C[CH:2]([CH:6]1[C:14]2[C:9](=[CH:10][CH:11]=[CH:12][C:13]=2[N+:15]([O-:17])=[O:16])[NH:8][CH2:7]1)[C:3]([O-:5])=[O:4].[C:18](=O)(O)[O-].[Na+].[I-].[K+].Br[CH2:26][C:27]([O:29][CH2:30][CH3:31])=[O:28]>CC(C)=O>[N+:15]([C:13]1[CH:12]=[CH:11][CH:10]=[C:9]2[C:14]=1[CH:6]([CH2:2][C:3]([O:5][CH3:18])=[O:4])[CH2:7][N:8]2[CH2:26][C:27]([O:29][CH2:30][CH3:31])=[O:28])([O-:17])=[O:16]To a solution of (±)-methyl(4-nitro-2,3-dihydro-1H-indol-3-yl)acetate from Step B (700 mg, 3.0 mmol), sodium bicarbonate (471 mg, 4.4 mmol), and potassium iodide (98 mg, 0.59 mmol) in acetone (15 mL) was added ethyl bromoacetate (9.9 mL, 88.9 mmol). The mixture was heated at reflux for 18 h, then cooled to ambient temperature and concentrated in vacuo. The residue was partitioned between H2O (15 mL) and EtOAc (2×40 mL) and the organic extracts were washed with brine, dried over Na2SO4, filtered, and concentrated in vacuo to a volume of 50 mL. Hexane was added to the EtOAc solution and a precipitate formed. The desired crystals were collected by vacuum filtration to give the title compound. MS: m/z 323 (M+1).
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