Pyrrolidine (0.057 ml, 0.69 mmol) was added to a suspension of the methyl 3-(benzyloxy)-6-(3-formyl-4-methoxy-2-methylphenyl)pyridine-2-carboxylate produced in Example 11-1 (3.02 g) and 5,5-dimethylcyclohexane-1,3-dione (2.23 g, 15.92 mmol) in ethanol (60 ml) at room temperature, and the mixture thus obtained was then stirred at 80° C. for 2 hours. After air-cooling, the solvent was distilled away from the reaction solution under reduced pressure. The residue thus obtained was dissolved in chloroform (60 ml), and p-toluenesulfonic acid monohydrate (0.357 g, 2.08 mmol) was then added to the solution obtained above at room temperature. The mixture thus obtained was stirred at 70° C. for 1.5 hours. After air-cooling, water was added to the reaction solution, and the mixed solution was then extracted with ethyl acetate. The organic layer thus obtained was dried over anhydrous sodium sulfate. The solvent was distilled away under reduced pressure, and the residue thus obtained was then purified by silica gel column chromatography (ethyl acetate:hexane=2:3 to 1:1, v/v) to obtain the title compound (3.56 g, yield: 81%).
