"mino group, a hydroxyl group, a mercapto group, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom and an iodine atom) and a carboxyl group; more preferably an aryl group, an alkoxy group, an aryloxy group, a hydroxyl group and a halogen atom; even more preferably an alkoxy group and a hydroxyl group; and particularly preferably a hydroxyl group.) and N. X is more preferably C?" . . . .