The reaction of 2-chloroadenosine (Ila, 20 g, 66.3 mmol), 2,2-dimethoxypropane (DMOP, 60 mL) and 70% wt aqueous hydrochloric acid solution (3 mL) was stirred at room temperature for 8 h under nitrogen atmosphere. Subsequently, the pH of the reaction mixture was adjusted to 7-9 by slow addition of saturated aqueous sodium bicarbonate solution (about 120 mL). the mixture was stirred in an ice bath for 2 h. The mixture was subjected to filtration, and the filter cake was washed with water (50 mL), followed by drying under vacuum at 50 °C for 6 h to afford the title compound (Formula 11b) with 99% purity and 88% yield. The product was characterized by 1H NMR (400 MHz, DMSO-d6) and 13C NMR (100 MHz, DMSO-d6) with the following data: 1H NMR δ 8.36 (s, 1H), δ 7.87 (s, 2H), δ 6.06 (d, J = 2.4 Hz, 1H), δ 5.28 (dd, J = 6 Hz, 2.4 Hz, 1H), δ 5.08 (t, J = 5.6Hz, 1H), δ4.94 (dd, J = 6Hz, 2Hz, 1H), δ4.21 (m, 1H), δ3.54 (m, 2H), δ1.54 (s, 3H), δ1.33 (s, 3H); 13C NMR δ157.3, 153.6, 150.4, 140.4, 118.6, 113.6, 89.8, 87.2, 83.9, 81.7, 62.0, 27.5, 25.7.
