Polysaccharides ethers

Saito and Hayano (1981) have also interpreted the presence of a band between 3.3 and 4.6 ppm to indicate that there are polysaccharide ether structures in some of their samples. They found that this band was stronger in fulvic acids from marine sediments than the corresponding humic acids. The marine sediment fulvic acids were higher in oxygen than marine sediment humic acids. Aldrich humic, which is presumably terrestrial in origin, has a still lower oxygen content but does not have a band in this region. These data led Saito and Hayano to conclude that their marine sediment fulvic acids have a polysaccharide character. ... 

Physicochemical studies have also been performed on carboxymethyl-ated 0-methyl- and 0-(2-hydroxyethyl)-cellulose. As with other car-boxymethylated polysaccharides, the degree of substitution and the distribution of substituents play a dominant role in the viscosity of aqueous solutions of O-(carboxymethyl)starch. Viscosimetric "" and other measurements indicate that 0-(carboxymethyl)amylose exists as a random coil in solution, " and that the chains are stiffer than the corresponding cel-lulosic chains whereas the stiffness of the chains of 0-(carboxy-methyl)dextran is little different from that of other charged ether derivatives of dextran and dextran sulfate. Fractional precipitation is a useful procedure for obtaining homogeneous fractions of carboxymethylated polysaccharides, as with other polysaccharide ethers. Acetylated O-(carboxymethyl) cellulose provides a useful basis for the formation of desalination membranes. ... 

The Ramazol type of reactive dyes combines with polysaccharide hydroxyl groups by way of unsubstituted intermediates, to give polysaccharide ethers (27). Ramazol dyes, particularly Ramazol Rrilliant Blue R,... 

A variety of polysaccharide ethers are produced industrially. They include methyl, ethyl, hydroxyethyl, hydroxypropyl, and carboxymethyl ethers. Combinations of these with other subslitulions are often seen. Because of the wide range of properties produced and low cost, etherifications are among the most common industrial modifications. The mechanism for etherification varies, depending on the desired subslitulion. Methylalion can be achieved with a simple Williamson synthesis where the hydroxyl is exposed by the addition of caustic soda [Figure 2] (4). 

Surfactants and salts have an influence on aqueous solutions of HPC (158). In solutions of sodium dodecylsulfate and hydroxypropylcellulose, self-association of the surfactant is nucleated by lipophilic domains on the polysaccharide ether, at concentrations well below the critical micelle concentration (Fig. 37), a behavior even more highly pronounced... 

Carbon in CH(OH) groups ring C atoms of polysaccharides ether-bonded ali[4iatic C 65-85... 

The addition of two ether-forming reagents will often give products with completely new properties, compared with the individual polysaccharide ethers, or compared with a physical mixture of the two polysaccharide ether derivatives [8]. 

Chem. Descrip. C12-14 alkyl polysaccharide ether Ionic Nature Nonionic CAS 110615-47-9... 

Mono- and di saccharides are colourless solids or sjrrupy liquids, which are freely soluble in water, practically insoluble in ether and other organic solvents, and neutral in reaction. Polysaccharides possess similar properties, but are generally insoluble in water because of their high molecular weights. Both poly- and di-saccharides are converted into monosaccharides upon hydrolysis. 

Most polysaccharides are insoluble or sparingly soluble in cold water, insoluble in cold alcohol and ether, and rarely possess melting points. Only inuUn melts at about 178° (dec.) after drying at 130°. 

Step 1. Extraction and separation of the acidic components. Shake 5-10 g. of the sohd mixture (or of the residue R obtained after the removal of the solvent on a water bath) with 50 ml. of pure ether. If there is a residue (this probably belongs to Solubihty Group II or it may be a polysaccharide), separate it by filtration, preferably through a sintered glass funnel, and wash it with a Uttle ether. Shake the resulting ethereal solution in a smaU separatory funnel with 15 ml. portions of 5 per cent, aqueous sodium hydroxide solution until all the acidic components have been removed. Three portions of alkaU are usuaUy sufficient. Set aside the residual ethereal solution (Fj) for Step 2. Combine the sodium hydroxide extracts and wash the resulting mixture with 15-20 ml. of ether place the ether in the ETHER RESIDUES bottle. Render the alkaline extract acid to litmus with dilute sulphuric acid and then add excess of sohd sodium bicarbonate. 

An important characterization parameter for ceUulose ethers, in addition to the chemical nature of the substituent, is the extent of substitution. As the Haworth representation of the ceUulose polymer shows, it is a linear, unbranched polysaccharide composed of glucopyranose (anhydroglucose) monosaccharide units linked through thek 1,4 positions by the P anomeric configuration. 

In 1947, L-rhamnose was first recognized by Stacey as a constituent of Pneumococcus Type II specific polysaccharide. This finding was confirmed, in 1952, by Kabat et al. and in 1955 again by Stacey when 2,4- and 2,5-di-O-methyl-L-rhamnose were synthesized and the former was shown to be identical with a di-O-methylrhamnose, obtained by hydrolysis of the methylated polysaccharide. This result indicated a pyranose ring structure for the rhamnose units in the polysaccharide. Announcement of the identification of D-arabinofuranose as a constituent of a polysaccharide from M. tuberculosis aroused considerable interest. The L-enantiomer had been found extensively in polysaccharides, but reports of the natural occurrence of D-arabinose had been comparatively rare. To have available reference compounds for comparison with degradation products of polysaccharides, syntheses of derivatives (particularly methyl ethers) of both d- and L-arabinose were reported in 1947. 

D-Xylose, which is one of the most abundant sugars in plant polysaccharides, is a rare component of bacterial polysaccharides. It is found in the LPS of Type 1 Neisseria gonorrhoeae strain" GC 6. L-Xylose and its 3-methyI ether are components of the LPS of Pseudomonas maltophila strain NCTC 10257, and are j -pyranosidic. The d- and L-sugars, and different methyl ethers of these, have also been found in the LPS of some photosynthetic bacteria."... 

In this Section, ether and acetal substituents will be discussed. In some polysaccharides, the terminal reducing sugar is glycosidically linked to a non-sugar aglycon, and this will be discussed in a special part. 

Some sugar residues in bacterial polysaccharides are etherified with lactic acid. The biosynthesis of these involves C)-alkylation, by reaction with enol-pyruvate phosphate, to an enol ether (34) of pyruvic acid, followed by reduction to the (R) or (5) form of the lactic acid ether (35). The enol ether may also react in a different manner, giving a cyclic acetal (36) of pyruvic acid. 

The first known 1-carboxyethyl ether of a sugar was 2-amino-3-0-[(/ )-l-carboxyethyl]-2-deoxy-D-glucose or muramic acid (37). It is a component of the polysaccharide moiety of the peptidoglycan in the bacterial cell-wall. It is partially replaced by the mamo isomer, 2-amino-3-6>-[(/ )-l-carboxy-ethyl]-2-deoxy-D-mannose, in the peptidoglycan from Micrococcus lyso-deikticus. 

Stevens and coworkers used their c.d. data on the various D-glucans to assign, tentatively, the bands to specific chromophores. They found that derivatives of these polysaccharides that have all of their hydroxyl groups acetylated still exhibit the 177-nm band. They assigned this band (which occurs at somewhat shorter wavelengths for the helical polymers) to the ether of the acetal chromophore. This assignment is essentially consistent with the results obtained by Johnson and coworkers on unsubstituted monosaccharides. 

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