Preparation and Characterization of Branched β-Cyclodextrins Having α-L-Fucopyranose and a Study of Their Functions

Three positional isomers of 6(1),6(n)-di-O-(alpha-L-fucopyranosyl)-beta-cyclodextrin [6(1),6(n)-di-O-(alpha-L,-Fuc)-beta CD, n = 2-4] were chemically synthesized by using the corresponding authentic compounds, 6(1),6(n)-di-O(tert-butyldimethylsilyl)-beta CD (n = 2-4) as fucosyl acceptors and 2,3,4-tri-O-benzyl-L-fucopyranosyl trichloroacetimidate as a fucosyl donor. Their structures were analyzed by HPLC, MS and NMR spectroscopy. The hemolytic activities of the alpha-L-Fuc-beta CDs were lower than that of beta CD, while the water solubility of these branched beta CDs was much higher than that of beta CD. The molecular interaction between these compounds and the fucose-binding lectin, Aleuria aurantia lectin (AAL), was investigated by using an optical biosensor based on the surface plasmon resonance (SPR) technique. The order of binding affinity, as a function of the fucose-binding position, was 6(1),6(4)- > 6(1),6(3)- > 6(1),6(2)-di-O-(alpha-L-Fuc)-beta CD > 6-O-(alpha-L-Fuc)-beta CD.