4H-Quinolizine-1,2,3,4-tetracarboxylic acid, 7-methyl-, tetramethyl ester 5-22-04-00431 (Beilstein Handbook Reference) 909-41-1 BRN 0367625 NSC 220063 Tetramethyl 7-methyl-4H-quinolizine-1,2,3,4-tetracarboxylate