To a solution of chiral 1-((2R,3R,4S,5S)-3,5-difluoro-4-hydroxy-5-(hydroxymethyl)-3-methyltetrahydrofuran-2-yl)pyrimidine-2,4(1H,3H)-dione (150 mg, 539 μmol) prepared in Preparation 6 in THF (24 ml) was added a THF solution (Aldrich, 1 M) of tert-butylmagnesium chloride (1.35 mL, 1.35 mmol) dropwise. The mixture was stirred at room temperature for 15 min, followed by the addition of THF solution (0.5 M) of (2S)-isopropyl 2-(chloro(naphthalen-1-yloxy)phosphorylamino)propanoate (2.7 mL, 1.35 mmol). The reaction mixture was stirred at room temperature for 1 h, then additional THF solution (Aldrich, 1 M) of tert-butylmagnesium chloride (0.68 mL, 0.68 mmol) and THF solution (0.5 M) of (2S)-isopropyl 2-(chloro(naphthalen-1-yloxy)phosphorylamino)propanoate (1.35 mL, 0.68 mmol) were added. The reaction mixture was then stirred at room temperature for 3 h. Methanol (6 mL) was added to quench the reaction. The mixture was purified by flash chromatography (silica gel, 0-15% MeOH in DCM) and dried in vacuo to give the title compound as a white solid (0.2 g, 62%).
