Glycosiduronic acids

The synthesis of glycosiduronic acids includes two main approaches one involves selective oxidation of the primary hydroxyl group of a neutral glycoside, and the other, condensation of the agly-con with an appropriately protected alduronic acid derivative. The present Section is concerned mainly with the synthetic methods leading to glycosiduronic acids. An attempt has been made to collate information on the reactions of glycosiduronic acids, and to illustrate some of the physical methods that have contributed to the characterization of these compounds. 

O-substituted derivatives of methyl a-90 and /3-D-gl ucopy ranos ides into a carboxyl group,91 to give, after esterification with diazomethane, high yields of the corresponding methyl (methyl D-glucopyranosid)uron-ates. 

Hansson and Rosengren135 reported the first application of the ion-pair alkylation procedure136 to the formation of a glycosidic bond in the preparation of 45. Alkylation of tetrabutylammonium 2-(benzyl-oxy)-4-formylphenolate (prepared in situ from the aldehyde plus tetrabutylammonium hydrogensulfate, followed by extraction of the ion pair with dichloromethane) with the bromide 1 gave a mixture of 45 and methyl 3,4,5-tri-0-acetyl-2,6-anhydro-D-Zj/xo-hex-5-enonate (6) in 28 and 37% yield, respectively the former was obtained pure by chro- 

Depending on the reaction conditions, treatment of 52 with anhydrous, ethanolic ammonia at 0° led to 53, whereas heating of 52 in sealed tubes with anhydrous methanolic solutions of various amines was reported131 to give compounds of type 54. 

Signals (6 Values) of H-5 in the N.m.r. Spectra of Methyl (Aglycon Tri-0-acetyl-D-glucopyranosid)uronates° 

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For accurate results, correction factors must be established for the decomposition of each monosaccharide under the conditions of hydrolysis used. These corrections are of special importance when reliable values for a particular monosaccharide, present in only small proportion, are desired.24,33,34,83,92 96 When polysaccharides containing uronic acids are hydrolyzed, a further ambiguity is introduced, in that only partial cleavage of the glycosiduronic acid linkages may occur. 

Glycosiduronic acids, of animals, 9, 185-246 poly-, of plants, 1, 329-344 Glycosphingolipids, 24, 381-433 Glycosones, 3-deoxy-. See Glycosuloses, 3-deoxy-. 

Cellulose, Dextran, Dextrins, Fructans, Glycogen, Glycosiduronic acids (poly-), Pectic materials, Starch, and Xylan. 

On treatment of the labile ethyl 2,3,4-tri-O-methyl-a-D-giuco-hex-odialdo-l,5-pyranoside (76) with sodium methoxide, ethyl 4-deoxy-2,3-di-0-methyl-a-L-threo-hex-4-enodialdo-l,5-pyranoside (77) was formed in good yield 135 this product seems to react further on prolonged treatment with base. Preliminary studies indicated that compound 77 yields the furan 78 on mild, acid hydrolysis, with simultaneous release of the substituents at C-l, C-2, and C-3 (see Scheme 10). These reactions are thus analogous to those of the es-terified glycosiduronic acids (see Section IV,2, p. 214). 

Tubular proliferation of the tonoplast, and hydration of middle lamella and wall matrix material, began 7-14 days after petal fall. This hydration of the wall was associated with increasing aqueous extractability of wall poly(glycosiduronic acids), which became extreme during ripening that followed cessation of cell expansion. Loss of galactosyl and arabinosyl residues from the wall also became marked after cell expansion had ceased, and incorporation of D-[uC]glucose into wall polysaccharides ceased, but incorporation of L-[uC]proline into wall protein continued. 

Many glycosiduronic acids have been prepared in good yield by selective catalytic oxidation of alkyl glycopyranosides. The effect of the alkyl substituent on reactivity and selectivity has been studied.150... 

Base-catalyzed esterification of D-glucurono-6,3-lactone proceeds smoothly at room temperature.242 The acetylated glycuronic acids, and the per-O-acetylglycosyluronic halides of their methyl esters, are important precursors for the synthesis of glycosiduronic acids. D-Glucofuranurono-6,3-lactone... 

D. Keglevic, Glycosiduronic acids and related compounds, Adv. Carbohydr. Chem. Biochem., 36 (1979) 57-134. 

Bromine (hypobromite) and hypoiodite oxidations are particularly useful for the preparation of aldonic acids from aldoses and of aldaric acids from glycuronic acids. Primary alcohol groups also undergo oxidation by these reagents, although this conversion is of less value glycosides can thus be converted into glycosiduronic acids, and alditols into aldoses and aldonic acids. 

As previously reported (Ref. 1, pp. 1118, 1119) ketoses are essentially inert to the action of hypoiodites under the conditions used for the determination of aldoses, and aldosides are converted by hypoiodite or hypobromite into glycosiduronic acids in rather low yield. For example, methyl a-D-mannopyranoside (3) afforded methyl a-D-mannopyranosidu-ronic acid (4), although cleavage of carbon-carbon bonds also occurred to give 5 (Scheme 3). 

Phenyl 2,5-di-0-acetyl-/8-D-glucofuranosidurono-7-lactone was decomposed by sodium methoxide to give the corresponding methyl 0-D-gluco-furanosidurono-y-lactone38 (poorly characterized), which indicates that even phenyl-unsubstituted phenyl glycosiduronic acids can react with alkoxides under very mild conditions. 

Many polysaccharides of the xylan group contain residues of D-glucuronic acid or 4-0-methyl-D-glucuronic acid. Since glycosiduronic acids are particularly resistant to acid hydrolysis, aldobiouronic acids may be isolated... 

GLYCOSIDURONIC ACIDS AND RELATED COMPOUNDS By Dina Keglevic... 

II. Sugar Intermediates Used in the Synthesis of Glycosiduronic Acids. .. 59... 

As the nature of protective groups on the sugar component is of the utmost importance in the synthesis of many glycosiduronic acids, a Section (II) dealing with the preparation and properties of intermediates has been included at the beginning of this Chapter. 

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