Preparation and characterization of 6I,6n-di-O-(L-fucopyranosyl)-beta-cyclodextrin (n=II-IV) and investigation of their functions.

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