Abstract: A compound represented by the following formula: wherein R is a substituted or unsubstituted benzene ring, a fused polycyclic hydrocarbon ring which is substituted or unsubstituted, a monocyclic heterocyclic ring which is substituted or unsubstituted, a polycyclic heterocyclic ring which is substituted or unsubstituted, A and E are independently a single bond, a lower alkylene group or the like, G is a single bond, an oxygen atom or the like, and Y is a —SO3H group or the like, a prodrug of said compound, or a pharmaceutically acceptable salt of said compound or prodrug is useful as a therapeutic or prophylactic agent for diseases caused by the acceleration of the sodium/proton exchange transport system.