2,2-Dimethoxypropane → ((3aR,4R,6R,6aS)-6-(6-chloro-9H-purin-9-yl)-2,2-dimethyltetrahydro-3aH-cyclopenta[d][1,3]dioxol-4-yl)methanol

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Reaction Steps

The above crude ((3aR,4R,6R,6aS)-6-(6-chloro-9H-purin-9-yl)-2-ethoxytetrahydro-3aH-cyclopenta[d][1,3]dioxol-4-yl)methanol was taken up in 2,2-dimethoxypropane (214 mL, 1740 mmol) and treated with p-toluenesulfonic acid monohydrate (13.2 g, 69.5 mmol) to afford a brown oil partially suspended in a cloudy solution, which was stirred at rt for 1 h 20 min; HPLC/LC MS indicated complete conversion to the desired product. The reaction was quenched by the careful addition of sodium bicarbonate (8.76 g, 104 mmol) and a minimal amount of water. The volatiles were removed in vacuo and the remaining aqueous layer was diluted with water (100 mL) and extracted with CH2Cl2 (3×400 mL). The combined organics were dried (Na2SO4) and concentrated in vacuo to afford a brown oil. Purification by column chromatography (7×16 cm silica; 0-5% MeOH/CH2Cl2) afforded the title compound (8.30 g, 74% over 3 steps) as a yellow foam: MS (ESI+) for C14H17ClN4O3 m/z 325.1 (M+H)+; MS (ESI−) for C14H17ClN4O3 m/z 369.0 (M+HCO2)−; HPLC purity >95 area %.

Provenance & Evidence