A compound represented by the formula (I): wherein ring A represents an aromatic ring; X represents a bond, oxygen, NR.sup.4 (R.sup.4 represents hydrogen, a hydrocarbon group, or a heterocyclic group), or alkylene; R.sup.1 represents a hydrocarbon group, or a heterocyclic group; R.sup.2 represents --COYR.sup.5 (Y represents a bond, alkylene, oxygen, sulfur, or NR.sup.6 (R.sup.6 represents hydrogen, a hydrocarbon group, or a heterocyclic group), and R.sup.5 represents a hydrocarbon group, or a heterocyclic group), a hydrocarbon group, or a heterocyclic group; and R.sup.3 represents a hydrocarbon group, a heterocyclic group, optionally substituted hydroxy, optionally substituted amino, or --S(O).sub.nR.sup.7 (R.sup.7 represents a hydrocarbon group, or a heterocyclic group, and n is 0 to 2), a salt of the compound, or a prodrug or either is useful as an agent for modulating the function of an RFRP receptor.