A compound represented by the formula (I) ##STR1##

wherein one of R¹ and R² is a hydrogen atom or a substituent and the other is an optionally substituted cyclic group; W is a bond or a divalent aliphatic hydrocarbon group; Y is a group of the formula: —OR³ (wherein R³ is a hydrogen atom, an optionally substituted hydrocarbon group, an optionally substituted heterocyclic group or an optionally substituted acyl group) or an optionally esterified or amidated carboxyl group, or a salt thereof or a prodrug thereof has a superior insulin secretion promoting action and a hypoglycemic action and shows low toxicity. Therefore, the compound is useful as a pharmaceutical agent, particularly as an agent for the prophylaxis or treatment of diabetes and diabetic complications, and the like.