7-Benzyl-3,8-dimethylxanthine (500 mg, 1.85 mmol) was added to a suspension of sodium hydride (50.5 mg) in anhydrous DMSO (20 ml) and stirred for 30 min. (R)-5-acetoxy-1-chlorohexane (357 mg) (prepared according to Kline et al. U.S. Pat. No. 5,629,423 (1997)) was added and the mixture was heated at 70-80° C. for 12 h. After cooling to room temperature, the reaction was quenched by the addition of water (50 ml) and extracted with ethyl acetate (3×75 ml). The combined extracts were washed with water (2×50 ml), with saturated aqueous sodium chloride solution (50 ml), dried over magnesium sulfate and concentrated. The product was purified by flash chromatography (silica gel) eluting with ethyl acetate. Yield=638 mg.
