The title compound was prepared according to the process disclosed in Japanese Unexamined Patent Publication No. 106593/1986. The process was carried out as follows. A 5.0 g quantity of 2'-deoxy-5'-O-trityl-5-fluorouridine was dissolved in 40 ml of tetrahydrofuran. To the solution was added 856 mg of 60% sodium hydride, followed by 1 hour of stirring at room temperature. After addition of 2.58 g of 4-chloro-2-fluorobenzyl bromide, the mixture was stirred at room temperature for 2 hours. The reaction mixture was cooled to 0° C. and saturated ammonium chloride was added in excess. The tetrahydrofuran layer was washed with a saturated aqueous solution of sodium chloride and dried over magnesium sulfate. The solvent was distilled off at reduced pressure, and the residue was purified by silica gel column chromatography (eluate: n-hexane-ethyl acetate (3:2)), giving 5.03 g of the title compound (yield 78%).
