Synthesis of (1----4)-linked galacturonic acid trisaccharides, a proposed plant wound-hormone and a stereoisomer

Synthesis of Two Tetrasaccharide Pentenyl Glycosides Related to the Pectic Rhamnogalacturonan I Polysaccharide

The synthesis of two protected tetrasaccharide pentenyl glycosides with diarabinan and digalactan branching related to the pectic polysaccharide rhamnogalacturonan I is reported. The strategy relies on the coupling of N-phenyl trifluoroacetimidate disaccharide donors to a common rhamnosyl acceptor. The resulting trisaccharide thioglycosides were finally coupled to an n-pentenyl galactoside acceptor to access the two protected branched tetrasaccharides.

Improved catalytic and stereoselective glycosylation with glycosyl N-trichloroacetylcarbamate: application to various 1-hydroxy sugars

Efficient catalytic and stereoselective glycosylation was achieved by activating a glycosyl N-trichloroacetylcarbamate with a catalytic amount of Lewis acid in the presence of a glycosyl acceptor and 5A molecular sieves. Catalytic one-pot dehydrative glycosylation of a 1-hydroxy carbohydrate was achieved stereoselectively by reaction with trichloroacetyl isocyanate, followed by activation with a catalytic amount of activators.

Synthesis of sialyl Lewis(x) mimics. Modifications of the 6-position of galactose

Seven sLe(x) mimics where the -CH2OH group of the galactose moiety is replaced by -CH2NH3+, -CH2NHAc, -CH2NHBz, -CH2OSO3Na, -COONa and -CONH2 have been prepared and tested for their binding affinity to E-selectin.

Synthesis of the tetrasaccharide repeating unit of the antigen from Klebsiella type 2

The disaccharide ethyl 2,4,6-tri-O-acetyl-3-O-(2,3,4,6-tetra-O-benzyl-alpha- D-glucopyranosyl)-1-thio-beta-D-glucopyranoside (6) and methyl 2,6-di-O-benzyl-3-O-(methyl 2,3,4-tri-O-benzyl-alpha-D- glucopyranosyluronate)-beta-D-mannopyranoside (21) have been synthesized and condensed in the presence of methyl triflate to afford a tetrasaccharide derivative. Removal of protecting groups gave methyl 3-O-(methyl alpha-D-glucopyranosyluronate)-4-O-(3-O-alpha-D- glucopyranosyl-beta-D-glucopyranosyl)-beta-D-mannopyranoside (23), the repeating unit of the antigen from Klebsiella type 2, in the form of its methyl ester methyl glycoside.

The preparation and susceptibility to hydrolysis of novel O-galacturonoyl derivatives of carbohydrates

D-Galacturonic acid or (1-->4)-alpha-D-galacturonan reacted in aqueous pyridine in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide with alcohols to yield esters. The alcohols that gave high yields of D-galacturonoyl derivatives were primary and included methanol, ethanol, 1-propanol, D-glucose, D-galactose, methyl beta-D-glucopyranoside, methyl beta-D-galactopyranoside, and cellulose. D-Galacturonic acid itself readily gave an O-D-galacturonoyl-D-glacturonic acid. The proposed structure of one compound, methyl 6-O-D-galacturonoyl-beta-D-glucopyranoside, was supported by 1H and 13C NMR data and the FAB mass-spectral data. Each ester was hydrolysed at pH 11 and 25 degrees C within 1 h. O-D-Galacturonoyl-D-glucose was considerably more alkali labile than O-polygalacturonoyl-D-glucose, and O-D-galacturonoylcellulose had an intermediate stability. The esters were relatively stable to cold acid, but could be hydrolysed by M trifluoroacetic acid at 100 degrees C for 1 h. The esters tested were resistant to digestion by 'Driselase', although the glycosidic bonds of O-polygalacturonoyl-D-glucose were hydrolysed to yield O-oligogalacturonoyl-D-glucoses of low molecular weight. The possible application of these analytical methods to the detection of O-uronoyl-type cross-links in cell-wall polysaccharides is discussed.

Stereoselective total synthesis of dodecagalacturonic acid, a phytoalexin elicitor of soybean

O-(alpha-D-Galactopyranosyluronic acid)-[(1----4)-O-(alpha-D-galactopyranosyluronic acid)]10-D-galactopyranuronic acid (1), an endogenous elicitor of the phytoalexin of soybean, was synthesized by way of highly stereoselective glycosylations that involved glycosyl fluorides as the donors and oxidation of the twelve primary hydroxyl groups in the alpha-(1----4)-linked galactododecaoside derivative.