The object is to provide: a compound having an analgesic activity a pharmaceutical composition and an analgesic agent, each of which comprises the compound an analgesic treatment method using the compound and use of the compound in an analgesic treatemnt. Disclosed is a compound represented by the formula (I) or a salt thereof. (I) wherein R1 represents a hydrogen atom or a halogen atom R2, R3, R4 and R5 independently represent a hydrogen atom, a hydroxy group, an alkoxy group which may have a substituent or the like and R6 represents an alkoxycarbonyl group which may have a substituent or a carboxy group.
