Enantiomeric separation by MEKC using dodecyl thioglycoside surfactants: importance of an equatorially oriented hydroxy group at C-2 position in separation of dansylated amino acids.

To investigate the influence of stereogenic centers of sugar-based surfactants for enantiomeric separation, four n-dodecyl thioglycoside sulfates (CMC 1.5-3.6 mM) were chosen as micelle-forming surfactants and five dansylated hydrophobic amino acids were used as test analytes. The analytes were mutually separated by these micelles exhibiting almost similar migration times independent of the used surfactant. Baseline separations of all enantiomers were achieved using both beta-D-glucose and beta-D-galactose derivates that have an equatorially oriented hydroxy group at C-2 position. In contrast, the ability of enantioseparation was markedly decreased in the case of beta-D-mannose and 2-deoxy-beta-D-glucose derivatives. These results suggested that the structure of C-2 position of the sugar unit, namely presence of an equatorially oriented hydroxy group, is highly important for the enantiomeric separation of the chosen hydrophobic dansylated amino acids.

Pre-activation of fully acetylated dodecyl thioglycosides with BSP-Tf2O led to efficient glycosylation at low temperature.

Fully acetylated dodecyl thioglycosides were found to be useful as glycosyl donors by activation with 1-benzenesulfinyl piperidine (BSP) and triflic anhydride (Tf(2)O) at -78 degrees C. The glycosyl acceptor was added to the reaction mixture at the same temperature to furnish various disaccharide, including the protected Lewis a (Le(a)) trisaccharide, in good yields.

Stereoselective tris-glycosylation to introduce beta-(1-->3)-branches into gentiotetraose for the concise synthesis of phytoalexin-elicitor heptaglucoside.

Dodecyl thioglycosides (3, 4, 5) were prepared by conventional transformation of d-glucose and used as new glycosyl donors for a short-step synthesis of phytoalexin elicitor heptaglucoside. A gentio-tetraoside derivative (6) having three hydroxyl groups was synthesized by NIS-TfOH promoted glycosylate in more than 90% yield followed by selective removal of temporary protective groups. Undesired formation of alpha-glycosides at the introduction of beta-(1-->3)-branches into gentio-oligosaccharides was found to be suppressed by use of a thiophilic reagent system, BSP (1-benzenesulfinyl piperidine)-Tf2O, giving the heptaglucoside in only four glycosylation steps.

Dodecyl thioglycopyranoside sulfates: novel sugar-based surfactants for enantiomeric separations by micellar electrokinetic capillary chromatography.

Four novel chiral anionic surfactants having carbohydrate hydrophilic heads, sodium n-dodecyl 1-thio-beta-D-glucopyranoside 6-hydrogen sulfate (6-betaGlcD), sodium n-dodecyl 1-thio-beta-L-glucopyranoside 6-hydrogen sulfate (6-betaGlcL), sodium n-dodecyl 1-thio-beta-L-fucopyranoside 3-hydrogen sulfate (3-betaFucL), and sodium n-dodecyl 1-thio-alpha-L-rhamnopyranoside 3-hydrogen sulfate (3-alphaRhaL), were synthesized by selective sulfation of the corresponding thioglycosides. Their CMC determined by fluorescence using pyrene as a probe in water was 1.3-2.7 mM. These surfactants found to be useful as chiral selectors for enantiomeric separation by MEKC. The enantiomeric separation was optimized with respect to pH, buffer concentration, and surfactant concentration. Under the optimized conditions (50 mM phosphate buffer at pH 6.5, 30 mM surfactant, 20 kV), the enantiomeric separations of five dansylated amino acids (Dns-AAs) were achieved within approximately 20 min with the migration order of Val