Ketoses, synthesis

L-perseulose. The enantiomorphic D-perseiilose has been synthesized recently by Wolfrom, Brown and Evans (p. 12, ref. 36) from o-galactonyl chloride pentaacetate by Wolfrom s new method of higher-carbon ketose synthesis. 

Pyridine has found some use as a catalyst for the transformation— especially in applications to ketose synthesis. The base has usually been employed as both catalyst and solvent (in anhydrous form). Under these conditions, it appears to act sluggishly—a conclusion which, since anhydrous pyridine solutions of a reducing sugar contain no acid except the sugar itself, is in accord with the idea that the transformation requires an acid as well as a base for its catalysis. The possibility of increasing the reaction rates by incorporating an appropriate acid catalyst, such as phenol, into these pyridine mixtures should be explored. Other nitrogenous bases which have been reported as catalysts for the transformation are ammonia, quinoline, and quinaldinc. ... 

The Action of Diazomethane upon Acyclic Sugar Derivatives. IV. Ketose Synthesis, M. L. Wolfrom, Robert L. Brown, and Evan F. Evans, ]. Amer. Chem. Soc., 65, 1021-1027 (1943). 

Benaissi K, Helaine V, Prevot V, Forano C, Hecquet L. Efficient immobilization of yeast transketolase on layered double hydroxides and application for ketose synthesis. Adv. Synth. Catal 2011 353 1497-1509. 

Ketose (Section 25 1) A carbohydrate that contains a ketone carbonyl group in its open chain form Kiliam-Fischer synthesis (Section 25 20) A synthetic method for carbohydrate chain extension The new carbon-carbon bond IS formed by converting an aldose to its cyanohydnn Reduction of the cyano group to an aldehyde function com pletes the synthesis... 

The parallel synthesis of furans from a-hydroxycarbonyl compounds is frequently conducted using aldoses or ketoses as readily available sources of this functional grouping, especially as the resulting polyhydroxyalkyl side-chain can be removed easily by oxidative degradation (Schemes 67d and 67e) 56MI30300). 

It is well known that the 1-phosphates of the ketoses, L-fuculose (51) and L-rhamnulose (52) have considerable biochemical interest. Their chemical synthesis has not been described as far as is known to the writer, but the rate of acid hydrolysis of L-fuculose 1-phosphate, obtained by enzymatic synthesis, has been determined by Heath and Ghalambor (20) and that of L-rhamnulose 1-phosphate by H. Sawada (48) and by Chiu and Feingold (II). They found that the rate of... 

A more general access to biologically important and structurally more diverse aldose isomers makes use of ketol isomerases for the enzymatic interconversion of ketoses to aldoses. For a full realization of the concept of enzymatic stereodivergent carbohydrate synthesis, the stereochemically complementary i-rhamnose (Rhal EC 5.3.1.14) and i-fucose isomerases (Fuel EC 5.3.1.3) from E. coli have been shown to display a relaxed substrate tolerance [16,99,113,131]. Both enzymes convert sugars and their derivatives that have a common (3 J )-OH configuration, but may deviate in... 

In order to develop potent D-glucosidase inhibitors, a synthesis of carba-disaccharides containing valiolamine (205) was attempted by Horii and his coworkers utilizing method c. Coupling 205 with the 4-ketose 403, using NaBHjCN and hydrochloric acid, was effective in DMF, giving, after deprotection, the epimeric carba-disaccharides (404 and 405). The saturated... 

The synthesis of cellulose by A. xylinum from various polyalcohols14 is accompanied by the formation of carbon dioxide, formic acid, nonvolatile acids, ketoses and sometimes ethanol. The much greater variety of substrates suitable for cellulose synthesis, as compared with the small number for dextran or levan, may account for the widespread natural occurrence of cellulose. 

The exact nature of levansucrase activity08 is not clear. It differs in certain respects from invertase, polymerase, fructosaccharase, and phosphorylase. Possibly the aldoside part of the substrate molecule is replaced by an enzyme-linked group, and partial decomposition of this levan precursor to aldose and ketose may furnish the energy necessary for levan synthesis. 

A review is available of the synthesis of polyhydroxyalkyl substituted heterocycles, including furans, by condensations of aldose and ketose sugars with / -dicarbonyl compounds.Ih... 

In contrast to aldoses, ketoses, and compound 2, which, on treatment with phenylhydrazine, form phenylosazones, compound 4, under the same conditions, yields116 the phenylhydrazone of aldehydo-D-glucuronic phenylhydrazide (69). In a series of papers, Momose and coworkers117 120 described the synthesis of N-... 

Ketone synthesis, 72 173-174 73 667-668 Ketone-water azeotropes, 74 563 Ketone-water mixture properties, 74 568-569t Ketose, 4 696... 

Rare or unnatural monosaccharides have many useful applications as nonnutritive sweeteners, glycosidase inhibitors and so on. For example, L-glucose and L-fructose are known to be low-calorie sweeteners. In addition, rare or unnatural monosaccharides are potentially useful as chiral building blocks for the synthesis of biologically active compounds. Therefore, these compounds have been important targets for the development of enzymatic synthesis based in the use of DHAP-dependent aldolases alone or in combination with isomerases. Fessner et al. showed that rare ketose-1-phosphates could be reached not only by aldol addition catalyzed by DHAP-dependent aldolases, but by enzymatic isomerization/ phosphorylation of aldoses [35]. Thus, for example, L-fructose can be prepared... 

Com. Esp. Deterg., 11th, 1980, S. 255-266 . .Synthesis of Detergents. l-n-Alkylamino-l-deOxy-2-ketoses, 2-n-Alkylamino-2-deoxy-D-glusoses, and Derivatives11. 

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