An efficient synthetic route to O-(2-O-benzyl-3,4-di-O-acetyl-α/β-l-fucopyranosyl)-trichloroacetimidate.

An efficient synthetic route to prepare O -(2- O -benzyl-3,4-di- O -acetyl-α/β- l -fucopyranosyl)-trichloroacetimidate from l -fucose was developed by introducing the thiophenyl group at the anomeric center and the benzylidene functional group to protect the 3 and 4 positions. Although three approaches were considered, the best result was obtained when, after the 2-hydroxyl benzylation, both protective groups were simultaneously removed by using acetic anhydride and perchloric acid supported on silica as catalyst. Selective deacetylation of the obtained tri- O -acetate followed by the reaction of the resultant hemiacetal with trichloroacetonitrile and DBU afforded the trichloroacetimidate with an overall yield of 56% from the l -fucose. Image 1 • The trichloroacetimidate yield obtained is almost 2.5 times higher than the reported. • The protection with thiophenyl and benzylidene groups avoids mixed acetal formation. • One less step was required when acetic anhydride-perchloric acid on Silica was used. • Less chromatographic purification is required as compared with the reported method. [ABSTRACT FROM AUTHOR]