Sugar preparation

Fig. 8. Typical examples of calyx sugars prepared through various ligation strategies.

A. Vasella, P. Uhlmann, C. A. A. Waldraff, F. Diederich, and C. Thielgen, Fullerene sugars Preparation of enantiomerically pure, spiro linked C-glyco-sides of C50, Angew. Chem. Int. Ed. Engl., 31 (1992) 1388-1390. 

For each reference sugar, prepare a set of calibration standards in duplicate using the stock and working reference standard solutions. 

Table VII gives a list of nucleotide-sugars prepared with immobilized enzymes.

Colour Reactions.—These are used for the detection of commercial invert sugar and are based on the colorations given by certain substances with methylfurfural and hydroxymethylfurfural, which occur in commercial invert sugar as decomposition products formed from the levulose during the inversion of saccharose by acids. Invert sugar prepared with invertase or by other special methods does not contain these decomposition products and consequently does not give the colour reactions. The most reliable of the latter are as follows ... 

R. E. Arrick, D. C. Baker, and D. Horton, Chromium trioxide-dipyridine complex as an oxidant for partially protected sugar preparation of aldehydo and certain keto sugar derivatives, Carbohydr. Res., 26 (1973) 441 147. 

The main interest in unsaturated sugars prepared by the Wittig reaction (and described in this Section) has concerned their synthetic utilization. The pathways of the latter depend on the structure of the unsaturated precursor. In the case of C-glycosylated alkenes, addition to the double bond (mainly hydration and hydrogenation) leads to a branched-chain or long-chain sugar, although correct choice of the reactant to be added may provide a variety of derivatives. 

Deoxylodo sugars. Preparation of these compounds by displacement reactions usually has limitations because of the vigorous conditions commonly required. Replacement of a triflate group (4, 533) by iodine using tetra-n-butylammonium iodide, however, proceeds under relatively mild conditions (refluxing benzene, 15 hours). In six reported examples, overall yields were 85-95%. ... 

Method 14 involves the sol-gel synthesis of OMS-2. In this case dicarboxylic acids like maleic acid are used to reduce KMn04. Highly crystalline low surface area OMS-2 materials can be made in this manner. The dicarboxylic acids are oxidized to CO2 as is the case for the sol-gel sugar preparations (Method 3). It is apparent from studies of sol-gel syntheses that strong acids react very rapidly and do not generate stable sols. For this reason, weak acidic material like dicarboxylic adds, sugars, cyclodextrins and similar materials need to be used. 

Vasella, A, Uhlmann, P, Waldraff, C A A, Diederich, F, Glycosylidenecarbenes. 9. Fullerene sugar preparation of an enantiomerically-pure, spiro-bound C-glycoside of Ceo, Angew. Chem. Int. Ed. Engl, 31, 1388-1390, 1992. 

Jarosz, S, Mach, M, Phosphonate versus phosphorane method in the synthesis of higher carbon sugars. Preparation of D-erythro-L-manno-D-gluco-dodecitol, J. Chem. Soc., Perkin. Trans. 1, 3943-3948, 1998. 

No method has yet been devised for bringing about formation of a single product from a nonenzymic Lobry de Bruyn-Alberda van Ekenstein transformation. However, this feat should be possible, since the reactions involved are reversible. Yields can be improved by choosing catalysts which limit side-reactions. Thus, a low concentration of hydroxide ion minimizes the aldol condensation, the seriousness of which, as a side reaction, is sufficient reason for avoiding even moderate concentrations of hydroxide ion. It is interesting to note that lime-water and anhydrous pyridine, which have been the most used as catalysts in sugar preparations by these reactions, both meet this requirement. The hydroxide-ion concentrations of the former solution have usually been low, and the calcium... 

D-Glycopyranosiduronic Acids from Amino Sugars, Prepared by Catalytic Oxidation... 

Unknown(s) containing two or more of the above sugars prepared as above. Solvents methanol, ethanol, acetone, acetic acid, chloroform and ethyl acetate. 

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