This invention provides a compound of the formula (I): ##STR00001## wherein X represents a carbon atom or the like: Y represents imino, or the like: R.sup.1 represents an alkyl group having from 1 to 6 carbon atoms or the like: R.sup.2 and R.sup.3 independently represents a hydrogen atom or the like. These compounds are useful for the treatment of disease conditions mediated by prostaglandin such as pain, or the like in mammalian. This invention also provides a pharmaceutical composition comprising the above compound.