[CH3:1][O:2][C:3]([C:5]1[CH:10]=[CH:9][N:8]=[C:7]([C:11]([OH:13])=O)[CH:6]=1)=[O:4].[Cl-].[Mg+2].[Cl-].Cl.[CH2:18]([NH2:20])[CH3:19].C(N(CC)CC)C>ClCCl>[CH2:18]([NH:20][C:11]([C:7]1[CH:6]=[C:5]([CH:10]=[CH:9][N:8]=1)[C:3]([O:2][CH3:1])=[O:4])=[O:13])[CH3:19]A mixture of 4-(methoxycarbonyl)picolinic acid (1.00 g, 5.12 mmol) and magnesium chloride (312 mg, 3.28 mmol) in dichloromethane (10 mL) is stirred at room temperature for 0.5 hour. Then, ethylamine hydrochloride (627 mg, 7.69 mmol) and triethylamine (1.07 mL, 7.69 mmol) are added. After stirring at room temperature for 20 hours, the mixture is poured onto water (50 mL). The aqueous phase is extracted with EtOAc (50 mL×2). The combined organic layer is dried over sodium sulfate and concentrated in vacuo. The residue is purified by column chromatography on silica gel eluting with n-hexane/ethyl acetate (3:11:1) to give 525 mg (49% yield) of the title compound as a white solid.
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