267 mg 2-[(3R)-3-aminopyrrolidin-1-yl]-5-trifluoromethylpyridine, 331 mg 6-chloropurineriboside, 233 mg triethylamine, and 0.5 mL ethanol are combined and heated in a sealed vessel at 100° C. for about 5 hours. The mixture is cooled, partioned between methylene chloride (with some isopropyl alcohol added) and sodium bicarbonate. The organic layer is washed with brine, dried over magnesium sulfate, evaporated, and the residue purified by flash chromatography, eluting with 5% methanol in methylene chloride, to give (2R,3S,4R,5R)-2-hydroxymethyl-5-[6-[1-(5-trifluoromethylpyridin-2-yl)-pyrrolidin-3(R)-ylamino]purin-9-yl]tetrahydrofuran-3,4-diol, as the hemihydrate, m.p. 166-170° C.
