A novel compound which is useful as an agent for treating and/or preventing emesis, vomiting and/or constipation. A compound represented by the formula (I):wherein R1 and R2 are each independently hydrogen, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted cycloalkyl, optionally substituted aryl etc., R3 is hydrogen, hydroxy, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted lower alkynyl, optionally substituted lower alkoxy etc., R4 is hydrogen or lower alkyl, R5 is hydrogen, lower alkyl, cycloalkyl lower alkyl or lower alkenyl, or a pharmaceutically acceptably salt, or a solvate thereof is provided.
