N,O-Bistrimethylsilylacetamide (0.34 ml, 1.4 mmol) was added to a stirred suspension of N-({6-[(2,2-diphenylethyl)amino]-9H-purin-2-yl}methyl)-N′-[2-(1-piperidinyl) ethyl]urea (100 mg, 0.2 mmol) (Preparation 5) in 1,1,1-trichloroethane (20 ml) at 50° C. The reaction mixture was stirred at this temperature for 30 minutes, allowed to cool to room temperature and then evaporated under reduced pressure. Toluene (5 ml) was added and the solvent was removed under reduced pressure. The residue was redissolved in toluene (20 ml) and (2R,3R,4R,5S)-4,5-bis(acetyloxy)-2-[(acetyloxy)methyl]tetrahydro-3-furanyl acetate (0.064 g, 0.2 mmol) and then trimethylsilyltrifluoromethanesulphonate (0.1 ml, 0.35 mmol) were added. The reaction mixture was then heated under reflux for 2 hours. The reaction was allowed to cool to room temperature and diluted with ethyl acetate (100 ml). The solution was washed with saturated aqueous sodium hydrogen carbonate solution (50 ml) and saturated aqueous sodium chloride solution (50 ml) and then dried over anhydrous magnesium sulphate. The solvent was removed to give a residue that was purified by column chromatography on silica gel eluting with dichloromethane:methanol:0.88 concentrated aqueous ammonia (90:10:1 by volume) to give the title compound as an oil (100 mg).
