Carbohydrate oximes

M. B. Thygesen, J. Sauer, and K. J. Jensen, Chemoseleetive capture of glycans for analysis on gold nanoparticles Carbohydrate oxime tautomers provide functional recognition by proteins, Chem. Eur. J., 15 (2009) 1649-1660. 

Boron-oxygen-boron bridged gluconatoborate (76) and related conq>lexes of boron with gluconate ions have been prepared and characterized by a variety of analytical techniques. The examination by "B- and C-n.mx. spectroscopy of borate esters derived firom carbohydrate oximes in solution indicated the formation of relatively stable 6-membered borate ester rings between the oxime-OH and C-2-0H. ... 

The binding specificity of d-[ C]glucose by the taste-papillae membranes, compared to that of control membranes isolated from epithelial tissue, has been confirmed in two studies. One inherent problem in the approach is that the stimuli, primarily carbohydrate sweeteners, are not ideal model compounds to use, as they are not active at low concentrations and do not show sufficiently high binding-constants. The use of other stimulus compounds that are at least several hundred times sweeter than sucrose, such as saccharin, dihydrochalcone sweeteners, dipeptide sweeteners, stevioside, perillartine and other sweet oximes, the 2-substituted 5-nitroanilines, and... 

This chapter, therefore, ends the monograph with a potpourri of reactions all of which occur without a change in oxidation state. In many cases, the reaction is one of nucleophilic attack at an electrophilic C-atom. The result is often hydrolytic bond cleavage (e.g., in carbohydrate conjugates, disubstitut-ed methylene and methine groups, imines, oximes, isocyanates, and nitriles, and various ring systems) or a nucleophilic substitution (e.g., hydrolytic de-halogenation of halocarbons and chloroplatin derivatives, and cyclization reactions). The formation of multiple bonds by dehydration is a special case to be discussed separately. 

Intramolecular oxime-alkene cycloaddition has been proved to proceed with complete stereoselectivity in carbohydrate derived hydroxylamine 171 (equation 112). 

Optically active aldehydes are available in abundance from amino and hydroxy acids or from carbohydrates, thereby providing a great variety of optically active nitrile oxides via the corresponding oximes. Unfortunately, sufficient 1,4- or 1,3-asymmetric induction in cycloaddition to 1-alkenes or 1,2-disubstituted alkenes has still not been achieved. This represents an interesting problem that will surely be tackled in the years to come. On the other hand, cycloadditions with achiral olefins lead to 1 1 mixtures of diastereoisomers, that on separation furnish pure enantiomers with two or more stereocenters. This process is, of course, related to the separation of racemic mixtures, also leading to both enantiomers with 50% maximum yield for each. There has been a number of applications of this principle in synthesis. Chiral nitrile oxides are stereochemicaUy neutral, and consequently 1,2-induction from achiral alkenes can fully be exploited (see Table 6.10). 

Intramolecular cycloaddition of fV-benzyl-substituted 3-O-allylhexose nitrones furnishes chiral oxepane derivatives. The regioselectivity of the cycloaddition depends on several factors such as (1) the structural nature of the nitrone, (2) substitution and stereochemistry at 3-C of the carbohydrate backbone, and (3) substitution at the terminus of the O-allyl moiety. A mixture of an oxepane and a pyran is formed in the intramolecular oxime olefin cycloaddition of a 3-O-allyl carbohydrate-derived oxime <2003T4623>. The highly stereoselective synthesis of oxepanes proceeds by intramolecular nitrone cycloaddition reactions on sugar-derived methallyl ethers <2003TA3899>. 

In the classic carbohydrate chemistry addition reactions of carbonyl groups served as valuable tools for sturctural studies of carbohydrates. For example, hydroxyl amine, hydrazine, and phenyl hydrazine react with carbonyl groups to yield oximes and hydrazones. In the presence of an excess... 

J. Marco-Contelles, P. Gallego, M. Rodriguez-Femandez, N. Khiar, C. Destabel, M. Bemanbe, A. Marinez-Grau, and J. L. Chiara, Synthesis of aminocyclitols by intramolecular reductive coupling of carbohydrate derived <5- and 8-functionalized oxime ethers promoted by tributyltin hydride or samarium diiodide,./. Org. Chem., 62 (1997) 7397-7412. 

J. Marco-Contelles, C. Destabel, P. Gallego, J. L. Chiara, and M. Bemabe, A new synthetic approach to the carbocyclic core of cyclopentane-type glycosidase inhibitors Asymmetric synthesis of amino-cyclopentitols via free radical cycloisomerization of enantiomerically pure alkyne-tethered oxime ethers derived from carbohydrates, J. Org. Chem., 61 (1996) 1354-1362. 

Osborn HMl, Gemmell N, Harwood LM (2002) 1,3-dipolar cycloaddition reactions of carbohydrate derived nitrones and oximes. J Chem Soc Perkin Trans 1 2419-2438... 

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