C[O:2][C:3](=O)[CH:4]=[CH:5][C:6](=[C:11]([NH:13][CH2:14][C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)[CH3:12])[C:7]([O:9][CH3:10])=[O:8].C[O-].[Na+].[Br:25]N1C(=O)CCC1=O>CO>[CH3:10][O:9][C:7]([C:6]1[CH:5]=[C:4]([Br:25])[C:3](=[O:2])[N:13]([CH2:14][C:15]2[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=2)[C:11]=1[CH3:12])=[O:8]MeOH (28 mL) was added to a flask containing 4-(1-benzylamino-ethylidene)-pent-2-enedioic acid dimethyl ester (1.0 g, 3.46 mmol). NaOMe solution (7 mL, 3.46 mmol, 0.5M in MeOH) and N-bromosuccinimide (0.74 g, 4.15 mmol) were added. The resulting mixture was refluxed for 1 h. After cooling to r.t., the solvent was evaporated in vacuo. The residue was partitioned between saturated NH4Cl (50 mL) and CH2Cl2 (50 mL). The aqueous layer was extracted with additional CH2Cl2 and the organic layers were combined, dried over MgSO4, and concentrated. The crude product was chromatographed (0-40% EtOAc/hexanes) to give 0.77 g of the title compound. MS: (+) m/z 357.95, 359.92 (M+Na, 79/81Br).
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