To a suspension of sodium iodide (5.51 g, 36.8 mmol) in acetonitrile (50 ml) was added chlorotrimethylsilane (4.66 ml, 36.8 mmol), and the mixture was stirred at room temperature for 10 minutes. After to this solution was added the compound 27 (2.60 g, 6.13 mmol) under ice-cooling, this was stirred at the same temperature for 20 minutes. To the reaction solution was added a 5% sodium hydrogen sulfite solution, followed by extraction with ethyl acetate. The extract was washed with an aqueous saturated sodium bicarbonate solution and an aqueous saturated sodium chlorite solution, and dried with anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the resulting solid matter was recrystallized to obtain (acetone-diisopropyl ether) and methyl 5-(4-fluorobenzylcarbamoyl)-3-methoxy-4-oxo-1,4-dihydropyridine-2-carboxylate 28 (1.73 g, 84%) as a colorless crystal.
