[OH:1][CH2:2][C:3]1[CH:8]=[CH:7][C:6]([N:9]=[N:10][C:11]2[CH:16]=[CH:15][C:14]([OH:17])=[CH:13][CH:12]=2)=[CH:5][CH:4]=1.Br[CH2:19][C:20]([O:22][CH3:23])=[O:21].C([O-])([O-])=O.[K+].[K+]>CC(C)=O.CCOC(C)=O>[C:20]([CH2:19][O:17][C:14]1[CH:15]=[CH:16][C:11]([N:10]=[N:9][C:6]2[CH:5]=[CH:4][C:3]([CH2:2][OH:1])=[CH:8][CH:7]=2)=[CH:12][CH:13]=1)([O:22][CH3:23])=[O:21]Compound 1 (0.4 g, 1.75 mmol) and methyl bromoacetate (0.28 g, 1.83 mmol) were dissolved in 40 mL of acetone, and K2CO3 (0.726 mg, 5.26 mmol) was added at room temperature followed by stirring overnight. The reaction mixture was diluted with 100 mL of EtOAc and washed with water (2×50 ml), brine (50 ml), and dried over Mg2SO4. After evaporation of solvents under reduced pressure the residue was purified by silica gel column chromatography (EtOAc:n-hexane 4:6) affording compound 3. Yield: 0.395 g (75%). 1H NMR (400 MHz, DMSO-d6) δ 3.71 (s, 3H, Hg), 4.58 (s, 2H, He), 4.92 (s, 2H, Hf), 5.33 (s, 1H, —OH), 7.10-7.14 (m, 2H, Ha), 7.47-7.49 (m, 2H, Hd), 7.80-7.86 (m, 4H, Hb, Hc). 13C NMR (100 MH, DMSO-d6) δ 52.4 (Cg), 62.9 (Cf), 65.3 (Ce), 115.7, 122.6, 124.8, 127.6, 146.3, 147.1, 151.4, 160.6169.4. HRMS (ESI+) m/z: [M+H]+ calcd for C16H17N2O4 301.1188. Found 301.1176.
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