Toluene → 2,3,4,6-tetra-O-acetyl-alpha-L-mannopyranosyl bromide

Participants

Reaction Steps

1,2,3,4,6-penta-O-acetyl-L-mannopyranose (1) (21.04 g) was dissolved in dehydrated dichloromethane (150 ml), and the resulting solution was cooled in ice. 30% HBr/AcOH (27.5 ml) was added dropwise thereto over about 10 minutes, and after completion of the dropwise addition, the ice bath was removed, and the mixture was stirred at room temperature for 3 hours. The reaction mixture was concentrated under reduced pressure. Toluene was added to the resulting residue, and an azeotropic distillation procedure was performed twice. Ethyl acetate was added to the residue to dissolve the residue, and the resulting solution was washed sequentially with saturated NaHCO3 solution, water, and saturated saline. The organic layer was dried over anhydrous magnesium sulfate and filtered, and the filtrate was concentrated under reduced pressure. The obtained residue was dried well under reduced pressure, whereby a target product was obtained (crude yield: 21.45 g (which exceeded the theoretical yield because ethyl acetate and toluene were contained, and therefore, the molar amount thereof was taken as 49.96 mmol, and the subsequent reaction was performed)).

Provenance & Evidence