Reaction Steps
Methyl 3,4-di-O-benzyl-6-O-(4-chlorobenzyl)-β-D-glucopyranoside (0.233 g, 0.467 mmol) was dissolved in 5 mL CH2Cl2. Acetic anhydride (53 μL, 0.560 mmol) and DMAP (0.114 g, 0.934 mmol) were added and the reaction mixture was stirred at room temperature for 1 h. The solution was filtered through silica, eluted with EtOAc and concentrated. Purification by flash column chromatography on silica gel (30% EtOAc/Hexanes) gave 224 mg (89%) of 20 as a colorless oil. [α]24D: −0.5° (c 0.79, CH2Cl2); IR (thin film) 2867, 1747, 1233, 1087, 1060 cm−1; 1H-NMR (CDCl3) δ 7.35-7.27 (m, 12H), 7.20-7.18 (m, 2H), 5.00 (dd, J=7.9, 8.8 Hz, 1H), 4.81 (d, J=10.7 Hz, 1H), 4.80 (d, J=11.6 Hz, 1H), 4.68 (d, J=11.3 Hz, 1H), 4.59 (d, J=12.5 Hz, 1H), 4.56 (d, J=10.7 Hz, 1H), 4.52 (d, J=12.2 Hz, 1H), 4.30 (d, J=7.9 Hz, 1H), 3.74-3.67 (m, 4H), 3.51-3.37 (m, 4H), 1.99 (s, 3H); 13C-NMR (CDCl3) δ 169.8, 138.2, 138.0, 136.8, 129.2, 128.7, 128.6, 128.2, 128.1, 128.0, 102.0, 83.2, 78.1, 75.3, 75.2, 73.2, 72.9, 68.9, 56.9, 21.2; FAB MS m/z (M+Na)+: calcd 563.1813, obsd 563.1817.
