Mechanism and transition-state structure of hydride-transfer reactions mediated by nad(p)h-models

Reactivity and Biological Activity of the Marine Sesquiterpene Hydroquinone Avarol and Related Compounds from Sponges of the Order Dictyoceratida

“…However, the interpretation of the pathway of quinone redox cycling processes has been associated with a long-lasting controversy regarding the above mechanisms (reaction I vs. II). Various simple model systems, but also enzyme (or enzyme-like) models, under differently designed experimental conditions, offered mostly indirect evidence regarding the reaction pathway [23]. The frequently proposed successive one-electron transfer reaction (e-p-e) based on the well known redox potential depending ability of the quinone/hydroquinone (Q/QH 2 ) couple to reversibly form radical intermediates by chemical activation processes led to a quite conceivable interpretation that these intermediates can affect cellular components either directly, or indirectly, by producing toxic oxygen radicals responsible for cell damage [24][25][26] (Scheme 5).…”

Temperature Dependence of the Primary Kinetic Isotope Effect in Hydride Transfer Reactions with NAD+and NADH Models

“…In Table 2, also, thermodynamic parameters ⌬G ϩ , ⌬H ϩ and ⌬S ϩ , plus kinetic isotope effects (k HH /k DD ) for all three redox reactions were calculated at 25ЊC. For comparison, all above kinetic and thermodynamic parameters for another three substrates, 10-methyl-acridinium ion (7), 10-methyl-9-phenyl-acridinium ion (8), and compound-1 (8), were included in Table 2.…”

“…A very limited amount of experimental data has been published in the literature, concerning the TDKIE of hydride transfer reactions mediated by NADH-models (7)(8)(9). In this work, we have expanded this experimental basis by performing TDKIE 2 measurements with novel substrates, in order to better validate the TDKIE as a practical method to probe transition state structure of hydride transfer reactions.…”

“…In this work, we have expanded this experimental basis by performing TDKIE 2 measurements with novel substrates, in order to better validate the TDKIE as a practical method to probe transition state structure of hydride transfer reactions. For comparison, a study of a TDKIE of an enzymatic hydride transfer from 2-propanol-h 8 or 2-propanol-d 8 to NAD ϩ , catalyzed by yeast alcohol dehydrogenase, has been included.…”

A Study on the Reaction of 1‐(3‐Pyridyl)‐2,2‐di‐substituted Ethylenes with 1‐Benzyl‐1,4‐dihydronicotinamide

“…Pross-Shaik valence-bond configuration mixing (VBCM) model 3 shows that polar and electron transfer pathways in organic chemistry are closely related processes and an intermediate pathway between these two mechanistic extremes is feasible. Verhoeven and co-workers 4 have studied the mechanism and transition state structure of hydride transfer reaction mediated by NAD(P)H models using the VBCM model and rationalized the general occurrence of concerted hydride transfer as the lowest energy pathway. Furthermore, the results also explain why the activation energy of such a concerted pathway is often linearly related to that of a hypothetical electron transfer process.…”