Reaction Steps
2,3,4,6-Tetra-O-acetyl-α-galactopyranosyl bromide (2.0 g, 5 mmol) was dissolved in anhydrous acetonitrile (80 mL). To this sodium phenylthiosulfonate (2.02 g, 10.3 mmol) and tetrabutylammonium bromide (160 mg, 0.5 mmol) were added. The resulting mixture was stirred under argon at 70° C. After a 5 h period, t.l.c. (petrol:ethyl acetate, 1:1) indicated the formation of a product (Rf 0.4) with complete consumption of the starting material (Rf 0.6). The solution was concentrated in vacuo. The crude oil was partitioned between DCM (50 mL) and water (50 mL), and the aqueous layer re-extracted with DCM (2×50 mL). The combined organics were washed with brine (100 mL), dried (MgSO4), filtered and concentrated in vacuo. The residue was purified by flash column chromatography (petrol:ethyl acetate, 2:1) to afford the title product (1.7 g, 65%, 2 steps) as a white crystalline solid; mp 53-54° C.; [α]D27+24.2 (c, 1.0 in CHCl3); δH (400 MHz, CDCl3) 1.98, 2.03, 2.06, 2.11 (4×3H, 4×s, 4×OAc), 3.85 (1H, dd, J5,6 8.8 Hz, J6,6′ 14.0 Hz, H-6), 3.95-4.00 (2H, m, H-5, H-6), 5.11 (1H, dd, J2,3 9.7 Hz, J3,4 3.3 Hz, H-3), 5.23 (1H, at, J10.3 Hz, H-2), 5.25 (1H, d, J1,2 10.2 Hz, H-1), 5.43 (1H, dd, J3,4 3.6 Hz, J4,5 1.0 Hz, H-4), 7.54-7.68 (3H, m, Ar—H), 7.93-7.97 (2H, m, Ar—H).
