Dimethyl 2,6-pyridinedicarboxylatedimethyl pyridine-2,6-dicarboxylate2,6-dimethyl pyridine-2,6-dicarboxylate2,6-Pyridinedicarboxylic acid dimethyl esterDimethyl 2,6-pyridinedicarboxylate吡啶-2,6-二羧酸二甲酯Pyridine-2,6-dicarboxylic acid dimethyl ester2,6-吡啶二羧酸二甲酯Dimethyl pyridine-2,6-dicarboxylate