C([O:3][C:4]([C:6]1[CH:7]=[C:8]2[C:12](=[CH:13][C:14]=1[NH:15][C:16]([C:18]1[C:27](=[O:28])[C:26]3[C:21](=[CH:22][CH:23]=[CH:24][CH:25]=3)[NH:20][CH:19]=1)=[O:17])[NH:11][CH:10]=[CH:9]2)=[O:5])C.[OH-].[Na+]>C1COCC1>[O:28]=[C:27]1[C:26]2[C:21](=[CH:22][CH:23]=[CH:24][CH:25]=2)[NH:20][CH:19]=[C:18]1[C:16]([NH:15][C:14]1[CH:13]=[C:12]2[C:8]([CH:9]=[CH:10][NH:11]2)=[CH:7][C:6]=1[C:4]([OH:5])=[O:3])=[O:17]A mixture of 6-[(4-oxo-1H-quinolin-3-yl)carbonylamino]-1H-indole-5-carboxylic acid ethyl ester (188) (450 mg, 1.2 mmol) and 1N NaOH solution (5 mL) in THF (10 mL) was heated at 85° C. overnight. The reaction mixture was partitioned between EtOAc and water. The aqueous layer was acidified with 1N HCl solution to pH 5, and the precipitate was filtered, washed with water and air dried to yield 6-[(4-oxo-1H-quinolin-3-yl)carbonylamino]-1H-indole-5-carboxylic acid (188-I) (386 mg, 93%). 1H-NMR (400 MHz, DMSO-d6) δ 12.92-12.75 (m, 2H), 11.33 (s, 1H), 8.84 (s, 1H), 8.71 (s, 1H), 8.30 (dd, J=8.1, 0.9 Hz, 1H), 8.22 (s, 1H), 7.80-7.72 (m, 2H), 7.49 (t, J=8.0 Hz, 1H), 7.41 (t, J=2.7 Hz, 1H), 6.51 (m, 1H); HPLC ret. time 2.95 min, 10-99% CH3CN, 5 min run; ESI-MS 376.2 m/z (MH+).
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