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 R 1 and R 2 are each independently hydrogen, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted cycloalkyl, optionally substituted aryl etc., R 3 is hydrogen, hydroxy, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted lower alkynyl, optionally substituted lower alkoxy etc., R 4 is hydrogen or lower alkyl, R 5 is hydrogen, lower alkyl, cycloalkyl lower alkyl or lower alkenyl, or a pharmaceutically acceptably salt, or a solvate thereof is provided.
