3066-90-8Relevant articles and documents
The Trapping of the OH Radical by Coenzyme Q. A Theoretical and Experimental Study
Espinosa-Garcia,Gutierrez-Merino
, p. 9712 - 9723 (2003)
Several pathways for the attack of the hydroxyl radical on coenzyme Q, as a prototypical chemical reaction involved in biological antioxidant actions, were theoretically analyzed by hybrid density functional theory computations, at the BHandHLYP/6-31G level. We found that the most favorable pathways are the hydrogen abstraction reaction from the phenolic hydrogen on the reduced form (ubiquinol), and the electrophilic OH addition on the oxidized form (ubiquinone). The reaction paths for the two mechanisms were traced independently. Following the direct dynamics method, the respective thermal rate constants were calculated using variational transition-state theory with multidimensional small-curvature tunneling. The experimental rate constants for the reaction of ubiquinol and ubiquinone with hydroxyl radicals produced via the Fenton's reaction in phosphate-buffered water solution at pH 7 were also measured. We found, first, that the reactivity in gas-phase (theoretical approach) is dominated by the OH addition mechanism on ubiquinone, and second, that a good agreement exists between the ratio of the rate constants determined from theoretical and experimental approaches for the reaction of oxidized and reduced forms of coenzyme Q with hydroxyl radicals. It is a very fast reaction, practically diffusion-controlled, with an inverse dependence of the thermal rate constants on temperature and therefore, a negative activation energy, both theoretically and experimentally. The influence of the tunneling factor was negligible. The analysis of the enthalpy and entropy contributions to the Gibbs free energy profile allowed us to understand the negative value of the activation energy.
A ubiquinol-based charge-transfer complex obtained from a solvent-free approach
Bouvet, Marcel,Malezieux, Bernard,Herson, Patrick,Villain, Francoise
, p. 453 - 461 (2009)
Quinones (=cyclohexa-2,5-diene-1,4-diones) and hydroquinones (=benzene-1,4-diols) belong to species that are balanced between their redox character and their ability to build supramolecular complexes. Considering the ubiquinol 2,3-dimethoxy-5-methyl-1,4-dihydroquinone (=2,3-dimethoxy-5- methylbenzene-1,4-diol; 1), the tendency to undergo an oxidation side reaction was overcome by combining this electron-donating species 1 with a nonreactive partner, benzene-1,2,4,5-tetracarbonitrile (TCNB; 3), to yield a 2 : 1 charge-transfer (CT) complex 4. This work illustrates how very convenient the solvent-free techniques are to access intermolecular species. X-Ray diffraction studies revealed that pure ubiquinol 1 (structure included) crystallizes in two enantiomeric conformations, while the triads 4 formed with TCNB (3) exist as meso forms assembled via H-bonds in zigzag-chains patterns.
SPERMINE PRO-DRUGS
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Paragraph 0011, (2021/01/26)
Disclosed herein are novel spermine prodrugs and methods of use for treating subjects exhibiting symptoms of a low spermine disorder. Also disclosed are methods of synthesizing spermine prodrugs. Compositions containing spermine prodrugs are also disclosed.
Metal-free reduction of unsaturated carbonyls, quinones, and pyridinium salts with tetrahydroxydiboron/water
Li, Tiejun,Peng, Henian,Tang, Wenjun,Tian, Duanshuai,Xu, Guangqing,Yang, He
, p. 4327 - 4337 (2021/05/31)
A series of unsaturated carbonyls, quinones, and pyridinium salts have been effectively reduced to the corresponding saturated carbonyls, dihydroxybenzenes, and hydropyridines in moderate to high yields with tetrahydroxydiboron/water as a mild, convenient, and metal-free reduction system. Deuterium-labeling experiments have revealed this protocol to be an exclusive transfer hydrogenation process from water. This journal is
Catalytic Electrophilic Alkylation of p-Quinones through a Redox Chain Reaction
Xu, Xiao-Long,Li, Zhi
supporting information, p. 8196 - 8200 (2017/06/30)
Allylation and benzylation of p-quinones was achieved through an unusual redox chain reaction. Mechanistic studies suggest that the existence of trace hydroquinone initiates a redox chain reaction that consists of a Lewis acid catalyzed Friedel–Crafts alkylation and a subsequent redox equilibrium that regenerates hydroquinone. The electrophiles could be various allylic and benzylic esters. The addition of Hantzsch ester as an initiator improves the efficiency of the reaction.