[CH3:1][N:2]1[C:10]2[C:5](=[C:6]([O:12][CH3:13])[CH:7]=[CH:8][C:9]=2Br)[CH:4]=[CH:3]1.C([Li])(C)(C)C.[C:19](OC)(=[O:24])[C:20]([O:22][CH3:23])=[O:21]>C1COCC1>[CH3:23][O:22][C:20](=[O:21])[C:19]([C:9]1[CH:8]=[CH:7][C:6]([O:12][CH3:13])=[C:5]2[C:10]=1[N:2]([CH3:1])[CH:3]=[CH:4]2)=[O:24]A solution of 1-methyl-4-methoxyl-7-bromoindole (1.17 g, 4.87 mmol) in THF (33 mL) was cooled to −78° C. and a solution of tert-butyl lithium in pentanes (1.7 M, 6.3 mL, 10.7 mmol) added dropwise over 30 min. After 30 min at −78° C., the mixture was treated with dimethyl oxalate (1.44 g, 12.2 mmol) in one portion. After 15 min, the mixture was allowed to warm to room temperature and stirred 4 h. The reaction mixture was quenched with water and extracted with ethyl acetate. The extract was washed with brine and dried (Na2SO4), and concentrated. Flash chromatography (EtOAc/hexanes) afforded the title compound (0.7 g, 58.1%). 1H NMR (400 MHz, CDCl3) 3.95 (s, 3H), 4.0 (s, 3 H), 4.02 (s, 3H), 6.56 (d, J=8.61 Hz, 1H), 6.67 (d, J=3.13 Hz, 1H), 6.99 (d, J=3.13 Hz, 1H), 7.61 (d, j=8.6 Hz, 1H); MS (ES, m/z): C13H13NO4: 248.16 (M++1).
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