A compound represented by the formula (I) or a pharmaceutically acceptable saltthereof: (I) wherein X to X independently represent acarbon atom or the like； the ring A represents a 5- to 6-membered heteroaryl having1 to 4 heteroatoms independently selected from the group consisting of a nitrogenatom, a sulfur atom and an oxygen atom； X represents an oxygen atomor the like； X represents a carbon atom or the like； Het represents a 5- or 6-memberedaliphatic heterocycle； R represents an aryl or the like； Rrepresents a formyl group or the like； and R represents a -Calkyl or the like. The compound or salt has a glucokinase activation effect andis useful as a therapeutic agent for diabetes.
