2'-Deoxy-2'-fluorouridine (3.00 g, 12.2 mmol) was dissolved in anhydrous pyridine, and the decompression concentration operation was repeated three times to achieve dehydration azeotropic distillation. Subsequently, the reaction mixture was dissolved in anhydrous pyridine (120 mL) under argon protection, 4,4'-dimethoxytrityl chloride (4.55 g, 13.4 mmol) was added, and the reaction was stirred for 3 hours at room temperature. After completion of the reaction, ethyl acetate (150 mL) and water (60 mL) were added to the reaction mixture and layered. The organic layer was washed sequentially with 5% aqueous sodium bicarbonate (20 mL x 3), water (20 mL) and saturated saline (20 mL), followed by drying with anhydrous sodium sulfate. After filtration, the solvent was removed by evaporation and the residue was purified by silica gel column chromatography (eluent: hexane/ethyl acetate = 50:50 to 0:100 (v/v) containing 1% triethylamine). The fraction containing the target product was collected and concentrated to give 1-((2R,3R,4R,5R)-5-((bis(4-methoxyphenyl)(phenyl)methoxy)methyl)-3-fluoro-4-hydroxytetrahydrofuran-2-yl)pyrimidine-2,4(1H,3H)-dione (8.48 g, quantitative yield).
