This invention provides the compounds of formula (I): ##STR00001## or a pharmaceutically acceptable ester of such compound, or a pharmaceutically acceptable salt thereof, wherein R.sup.1 and R.sup.2 independently represent a hydrogen atom or the like; R.sup.3 represents an aryl group having from 6 to 10 ring atoms or the like; X represents an oxygen atom, or the like; Y represents an oxygen atom or the like; and n represents an integer 0, 1 or 2. These compounds have ORL1-receptor antagonist activity; and therefore, are useful to treat diseases or conditions such as pain, various CNS diseases etc.