(wherein R1 and R2 are each independently a hydrogen atom, a halogen atom, an amino group, a hydroxyl group, a hydroxyamino group, a nitro group, a cyano group, a sulfamoyl group, a C1 to C6 alkyl group, a C1 to C6 alkoxy group, a C1 to C6 alkylsulfanyl group, a C1 to C6 alkylsulfinyl group, a C1 to C6 alkylsulfonyl group, or a C1 to C6 alkoxy-C1 to C6 alkylsulfonyl group, and A is a substituted or unsubstituted heteroaryl group).