To a stirred solution of N-{(1S,2R,3S,4R)-4-[2-((R)-3-amino-pyrrolidin-1-yl)-6-(2,2-diphenyl-ethylamino)-purin-9-yl]-2,3-dihydroxy-cyclopentyl}-2-hydroxy-acetamide trifluoroacetate (Example 1) (1.1 g, 2 mmol) in NMP (2 ml) and MeOH (10 ml) is added dropwise phenyl chloroformate (0.47 g, 3 mmol). The reaction mixture is allowed to stir at room temperature for 3 hours and then treated with 3-hydroxybenzylamine (0.55 g, 4.45 mmol) and stirred for a further 2 hours at 80° C. Purification of the product by C-18 reverse phase column chromatography eluting with acetonitrile:water:TFA (0.1%) (gradient of 0 to 100% acetonitrile) yields the title compound. (MH+ 722.31)
