Saccharinic acids degradation

Xyloisosaccharinic acid [2,4-dihydroxy-2-(hydroxymethyl)butanoic acid] is one of the major, alkaline-degradation products of wood xylan, in particular, that of birch. The disaccharide, 2-O-D-xylopyranosyl-L-arabinose, which was isolated as a hydrolysis product of corn-cob hemicellulose, is readily degraded at 100° in 15 mM Ca(OH)2 to acidic products, primarily saccharinic acids. Xylan oligosaccharides from corn-cob hemicellulose produced 2,4-dihydroxy-2-(hydroxymethyl)buta-noic acid when exposed to 0.02 M Ca(OH)2 at 25°. However, it was noted that the xylan, itself, was stable at 100° in Af NaOH. The major acidic component of the hemicellulose fraction of slash pine Pinus el-liotti) after acid hydrolysis was identified as 4-O-methyl-D-glucuronic... 

It has been postulated (37) that lactulose is formed from lactose by the Lobry de Bruyn and Alberda van Ekenstein transformation, whereby glucose is isomerized to fructose via an enol intermediate. In turn, two mechanisms have been proposed for the degradation of this intermediate (38)- One involves the addition of a proton to the enediol resulting in epimeric aldoses and the original ketose, while the other involves 8-elimination to yield galactose and saccharinic acids. The authors experimental data would tend to better support the second pathway. 

The 1-deoxyosone represents the most elusive of the three intermediates, but also the most important from the standpoint of food flavor and aroma production. A large number of methyl-containing furanones, pyrones and related compounds are found in food preparations that are consistent with having been formed from this intermediate. A synthesis of this material was reported some years ago by Isuzu, et al. (10), but the yields were very low and the product was not well characterized. The workers reported that the compound gave one of the two reported isomers of "saccharinic acid", the expected degradation product in alkaline solution, along with fragmentation products. This material will be addressed (vide infra) in a later section. 

However, Head showed that glyoxal is produced by the treatment of both oxycellulose and periodate-oxidized methyl fl-cellobioside (121) with alkali. The other theory was that of Haskins and Hogshead, based on the p-alkoxycarbonyl elimination mechanism of Isbell for the formation of saccharinic acids on treatment of sugars with alkali. They suggested that fission of the C5—O bond would yield glyoxal and n-erythrose. Recent work has indicated that the degradation is, indeed, based on a jS-alkoxycarbonyl elimination, but the products are different from those postulated above. 

Earlier investigators of the alkaline-degradation products of lactose found succinic acid, formic acid, and a crystalline lactone, later identified by Kiliani as a -D-isosaccharinic lactone. This lactone was obtained in about 20% yield from the action of lime-water on lactose also detected as products of this reaction were D-galactose, lactic acid, pyruvaldehyde, formaldehyde, and other saccharinic acids. The... 

The epimerie D-glucometasaccharinic acids were first isolated by Nef from the interaction of n-glucose and hot, concentrated sodium hydroxide. D-Glucose is isomerized and smoothly degraded under these conditions to a mixture of saccharinic acids, in a yield of over 80%. 

Kenner, J. 1955. The alkaline degradation of carbonyl oxycelluloses and the significance of saccharinic acids for the chemistry of carbohydrates, Chem. Ind., pp. 727-730. 

The Lobry de Bruyn-Alberda van Ekenstein transformation is the basic mechanism for a better miderstanding of the relationship between ketoses, aldoses, and the degradation products thereof [such as the saccharinic acids, 5-(hydroxymethyl)-2-furaldehyde, and the 3-deoxyglycosuloses]. ... 

In a later investigation comparing the influence of different alkaline media, it was found that the methyl 3-keto-/3-n-glucoside (91 A) is degraded somewhat more slowly in sodium hydroxide (0.018 N, at 23°) than in lime-water of the same concentration. Further reaction of the dicarbonyl intermediate (112 B), to give acids, was much faster with lime-water, in accordance with the established catalyzing effect of calcium on saccharinic acid formation." ... 

A wide range of carbohydrates is degraded by acids to furan compounds. For example, pentoses give 2-furaldehyde, and hexoses, 5-(hydroxymethyl)-2-furaldehyde (58), which may react further to yield levulinic acid. In 1910, Nef suggested the first mechanism, (55) to (58), for the formation of 5-(hydroxymethyl)-2-furaldehyde. His proposal was made at the end of his classical paper on the saccharinic acids, and was overlooked by subsequent workers and reviewers. In 1944, Haworth and Jones advanced an identical mechanism for the formation of 5-(hydroxymethyl)-2-furaldehyde from D-fructose. 

In alkaline degradation, the initial reaction is the transformation via the 1,2- and 2,3-enediol. Under strong alkaline conditions, continuous enolization progresses along the carbon chain, resulting in a complex mixtnre of cleavage products such as saccharinic acid, lactic acid, and 2,4-dihy-droxybutyric acid. The development of color is very complex and involves a series of polymerization reactions. 

Syntheses of some pentonohydroxamic acid derivatives are covered in Chapter 10. Alkaline degradation of 5-O-a-D-glucopyranosyl-D-fructopyranose (leucrose) has afforded two novel saccharinic acids, 2-C-(2-hydroxyethyl)eiy-thronic acid and 2-C-(2-hydroxyethyl)threonic acid. Treatment of 4,6-O-ethyl-idene-D-glucose with the sulfur ylid JNr,iST-diethyl trimethylsulfonium-acetamide gave the epoxyaldonamide 6 as well as stereoisomers. ... 

Alkaline degradation of branched polysaccharides under controlled conditions has been used to eliminate the backbone of the molecule and convert branches linked through positions 6 of the backbone into oligosaccharides terminated with saccharinic acid residues. ... 

Dilute alkali may also cause degradation of reducing sugars and the enolisation may extend to the 2,3-dienol together with the production of such breakdown products as glyceraldehyde. Rearrangements can also take place with concentrated alkali with the formation of saccharinic acids. D-Glucose (CLI) yields saccharinic acid (CL) with dilute alkali and a mixture of iso- (CLII) and wcte-saccharinic acid (CLIII) with more concentrated alkali. 

Soil. In unsterilized soils, 58% of C-labeled sulfometuron-methyl degraded after 24 wk. Metabolites identified were 2,3-dihydro-3-oxobenzisosulfonazole (saccharin), methyl-2-(amino-sulfonyl) benzoate, 2-aminosulfonyl benzoic acid, 2-(((aminocarbonyl)amino)sulfonyl) benzoate, and [ C]carbon dioxide. The rate of degradation in aerobic soils was primarily dependent upon pH and soil type (Anderson and Dulka, 1985). The reported half-life in soil was approximately 4 wk (Hartley and Kidd, 1987). 

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