Patent ID: 7183412

Claim:
An ester compound of formula (I) or a pharmaceutically acceptable salt thereof, wherein formula (I) is: wherein: X 1 to X 4 each independently represents C or N, provided that at least three of X 1 to X 4 represents C; Y represents O; R 1 represents a C 1 to C 6 alkyl group; R 2 represents (a) a C 3 to C 10 alkyl group, or (b) an aryl-C 1 to C 10 alkyl group and that the aryl may be substituted with from one to three of halogen, C 1 to C 6 alkyl, C 1 to C 6 alkyl-O—, nitro, cyano, amino, hydroxycarbonyl, C 1 to C 6 alkyl-NH—, or di-C 1 to C 6 alkyl=N—; R 3 represents H, a C 1 to C 6 alkyl group, an aryl-C 1 to C 6 alkyl group, a heteroaryl-C 1 to C 6 alkyl group, a cycloalkyl-C 1 to C 6 alkyl group, an aryl group, a heteroaryl group, or a cycloalkyl group, provided that the aryl, heteroaryl, and cycloalkyl group may each be substituted with from one to three of halogen, C 1 to C 6 alkyl, C 1 to C 6 alkyl-O—, nitro, cyano, amino, hydroxycarbonyl, C 1 to C 6 alkyl-NH—, or di-C 1 to C 6 alkyl=N—; and R 4 to R 7 may be the same or different and each represents H, a halogen, a nitro group, a cyano group, an amino group, a hydroxycarbonyl group, a C 1 to C 6 alkyl group, a C 1 to C 6 alkyl-O— group, a C 1 to C 6 alkyl-NH group, or a di-C 1 to C 6 alkyl=N— group, provided that in the case where X 1 to X 4 each represents N, R 4 to R 7 to be bound thereto are not present and that R 3 and R 4 may be taken together to form a linear or branched C 1 to C 8 alkylene which may be inserted by N, O or S.