Patent ID: 8163770

Claim:
A compound of the formula (I): wherein: R 1 represents methyl or ethyl; R 2 each independently represents a hydrogen atom, a lower alkyl group (wherein the lower alkyl group may be substituted with a halogen atom), a lower alkoxy group (wherein the lower alkoxy group may be substituted with a halogen atom), or a halogen atom; X is an oxygen atom; Y is a sulfanyl group, a sulfinyl group or a sulfonyl group; Ar represents a divalent group derived from a benzene ring, a pyridine ring, a pyrimidine ring, a pyrazine ring or a pyridazine ring by removing two hydrogen atoms therefrom (wherein the divalent group may be substituted with a halogen atom, a hydroxyl group, a lower alkoxy group, wherein the lower alkoxy group may be substituted with a halogen atom, a lower alkyl group, wherein the lower alkyl group may be substituted with a halogen atom); X 1 represents a carbon atom, a nitrogen atom, a sulfur atom or an oxygen atom; X 2 represents a group of a formula (III): wherein the point of attachment of group of the formula (III) is other than through the nitrogen atom, and wherein R 6 represents a lower alkyl group (wherein the lower alkyl group may be substituted with a halogen atom), or a cycloalkyl group (wherein the cycloalkyl group may be substituted with a lower alkyl group or a halogen atom), n indicates from 0 to 4, X 3 to X 6 each independently represent —CR 2 — or a nitrogen atom, n indicates from 0 to 4; however, not more than one of X 3 to X 6 is a nitrogen atom; the formula (V): indicates a single bond or a double bond; or a pharmaceutically acceptable salt thereof.