[NH2:1][C:2]1[C:3]([O:13][CH3:14])=[N:4][C:5]2[C:10]([N:11]=1)=[CH:9][C:8]([F:12])=[CH:7][CH:6]=2.Cl[C:16]([O:18][CH2:19][CH3:20])=[O:17].N1C=CC=CC=1>ClCCl>[F:12][C:8]1[CH:9]=[C:10]2[C:5](=[CH:6][CH:7]=1)[N:4]=[C:3]([O:13][CH3:14])[C:2]([NH:1][C:16](=[O:17])[O:18][CH2:19][CH3:20])=[N:11]23-Amino-6-fluoro-2-methoxyquinoxaline (580 mg, 3.00 mmol) and ethyl chloroformate (391 mg, 3.60 mmol) were dissolved in dichloromethane (50 ml) at room temperature and thereto pyridine (285 mg, 3.60 mmol) was added. The mixture was stirred at room temperature for 10 hours and concentrated under the reduced pressure to remove the solvent, and purified by SiO2 column chromatography. Extraction of the residue with a n-hexane:ethyl acetate (3:1) mixture and concentration gave 740 mg of the titled compound (yield, 93%).
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