Reaction Steps
2,3,4,6-Tetra-O-acetyl-α-D-glucopyranosyl bromide (207 mg, 0.5 mmol) was dissolved in anhydrous acetonitrile (5 mL). To this sodium phenylthiosulfonate (201 mg, 1 mmol) and tetrabutylammonium bromide (16 mg, 0.05 mmol) were added. The resulting mixture was stirred under argon at 70° C. After a 4.5 h period, thin layer chromatography (t.l.c.) (petrol:ethyl acetate, 1:1) indicated the formation of a product (Rf 0.5) with complete consumption of the starting material (Rf 0.3). The solution was concentrated in vacuo. The crude solid was partitioned between dichloromethane (DCM, 20 mL) and water (20 mL), and the aqueous layer re-extracted with DCM (2×20 mL). The combined organics were washed with brine (20 mL), dried over MgSO4, filtered and concentrated in vacuo. The residue was purified by flash column chromatography (petrol:ethyl acetate, 1:1) to afford the title product (225 mg, 88%) as a white crystalline solid; mp 129-130° C.; [α]D25+51.2 (c, 1.0 in CHCl3); νmax (KBr) 1754 (s, C═O), 1376 (s, C═C) cm−1; δH; (400 MHz, C6D6) 1.68, 1.72, 1.73, 1.75 (4×3H, 4×s, 4×OAc), 3.09 (1H, ddd, J4,5 10.2 Hz, J5,6 2.4 Hz, J5,6′ 4.2 Hz, H-5), 3.83 (1H, dd, J5,6 2.4 Hz, J6,6′ 12.7 Hz, H-6),4.08 (1H, dd, J5,6′ 4.2 Hz, J6,6′ 12.6 Hz, H-6′), 5.17-5.23 (2H, m, H-2, H -4), 5.40 (1H, d, J1,2 10.2 Hz, H-1), 5.44 (1H, at, J9.4 Hz, H-3), 6.98-7.03 (3H, m, Ar—H), 7.90-7.92 (2H, m, Ar—H). The structure of the product was further confirmed by single crystal X-ray diffraction.
