Carbohydrate-derived polymers

Carbohydrate-derived polymers may overcome these negative attributes (9), Previously published work (10-13) demonstrated the potential for improved functional characteristics of dextrinized, oxidized and native starches by simple... 

Fig. 6. Comparison of the biological activities of monovalent glucose and mannose derivatives, multivalent carbohydrate-substituted polymer with two saccharide epitopes per repeat unit, and the less sterically congested carbohydrate-substituted polymer with a single recognition element per repeat unit. All polymers were generated by ROMP using RuC13...

As had been observed in the synthesis of carbohydrate-substituted polymers of different lengths, the reactivity of the monomers was an important parameter in generating the triblock polymers. If the mannose-substituted 7-oxanor-bornene derivative was first polymerized, followed by the galactose-derivatized norbornene and the mannose-substituted norbornene monomers, two distinct sets of products were observed. These were identified by modification of the resulting polymers by acetylation, and analysis of the products by GPC. With this protocol, it was found that the product was composed of short polymers (DP=... 

Not only chiral separations have been achieved with Mi-stationary phases. It has also been demonstrated that the MIP could distinguish between ortho- and para-isomers of carbohydrate derivatives. For example, a polymer imprinted with o-aminophenyl tetraacetyl P-D-galactoside was used to analyze a mixture of p-and o-aminophenyl tetraacetyl P-D-galactoside. As expected, the imprinted ortho analyte eluted after the non-imprinted para component see Fig. 5. Although baseline separation was not obtained, a separation factor of a = 1.51 was observed [19]. 

Zinc chloride-doped natural phosphate was shown to have catalytic behavior in the 1,3-dipolar cycloadditions of nucleoside acetylenes with azides to form triazolonucleosides <99SC1057>. A soluble polymer-supported 1,3-dipolar cycloaddition of carbohydrate-derived 1,2,3-triazoles has been reported <99H(51)1807>. 2-Styrylchromones and sodium azide were employed in the synthesis of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles <99H(51)481>. Lead(IV) acetate oxidation of mixed bis-aroyl hydrazones of biacetyl led to l-(a-aroyloxyarylideneamino)-3,5-dimethyl-l,2,3-triazoles <99H(51)599>. Reaction of 1-amino-3-methylbenzimidazolium chloride with lead(fV) acetate afforded l-methyl-l/f-benzotriazole <99BML961>. Hydrogenation reactions of some [l,2,3]triazolo[l,5-a]pyridines, [l,2,3]triazolo[l,5-a]quinolines, and [l,2,3]triazolo[l,5-a]isoquinolines were studied <99T12881>. 

The above discussion dealt primarily with synthetic polyelectrolytes, which behave in solution more or less as flexible polymers. Another important group, the natural polyelectrolytes, will not be discussed here. They include polynucleic acids, proteins, carbohydrate derivates, etc. They generally behave as rigid-chain polymers, due to their helix conformation. 

Carbohydrates are the most abundant of all organic compounds in the biosphere. Many members of the carbohydrate class have the empirical formula Cx(H20)y, and are literally hydrates of carbon. The fundamental units of the carbohydrate class, the monosaccharides, are polyhydroxy aldehydes or ketones and certain of their derivatives. As with other classes of biologically important compounds, much of the function of the carbohydrates derives from the ability of the monosaccharides to combine, with loss of water, to form polymers oligosaccharides and polysaccharides. The chemistry of carbohydrates is, at its core, the chemistry of carbonyl and hydroxyl functional groups, but these functional groups, when found in the same compound, sometimes exhibit atypical properties. The discussion that follows is designed to review the aspects of carbohydrate chemistry that are especially important for isolation, analysis, and structure determination of biologically important carbohydrates. 

Fast pyrolysis of pine sawdust in a small vortex reactor operating at 10 to 20 kg/h and 480 to 520 °C produces high yields of primary pyrolysis oils (over 55% by weight on a dry basis). The vortex reactor transmits very high heat fluxes to the sawdust, causing primarily depolymerization of the constituent polymers into monomers and oligomers. A preliminary scheme separates the raw oils into a carbohydrate-derived aqueous fraction and a phenolic-rich ethyl acetate (EA) soluble fraction. The EA fraction is washed with water and with aqueous sodium bicarbonate to remove acids yielding 20% to 25% of the feed as phenols and neutrals (P/N) in the EA solution. 

Acylated carbohydrate derivatives. Treatment of glycosides with polymer-supported boronic acid (1) with azeotropic removal of water aSords the more stable five- or six-membered boronate. The unprotected hydroxyl groups of the protected glycosides can be acylated, often in yields higher than those realized by classical methods. 

This review will be limited to a discussion of the structures and reactions of the aldehydes obtained from oxidation of cyclic carbohydrate derivatives. Such products as that from the oxidation of 1,2-0-isopropylidene-D-glucofuranose, which is a monoaldehyde, will not be dealt with. A monosaccharide derivative will normally give rise to a dialdehyde, a disaccharide derivative to two dialdehyde units linked together (or a tetra-aldehyde), and a polysaccharide will give a dialdehyde polymer (a polyaldehyde). All of these classes of compounds will be discussed. 

Multivalent arrays of carbohydrate derivatives show range of affinities for ConA. Relative potency IC50 polymer/(n)(IC5o o -Me-glucoside)... 

These compounds are less aggregated in solution. For instance, 2,2-dibutyl-l,3,2-dioxastannolane, a polymer in the solid state, has been shown, by variable temperature Sn NMR spectroscopy, to be a mixture of dimers, trimers, and tetramers in solution, with dimers predominating at room temperature and above. This technique has also indicated that most carbohydrate-derived stannylene acetals are present predominantly as dimers in solution." " " Supporting evidence has been obtained from mass spectral studies and by comparison of solid-state NMR spectra with those of solutions." Some dibutylstannylene acetals derived from cw-diols contain an observable proportion of higher oligomers benzyl 4,6-0-benzylidene-2,3-0-dibutylstannylene-o -D-mannopyranoside is present as a mixture of a dimer and a trimer in chloroform-d at -60 °C but, in the less polar solvent toluene-dg, is mainly present as a tetramer at that temperature. ... 

Carbohydrate-based synthetic polymers can be prepared by polymerization of small, activated carbohydrate-derived monomers. A pioneering study in this field was the preparation and polymerization26 of methyl 2,3,4,6-telra-O-allyl-a-D-glucopyranoside (1). Under the influence of oxygen and heat, compound 1 gradually polymerizes, first to a viscous liquid and finally to a colorless, transparent resin. Similarly, acrylate and... 

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