| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1988: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1987: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
Lipoic acid has two different binding sites: the carboxylic group and the disulfide linkage, and is noted to function as a coenzyme for the oxidative decarboxylation of -keto acids which are metabolic intermediates in case of an interchange of energy in living systems.
Apart from these reactions of lipoic acid in living systems, the reaction of lipoic acid with copper(II) ion was investigated in the liquid-liquid extraction system which consists of the reactions in the aqueous and organic solutions, and patition of some chemical species between the aqueous and organic phase. It was proved that lipoate anion coordinates to copper(II) with the carboxylate group without a remarkable participation of the disulfide moiety in the coordination. Lipoic acid as an extracting agent for copper(II) was found to resemble the straight-chain aliphatic carboxylic acids. This would be attributed to the shielding of the electron-withdrawing effect of the disulfide group by four methylene groups.
Subsequen
… More
tly,he solvent extraction of copper(II) with 2-thiophenecarboxylic acid, in which the carboxyl group directly attached to the carbon atom at the 2-position of thienyl group, were carried out. It has been found that copper(II) ion coordinates not to the sulphur atom, but to the carboxyl group of 2-thiophenecarboxylic acid in the same manner as copper(II) lipoate. In the extraction equilibrium, however, 2-thiophenecarboxylic acid has proved to resemble benzoic acid rather than lipoic acid from the fact that no dimerization of copper(II) carboxylate occurs to any appreciable extent. 2-Thiophenecarboxylic and benzoic acids are heteroaromatic and aromatic acids, respectively. Then the formation of the dimeric copper(II) carboxylate can be expected to be influenced by a conjugated system in both acids. Further, benzoic acid is noted to be an efflorescence hormont for "SprodelaPpolyrhiza Schleid". Taking into account these interesting actions of lipoic and benzoic acids in living systems, we would discusse in detail the results obtained from the extraction of copper(II) with lipoic, 2-thiophenecarboxylic, benzoic, and monosubstituted benzoic acids. Less
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