Reaction Steps
BF3.Et2O (8.5 mL, 67.0 mmol) was added dropwise to a solution of of 1,2,3,4,6-penta-O-acetyl-α,β-D-galactose (5e) (See FIG. 7) (5.1 g, 13.1 mmol) and Br(CH2)2OH (1.15 mL, 16.2 mmol) in CH2Cl2 (24 mL) at 0° C. under N2. After 1 hour, the solution was warmed to room temperature. After 24 hours, the reaction solution was added to ice water (20 mL) and extracted with CH2Cl2 (30 mL×3). These extracts were combined, washed with water (20 mL), sat. NaHCO3 (aq., 20 mL), water (20 mL), dried (MgSO4), filt Vögtle ered, and the solvent removed. The residue purified by flash chromatography (EtOAc:hexane, 1:3) to give 2-bromoethyl 2,3,4,6-tetra-O-acetyl-β-D-galactopyranoside (4j) (See FIG. 7) (4.01 g, 67%) as a white solid; mp 116-117° C. (EtOAc/hexane) [lit., (Coles et al., J. Am. Chem. Soc., 60:1020-1022 (1938), which is hereby incorporated by reference) 111° C.; lit., (Dahmén et al., “2-Bromoethyl Glycosides—Synthesis and Characterization,” Carbohydr. Res., 116:303-307 (1983), which is hereby incorporated by reference) 114-116° C. (EtOAc/light pet. ether)]; [α]27D=−3.8 (c 0.81, CHCl3) [lit., (Dahmén et al., “2-Bromoethyl Glycosides—Synthesis and Characterization,” Carbohydr. Res., 116:303-307 (1983), which is hereby incorporated by reference) [a]23D=−5 (c 1.4, CDCl3)]; 1H NMR (200 MHz, CDCl3) δ 1.98, 2.05, 2.08, 2.15 (s×4, 3H×4, Ac×4), 3.43-3.50 (m, 2H), 3.75-3.95 (m, 2H), 4.12-4.24 (m, 3H), 4.53 (d, J1,2 8 Hz, 1H, H-1), 5.02 (dd, J2,3 11 Hz, J2,3 3 Hz, 1H, H-3), 5.23 (dd, J1,2 8 Hz, J2,3 11 Hz, 1H, H-2), 5.40 (br d, J3,4 3 Hz, 1H, H-4). NaSSO2CH3 (85 mg, 0.63 mmol) was added to a solution of 4j (See FIG. 7) (223 mg, 0.49 mmol) in DMF (6 mL) under N2 and warmed to 55° C. After 30 hours, the solution was cooled and the solvent removed. The residue was purified by flash chromatography (EtOAc:hexane, 1:1) to give 1j (See FIG. 7) (198 mg, 83%) as a white foam; [α]27D=+9.1 (c 1.41. CHCl3); IR (film) 1747 cm−1 (C═O), 1320, 1133 cm−1 (S—SO2); 1H NMR (500 MHz, CDCl3) δ 1.98, 2.05, 2.09, 2.15 (s×4, 3H×4, Ac×4), 3.35 (s, 3H, CH3SO2—), 3.35-3.38 (m, 2H, —CH2S—), 3.84 (ddd, J 6.1 Hz, J 7.1 Hz, J 10.5 Hz, 1H, —OCHH′—), 3.92 (td, J4,5 1.1 Hz, Jt 6.6 Hz, 1H, H-5), 4.10-4.21 (m, 3H, H-6, H-6′, —OCHH′—), 4.52 (d, J1,2 8.0 Hz, 1H, H-1), 5.01 (dd, J2,3 10.3 Hz, J3,4 3.5 Hz, 1H, H-3),5.20 (dd, J1,2 8.0 Hz, J2,3 10.3 Hz, 1H, H-2), 5.40 (dd, J3,4 3.5 Hz, J4,5 1.1 Hz, 1H, H-4); 13C NMR (100 MHz, CDCl3) δ 20.6,20.7, 20.8 (CH3COO—×4), 36.1, (—CH2S—), 50.6 (CH3SO2—), 61.2 (—OCH2—), 67.0, 68.3, 68.5, 70.8, 71.0 (C-2, C-3, C-4, C-5, C-6), 101.3 (C-1), 169.5, 170.0, 170.1, 170.4 (CH3COO—×4); HRMS m/z (FAB+): Found 487.0936 (M+H+); C17H27O12S2 requires 487.0944.
