The present invention relates to a compound represented by the formula (I):or a pharmacologically acceptable salt thereof, wherein R1, R2, R3, and R4are the same or different and each represent a hydrogen atom or a C1-6 alkyl group； X1represents a C1-6 alkylene group that may be substituted； Xarepresents a methoxy group or a fluorine atom； Xbrepresents an oxygen atom or a methylene group, provided that Xbis only an oxygen atom when Xais a methoxy group； and Ar1represents an aryl group, pyridinyl group, aryloxy group, or pyridinyloxy group that may have a substituent such as a halogen atom； and to use of the compound or salt as a pharmaceutical agent.本發明關於式(I)所代表之化合物或其藥理學上可接受之鹽類：其中R1、R2、R3及R4係為相同或不同，以及各自代表氫原子或C1－6烷基；X1代表可經取代之C1－6伸烷基；Xa代表甲氧基或氟原子；Xb代表氧原子或伸甲基，其限制條件為當Xa為甲氧基時，Xb僅為氧原子；以及Ar1代表芳基、吡啶基、芳氧基，或吡啶氧基，其具有例如鹵素原子之取代基；以及關於化合物或鹽類作為藥劑之用途。
