反应详情

L-Fucose is then acetylated with acetic anhydride to produce fucose tetraacetate. Preferably, the reaction is carried out by suspending the L-fucose in a solvent, such as pyridine, and slowly adding the acetic anhydride. The mixture is stirred, poured into a separating funnel containing ice water, and extracted with chloroform. The organic extracts are washed with water, aqueous sodium bicarbonate, and dried over magnesium sulfate. The mixture is filtered and the solvent removed under reduced pressure. The residue is co-evaporated with toluene to remove any remaining pyridine or acetic acid. The fucose tetraacetate is then brominated to produce 2,3,4-tri-O-acetyl-L-fucopyranosyl bromide having the formula: ##STR13## It is to be noted that in the above formula, and elsewhere herein, the use of "Ac" is understood to represent the acetyl radical, i.e., ##STR14## The fucose tetraacetate is brominated with hydrogen bromide in acetic acid. The mixture is worked up similarly to that just described for preparing fucose tetraacetate, i.e., chloroform extraction from ice water.