A solution of 6-[(2,2-diphenylethyl)amino]-9-tetrahydro-2H-pyran-2-yl-9H-purine-2-carbonitrile (5.70 g, 13.18 mmol) (Preparation 5) in ethanol (200 ml) saturated with ammonia gas was treated with Pearlman's catalyst (1.00 g), pressurised to 414 kPa (60 psi) with hydrogen in a sealed vessel and stirred at room temperature for 30 hours. The suspension was filtered through a pad of Arbocel (trade mark) and the solvent was removed under reduced pressure. The residue was twice azeotroped from dichloromethane and then purified by column chromatography on silica gel eluting with dichloromethane:methanol (95:5 by volume) gradually changing to dichloromethane:methanol:0.88 ammonia (90:10:0.5 by volume) to afford the title compound (4.34 g).
