| abstract |
A compound represented by formula (I) or a pharmaceutically acceptable salt thereof: {wherein Ar represents a monocyclic heterocyclic ring represented by the following formula: which may be substituted with a substituent selected from the group consisting of a C1-alkyl group -C6, a phenyl group and a halogen atom, each of Y1, Y2 and Y3 represents a carbon atom or a nitrogen atom, A represents an oxygen atom, R1 represents a hydrogen atom, a C1-alkyl group C6 which may be substituted with one or more substituents selected from the following group [in which said group consists of a hydroxyl group, a halogen atom, a C1-C6 alkoxy group (in which said alkoxy group may be substituted with a group-phenyl) and a phenyl group (wherein said phenyl group may be substituted with one or more substituents selected from the group consisting of a halogen atom and a C1-C6 alkyl group)], a C3-C8 cycloalkyl group, a C2-C8 alkenyl group, a C2-C8 alkynyl group or a phenyl group, R2 represents a hydrogen atom, a C1-C6 alkyl group or a C3-C8 cycloalkyl group, R3 represents (i) a hydrogen atom, ( ii) a C1-C18 alkyl group, (iii) a C2-C8 alkenyl group that can be substituted with a phenyl group or a benzyloxy group, (iv) a C2-C8 alkynyl group that can be substituted with a phenyl group, (v) a C3-C8 cycloalkyl group which may be condensed with a benzene ring, (vi) a C1-C6 alkyl group substituted with one or more substituents selected from the following group [in which group consists of a halogen atom, a group phenyl (wherein said phenyl group may be substituted with 1 to 5 substituents selected from the group consisting of a phenyl group, a cyano group, a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, a trifluoromethyl group, a grupomethoxycarbonyl, a C1-C6 alkylthio group, a dimethylamino group, a group nitro and an acetamido group), a C3-C8 cycloalkyl group, a hydroxyl group, a C1-C6 alkylthio group, a C1-C6 alkoxy group, a benzyloxy group, a phenoxy group, a trifluoromethyl group, a difluoromethyl group, a benzenesulfonyl group , a naphthyl group, a C7-C10 tricycloalkyl group, a carbomethoxy (phenyl) methyl group, a diphenylmethyl group, a 1-phenylethyl group, an imidazolyl group, an indolyl group, a pyridyl group, an oxetanyl group, an oxolanyl group, a grupomethylpiperidinyl, a piperazino group that may be substituted with one or more C1-C6 alkyl groups, a benzylpiperidinyl group, a morpholino group, a 2-oxopyrrolidin-1-yl group, a 2-oxoimidazolidin-1-yl group, a group represented by the formula: |