反应详情

Dicyclohexylcarbodiimide (305 mg, 1.47 mmol) was added to a solution of 2,3,4,6-tetra-O-benzyl-D-glucopyranose (810 mg, 1.5 mmol), 2,2,2-trichloroethyl hydrogen malonate (330 mg, 1.4 mmol) and pyridine (196 mg, 2.48 mmol) in dry methylene chloride (6 mL). A white precipitate appeared almost immediately and a slight temperature increase was noticed. The mixture was stirred further for one hour, then diluted with ether (10 mL) and filtered. The solid was washed with ether (2×5 mL) and the filtrates were evaporated under reduced pressure in the presence of silica (2 g). Chromatography over silica gel (60-200 mesh, 40 g, elution with ether-hexanes, 1:1.5) afforded 2,3,4,6-tetra-O-benzyl-D-glucopyranosyl 2,2,2-trichloroethyl malonate 2 (929 mg, 1.22 mmol, 87%) as a viscous colorless syrup; NMR (CDCl3, 90 MHz): δ7.37+7.32 (aromatic protons), 6.43 (d, J=2 Hz, H-1, α-anomer), 5.71 (d, J=7 Hz, H-1, β-anomer), 4.92-4.42 (m, benzylic protons) with a high singlet at 4.78 (OCH2Cl3), 3.87-3.40 (m, sugar skeleton and malonyl protons); aromatic ratio, α:β=1.7 IR (CCl4): 3090, 3075, 3024, 2925, 2875, 1770 (s), 1755 (s), 1100 (s) cm-1.

1. temperaturea slight temperature increase
2. filtrationfiltered
3. washThe solid was washed with ether (2×5 mL)
4. customthe filtrates were evaporated under reduced pressure in the presence of silica (2 g)