- Preparation of S-glycoside surfactants and cysteine thioglycosides using minimally competent Lewis acid catalysis
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Here we report a method for the preparation of anomerically pure β-S-glycopyranosides (1,2-trans-glycosides) from the corresponding peracetate donors. S-glycosylation was performed in CHCl3 at reflux in the presence of a catalytic amount of InBr3. Deacylation of the intermediate peracetates were achieved under Zemplén conditions. Five pyranose examples, monosaccharides D-glucose and D-galactose and disaccharides cellobiose, maltose, and lactose, were used as donors, and five thiols including an α/ω dithiol and Fmoc-L-cysteine were used as acceptors. Melting points, high res MS, [α]D and NMR data (1H and 13C, including COSY, HSQC and HMBC) are reported for compounds not previously described.
- Szabó, Lajos Z.,Hanrahan, Dillon J.,Jones, Evan M.,Martin, Erin,Pemberton, Jeanne E.,Polt, Robin
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- Synthesis, purification and liquid-crystalline behaviour of several alkyl 1-thio-D-glycopyranosides
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This paper describes the synthesis, purification, and liquid- crystalline behaviour of a series of alkyl 1-thioglycopyranosides. The synthesis of these derivatives was carried out via a Lewis acid mediated coupling of the fully acetylated monosaccharide with an alkanethiol. The choice of the Lewis acid depends on the configuration of AcO-2. The carbohydrate-derived surfactants exhibit thermotropic liquid-crystalline behaviour. The alkyl 1-thioglycopyranosides form the expected smectic A phases upon heating. The clearing temperatures vary with alkyl chain length which is in accordance with the accepted model for the S(A) phase of amphiphilic carbohydrate mesogens. For the alkyl 1-thiotalopyranosides, the clearing points are much lower than expected, presumably due to the formation of an intramolecular hydrogen bond in the talose moiety.
- Galema, Saskia A.,Engberts, Jan B. F. N.,Van Doren, Henk A.
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p. 423 - 434
(2007/10/03)
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- Amphiphilic Carbohydrate-Based Mesogens, 11 Synthesis of Mesogenic 1-Alkylthio-1-deoxy-D-galactitols by Glycoside Reduction
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Alkyl-1-thio-α/β-D-galactopyranosides (hexyl-dodecyl, 1a-g) have been O-diethylborylated and then reduced with tetraethyldiboranes(6) in the presence of 9-methylsulfonyloxy-9-borabicyclononane (MSBBN) catalyst to give 1-alkylthio-1-deoxy-D-galactitols 3a-g after deprotection. 3 exhibit the smectic A liquid crystalline phase on melting. - Keywords: Carbohydrates, Liquid Crystals (Smectic), Alkyl-1-thio-α/β-D-galactopyranosides. 1-Alkylthio-1-deoxy-D-galactitols, Glycoside Reduction, X-Ray Diffraction (Small Angle)
- Dahlhoff, Wilhelm V.,Radkowski, Karin,Riehl, Klaus,Zugenmaier, Peter
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p. 1079 - 1085
(2007/10/02)
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