Methanol → 3-O-Benzyl-1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose

Participants

Reaction Steps

A solution of diacetone glucose (5) (Aldrich) (18.0 g, 69.1 mmol) in THF (80 ml) was added dropwise to a stirred suspension of sodium hydride, (50% dispersion in oil, 3.67 g, 76.5 mmol) and tetrabutylammonium iodide (0.2 g, 0.54 mmol) in THF (50 ml) at 0° C. The mixture was warmed to room temperature and benzyl bromide (9.04 ml, 13.0 g, 76.0 mmol) added, then heated to 50° C. for 2 hours. Methanol (20 ml) was added and the mixture stirred for a further 2 hours before cooling, filtering through celite and concentrating. The resulting oil was dissolved in dichloromethane (100 ml), washed with water (2×30 ml), dried, filtered and evaporated to give 3-O-benzyl-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (23.5 g, 97%) as a pale brown oil. A small quantity was purified by flash chromatography (ethyl acetate-hexane 1:5) to give a clear oil, [α]20D -29.8° (c, 1.06 in chloroform) [lit.43 -27.7° (c, 3.32 in ethanol)]; 1H NMR δ 1.32, 1.39, 1.44, 1.51 (12H, 4×s, 2×acetonide); 3.99-4.11 (5H, m, H-3, H-4, H-5, H-6,6'); 4.59 (1H, d, H-2); 4.59 (1H, d, H-2); 4.65, 4.70 (2H, 2×d, CH2Ph, JH,H' 11.8 Hz); 5.90 (1H, d, H-1, J1,2 3.7 Hz); 7.32-7.36 (5H, m, H-Ph).

Provenance & Evidence