Synthesis of (((3aR,4R,6R,6R,6aR)-6-(6-chloro-9H-purin-9-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl)methanol from (3R,4S,5R)-2-(6-chloro-9H-purin-9-yl)-2,2-dimethyltetrahydrofuro[3,4-d][1,3]dioxol-4-yl) and acetone The general procedure was as follows: to a stirred suspension of anhydrous acetone (300 mL) of (3R,4S,5R)-2-(6-chloro-9H-purin-9-yl)-5-(hydroxymethyl)tetrahydrofuran-3,4-diol (3.0 g, 10.5 mmol) was added to toluenesulfonic acid monohydrate (19.8 g, 104 mmol). the solid was completely solubilized after 15 minutes. After 2 hours of reaction, the reaction solution was slowly poured into a stirred aqueous 0.5 N NaHCO3 solution (300 mL). After removing the acetone under vacuum, the mixture was extracted with dichloromethane (DCM, 100 mL x 5). The organic layers were combined, washed sequentially with water (100 mL) and brine (100 mL), dried over anhydrous Na2SO4, filtered and concentrated to give the target product (3.0 g, 87% yield, purity >96%) as a pale white solid. The product was characterized by 1H NMR (500 MHz, CD3OD) and LCMS (m/z: 327.1 [M+1]+).
