Reaction Steps
A solution of compound 16 (3 g, 5.25 mmol) in anhydrous DCM (30 mL) was cooled to −10° C. under a nitrogen atmosphere. Freshly prepared sodium methoxide solution [sodium (48 mg, 2.10 mmol) in dry methanol (30 mL)] was added slowly to the reaction mixture and stirred at 0° C. for 3 hours. Reaction mixture was neutralized by adding amberlyst IR 120 resin and filtered. Solvents were removed at reduced pressure to get p-nitrobenzyl 2-deoxy-2-phthalimido-β-D-glucopyranoside in 98% yield. 1H-NMR (600 MHz, CD3OD) δ 7.86-7.90 (m, 2H), 7.60-7.84 (m, 4H), 7.24-7.32 (m, 2H), 5.18 (d, 1H, J=9.0 Hz), 4.92 (d, 1H, J=13.2 Hz), 4.65 (d, 1H, J=13.2 Hz), 4.23 (dd, 1H, J=9.0, 10.8 Hz), 4.04 (dd, 1H, J=9.0, 10.8 Hz), 3.94 (dd, 1H, J=2.4, 12.0 Hz), 3.75 (dd, 1H, J=5.4, 12.0 Hz), 3.38-3.46 (m, 2H); 13C-NMR (100 MHz, CD3OD) δ 148.3, 146.2, 135.3, 132.5, 129.1, 124.1, 98.9, 78.0, 72.2, 72.0, 70.5, 62.5, 58.2; ESI-MS: m/z: calcd for C21H20N2O9Na: 467.1. found: 467.1 [M+23]+. p-Nitrobenzyl 2-deoxy-2-phthalimido-β-D-glucopyranoside (1.5 g, 0.031 mol) was azeotropically refluxed with toluene (100 mL) using a Dean-Stark apparatus for 3 hours. Then temperature was lowered down to 90° C. At this temperature, DL-camphorsulfonicacid (0.844 mmol) was added followed by benzaldehyde dimethylacetal (0.54 g, 0.035 mol). After 30 minutes, the temperature was raised to reflux temperature. The reaction was quenched by adding triethylamine. Solvents were removed under reduced pressure. Residue was extracted in ethyl acetate and washed with saturated brine. The organic layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure. Flash column chromatography using hexanes/ethyl acetate (2:3) gave the pure compound 17 in 82% yield. 1H NMR (400 MHz, CDCl3) δ 7.86-7.90 (m, 2H), 7.68 (m, 4H), 7.46-7.49 (m, 2H), 7.33-7.35 (m, 3H), 7.20-7.26 (m, 2H), 5.56 (s, 1H), 5.27 (d, 1H, J=8.8 Hz), 4.91 (d, 1H, J=13.6 Hz), 4.57 (m, 2H), 4.38 (dd, 1H, J=4.0, 10.4 Hz), 4.27 (dd, 1H, J=8.8, 10.4 Hz), 3.79-3.85 (m, 1H), 3.56-3.65 (m, 2H), 2.98 (d, 1H, J=4.0 Hz); 13C-NMR (100 MHz, CDCl3) δ 147.5, 144.6, 137.1, 134.6, 131.6, 129.7, 128.7, 128.1, 126.5, 123.8, 102.2, 98.7, 82.3, 70.3, 68.8, 68.7, 66.5, 56.7; ESI-MS: m/z: calcd for C28H24N2O9Na: 555.1. found: 555.2 [M+Na]+.
