Carbohydrates, acidic derivatives complexes with borate

At pH 10, diphenylborinic acid gives a tetrahedral anion that complexes with various diol systems, and thus it can be used in electrophoresis like borate.109 In a more detailed study of such complexing,110 diols were examined by 13C-n.m.r. spectroscopy, before and after addition of sodium diphenylborinate, and complexes were detected, and their spectra observed, for a variety of carbohydrate derivatives. 1,2-Diol groupings in acyclic and cis-cyclic compounds, 1,3-related diols at C-4,C-6 of hexopyranosides, the 3,5-diols of glucofuranoses, and 2,4-diols of the anomeric methyl 3,6-anhydro-D-glucopyranosides were all found to react. No interaction occurred with l,6-anhydro-/3-D-glucopyranose (compare Section V,2). 

The complexings of D-glucose, D-fructose, and maltose with borate anions have been studied by polarimetric, conductivity, and pH measurements, and circular dichroism methods have been used to investigate the complexing of cuprammonium ions with carbohydrate diols and amino-alcohols. An examination of the c.d. spectra of fifteen methyl 3-acetamido-3,6-dideoxyhexopyranoside derivatives measured in methanol, 2,2,2-trifluoroethanol, and acetonitrile su ests that the amide group is not completely planar and may show chirality. The n it transition of the carboxylic acid carbonyl groups at... 

The literature on metal complexes of carbohydrates through 1965 has been fully reviewed by Rendleman (I), and we shall therefore only discuss recent work. We shall not discuss the complexes formed with strong bases, such as calcium and barium oxide these are salts in which the sugar acts as a weak acid, losing one or several protons. Nor shall we discuss the complexes formed with anions of oxyacids—e.g., borate, stannate, periodate, etc. ions all these are compounds formed by covalent bonds in alkaline solution. We are concerned only with complexes formed with cations in neutral aqueous solution there is no evidence for the formation of complexes between sugars and simple anions in neutral aqueous solution. (For an example of complex formation between a sugar derivative and chloride ion in chloroform solution, see Reference 3.)... 

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