1047-87-6 2,6-Pyridinedicarboxylic acid, 4-((N-(1,3-dicarboxypropyl)formimidoyl)methylene)-1,2,3,4-tetrahydro- 4-((N-(1,3-Dicarboxypropyl)formimidoyl)methylene)-1,2,3,4-tetrahydro-2,6-pyridinedicarboxylic acid