Boron trifluoride etherate → 2-Bromoethyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside

BF3.Et2O (3.3 mL, 26.0 mmol) was added dropwise over the course of 15 minutes to a solution of 1,2,3,4,6-penta-O-acetyl-α,β-D-glucose (2 g, 5.1 mmol) and Br(CH2)2OH (0.45 mL, 6.3 mmol) in CH2Cl2 (9 mL) at 0° C. under N2. After 1.5 hours, the solution was warmed to room temperature. After 20 hours the reaction solution was added to ice water (15 mL) and extracted with CH2Cl2 (15 mL×3). These extracts were combined, washed with water (15 mL), sat. NaHCO3 (aq., 15 mL), water (15 mL), dried (MgSO4), filtered, and the solvent removed. The residue was purified by flash chromatography (EtOAc:hexane, 1:3) to give 2-bromoethyl 2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside (4h) (See FIG. 6) (1.42 g, 61%) as a white solid; mp 118-120° C. (EtOAc/iso-octane) [lit., (Coles et al., J. Am. Chem. Soc., 60:1020-1022 (1938), which is hereby incorporated by reference) mp 117.3° C. (EtOH)]; [α]27D=−11.9 (c 1.65, CHCl3) [lit., (Helferich et al., Just. Lieb. Ann. Chem., 541:1-16 (1939), which is hereby incorporated by reference) [α]20D=−12.3 (c 0.2, CHCl3)]; 1H NMR (200 MHz, CDCl3) δ 2.00, 2.02, 2.07, 2.09 (s×4, 3H×4, Ac×4), 3.42-3.51 (m, 2H), 3.67-3.87 (m, 2H), 4.10-4.31 (m, 3H), 4.57 (d, J1,2 8 Hz, 1H, H-1), 4.97-5.27 (m, 3H). NaSSO2CH3 (260 mg, 1.94 mmol) was added to a solution of 4h (See FIG. 6) (640 mg, 1.41 mmol) in DMF (18 mL) under N2 and warmed to 50° C. After 25 hours, the solution was cooled and the solvent removed. The residue was purified by flash chromatography (EtOAc:hexane, 1:1) and the resulting solid recrystallized from EtOAc/hexane to give 1h (See FIG. 6) (544 mg, 80%) as a white solid; mp 115-116° C. (EtOAc/hexane); [α]27D=+5.4 (c 1.06. CHCl3); IR (KBr) 1758, 1741 cm−1 (C═O), 1314, 1133 cm−1 (S—SO2); 1H NMR (500 MHz, CDCl3, COSY) δ 1.99, 2.02, 2.06, 2.08 (s×4, 3H×4, Ac×4), 3.30-3.38 (m, 2H, —CH2S—), 3.34 (s, 3H, CH3SO2—), 3.70 (ddd, J4,5 9.9 Hz, J5,6 2.2 Hz, J5,6 4.6 Hz, 1H, H-5), 3.83 (ddd, J 5.6 Hz, J 7.4 Hz, J 10.5 Hz, 1H, —OCHH′—), 4.13-4.18 (m, 2H, H-6, —OCHH′—), 4.24 (dd, J5,6′ 4.6 Hz, J6,6 12.4 Hz, 1H, H-6′), 4.55 (d, J1,2 8.1 Hz, 1H, H-1), 4.98 (dd J1,2 8.1 Hz, J2,3 9.7 Hz, 1H, H-2), 5.07 (t, J 9.9 Hz, 1H, H-4), 5.19 (t, J 9.6 Hz, 1H, H-3); 13C NMR (125 MHz, CDCl3 DEPT) δ 20.5, 20.7 (q×2, CH3COO—×4), 36.0, (t, —CH2S—), 50.6 (q, CH3SO2—), 61.6 (t, —OCH2—), 68.1, 70.8, 71.9, 72.5 (d×4, C-2, C-3, C-4, C-5), 68.4 (t, C-6), 100.8 (d, C-1), 169.3, 170.0, 170.5 (s×3, CH3COO—×4); HRMS m/z (FAB+): Found 487.0940 (M+H+); C17H27O12S2 requires 487.0944.