Reaction Steps
Under an atmosphere of N2(g), 2-chloroadenine (A (9), 50 g, 294.9 mmol), MeCN (600 mL), and BSTFA (227.5 g, 883.8 mmol) were stirred and heated under reflux until the mixture turned mostly clear (about 1 h). TfOH (8.77 g, 58.5 mmol) and 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (C, 142.5 g, 282.5 mmol) were sequentially added into the mixture and were stirred at reflux for about 1 h. The mixture was cooled to 20-35° C. and diluted with MTBE (500 mL), and washed over a 0.5 to 1 h period with saturated NaHCO3 (750 mL). The organic phase was evaporated in vacuo at 40 to 50° C. to give 2′,3′,5′-tri-O-benzoyl-2-chloroadenosine (D): 1H NMR (300 MHz, CDCl3) δ 7.9-8.1 (m, 6H), 7.94 (s, 1H), 7.3-7.6 (m, 9H), 6.45 (d, J=2.7 Hz 1H), 6.15 (m, 2H), 5.30 (s, 2H), 4.90 (dd, J4′,5a=3.2 Hz, J5′a,5′b=12.0 Hz, 1H), 4.82 (m, 1H), 4.72 (dd, J4′,5a=4.1 Hz, J5′a,5′b=12.0 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 166.3, 165.5, 165.4, 156.4, 154.7, 151.1, 139.1, 134.1, 134.1, 133.8, 130.2, 130.1, 129.9, 129.4, 129.0, 128.8, 128.5, 119.1, 86.5, 81.3, 74.6, 71.7, 64.0.
