Reaction Steps
To a solution of compound 44 (0.08 g, 0.31 mmol) in anhydrous pyridine (0.5 cm3) was added 4,4′-dimethoxytrityl chloride (0.203 g, 0.6 mmol) at 0° C. and the mixture was stirred at room temperature for 2 h. The reaction was quenched with ice-cold water (10 cm3) and extracted with dichloromethane (3×4 cm3). The combined organic phase was washed with saturated aqueous solutions of sodium hydrogencarbonate (3×3 cm3) and brine (2×3 cm3) and was dried (Na2SO4). The solvent was removed under reduced pressure and the residue was purified by silica gel column chromatography using dichloromethane/methanol (98:2, v/v) as eluent to give nucleoside 45 as a white solid material (0.12 g, 69%). δH (CDCl3) 9.25 (1H, br s, NH), 7.93 (1H, d, J 7.2, 6-H), 7.50-7.15 (9H, m, DMT), 6.88-6.78 (4H, m, DMT), 5.63 (1H, s, 1′-H), 5.59 (1H, d, J 8.0, 5-H), 4.48 (1H, s, 2′-H), 4.26 (1H, s, 3′-H), 3.88 (1H, d, J 8.1, 1″-Ha), 3.85-3.55 (7H, m, 1″-Hb, OCH3), 3.58-3.40 (2H, m, 5-Ha, 5′-Hb). δC (CDCl3) 164.10 (C-4), 158.60 (DMT), 150.45 (C-2), 147.53 (DMT), 144.51 (C-6), 139.72, 135.49, 135.37, 130.20, 129.28, 128.09, 127.85, 127.07 (DMT), 113.39, 113.17 (DMT), 101.79 (C-5), 88.20, 87.10, 86.87 (C-1′, C-4′, DMT), 79.25, 71.79, 69.70, 58.13 (C-2′, C-3′, C-5′, C-1″), 55.33 (OCH3). FAB-MS m/z 559 [M+H]+.
