Reaction Steps
To a stirred solution of nucleoside 2 (1.00 g, 2.09 mmol) in THF (5.4 cm3) and water (5.4 cm3) was added sodium periodate (1.34 g, 6.27 mmol) and a 2.5% solution of osmium tetraoxide in tert-butanol (w/w, 0.265 cm3, 19 μmol). The solution was stirred at room temperature for 45 min. Water (25 cm3) was added and the solution was extracted with dichloromethane (2×50 cm3). The organic phase was washed with a saturated aqueous solution of sodium hydrogencarbonate (3×30 cm3) and dried (Na2SO4). The solvent was removed under reduced pressure and the residue was redissolved in THF (5.4 cm3) and water (5.4 cm3). The mixture was stirred at room temperature and sodium boronhydride (79 mg, 2.08 mmol) was added. After stirring for 1.5 h, water (25 cm3) was added and the solution was extracted with dichloromethane (2×50 cm3). The organic phase was washed with a saturated aqueous solution of sodium hydrogencarbonate (3×30 cm3) and 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 9 as a white solid material (488 mg, 48%). δH (CDCl3) 9.14 (1 H, br s, NH), 7.60 (1 H, d, J 1.1, 6-H), 7.40-7.22 (10 H, m, Bn), 6.25 (1 H, d, J 7.7, 1′-H), 4.59 (1 H, d, J 7.1 Bn), 4.49 (1 H, d, J 7.1 Bn), 4.39-3.30 (m, 8H, 4′-H, 2′-H, Bn, 5′-Ha, 5′-Hb, 2″-Ha, 2″-Hb), 2.23-2.00 (2 H, m, 1″-Ha, 1″-Hb), 1.49 (3 H, d, J 0.7, CH3). δC (CDCl3) 163.5 (C-4), 151.2 (C-2), 137.1, 136.5 (Bn), 135.7 (C-6), 128.7, 128.5, 128.2, 127.8, 127.6, 127.2 (Bn), 111.3 (C-5), 87.0, 82.7, 81.1, 78.3 (C-1′, C-2′, C-3′, C-4′), 73.7, 69.6 (Bn), 64.4 (C-5′), 57.0 (C-2″), 32.4 (C-1″), 11.8 (CH3) (Found: C, 63.9; H, 6.3; N, 5.4. C26H30N2O7,0.25H2O requires C, 64.1; H 6.3; N, 5.75%).
