A stirred solution of ethyl 5-amino-1-methoxymethyl-uracilylacetate (8.0 g, 31 mmole) and 2,4,6-collidine (13.7 mL, 62 mmole) in tetrahydrofuran (50 mL) is cooled in an ice bath. A solution of benzylsulfonyl chloride (5.93 g, 31 mmole) in tetrahydrofuran (50 mL) is added over a 30-minute period. After addition is complete, the solution is stirred for 1 hour at 0° C., then 3 hours at room temperature. The reaction mixture is diluted with ethyl acetate, washed with 1.0N HCl (until aqueous layer is pH 1), water, saturated sodium bicarbonate, and brine. The organic layer is dried over anhydrous magnesium sulfate, and the solvent is removed. The title compound is isolated.
