To a mixture of 5-fluorouracil (0.85 g, 6.54 mmol) and compound 2 (3.0 g, 5.94 mmol) in anhydrous MeCN (100 ml) were successively added HMDS (1.25 ml, 5.95 mmol), ClSiMe3 (0.6 ml, 4.76 mmol) and SnCl4 (0.83 ml, 7.13 mmol). The resulting clear solution was refluxed for 1 hour when TLC indicated completion of the reaction. The solvent was evaporated and the residue dissolved in EtOAc (250 ml), washed with NaHCO3 and H2O. The EtOAc layer was dried, filtered and evaporated to give a white solid and it was crystallized from CHCl3 /MeOH (1-2%) to give compound 5 (2.11 g, 61.9%) as white crystals: m.p. 208°-209° C.
