The present compounds represented by the formula: ##STR1## (wherein R.sup.1 is a phenyl group, a halophenyl group or a cycloalkyl group having 3 to 8 carbon atoms, R.sup.2 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R.sup.3 is a hydrogen atom, an alkyl group having 1 to 7 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an alkenyl group having 3 to 5 carbon atoms or a benzyl group, or R.sup.2 and R.sup.3 are bonded together to form a 5- to 7-membered heterocycle) and salts thereof have potent anti-inflammatory, antipyretic, analgesic and anti-allergic actions with less side effects such as gastrointestinal disorders and with such a high safety as to permit long-term administration.
