Sugars acetals and

Cellobiose was prepared first by Skraup and Konig by the saponification of the octaacetate with alcoholic potassium hydroxide, and the method was improved by Pringsheim and Merkatz.3 Aqueous barium hydroxide also has been employed for the purpose, and methyl alcoholic ammonia has been used extensively for the hydrolysis of carbohydrate acetates. The method of catalytic hydrolysis with a small quantity of sodium methylate was introduced by Zemplen,i who considered the action to be due to the addition of the reagent to the ester-carbonyl groups of the sugar acetate and the decomposition of the addition compound by reaction with alcohol. The present procedure, reported by Zemplen, Gerecs, and Hadacsy, is a considerable improvement over the original method (see Note 2). 

The Hines64 showed that, as acids, ethanol, isopropyl alcohol, and tert-butyl alcohol are weaker than water, whereas methanol is stronger. The influence of the solvent could thus be interpreted in terms of equation 1. In methanol, the equilibrium would be more displaced to the right, and the rate of simple ammonolysis and transesterification would be enhanced, with concomitant decrease in the yields of amido sugars. In water (for the ammonolysis of sugar acetates) and in alcohols other than methanol, the equilibrium would be displaced to the left and this would allow operation of the orthoester mechanism a better chance. The isolation, from the reaction in isopropyl alcohol, of mono-O-benzoylated bis(benzamido)alditols, could also be explained on this basis. 

Further Experiments on the Oxidation of Sugar Acetals and Thioacetals by Aceto-bacter suboxydans, D. T. Williams and J. K. N. Jones, Can. J. Chem., 45 (1967) 741-744. 

Relative Rates of Exchange of Acetate Between 1, -trans Sugar Acetates and Stannic Trichloride Acetate ... 

A chromatographic series showing the adsorptive strength between certain sugar acetates and a hydrated calcium acid silicate (Silene EF) has been prepared (see Table Silene EF is a weaker acetate adsorbent... 

The infrared spectra of a large number of carbohydrates have been published aU of these will be useful for future comparative work. The work of Kuhn and of Stevenson and Levine has already been mentioned. In addition, Solms, Denzler and Deuel have recently pubUshed the spectra of several derivatives of poly-D-galacturonic acid. The collection of infrared spectra of the sugar acetates and related compounds also forms a valuable source of data for comparative work. ... 

Chromatography of Sugar Acetates and Methyl Ethers on Magnesol, M. L. Wolfrom, Rosa M. de Lederkremer, and L. E. Anderson, Anal. Chem., 35,1357-1359 (1963). 

Kuribayashi T, Ohkawa N, Satoh S (1998) AgOTfa/SnCL a powerful new promoter combination in the aryl C-glycosidation of a diverse range of sugar acetates and aromatic substrates. Tetrahedron Lett 39 4537-4540... 

Other methods of production iaclude hydrolysis of glycolonittile [107-16 ] with an acid (eg, H PO or H2SO2) having a piC of about 1.5—2.5 at temperatures between 100—150°C glycolonittile produced by reaction of formaldehyde with hydrogen cyanide recovery from sugar juices and hydrolysis of monohalogenated acetic acid. None of these has been commercially and economically attractive. 

When used at room temperature in the presence of an active platinum catalyst in an inert solvent, e.g., acetone or ethyl acetate, oxygen will oxidize nonhindered, saturated hydroxyl groups and exposed allylic alcohols. This reagent has found extensive use in sugar chemistry and is particularly suited for the selective oxidation of either 3a- or 3j -alcohols of steroids. Other hydroxyl groups on the steroid skeleton are much less sensitive to oxidation. As a result, this reaction has been used extensively in research on polyhydroxy cardiac-active principles, e.g., the cardenolides and bufadienolides, where the 3-hydroxyl group is easily oxidized without extensive oxidation or dehydration of other hydroxyl groups. The ordinarily difficult selective oxidation of the... 

Digestion (Section 29.1) The first stage of catabolism, in which food is broken down by hydrolysis of ester, glycoside (acetal), and peptide (amide) bonds to yield fatty acids, simple sugars, and amino acids. 

In this Section, ether and acetal substituents will be discussed. In some polysaccharides, the terminal reducing sugar is glycosidically linked to a non-sugar aglycon, and this will be discussed in a special part. 

After extraction, an extract purification stage is generally reconunended. This is most often done by liquid-solid exchange using resins such as Sephadex, Amber-lite XAD-7, or Cjg mini-columns. ° All the polar compounds are first trapped on the resin, and then in succession the sugars, acids, and other polar compounds (excluding polyphenolic compounds), polyphenolic compounds (excluding anthocyanidins), and anthocyanidins are respectively eluted with acidified water (HCl 0.01% v/v), ethyl acetate, and acidified methanol (HCl 0.01% v/v). 

Sugar composition. Desalted fractions (IPN1-IPN14) were hydrolyzed using 2N TFA for 1.5h at 121 C. The released neutral sugars were converted to their alditol acetates and analysed by GC as described [12]. 

Just as certain pyranose sugars can give rise to bis-acetal or bis-ketal derivatives which constitute linearly fused 5 6 6 systems (cf. Section 12.17.2.1.7), another set of bis-acetals and bis-ketals - in many cases derived from the same sugars - correspond to angularly fused 5 6 6 systems. These, like their linearly fused analogues, serve to protect, selectively, four hydroxyl groups of the parent sugars, and cyclic carbonates (l,3-dioxolan-2-ones) may fulfill similar functions. 

P. M. Bhaskar, M. Mathiselvam, and D. Loganathan, Zeolite-catalyzed selective deprotection of di- and tri-O-isopropylidene sugar acetals, Carbohydr. Res., 343 (2008) 1801-1807. 

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