To a solution of 2-({2-[(1-methylethyl)oxy]ethyl}oxy)-8-(methoxy)-9H-purin-6-amine trifluoroacetate salt (400 mg) in dry N,N-dimethylformamide (6.4 ml) was added potassium carbonate (579 mg). The reaction was stirred at 60° C. for 1.5 hours. The reaction was cooled and tetrahydro-2H-pyran-4-ylmethyl methanesulfonate (224 mg) was added. The reaction was stirred at 90° C. for 4 hours. The reaction was cooled and taken up in ethyl acetate and washed twice with water. The organic layer was separated, dried over magnesium sulphate, filtered and concentrated in vacuo to yield a yellow oil (432 mg). The product was purified by C18 reverse phase chromatography using water (containing 0.1% formic acid)-acetonitrile (containing 0.05% formic acid) as eluant (20-50%) to afford the title compound as a clear viscous oil (166 mg).
