Polysaccharides sulfates, desulfation

M. Matsuo, R. Takano, K. Kamei-Hayashi, and S. Hara, A novel regioselective desulfation of polysaccharide sulfates Specific 6-O-desulfation with N, 0-bis(trimethylsilyl)acetamide, Carbohydr. Res.,2A (1993) 209-215. 

Dermatan sulfate, also termed chondroitin sulfate B, a related glycosaminoglycan constituent of connective tissue, was known to be composed of galactosamine and a uronic acid, originally believed to be glucuronic acid but then claimed to be iduronic acid based largely on color reactions and paper chromatography. However, the d or L-enantiomer status of the latter monosaccharide was not clear. Jeanloz and Stoffyn unequivocally characterized the monosaccharide as L-iduronic acid by consecutive desulfation, reduction, and hydrolysis of the polysaccharide, followed by isolation of the crystalline 2,3,4-tri-0-acetyl-l,6-anhydro-/ -L-idopyranose, which was shown to be identical to an authentic specimen synthesized from 1,2-0-isopropylidene-/ -L-idofuranose.34... 

For structure elucidation, it is desirable to methylate the polysaccharide in its original and in its desulfated form. In this case the sulfate group was alkali-resistant. Haas and Russell-Wells58 showed that sulfate hydrolysis, in 3% sodium hydroxide for 16.5 hours at 110°, proceeded to the extent of only 20%, a fact confirmed by Percival and coworkers.82 Mori and Tsuchiya,78 and Mori,84 also experienced difficulty in the alkaline desulfation of the mucilages from C. oceUatus and I. laminarioides. 

Previous studies revealed that the sodium spirulan isolated from Spir-ulina platensis consists of 3-linked rhamnopyranosyl, 2-linked 3-O-methyl-rhamnopyranosyl, and 3,4-linked hexuronopyranosyl residues the first unit was sulfated on C-2 or disulfated on C-2 and C-4, and the second one was sulfated on C-4. Recently, Lee et al. [29] evaluated the effect of partial desulfation and oversulfation of this polysaccharide against HSV-1 and HSV-2 (see below). 

At the same time, the 13C NMR spectra of desulfation and periodate oxidation products of native xylogalactans were sufficiently resolved to be completely assigned.166 Combined chemical and spectral evidence made it possible to evaluate the following specific structural features for sulfated polysaccharides of corallinean red algae594 ... 

D. A. Navarro, M. L. Flores, and C. A. Stortz, Microwave-assisted desulfation of sulfated polysaccharides, Carbokydr. Polym., 69 (2007) 742-747. 

Compared to the desulfation procedures, regioselective chemical sulfation of heparin-related saccharides poses more of a challenge. Re-O-sulfation of O-dcsulfalcd heparin (usually performed on pyrididium salts, with pyridine SO3 or SO3 DMF in aprotic solvents) fails to restore the sulfation pattern of the original polysaccharide, since it leads to preferential 3-0-sulfation (rather than... 

The action of aqueous hydrazine on sugar sulfates is different from that of anhydrous hydrazine on sulfated polysaccharides of the chondroitin type. Anhydrous hydrazine is a reagent for cleaving the amide linkage in, for instance, proteins. It has been applied to chondroitin A sulfate to effect Af-deacetylation, and then gave a partly desulfated, as well as N-deacetylated, polymer. In contrast, the aqueous hydrazine reagent has no effect on chondroitin sulfates A and C. ... 

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