| Research Abstract |
Effective synthetic procedures, transformations and development of methods of molecular recognition for sugars and amino acids or their derivatives are highly desirable in the field of medicinal chemistry, biochemistry, and industry. In our laboratory, we have extensively studied the synthesis and characterization of nickel(II) complexes containing N-glycosides derived from the reaction of monosaccharides and diamines as a class of substitution labile. Metal complexes are divided into two classes such as substitution inert and substitution labile on the basis of their chemical properties. Therefore, it is interesting to examine these two types of complexes in order to elucidate the interaction of sugars with metals.
Form this point of view, in this project we firstly have studied on the typically substitution inert cobalt(III) complexes containing an N-glycoside derived from ethylenediamine and aldoses. During our investigations on sugar complexes, we previously found that aldoses are epimerized at C-2 in a very short time by a nickel (II) N,N,N'-Me_3en complex, [Ni(H_2O)_2(N,N,N'-Me_3en)_2]Cl_2 (N,N,N'-Me_3 en = 1-(di methylamino)-2-(methylamino)ethane), which was accompanied by a stereoselective complexation of some mannose-type epimers. And under mild conditions, these aldoses were smoothly recovered from complexes by treatment with a slightly acidic aqueous solution. We applied the newly discovered sugar transformation reaction using [Ni(H_2O)_2 (N,N,N'-Me_3en)_2]^<2+> applied to the synthesis of the disaccharides having the mannoge reducing terminal from their C-2 reducing terminal epimers which are abundant in nature and are very difficult to synthesize by organic procedures. Next we investigated the fundamental study concerning molecular recognition by an aminopoly-carboxylate cobalt(III) complex. Finally we examined the reaction of an amino acid precursor with a cobalt(III)-polyamine complex.
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