2H-[1]benzopyrano[4,3-b]pyridine-3-carboxylic acid, 1,5-dihydro-2,5-dioxo-, ethyl ester InChI=1/C15H11NO5/c1-2-20-14(18)10-7-9-12(16-13(10)17)8-5-3-4-6-11(8)21-15(9)19/h3-7H,2H2,1H3,(H,16,17 ethyl 2,5-dioxo-1,5-dihydro-2H-chromeno[4,3-b]pyridine-3-carboxylate