To a solution of N2-butyl-8-methoxy-9H-purine-2,6-diamine trifluoroacetic acid salt (300 mg) in dry N,N-dimethylformamide (5.3 ml) was added potassium carbonate (474 mg). The reaction was stirred at 60° C. for ninety minutes. The reaction was cooled and 3-(tetrahydro-2H-pyran-3-yl)propyl methanesulfonate (209 mg) was added and the reaction heated at 90° C. for three hours. The reaction was cooled, diluted with ethyl acetate and washed with water (2×). The organic layer was separated, dried over magnesium sulphate, filtered and concentrated in vacuo. to afford a yellow oil. The product was purified by C18 reverse phase chromatography (43 g) (ISCO) using water (0.1% formic acid)-acetonitrile (0.05% formic acid) as eluant (30-80%) to afford the title compound as a yellow oily residue (198 mg).
