3-thiazolo[5,4-d]pyrimidines as xanthine oxidase inhibitors

Compounds of the following formula (I) or salts thereof

• in which
• R1 represents an aryl group having 6-10 carbon atoms or a hetero-aryl group which may have a substituent selected from the group consisting of an alkyl group having 1-8 carbon atoms, a halogen-substituted alkyl group having 1-8 carbon atoms, an alkoxy group having 1-8 carbon atoms, an alkoxy group having 1-8 carbon atoms which is substituted with an alkoxy group having 1-8 carbon atoms, an alkoxycarbonyl group having 2-8 carbon atoms, formyl, carboxyl, halogen, hydroxyl, nitro, cyano, amino, an aryl group having 6-10 carbon atoms, and an aryloxy group having 6-10 carbon atoms;
• R2 represents cyano, nitro, formyl, carboxyl, carbamoyl, or an alkoxycarbonyl group having 2-8 carbon atoms;
• R3 represents hydroxyl, amino, carboxyl, mercapto, OR4 or NHR5 in which each of R4 and R5 is an alkyl group having 1-8 carbon atoms which may have a substituent selected from the group consisting of halogen, hydroxyl, nitro, cyano, amino, an aryl group having 6-10 carbon atoms, and an aryloxy group having 6-10 carbon atoms;
• X represents oxygen, —N(R6)—, or —S(O)n— in which R6 is hydrogen, an alkyl group having 1-8 carbon atoms, or the group for R1, and n is an integer of 0 to2;
• and
• Y represents sulfur.