Osonic acids

C H19N09-2H20 5-Acetamido-3,5-dideoxy-D-gh/eero-/ -D-galacto-nonulopyran-osonic acid, dihydrate (N-acetylneuraminic acid, dihydrate) (sialic acid, dihydrate) SIALAC 31 350... 

CI2HI807-H20 2,3 4,6-Di-0-isopropylidene-a-L-xy/o-2-hexulofuran-osonic acid, monohydrate (DIPKGA)64... 

Sialic acids are a family of 3-deoxy-2-ulosonic acids found most frequently as a-glycosidically linked terminal residues of glycoproteins and glycolipids. The most abundant sialic acid is N-acetylneuraminic acid (5-acetamido-3,5-di-deoxy-D-glycero-D-galacto-nonu osonic acid, NeuSAc, 1), which was first isolated in the 1930s. To date, 36 sialic acids have been isolated, many of which are 0-acetylated derivatives of N-acylated neuraminic acid [1]. 

Natural sialic acids (Schauer 1982 1991) are derivatives of 5-amino-3,5-dideoxy- D-glycero-D-galacto-nonu osonic acid 12.1. This awkward name has been replaced by neuraminic acid . The most common derivative is N-acetyl-neuraminic acid 12.2 whose configuration is easy to memorize because, in the Fischer representation, 12.3, it is presented as an aldolic condensation product of N-acetylmannosamine (2-acetamido-2-deoxy-D-mannose) and pyruvic acid. When the expression sialic acid is used without any other precision, it is in reference to derivative 12.2. It exists in the free state or glycosidated in the d-conformation, which allows an equatorial disposition of the three-carbon side chain. Structure 12.2 represents the stable /3-anomer of the free sugar with an axial anomeric hydroxyl group and all-equatorial non-anomeric substituents. An X-ray spectrum of this crystallized /3- anomer confirms this conformation and reveals, moreover, that the side chain has the zig-zag conformation with two... 

IIcxu(osonic acid, I+deoxy-o-eryfftro- C.II.,0. -2il.2 (c 6, Ca salt)... 

The keto aldonic acids of the hexose series are of the 2- and 5-keto types. The 2-keto acids have been called osonic acids because of their preparation by the oxidation of osones. The 5-keto acids have been termed keturonic... 

A synthesis of 3-deoxy- D-glycero-D-galacto-2-nonu osonic acid from d-mannose involved use of a keto-thiazole Wittig reagent,while addition of lithiated thiazole to a 2-deoxy-hexono-1,4-lactone featured in a synthesis of 3-deoxy-D-ara )j>io-hept-2-ulosonic acid. 

N- Acetyl-7,8-di-O-acetylneuraminic acid or N-Acetyl-7,9-di-O-acetyIneuraminic acid 5- Acetamido-7,8(or 7,9)-di-0-acetyl-3,5-dideoxy-D-g/y-cero-D-galacto-nonu osonic acid C15H23NO11... 

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

The nomenclature adopted in the designation of the analogs of L-ascorbic acid is based for convenience upon the name of the sugar from which the osone was prepared. For example, D-xylose (XVIII)... 

In addition to L-ascorbic acid this method, involving the use of osones and potassium cyanide, has afforded the following analogs ... 

The 2-keto acids such as 2-keto-D-galactonic acid (XXIV) can be derived from the corresponding osone (XXIII) by oxidation with bromine.10 Oxidation of L-gulosone by the same method has provided 2-keto-L-gulonic acid. The success of this oxidation depends to a large extent upon the purity of the osone subjected to oxidation and this, as previously stated, is controlled by the purity of the osazone. 

It has recently been reported21 that a mixed osazone of 3,4-di-O-methyl-D-glucose can be converted, by treatment with p-nitrobenzaldehyde, into an osone which reacts with phenylhydrazine to give 3,4-di-O-methyl-D-glucose phenylosazone. Von Lebedev29 claimed to have obtained D-glu-cosone 6-phosphate, isolated as an amorphous lead salt, by the action of hydrochloric acid on the phenylosazone prepared from D-fructose 6-phosphate. 

Evans, Nicoll, Strause and Waring46 oxidized D-glucose and D-fructose in aqueous solution with excess cupric acetate at 50° for the purpose of ascertaining whether the general principles underlying the mechanism of carbohydrate oxidation in alkaline solutions are sufficient to explain the course of such oxidations in acid solutions. D-Glucosone was claimed to be one of the first products of oxidation the osone was not isolated, and,... 

They showed that osone formation is accompanied by the production of formic acid, thought to arise from the oxidation of hydroxymethylene formed by rupture of IV. 

In the preparation of D-glucosone by the direct oxidation of D-glucose, D-fructose, or D-mannose by such reagents as that of Fenton,37 cupric acetate,16- 46- 46 selenious acid,16-61 etc., the degree of oxidation must be carefully controlled if the osone, which is the first product, is to be the main product of the reaction. The nature and mechanism of formation of the products of further oxidation of D-glucosone are discussed on p. 68. 

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