To 6-(2,2-diphenyl-ethylamino)-9H-purine-2-carboxylic acid methyl ester (5 g 13.4 mmol) under an atmosphere of argon is added dry deoxygenated tetrahydrofuran (100 ml) and dry dimethyl sulfoxide (2 ml). Sodium hydride 95% (0.32 g, 13.4 mmol) is then added and the solution is stirred at 40° C. Separately to (1S,4R)-cis 4-Acetoxy-2-cyclopenten-1-ol (1.89 g. 13.4 mmol), triphenylphosphine (0.53 g, 2.0 mmol) and tris(dibenzylideneacetone)dipalladium(0) (0.69 g, 0.67 mmol) is added dry deoxygenated tetrahydrofuran (20 ml) and the mixture stirred at room temperature for 10 minutes. This solution is added to the anion solution via syringe and the resulting mixture is then stirred at 80° C. The reaction is shown to be complete by LCMS after 2 hours. The reaction mixture is allowed to cool, methanol is added and a solid is filtered. The filtrate is concentrated in vacuo and the title compound is obtained by precipitation from dichloromethane/hexane. 1H NMR (MeOD, 400 MHz); 8.15(s, 1H), 7.40-7.15(m, 10H), 6.20(m, 1H), 5.95(m, 1H), 5.50(m, 2H), 4.75(m, 2H), 4.55(m, 1H), 4.10(m 2H), 3.90(s, 2H), 3.80(s, 1H), 2.9(m, 1H), 1.75(m, 1H).
