To a solution of 6-chloropurine riboside (10.0 g, 35 mmol) in ethanol (350 mL) was added triethylamine (10.0 mL, 100 mmol) and (1R,2R)-2-(benzyloxy)-cyclopentylamine (5.2 g, 52 mmol). The mixture was refluxed for 24 hours, during which the reaction went from a suspension to a clear solution. The ethanol was removed under reduced pressure, and the residue was partitioned between ethyl acetate and water (100 mL:200 mL). The organic layer was separated and the aqueous layer washed with ethyl acetate (2×75 mL). The combined organic layers were dried (sodium sulfate), and the solvent was removed under reduced pressure. The residue was dissolved in ethyl acetate (150 mL), and product precipitated by addition of hexane, to afford 2-(6-{[(1R,2R)-2-(phenylmethoxy)cyclopentyl]amino}purin-9-yl)(4S,3R,5R)-5-(hydroxymethyl)oxolane-3,4-diol as a white solid, (12.0 grams, 77%).
