Tetrafluoroborate → 2,3,4,6-Tetra-O-benzyl-D-glucopyranosyl Fluoride

To a solution of 2,3,4,6-tetra-O-benzyl-D-glucopyranose (100 mg, 0.18 mmol) and DBU (44 μL, 0.28 mmol) in dichloromethane (0.5 mL) is added diethylaminodifluorosulfinium tetrafluoroborate (68 mg, 0.28 mmol) at room temperature and under nitrogen. After 90 min of stirring, the reaction mixture is quenched at room temperature with a 5% aqueous sodium bicarbonate solution, stirred for 15 min, and the resulting mixture is extracted twice using dichloromethane. The organic phases are combined, dried over magnesium sulfate and filtered through a pad of silica gel. Solvents are evaporated to provide 2,3,4,6-tetra-O-benzyl-D-glucopyranosyl fluoride (96 mg, 96%, β:α anomers in a 1.1:1 ratio respectively) as a foam. 1H NMR (CDCl3, 300 MHz) δ 7.47-7.15 (m, 20H), 5.61 (dd, 2JH-F=53.2 Hz, 3JH-H=2.3 Hz, 0.48H, α-anomer), 5.31 (dd, 2JH-F=51.8 Hz, 3JH-H=6.4 Hz, 0.52H, β-anomer), 5.07-4.48 (m, 8H), 4.11-3.54 (m, 6H); 19F NMR (CDCl3, 282 MHz) δ −138.0 (dd, 1JF-H=53.4 Hz, 2JF-H=10.6 Hz, β-F), −149.44 (dd, 1JF-H=54.4 Hz, 2JF-H=25.8 Hz, α-F); 13C NMR (CDCl3, 75 MHz) δ 138.5, 138.3, 138.1, 137.9, 137.5, 128.6, 128.5, 128.2, 128.1, 128.0, 127.9, 127.8, 112.8 (d, 1JC-F=215.2 Hz, β-anomer), 108.6 (d, 1JC-F=228.7 Hz, α-anomer), 83.6, 83.4, 81.7, 81.5, 81.4, 79.5, 79.2, 77.5, 77.1, 77.0, 77.7, 75.9, 75.5, 75.2, 75.0, 74.9, 74.8, 74.5, 73.6, 73.5, 72.7, 68.4, 67.8.