Because carbonyl groups can participate in both hydrogen bonds and n→π* interactions, these two interactions likely affect one another. Herein, enhancement of an amidic n→π* interaction is shown to reduce the ability of β-keto amides to tautomerize to the enol, indicating decreased hydrogen-bonding capacity of the amide carbonyl group. Thus, an n→π* interaction can have a significant effect on ...

zoanthamine-type alkaloids display a wide spectrum of biological effects. this study aimed to examine the inhibitory effects of norzoanthamine and its ten homologues of zoanthamine class on human fibroblast collagenase by modeling a three-dimensional structure of the ligands at collagenase using energy minimization, docking, molecular dynamics simulation and mm-pb/gbsa binding free energy calcu...

Increasingly grim environmental pollutions are closely related with the occurrence and development of diseases. However, it’s obscure how stress disturbs normal physiological process, then endogenous reactive species mend cases. Hypoxia/reperfusion (H/R), a common intractable injury in aquaculture clinic, can induce oxidative ultimately cause irreversible to organism. Cysteine (Cys) plays essen...

Pulse Radiolysis, OH Radicals, Acetylacetone, Reaction Mechanisms Pulse radiolysis experiments monitoring optical absorbance as well as conductivity and in-situ ESR radiolysis studies show that the OH radical reacts with the enol (k = 8.6 x 109 M_1 s_1) and the enolate (k = 7.4 X 109 M_1 s-1) forms of acetylacetone by addition to the C = C double bond in aqueous N2O saturated solution. The OH r...

The title bis-piperidine, C26H28N2O3, was unexpectedly obtained via a dimerization mechanism promoted by acetic acid when performing the Dieckmann cyclization of a chiral amido ester. The S,S configuration was assigned by reference to the enanti-omerically pure starting material. In the mol-ecule, two core heterocycles are linked by a σ bond. One ring includes a keto-enol group, while the other...

Recent studies have shed light on the energy dissipation mechanism of oxybenzone, a common ingredient in commercial sunscreens. After UVA photoexcitation, the dissipation mechanism may be understood in terms of an initial ultrafast excited state enol → keto tautomerisation, followed by nonadiabatic transfer to the ground electronic state and subsequent collisional relaxation to the starting eno...

O estudo do tautomerismo ceto-enólico e da estereoquímica de uma benzofenona natural com propriedades inibitórias sobre HIV, denominada (1R,5R,7R,8S)-(+)-3-(10-(3,4diidroxifenil)-10-hidroximetileno)-8-metil-1,5,7-tris(3-metil-2-butenil)-8-(4-metil-3-pentenil)biciclo[3.3.1]nonano-2,4,9-triona (a), a qual foi isolada das sementes de Garcinia brasiliensis, é apresentado. A estrutura cristalina de ...

Proton transfer and hydrogen bonding are two aspects of the chemistry of hydrogen that respectively govern the behaviour and structure of many molecules, both simple and complex. All the theoretical enol and keto conformations of 1,3-diphenyl-1,3propandion known as dibenzoylmethane (DBM), have been investigated by means of atoms in molecules (AIM) theory. It was found that the most stable confo...

In the solid state the title Schiff base, 0.58C(28)H(20)N(2)O(2)·0.42C(28)H(20)N(2)O(2), exists both as the keto-imino and as the enol-amino tautomer, which is manifested in the disorder of the H atom in the intra-molecular hydrogen-bonded ring. The naphthalene ring systems show some distortion, which is consistent with the quinoid effect. The ratio of the enol form refined to 58 (5)%. The mol-...

The chlorophyll a (Chl a) special-pair model of the primary donor of photosystem I (P700) does not account in a completely adequate fashion for the magnetic resonance properties observed for P700(+). Moreover, P700 is at least 420 mV easier to oxidize than is Chl a in vitro. Neither Chl a dimer formation nor selective ligation of Chl a can account for this potential difference. Enolization of t...