Benzamidine derivatives of formula (I) or pharmaceutically acceptable salts thereof exhibit excellent inhibitory activity against factor Xa and are useful for treating or preventing blood coagulation disorders:
wherein R1 represents a hydrogen atom, a halogen atom, an alkyl group or a hydroxyl group; R2 represents a hydrogen atom, a halogen atom or an alkyl group, R3 represents a hydrogen atom, an optionally substituted alkyl group, an aralkyl group, an optionally substituted alkanoyl group or an optionally substituted alkylsulfonyl group, R4 and R5 are the same as or different from each other and each represent a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group or an optionally substituted carbamoyl group, and R6 represents a substituted pyrrolidine group or substituted piperidine group.
To develop a potent and oral anticoagulant, a series of compounds with cinnamyl moiety was synthesized and their factor Xa (FXa) inhibitory activities were examined. As a result, some cinnamyl derivatives showed potent FXa inhibitory activities in vitro. Among them, compounds with substituent at the 3-position on the central benzene ring represented by (N-4-[1-(acetimidoyl)piperidin-4-yloxy]-3-chlorophenyl}-N-[(E)-3-(3-amidinophenyl)-2-propenyl]sulfamoyl)acetic acid dihydrochloride (45b) and (N-4-[1-(acetimidoyl)piperidin-4-yloxy]-3-carbamoylphenyl}-N-[(E)-3-(3-amidinophenyl)-2-propenyl]sulfamoyl)acetic acid dihydrochloride (45j) exhibited potent FXa inhibitory activities with IC50 values of less than 10 nM in vitro. These compounds also showed potent anticoagulant activities both in vitro and ex vivo. Furthermore, these compounds exhibited no lethal toxicity (30 mg/kg, i.v.).