A solution of Oxone (trade mark)(potassium peroxymonosulphate) (44 g, 71.7 mmol) in water (200 ml) was added dropwise over 2 hours to a solution of N-(2,2-diphenylethyl)-2-(methylsulfanyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (Preparation 3) (25 g, 56.2 mmol) and sodium hydrogencarbonate (20 g, 238 mmol) in acetone (1000 ml) and water (250 ml). The resultant mixture was stirred at room temperature for 24 hours, filtered and the residue washed with acetone. The acetone was removed from the filtrate under reduced pressure and the resulting aqueous residue extracted with ethyl acetate and then dichloromethane. The combined organic layers were washed with brine, dried with anhydrous magnesium sulphate, filtered and the solvent removed under reduced pressure. The residue was triturated with diethyl ether, filtered, washed with diethyl ether and pentane and then dried to afford the title compound as a white solid (20.32 g).
