A solution of (1S,2R,3S,5R)-3-amino-5-[2-chloro-6-(2,2-diphenyl-ethylamino)-purin-9-yl]-cyclopentane-1,2-diol hydrochloride (an intermediate for preparing the compound of Example 22) (100 mg, 0.2 mmol) in dry THF (1 ml) is treated with diisopropylethylamine (0.17 ml, 1 mmol) and 3-phenyl-propionyl chloride (0.03 ml, 0.2 mmol) and the mixture is stirred at room temperature for 18 hours. The solvent is removed under reduced pressure and the residue is dissolved in dichloromethane (2 ml) and washed with dilute hydrochloric acid (2 ml). The organic layer is separated and evaporated under reduced pressure to afford the title compound. LCMS (electrospray): m/z [MH+] 597.32
