Fucosylated Molecules Competitively Interfere with Cholera Toxin Binding to Host Cells.

Cholera toxin (CT) enters host intestinal epithelia cells, and its retrograde transport to the cytosol results in the massive loss of fluids and electrolytes associated with severe dehydration. To initiate this intoxication process, the B subunit of CT (CTB) first binds to a cell surface receptor displayed on the apical surface of the intestinal epithelia. While the monosialoganglioside GM1 is widely accepted to be the sole receptor for CT, intestinal epithelial cell lines also utilize fucosylated glycan epitopes on glycoproteins to facilitate cell surface binding and endocytic uptake of the toxin.

Mild Method for 2-Naphthylmethyl Ether Protecting Group Removal Using a Combination of 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and β-Pinene.

The use of a combination of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and β-pinene permits the removal of 2-naphthylmethyl (Nap) ether protecting groups on highly sensitive substrates. The reaction tolerates both acid and base sensitive protecting groups, and products are afforded in 68-96% yield. The utility of the method is demonstrated by the removal of the Nap protecting groups on highly sensitive 2,6-dideoxy-sugar disaccharides.

Reagent-Controlled α-Selective Dehydrative Glycosylation of 2,6-Dideoxy- and 2,3,6-Trideoxy Sugars.

We have found that activating either 2,3-bis(2,3,4-trimethoxyphenyl)cyclopropenone or 2,3-bis(2,3,4-trimethoxyphenyl)cyclopropene-1-thione with oxalyl bromide results in the formation of a species that promotes the glycosylation between 2,6-dideoxy-sugar hemiacetals and glycosyl acceptors in good yield and high α-selectivity. Both reactions are mild and tolerate a number of sensitive functional groups including highly acid-labile 2,3,6-trideoxy-sugar linkages.