Reaction Steps
A solution of 201 (3.32 g, 7.34 mmol) in anhydrous DMF (25 mL) was stirred at 0° C. and a 60% oil dispersion of sodium hydride (700 mg, 16.9 mmol) was added. The mixture was stirred at room temperature for 90 min, quenched with water (300 mL) and extracted with diethyl ether (2×300 mL). The combined extract was washed with water (200 mL) and dried (MgSO4). The solvent was removed under reduced pressure and the residue was purified by chromatography over silica gel with dichloromethane as eluent to give the two products 202 and 203 as clear oils (1.571 g, 60% and 0.777 g, 30% respectively). (1S,3R,4R,7S)-7-Benzyloxy-1-benzyloxymethyl-3-methoxy-2,5-dioxabicyclo[2.2.1]heptane (202). 1H NMR (CDCl3): δ7.36-7.26 (10H, m, Bn), 4.81 (1H, s, H-1), 4.65 (1H, d, J 11.9 Hz, Bn), 4.61 (2H, s, Bn), 4.56 (1H, d, J 11.9 Hz, Bn), 4.11 (1H, s, H-2), 4.09 (1H, s, H-3), 4.01 (1H, d, J 7.5 Hz, H-5′), 3.80-3.77 (3H, m, H-5′, H-5), 3.39 (3H, s, OCH3); 13C NMR (CDCl3): δ138.05, 137.36, 128.47, 128.44, 127.88, 127.73, 127.63 (Bn), 104.97 (C-1), 85.13 (C-4), 79.16 (C-3), 77.18 (C-2), 73.64 (Bn), 72.26, 72.10 (Bn, C-5′), 66.50 (C-5), 55.34 (OCH3); MS FAB: 379 (M+Na, 28%), Found: C, 70.55; H, 6.97; C21H24O5 requires C, 70.77; H, 6.79%. (1S,3R,4R,7S)-7-Benzyloxy-1-benzyloxymethyl-3-methoxy-2,5-dioxabicyclo-[2.2.1]heptane (203). 1H NMR (CDCl3): δ7.36-7.26 (10H, m, Bn), 5.00 (1H, s, H-1), 4.67-4.54 (4H, m, Bn), 4.18 (1H, s, H-2), 3.99 (1H, s, H-3), 3.99-3.90 (2H, m, H-5′), 3.75-3.68 (2H, m, H-5), 3.49 (3H, s, OCH3); 13C NMR (CDCl3): δ137.83, 137.53, 128.51, 128.48, 127.96, 127.82, 127.71, 127.62 (Bn), 104.05 (C-1), 88.4 (C-4), 79.54 (C-3), 77.16 (C-2), 73.68 (Bn), 72.61 (C-5′), 72.24 (Bn), 65.73 (C-5), 56.20 (OCH3); MS FAB: 379 (M+Na, 100%).
