Reaction Steps
To a solution of thioglycoside 78 (1.40 g, 3.10 mmol) in 15 mL of methylene chloride is added N,N-diisopropylethylamine (0.64 mL, 3.70 mmol), followed by 2-(trimethylsilyl)ethoxymethyl chloride (0.60 mL, 3.40 mmol). The mixture is stirred at room temperature for 2 h, poured into saturated NaCl (50 mL) and extracted with CH2Cl2 (2×50 mL), dried over Na2SO4, concentrated, and purified by flash chromatography (40% EtOAc/hexane) to give 1.60 g (89%) of 1-deoxy-1-{4-[2(trimethylsilyl)ethoxymethoxy]phenylthio}-2,3,4,6-tetra-O-acetyl-β-D-galactopyranose 79 as a colorless oil: Rf 0.4 (33% EtOAc/hexane); 1H NMR (CDCl3, 270 MHz) δ 7.46 (d, J=8.4 Hz, 2H), 6.98 (d, J=8.4 Hz, 2H), 5.40 (d, J=3.3 Hz, 1H, H-4), 5.22 (s, 2H, SEM), 5.20 (dd, J=9.9, 9.9 Hz, 1H, H-2), 5.02 (dd, J=3.3, 9.9 Hz, 1H, H-3), 4.58 (d, J=9.9 Hz, 1H, H-1), 4.18 (dd, J=6.6, 11.2 Hz, 1H), 4.10 (dd, J=6.6, 11.2 Hz, 1H), 3.89 (dd, J=6.6, 6.6 Hz, 1H, H-5), 3.75 (t, J=8.4 Hz, 2H, SEM), 2.11 (s, 3H, OAc), 2.10 (s, 3H, OAc), 2.04 (s, 3H, OAc), 1.98 (s, 3H, OAc), 0.94 (t, J=8.4 Hz, 2H, CH2 --TMS), 0.01 (s, 9H, SiMe3).
