Synthesis, Nmr, and Conformational Studies of Fucoidan Fragments. Iii. Effect of Benzoyl Group at O-3 on Stereoselectivity of Glycosylation by 3-O- And 3,4-Di-O-Benzoylated 2-O-Benzylfucosyl Bromides

The effect of a benzoyl group at O-3 on stereoselectivity of glycosylation by 3-O- and 3,4-di-O-benzoylated 2-O-benzyl-L-fucopyranosyl bromides was studied by direct chemical experiments and computational chemistry. The influence of a benzoyl group at O-3 of the fucosyl donors was shown to have a larger effect on the efficiency of α-fucosylation than a benzoyl group at O-4. It is hypothesized that this is a result of the ability of a benzoyl group at O-3 to participate in glycosyl cation stabilization.