58971-05-4Relevant articles and documents
Enhanced Ene-Reductase Activity through Alteration of Artificial Nicotinamide Cofactor Substituents
L?w, Sebastian A.,L?w, Isabell M.,Weissenborn, Martin J.,Hauer, Bernhard
, p. 911 - 915 (2016/03/15)
The reduction of activated C=C double bonds is an important reaction in synthetic chemistry owing to the potential formation of up to two new stereogenic centers. Artificial nicotinamide cofactors were recently presented as alternative suppliers of hydride equivalents needed for alkene reduction. To study the effect of cofactors on the reduction of activated alkenes, a set of N-substituted synthetic nicotinamide cofactors with differing oxidation potentials were synthesized and their electrochemical and kinetic behavior was studied. The effects of the synthetic cofactors on enzyme activity of four ene reductases are outlined in this study, where the cofactor mimic with an N-substituted 4-hydroxy-phenyl residue led to a sixfold higher vmax relative to the natural cofactor NADH. Artificial nicotinamide cofactor substituents: A set of N-substituted synthetic nicotinamide cofactors with differing oxidation potentials were synthesized and their electrochemical and kinetic behavior was studied. The effects of the synthesized cofactors on the enzyme activity of four ene reductases are outlined. The cofactor mimic with an N-substituted 4-hydroxy-phenyl residue led to a sixfold higher vmax relative to the natural cofactor NADH.
Determination of the C4-H bond dissociation energies of NADH models and their radical cations in acetonitrile
Zhu, Xiao-Qing,Li, Hai-Rong,Li, Qian,Ai, Teng,Lu, Jin-Yong,Yang, Yuan,Cheng, Jin-Pei
, p. 871 - 880 (2007/10/03)
Heterolytic and homolytic bond dissociation energies of the C4-H bonds in ten NADH models (seven 1,4-dihydronicotinamide derivatives, two Hantzsch 1,4-dihydropyridine derivatives, and 9,10-dihydroacridine) and their radical cations in acetonitrile were evaluated by titration calorimetry and electrochemistry, according to the four thermodynamic cycles constructed from the reactions of the NADH models with N,N,N′,N′-tetramethyl-p-phenylenediamine radical cation perchlorate in acetonitrile (note: C9-H bond rather than C4-H bond for 9,10-dihydroacridine; however, unless specified, the C9-H bond will be described as a C4-H bond for convenience). The results show that the energetic scales of the heterolytic and homolytic bond dissociation energies of the C4-H bonds cover ranges of 64.2-81.1 and 67.9-73.7 kcal mol-1 for the neutral NADH models, respectively, and the energetic scales of the heterolytic and homolytic bond dissociation energies of the (C4-H).+ bonds cover ranges of 4.1-9.7 and 31.4-43.5 kcal mol-1 for the radical cations of the NADH models, respectively. Detailed comparison of the two sets of C4-H bond dissociation energies in 1-benzyl-1,4-dihydronicotinamide (BNAH), Hantzsch 1,4-dihydropyridine (HEH), and 9,10-dihydroacridine (AcrH2) (as the three most typical NADH models) shows that for BNAH and AcrH2, the heterolytic C4-H bond dissociation energies are smaller (by 3.62 kcal mol-1) and larger (by 7.4kcal mol-1), respectively, than the corresponding homolytic C4-H bond dissociation energy. However, for HEH, the heterolytic C4-H bond dissociation energy (69.3 kcal mol-1) is very close to the corresponding homolytic C4-H bond dissociation energy (69.4 kcal mol-1). These results suggests that the hydride is released more easily than the corresponding hydrogen atom from BNAH and vice versa for AcrH2, and that there are two almost equal possibilities for the hydride and the hydrogen atom transfers from HEH. Examination of the two sets of the (C4-H).+ bond dissociation energies shows that the homolytic (C4-H).+ bond dissociation energies are much larger than the corresponding heterolytic (C4-H).+ bond dissociation energies for the ten NADH models by 23.3-34.4 kcal mol-1; this suggests that if the hydride transfer from the NADH models is initiated by a one-electron transfer, the proton transfer should be more likely to take place than the corresponding hydrogen atom transfer in the second step. In addition, some elusive structural information about the reaction intermediates of the NADH models was obtained by using Hammett-type linear free-energy analysis.
Reactivity of biologically important reduced pyridines. 4. Effect of substitution on ferricyanide-mediated oxidation rates of various 1,4-dihydropyridines
Brewster,Simay,Czako,Winwood,Farag,Bodor
, p. 3721 - 3726 (2007/10/02)
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