Cl.[N:2]1[CH:7]=[CH:6][CH:5]=[C:4]([CH2:8][CH2:9][C:10]([OH:12])=[O:11])[CH:3]=1.[CH2:13](O)[C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1.O.C1(C)C=CC(S(O)(=O)=O)=CC=1.C(=O)([O-])O.[Na+]>C(OCC)(=O)C>[N:2]1[CH:7]=[CH:6][CH:5]=[C:4]([CH2:8][CH2:9][C:10]([O:12][CH2:13][C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)=[O:11])[CH:3]=1To a suspension of 3-(3-pyridyl)propionic acid hydrochloride (1.51 g, 10.0 mmol) in benzyl alcohol (3.1 mL, 30 mmol) was added p-toluenesulfonic acid monohydrate (181.8 mg, 0.96 mmol), and the mixture was stirred at 130° C. for 20 h. The reaction mixture was diluted with ethyl acetate and a saturated aqueous sodium hydrogen carbonate solution was added to separate the phases. The aqueous layer was extracted again with ethyl acetate, and the combined organic layer was concentrated with reduced pressure. The residue was subjected to silica gel column chromatography (hexane-ethyl acetate 1:1→1:3) to give 1.69 g of the title compound as oil (yield: 70%).
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