[C:1]([C:5]([C:16]1[CH:17]=[CH:18][N:19]2[C:24]([CH:25]=1)=[CH:23][CH:22]=[C:21]([C:26]([O:28]CC)=[O:27])[C:20]2=[O:31])(C(OC)=O)[CH2:6][C:7]([O:9]CC)=[O:8])([O:3]C)=[O:2].O=C1N2C(C=CC=C2)=CC=C1C(OCC)=O>>[C:1]([CH:5]([C:16]1[CH:17]=[CH:18][N:19]2[C:24]([CH:25]=1)=[CH:23][CH:22]=[C:21]([C:26]([OH:28])=[O:27])[C:20]2=[O:31])[CH2:6][C:7]([OH:9])=[O:8])([OH:3])=[O:2]Saponification of (20) was done as described for (1). After completion of the reaction, the solvent was evaporated in vacuo, and the resulting yellow solid was dissolved in water. The aqueous layer was acidified to pH 1, and extracted three times with ethyl acetate. Evaporation of the organic solvent gave 8-(1,2-dicarboxyethyl)-4-oxo-4H-quinolizine-3-carboxylic acid (20a) as a yellow solid in 48% yield. M.p. 250° C. 1H NMR (δ, DMSO-d6): 2.72-2.76 (m, 2H), 3.02-3.06 (m, 1H), 7.14 (d, J=9 Hz, 1H), 7.60 (dd, J=2 Hz, J=9 Hz, 1H), 7.99 (s, 1H), 8.34 (d, J=9 Hz, 1H), 9.20 (d, J=9 Hz, 1H). MS: m/z 261.0601 (M-CO2); required for C13H11NO5: 261.0637.
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