The conjugate with human serum albumin (HSA) of the
S-linked thioanalogue of the branched tetrasaccharide repeating unit of the polysaccharide, schizophyllan, was synthesized from 1,2,4,6-tetra-
...O-acetyl-3-
S-2,4-di-
O-acetyl-3,6-di-
S-(2,3,4,6-tetra-
O-acetyl-β-
d-glucopyranosyl)-3,6-dithio-β-
d-glucopyranosyl-3-thio-β-
d-glucopyranose M.O. Contour-Galcera et al.,
Carbohydr. Res., 281 (1996) 119–128 in five steps, and its potential immunomodulatory activity was evaluated in human blood mononuclear cells. The protein glycoconjugate did not effect proliferation or production of IL-4, IL-5 and IFN-g in a significant way.
Controlled selective protonic activation of the fructosyl moiety in sucrose and fructo-oligosaccharides, with pyridinium poly (hydrogen fluoride) at 20 degrees C, yielded either the kinetic product ...alpha-D-fructofuranose beta-D-fructofuranose 1,2':2,1'-dianhydride (1), or its thermodynamically more stable isomer alpha-D-fructofuranose beta-D-fructopyranose 1,2':2,1'-dianhydride (2), depending on the hydrogen fluoride-pyridine ratio. A similar reaction was performed with 6,6'-dichloro-6,6'-dideoxysucrose, or 6,6'-dideoxy-6,6'-diiodosucrose, using a slightly higher ratio of HF, resulting in the corresponding 6-deoxy-6-halo-alpha-D-fructofuranose 6'-deoxy-6'-halo-beta-D-fructofuranose 1,2':2,1'-dianhydride derivatives. Both 6,6'-dihalides were converted, upon action of the appropriate nucleophile, into the difructofuranose dianhydride derivatives bearing the 6,6'-di-S-heptyl-6,6'-dithio, 6,6'-diazido-6,6'-dideoxy and then 6,6'-diamino-6,6'-dideoxy functionalities. 6-Chloro-6-deoxy and 6-deoxy-6-iodo derivatives of 2 were also prepared by direct halogenation, and further converted into the 6-S-heptyl-6-thio, 6-azido-6-deoxy and then 6-amino-6-deoxy derivatives of 2. Reaction of chloromethyloxirane with 1 or 2 yielded hydrophilic polymers. The 6,6'-di-S-heptyl-6,6'-dithio derivative of 1 displayed liquid crystal properties. The 6,6'-dideoxy-6,6'-diiodosucrose precursor was prepared by the reaction of Garegg's iodine-imidazole-triphenylphosphine reagent with sucrose in N,N-dimethylformamide solution.
Thioureido-β-cyclodextrins as molecular carriers Fernández, José M. García; Mellet, Carmen Ortiz; Maciejewski, Sylwester ...
Chemical communications (Cambridge, England),
1996
24
Journal Article
1‘-Thiotrehalulose (1-S-α-d-glucopyranosyl-1-thio-d-fructose, 6) and 1‘-epi-thiotrehalulose (1-S-β-d-glucopyranosyl-1-thio-d-fructose, 12) have been prepared, and their reactivity toward base and ...acid catalysts has been compared with that of their α-O-linked natural counterpart trehalulose (14). Under conventional, pyridine-catalyzed acetylation conditions, 6 and 12 afforded exclusively the C-2 E open-chain enol acetates at the d-fructose moiety 7 and 13, when 14 led to the expected peracetylated disaccharides. Upon protonic activation, 6, 12, and 14 underwent intramolecular glycosidation reactions, yielding d-fructosyl d-glucosyl 1,1‘:2,2‘ mixed thioacetals and acetals, respectively, whose structures are under control of stereoelectronic factors. A much higher intramolecular glycosylation reaction rate was observed for the S-linked thioanalogues as compared to trehalulose, supporting involvement of episulfonium intermediates at the anomeric position activation step. Nevertheless, the close transformation patterns with either S- or O-linked disaccharides favors in both cases oxocarbenium entities as main intermediates in glycosylation reactions involving protonic activation. An unexpected tautomerization reaction at the d-glucose moiety, resulting in a fructofuranosyl glucofuranosyl spiro-oxathiane derivative presumably via a sulfonium intermediate, was also observed for derivatives of 6 and 12 under strong protonating conditions. These results stress on the importance of sulfur atom participation reactions in thiooligosaccharide chemistry.
beta-(1-->4)-Linked 2-amino-2-deoxy-D-glucopyranosyl oligosaccharides, in the form of their alpha-glucopyranosyl fluorides at the reducing end, were obtained by fluorolysis of chitosan in anhydrous ...hydrogen fluoride at room temperature. The average dp depended on the reaction time and was conveniently monitored by 13C NMR spectroscopy, using the signal ratios for beta-(1-->4) bonded C-1 at approximately 98.5 ppm and the C-1 doublet for the terminal glycosyl fluoride moiety at approximately 104 ppm. Preparative fractionation of dp 2-11 glycosyl fluoride oligosaccharides, obtained after 18 h of fluorolysis, was achieved by gel-permeation chromatography on Bio-Gel P-4 with aqueous acetic acid-ammonium acetate as eluent. Hydrolysis of the anomeric fluoride, with either aqueous perchloric acid, or by a sequence involving formation of the C-2 N-trifluoroacetate and subsequent simultaneous hydrolysis of the glycosyl fluoride and the amide substituent with aqueous methanol, yielded the free beta-(1-->4)-linked 2-amino-2-deoxy-D-glucopyranosyl oligosaccharides which were separated, for dp 2-11, by the same gel-exclusion technique. Both oligosaccharide series, either free or in the form of their alpha-glycopyranosyl fluorides, were fully characterized.
