Reaction Steps
A solution of nucleoside 3 (3.59 g, 6.45 mmol) in ethanol (72 cm3), water (72 cm3) and 1 M aqueous sodium hydroxide (20.6 cm3) was stirred under reflux for 18 h. After neutralisation with dilute hydrochloric acid, the solvent was removed under reduced pressure and the residue was dissolved in dichloromethane (3×150 cm3). The organic phase was washed with a saturated aqueous solution of sodium hydrogencarbonate (3×200 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, v/v) as eluent to give 4 as a white solid material (2.32 g, 74%). δH (CDCl3) 7.60 (1H, d, J 1.2, 6-H), 7.50-7.23 (10H, m, Bn), 6.22 (1H, d, J 2.9, 1′-H), 5.80 (1H, m, 2″-H), 5.15-5.08 (2H, m, 3″-Ha, 3″-Hb), 4.86-4.33 (6H, m, 2×Bn, 2′-H, 4′-H), 3.82-3.71 (2H, m, 5′-Ha, 5′-Hb), 2.72 (1H, m, 1″-Ha), 2.52 (1H, dd, J 7.6, 16.1, 1″-Hb), 1.70 (3H, d, J 0.9, CH3). δC (CDCl3) 165.1 (C-4), 150.4 (C-2), 138.4, 136.8 (Bn), 137.7 (C-6), 132.3 (C-2″), 128.77 128.4, 128.3, 128.0, 127.9, 127.6 (Bn), 118.5, (C-3″), 107.8 (C-5), 88.0, 87.8, 83.7 (C-1′, C-3′, C-4′), 73.7, 72.9, 69.4 (Bn, C-2′), 64.7 (C-5′), 31.1 (C-1″), 12.4 (CH3) (Found. C, 67.5; H, 6.3; N, 5.3. C27H30N2O6, 0.25H2O requires C, 67.1; H, 6.4; N, 5.8%).
