This invention provides a compound of the formula (I): ##STR1##

wherein:

R¹ represents a hydrogen atom, an alkyl group, etc.; R² represents a hydrogen atom, a halogen atom, etc.; R³ represents an alkyl group, etc.; R⁴ represents an aryl group, etc.;

A represents an aryl¹, etc; B represents an alkylene etc.; X represents NH, etc.;

or a pharmaceutically acceptable ester of such compound,

and pharmaceutically acceptable salts thereof.

These compounds are useful for the treatment of medical conditions mediated by prostaglandin such as pain, fever or inflammation, etc. This invention also provides a pharmaceutical composition comprising the above compound.