Reaction Steps
A solution of nucleoside 25 (2.53 g, 4.66 mmol) in a mixture of ethanol (50 cm3), water (50 cm3) and 1 M aqueous sodium hydroxide (15 cm3) was stirred under reflux for 16 h. The mixture was neutralised using dilute aqueous hydrochloric acid, the solvent was evaporated under reduced pressure, and the residue was extracted with dichloromethane (3×120 cm3). The combined extract was washed with saturated aqueous sodium hydrogencarbonate (3×150 cm3) and dried (Na2SO4). The solvent was removed under reduced pressure and the residue was purified by silica gel column chromatography using dichloromethane/methanol (99:1) as eluent to give 26 as a white foam (1.61 g, 74%). δH (CDCl3) 9.89 (1H, br s, NH), 7.50 (1H, d, J 1.1, 6-H), 7.41-7.26 (Bn), 6.28 (1H, d, J 2.8, 1′-H), 6.05 (1H, dd, J 11.1, 17.9, 1″-H), 5.58-5.50 (2H, m, 2″-Ha, 2″-Hb), 4.98 (1H, d, J 9.0, 2′-OH), 4.64-4.31 (6H, m, 2′-H, 4′-H, Bn), 3.73 (2H, m, 5′-Ha, 5′-Hb), 1.73 (1H, d, J 0.6, CH3). δC (CDCl3) 165.1 (C-4), 150.5 (C-2), 138.4, 138.0, 136.7 (C-6, Bn), 130.4 (C-1″), 128.8, 128.6, 128.5, 128.1, 128.0, 127.8 (Bn), 120.6 (C-2″), 108.1 (C-5), 88.6 (C-1′), 87.9 (C-3′), 87.2 (C-4′), 73.7 (C-2′), 71.8 (C-5′), 69.7, 66.3 (Bn), 12.3 (CH3). Found: C, 66.8; H, 6.2; N, 5.9; C26H28N2O6 requires C, 67.2; H, 6.1; N, 6.0.
