Pyridine-3,4-dicarboxylic acid anhydride1,3-Dihydrofuro[3,4-c]pyridine-1,3-dioneFuro[3,4-c]pyridine-1,3-dione3,4-Pyridinedicarboxylic acid anhydrideCinchomeronic anhydride3,4-吡啶二酸酐3,4-Pyridinedicarboxylic anhydride吡啶-3,4-二羧酸酐1,3-dihydrofuro[3,4-c]pyridine-1,3-dionePyridine-3,4-dicarboxylic anhydride吡啶-3,4-二甲酸酐