1H-indene-1,5-dicarboxylic acid, 2,3-dihydro-3-oxo-, diethyl ester InChI=1/C15H16O5/c1-3-19-14(17)9-5-6-10-11(7-9)13(16)8-12(10)15(18)20-4-2/h5-7,12H,3-4,8H2,1-2H diethyl 3-oxoindane-1,5-dicarboxylate