Periodate oxidation glycosides

Debenzylidenation of compound 24 yielded a crystalline glycoside 25 and the extent and rate of its periodate oxidation supports the structure and configuration shown. 

The dialdehydes, such as VI and XI, produced by periodate oxidation of sugar glycosides or polymers, very probably do not exist in the aldehydo form,212-214 but in a hydrated212 and cyclized structure.213 214... 

XVIII has now been excluded,42 since the methyl glycoside of the sugar reacts rather rapidly with one mole of periodate per mole furthermore, in contrast to the behavior of mycaminose (XXI), no moiety with one carbon atom less has been isolated from the products of periodate oxidation. Oxidation of mycarose with hypoiodite affords a crystalline lactone with the empirical formula C7H12O4 this observation eliminates the possibility of the keto structure XX. Thus, mycarose appears to be a 2,6-dideoxy-3-C -methylhexose (XIX). In the original compound, the isovaleryl group must be esterified to the alcohol function at C4, since the methyl glycoside isovalerate obtained from carbomycin is only attacked by periodate after alkaline hydrolysis. 

Structural investigations into the degree of branching and into the position and nature of glycosidic bonds and of non-carbohydrate residues in polysaccharides may include periodate oxidation and other procedures such as exhaustive methylation. X-ray diffraction and spectroscopic techniques such as nuclear magnetic resonance and optical rotatory dispersion also give valuable information especially relating to the three-dimensional structures of these polymers. 

In some cases where enzymes have a poor degree of surface amino groups, the covalent linkage can be established through the glycosidic chains by periodate oxidation of enzyme with subsequent coupling to activated nylon (Lopez, Braun Klein, 1996). 

Another 3,6-dideoxyhexose, ascarylose, was obtained by acid treatment 7 of ascaroside B, one of the glycosides in ascarylic alcohol, an unsaponifiable glycolipide found in the membrane of the eggs of Parascaris equorum. Periodate oxidation of the aldonic acid from ascarylose, and further oxi-... 

To determine the position of glycosidic bonds in glycosphingolipids, periodate oxidation and methylation are widely used. A characteristic feature of the periodate oxidation of glycosphingolipids is the stability, to oxidation under mild conditions,179 of the D-glucose residue that is located at the beginning of the carbohydrate chain and substituted at 0-4 this seems to be associated with steric hindrance caused by the close location of the lipid moiety. 

The readily available [77, 78] l,6-di-0-benzoyl-3,4-0-benzylidene-2,5-0-methy-lene-D-mannitol has been converted [79] into the benzyl ether (60), which on periodate oxidation and borohydride reduction gives the methylene acetal (61) which readily gives 1 -O-benzyl-L-glycerol for use in lipid synthesis. The acyl derivative (62) has been used [80] in glycolipid synthesis by glycosidation of the hydroxyl group. 

The structure of the uronic acid was established as follows (a) periodate oxidation, followed by bromine oxidation, gave 2-hydroxy-3-methoxy-L-erj/f/tro-succinic acid 1413 (b) reduction of the methyl glycoside methyl ester with lithium aluminum hydride, followed by hydrolysis, gave 4-0-methyl-D-glucose.13... 

These treatments convert to ionic substances, and remove, nearly all constituents of natural materials the acid treatments release any inositol present as phosphate, or combined in phospholipids, glycosides, etc. Glycerol remains in the deionized sample, but it can be oxidized separately, or be removed by heat decomposition or by repeatedly evaporating the solution to dryness. Such polyhydric alcohols of greater chain length as erythritol and mannitol, when present, would still interfere. However, corrections can be made for these compounds by determining the formaldehyde which they form on periodate oxidation, or they may be removed by chromatography on filter paper. The micro-periodate method is well suited to the analysis of samples eluted from filter paper, provided that care is exercised to remove the tiny particles of cellulose which are usually found in such eluates. 

As already pointed out, some of the products of periodate oxidation, especially the mixed acetals from the glycosidic derivatives of the sugars, are readily hydrolyzed by acids. Although the known compounds of this type are stable in dilute aqueous solution of iodic acid at room temperature, heating the acid solution would be expected to cause hydrolysis. Before isolation of these oxidation products, the reaction solution customarily is neutralized to a pH of 8-9. Barium hydroxide and strontium hydroxide have proved to be advantageous bases for neutralization of the reaction solution, since iodate and excess periodate are largely removed at the same time as the slightly soluble barium or strontium salts. Silver acetate and hydriodic acid also have been used to remove iodic add.128... 

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