| abstract |
R represents a hydrogen atom, an alkyl group, or an aryl group. G represents a group represented by any one of Formulae (G-1) to (G-4). A1 to A3 each represent a hydrogen atom, a carboxyl group, or a salt thereof. At least one of A1 to A3 is a carboxyl group or a salt thereof. X1 and X2 each represent —O—, —S—, and others. Ra represents an alkyl group and the like. Rb to Re each represent a hydrogen atom or a substituent. na represents 1 to 3. (G-1) to (G-4) are bonded to a pyridine ring in the portion of *. |