Mild acid hydrolysis of Escherichia coli O104 lipopolysaccharide released an O-specific polysaccharide, a tetrasaccharide repeating unit, the corresponding dimer, and a disaccharide fragment of the ...repeating unit. Complete and incomplete cores, and oligosaccharides comprising fragments of the repeating unit and the core region, were also obtained. On the basis of sugar and methylation analysis, FAB-mass spectrometry and NMR spectroscopy of the hydrolysis products, the repeating unit of the O-specific polysaccharide was shown to be the tetrasaccharide:-->4)-alpha-D-Galp-(1-->4)-alpha-Neup5,7,9Ac3++ +-(2-->3)-beta-D- Galp-(1-->3)-beta-D-GalpNAc (1-->. The linkage between the O-specific polysaccharide chain and the core region, which appeared to be of the R2 type, was established. These results indicate that N-acetylneuraminic acid, located in the O-specific polysaccharide, is an inherent lipopolysaccharide component.
The structure of four oligosaccharide fractions from the
Hafnia alvei strain 2 lipopolysaccharide (LPS) have been assigned by FABMS. This approach corroborates data previously established by NMR ...spectroscopy for the major oligosaccharides in these fractions A. Gamian, E. Romanowska, U. Dabrowski, J. Dabrowski,
Biochemistry 30 (1991) 5032–5038; E. Katzenellenbogen, A. Gamian, E. Romanowska, U. Dabrowski, J. Dabrowski,
Biochem. Biophys. Res. Commun. 194 (1993) 1058–1064; N. Ravenscroft, A. Gamian, E. Romanowska,
Eur. J. Biochem. 227 (1995) 889–896. In addition, the MS/MS with B/E linked scan technique allowed the detection of an additional oligosaccharide with the structure:
lacking the branched O-6 linked glucopyranose residue at the 3-linked Gal unit, which indicates a structural heterogeneity for the major oligosaccharide fraction.
The sulfur‐linked pentathiohexasaccharide 3I,3IV‐di‐β‐D‐glucopyranosylthiogentiotetraose (12) has been prepared by a convergent approach involving the reaction of ...1,2,4‐tri‐O‐acetyl‐6‐deoxy‐6‐iodo‐3‐S‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)‐3‐thio‐β‐D‐glucopyranose (10) with the sodium salt of 2,3,4‐tri‐O‐acetyl‐6‐S‐2,4‐di‐O‐acetyl‐3,6‐di‐S‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)‐3,6‐dithio‐β‐D‐glucopyranosyl‐1,6‐dithio‐β‐D‐glucopyranose (4). A further reaction, involving the sodium salt of the peracetylated β‐1‐thio derivative of 12 with 1,2,3,4‐tetra‐O‐acetyl‐6‐deoxy‐6‐iodo‐β‐D‐glucopyranose (26), afforded the homologous sulfur‐linked hexathioheptasaccharide 3II,3V‐di‐β‐D‐glucopyranosylthiogentiopentaose (28). Related sulfur‐linked positional isomers 3II,3IV‐di‐D‐β‐glucopyranosylthiogentiotetraose (34) and 3III,3V‐di‐β‐D‐glucopyranosylthiogentiopentaose (39) have been prepared using analogous synthetic strategies. Thus, SN2 displacement of the iodine atom in 10 by the sodium salt of 2,4‐di‐O‐acetyl‐3,6‐di‐S‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)‐1,3,6‐trithio‐β‐D‐glucopyranose afforded a tetrathiopentasaccharide, which resulted in the pentathiohexasaccharide 34 by a sequence of reactions involving the 1‐thioglycose 32 in reaction with 26. The hexathioheptasaccharide 39 was obtained conveniently by the reaction of 26 with the acetylated 1‐thio‐6I, 3II, 6II, 3IV, 6IV‐pentathio derivative 37, followed by deacylation. The four isomeric pentathiohexa‐ and hexathioheptasaccharides 12,34 and 28,39, respectively, were all found to be active in eliciting phytoalexin accumulation in soybean cotyledon tissue and in binding to a glucan‐binding protein of soybean, although to a lesser extent than the corresponding O‐oligosaccharides, the alternate thiohexa‐ and thioheptasaccharides 12,28 being more active as compared to the geminally branched isomers 34,39.
4-Aminophenyl 1,4-dithio-beta-cellobioside (6) was obtained by treatment of methyl 2.3,6-tri-O-benzoyl-4-O-triflyl-alpha-D-galactopyranoside with the sodium salt of 1-thio-beta-D-glucopyranose, ...followed by acetolysis and glycosylation of the corresponding bromide with 4-aminobenzenethiol and subsequent deacylation. A similar synthesis starting with the 1-thiolate of 1,4-dithio-beta-cellobiose led to the trisaccharide 4-aminophenyl 1,4,4'-trithiocellotrioside (16). The 4-acetamidophenyl di- and tri-thiocellooligosaccharides were found to be excellent competitive inhibitors of the hydrolysis of 4-methylumbelliferyl beta-lactoside with respective Ki values of 25 and 6.5mM. The two 4-aminophenyl oligosaccharides 6 and 16 were coupled to CH-Sepharose 4B, and the affinity gels were used for the purification of cellobiohydrolases from a crude commercial cellulolytic extract of T reesei. Cellobiohydrolases I or II were selectively desorbed from gels bearing ligands 6 and 16.
