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On the other hand, it has been reported that ortho-and para-hydroquinones and their quinone derivatives are abundant in nature and play important roles in many biological systems. [7][8][9][10][11] In addition, many chemicals of this category demonstrate an antioxidant activity and are able to prevent auto-oxidation via the radical formation inhibition.12) These compounds exhibit a wide variety of physiological and pharmacological properties.13) They participate in normal cell functions such as neurotransmitters. Furthermore, natural pyrocatechols extracted from plants (catechins and other polyphenols from green tea) have been found to illustrate anticancer properties. 14)For these reasons, knowledge of the redox properties of these compounds is important for a better understanding of their behavior in biological environments. Redox properties of some derivatives of these compounds in aqueous solutions is documented. [15][16][17][18][19][20][21][22] We thought that synthesis of a new 1,3-indandione derivatives with both structures of 1,3-indandione and hydroquinone would be useful from the point of view of pharmaceutical properties. This idea prompted us to development of a facile and environmentally friendly reagentless electrochemical method for the synthesis of some new 1,3-indandione derivatives in aqueous solutions with high atomic economy under ambient conditions and in an undivided cell using a graphite electrode and delineates the application of electrochemical studies in the design of an electrochemical method for the synthesis of new 1,3-indandione derivatives (5a-c).Electroorganic Reactions of 4-tert-Butylcatechol (1a) and 4-Methylcatechol (1b) Figure 1, CV a displays the typical successive cyclic voltammogram (CV) of 0.25 mM 4-tert-butylcatechol (1a) in aqueous media (H 2 O : AN, 90 : 10), containing phosphate buffer (pHϭ7.0, cϭ0.15 M). This figure demonstrates one anodic peak (A 1 ) (at 0.291 V) and one corresponding cathodic peak (C 1 ) (at 0.105 V), which corresponds to the transformation of 4-tert-butylcatechol (1a) to o-quinone-4-tert-butyl (2a) and vice versa within a quasireversible two-electron and two-proton process (DEpϭ 0.186 V). 23,24) A peak current ratio (I P A1 /I P C1 ) of nearly unity, particularly during the repetitive potential recycle, can be considered as a criterion for the stability of o-quinone produced on the electrode surface under the experimental conditions. In other words, any hydroxylation 25,26) or dimerization 27,28) reactions are too slow to be observed on the time scale of the cyclic voltammetry.The oxidation of 4-tert-butylcatechol (1a) in the presence of 2-phenyl-1,3-indandione (3) (pK a ϭ4.1) 29) as a nucleophile was studied in detail. Figure 1, CV b presents the cyclic voltammogram obtained for a 0.25 mM solution of 1a in the presence of 0.25 mM 3. The corresponding voltammogram exhibits one anodic peak at 0.364 V (A 1 ) vs. the reference electrode, where the cathodic counterpart of the anodic peak A 1 decreases. In this condition, the positive shift of the A 1 p...

Defects in the acd gene (which may be allelic to ubiH) result in the inactivation of the coenzyme A-linked acetaldehyde dehydrogenase activity of the multifunctional AdhE protein of Escherichia coli. This activity is restored by addition of ubiquinone-0 to cell extracts. However, the alcohol dehydrogenase activity of the AdhE protein is not decreased by an acd mutation. Abolition of ubiquinone biosynthesis by mutation of ubiA or ubiF does not affect either the acetaldehyde dehydrogenase or the alcohol dehydrogenase activity of AdhE. Guaiacol (2-methoxyphenol), which resembles the intermediate that builds up in ubiH mutants, except in lacking the octaprenyl side-chain, was found to inhibit ethanol metabolism in vivo, presumably via inhibition of acetaldehyde dehydrogenase. In vitro assays confirmed that guaiacol inhibited acetaldehyde dehydrogenase. This suggests that the acetaldehyde dehydrogenase activity of AdhE is specifically inhibited by intermediates of ubiquinone synthesis that accumulate in acd mutants and that this inhibition may be relieved by ubiquinone.

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