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.