Br[CH2:2][C:3]1[C:4]([C:13]2[S:14][CH:15]=[CH:16][CH:17]=2)=[N:5][O:6][C:7]=1[C:8]([O:10][CH2:11][CH3:12])=[O:9].[CH2:18]([O:20][C:21](=[O:35])[CH2:22][NH:23][CH2:24][C:25]1[CH:30]=[CH:29][C:28]([O:31][CH3:32])=[CH:27][C:26]=1[O:33][CH3:34])[CH3:19].C(=O)([O-])[O-].[K+].[K+].CCOC(C)=O>CN(C=O)C.O>[CH3:34][O:33][C:26]1[CH:27]=[C:28]([O:31][CH3:32])[CH:29]=[CH:30][C:25]=1[CH2:24][N:23]([CH2:2][C:3]1[C:4]([C:13]2[S:14][CH:15]=[CH:16][CH:17]=2)=[N:5][O:6][C:7]=1[C:8]([O:10][CH2:11][CH3:12])=[O:9])[CH2:22][C:21]([O:20][CH2:18][CH3:19])=[O:35]Ethyl 4-(bromomethyl)-3-(thiophen-2-yl)isoxazole-5-carboxylate (16.5 mmol) was dissolved in 35 mL of DMF. N-(2,4-dimethoxybenzyl)glycine ethyl ester (4.2 g, 16.5 mmol) and potassium carbonate (4.5 g, 32.9 mmol) were added, and the mixture was stirred at room temperature for 16 h. EtOAc (100 mL) and water (100 mL) were added and the aqueous layer was extracted with additional EtOAc. The combined organic layer was washed with water and brine, and dried over MgSO4. After solvent was removed in vacuo, the crude was purified by flash chromatography (0-40% EtOAc/hexanes) to give 2.2 g of the title compound. MS: (+) m/z 489.44 (M+1).
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