6-(Cyclopropylmethylamino)-9-[(2R,5S)-tetrahydro-5-(hydroxymethyl)-2-furyl]-9H-purine (0.310 g, 1.1 mmoles), 4-dimethylaminopyridine (10 mg, 0.1 mmoles, Aldrich Chemical Co., Madison, Wis.), and triethylamine (1.0 mL, 7 mmoles, Aldrich Chemical Co., Madison, Wis.) were dissolved in 50 mL acetonitrile. Heptanoyl chloride (800 μm, 5.0 mmoles, Aldrich Chemical Co., Madison, Wis.) was added and the reaction was stirred at room temperature for 6 hours. The reaction was quenched with methanol and solvents were evaporated in vacuo. The residue was dissolved in acetone and passed over a silica gel column (4.8×13 cm). The product containing fractions were combined, concentrated, and loaded onto preparative silica gel plates (20×20×0.2 cm). The plates were developed in a mixture of chloroform:acetone (80:20). The product was scraped from the preparative plate (Rf 0.5) and eluted from the silica gel with ethanol. After evaporation of the solvent the product was further purified on a Chromatotron (2 mm silica gel plate) with a mixture of hexane:acetone (80:20). Lyophilization afforded 0.227 g of 6-(cyclopropylmethylamino)-9-[(2R,5S)-5-[(heptanoyloxy)methyl]-tetrahydro-2-furyl]-9H-purine as an oil (51% yield).
