Reaction Steps
Acetobromogalactose 1 (1.1 g, 2.68 mmol) and sodium methanethiosulfonate (0.45 g, 3.35 mmol) in toluene (50 mL) were concentrated in vacuo to approximately 30 mL to remove any water as the azeotrope. The mixture was made up to 50 mL with more toluene and again concentrated to 30 mL. A catalytic amount of tetrabutylammonium iodide was added and the mixture heated at reflux for 75 minutes. After cooling, Celite (to stop the formation of a salt cake on top of the column) was added and the whole mixture loaded directly on to a flash silica column. Elution with 40% ethyl acetate in petroleum ether and recrystallization from petroleum ether/ethyl acetate gave the title compound (787 mg, 67%) as colorless prisms; mp 118-119° C. (petroleum ether/ethyl acetate); [α]23D=+8.5 (c 1.0, CHCl3); IR (KBr) 1753 (C═O), 1325, 1138 (S—SO2) cm−1;1H NMR (400 MHz, CDCl3) δ 1.99 (s, 3H, Ac), 2.50 (s, 3H, Ac), 2.08 (s, 3H, Ac), 2.17 (s, 3H, Ac), 3.43 (s, 3H, CH3SO2—), 4.05 (ddd, J 7.4, 4.2, 0.9 Hz, 1 H), 4.08 (dd, J 18.3, 7.5 Hz, 1H), 4.20 (dd, J 10.8, 4.3 Hz, 1H), 5.13 (dtd, J 10.7, 7.6, 3.4 Hz, 1H), 5.26 (s, 1H), 5.27 (dd, J 14.8, 10.3 Hz, 1H), 5.48 (dd, J 3.4, 0.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 20.5, 20.6, 20.6, 20.6 (4×CH3CO), 52.7 (CH3SO2—), 61.8 (C-6), 65.8, 67.0, 71.3, 75.3, 87.0 (1J1CH 165 Hz, C-1), 169.7, 169.7, 170.0, 170.2 (4×C═O); HRMS m/z (ES): found 460.0951; C15H26NO11S2 requires 460.0947.
