Reaction Steps
To a stirred solution of nucleoside 23 (3.90 g, 7.7 mmol) in anhydrous methanol (40 cm3) was added sodium methoxide (0.83 g, 15.4 mmol). The mixture was stirred at room temperature for 42 h and then neutralised with dilute aqueous hydrochloric acid. The mixture was extracted with dichloromethane (2×150 cm3), and the combined extract was washed with saturated aqueous sodium hydrogencarbonate (3×100 cm3) and dried (Na2SO4). The solvent was removed under reduced pressure to give nucleoside 24 as a white foam (3.48 g, 97%). δH (CDCl3) 8.89 (1H, br s, NH), 7.60 (1H, d, J 0.9, 6-H), 7.36-7.26 (10H, m, Bn), 6.23 (1H, d, J 7.8, 1′-H), 5.98 (1H, dd, J 11.2, 17.7, 1″-H), 5.66 (1H, d, J 17.7, 2″-Ha), 5.55 (1H, d, J 11.5, 2″-Hb), 4.75-4.37 (6H, m, 2′-H, 4′-H, Bn), 3.84 (1H, dd, J 2.7, 10.8, 5′-Ha), 3.58 (1H, d, J 11.2, 5′-Hb), 3.23 (1H, d, J 10.6, 2′-OH), 1.50 (3H, s, CH3). δC (CDCl3) 163.7 (C-4), 151 3 (C-2), 138.0, 136.9 (Bn), 136.0 (C-6), 131.2 (C-1″), 128.8, 128.6, 128.3, 127.8, 127.7, 127.3 (Bn), 120.7 (C-2″), 111.3 (C-5), 87.3 (C-1′), 84.6 (C-3′), 81.4 (C-4′), 78.0 (C-2′), 73.7 (C-5′), 70.0, 66.4 (Bn), 11.8 (CH3). Found: C, 66.8; H, 6.2; N, 5.9; C26H28N2O6 requires C, 67.2; H, 6.1; N, 6.0%.
