“Stable” selenenic acids

Reich, Hans J.; Willis, William W.; Wollowitz, Susan

doi:10.1016/s0040-4039(00)87604-2

Cited by 52 publications

(22 citation statements)

References 12 publications

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“…was added into the mixture, a new signal at δ = 1191 ppm was observed which is assigned to 24. The signal is also in the range of peaks expected for selenenic acids, for example: ortho-nitrobenzeneselenenic acid (1066) [25] and 2-[(cyclohexyl-methylamino)methyl]benzeneselenenic acid (1173 ppm).…”

Section: Resultsmentioning

confidence: 74%

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Stable Selenenium Cations: Unusual Reactivity and Excellent Glutathione Peroxidase‐Like Activity

Singh

Butcher

2010

Eur J Inorg Chem

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The syntheses of the three selenenium cations 17–19 derived from N‐[n‐butyl‐(3‐nitrobenzylimino)]phenyl selenide (14) are described. Precursor 14 was synthesized by treating N‐(2‐bromo‐3‐nitrobenzylimino)benzene (12) with in situ generated nBuSeNa. The selenenium cation 17 with chloride as counteranion was isolated when 14 was treated with sulfuryl chloride (SO2Cl2) in the presence of triethylamine (Et3N). The selenenium cations with bromide (18) and tribromide (19) as counteranions, were synthesized by treating 14 with Br2 in the presence of Et3N. Reaction of 19 with thiophenol afforded two unexpected products: the cyclic diselenide 20 and the bicyclic selenide 21. Oxidation of 18 with hydrogen peroxide afforded the ebselen derivative, 2‐(4‐bromophenyl)‐7‐nitro‐1,2‐benzisoselenazol(2H)‐3‐one Se‐oxide (22). The presence of nonbonding Se···O/Se–N intramolecular interactions in 18 and 19 have been confirmed by single‐crystal X‐ray studies. Glutathione peroxidase‐like antioxidant activities of 17–19 and related compounds have been determined by the coupled reductase assay. It is proved that the high GPx‐like activities of cations involve the formation of corresponding intermediate selenoxide in the catalytic cycle. The isolated selenoxide 22 shows the highest GPx‐like activity among the series of compounds. The compounds have been further investigated by density functional theory calculations at the B3LYP level of theory using the 6‐31+G(d) basis set to identify nonbonding Se···O/N interactions. The second perturbation energy was obtained through natural bond orbital (NBO) analysis and NBO charges were calculated to ascertain the positive charge at the selenium atom. Nucleus‐independent chemical shifts (NICS) calculations have also been carried out.

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Section: Resultsmentioning

confidence: 74%

“…[18b] Recent studies have shown that 2-phenyl-1,2-benzisoselenazol(2H)-3-one Se-oxide (25) is the more efficient catalyst in the reduction of hydroperoxide. It has been proposed that 25 is involved as the key intermediate in the catalytic cycle of ebselen at higher concentration of peroxide.…”

Section: Resultsmentioning

confidence: 99%

Stable Selenenium Cations: Unusual Reactivity and Excellent Glutathione Peroxidase‐Like Activity

Singh

Butcher

2010

Eur J Inorg Chem

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“…Compound 29 , presumably, resulted from the condensation of 28 . Compound 29 was characterized by comparing the spectroscopic data with the reported literature values 20a. The structure of 29 was unambiguously confirmed by single‐crystal X‐ray crystallographic analysis (see below).…”

Section: Resultsmentioning

confidence: 93%

Synthesis of Cyclic Selenenate/Seleninate Esters Stabilized byortho‐Nitro Coordination: Their Glutathione Peroxidase‐Like Activities

Singh

Butcher

2011

Chemistry An Asian Journal

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The syntheses of selenenate/seleninate esters and related derivatives by aromatic nucleophilic substitution (S(N)Ar) reactions of 2-bromo-3-nitrobenzylalcohol (13) and 2-bromo-3-nitrobenzaldehyde (17) with Na(2)Se(2)/nBuSeNa are described. The reaction of 13 with Na(2)Se(2) at room temperature afforded 7-nitro-1,2-benzisoselenole(3H) (15) instead of the desired diaryl diselenide 14. Oxidation of selenenate ester 15 with hydrogen peroxide afforded the corresponding selenium(IV) derivative, 7-nitro-1,2-benzisoselenole(3H) selenium oxide (18). 2-(Butylselanyl)-3-nitrobenzaldehyde (19) was synthesized by treating compound 17 with in situ generated nBuSeNa. The bromination reaction of selenide 19 did not afford the expected arylselenenyl bromide 20, instead, it resulted in the formation of the unexpected 7-nitro-1,2-benzisoselenol(3H)-3-ol (21) and 3,3'-oxybis(7-nitro-1,2-benzisoselenole(3H)) (22), respectively. The facile formation of heterocycles 21 and 22 is rationalized in terms of the aromatic ring strain in selenenyl bromide 20. The presence of intramolecular secondary Se···O interactions in esters 15, 18, 21, 22, and selenenic anhydride 29 has been confirmed by single-crystal X-ray diffraction studies as well as computational studies. The presence of an intramolecular Se···O interaction in esters 4b, 8, 15, 18, 21, and 22 has been further proved by natural bond orbital (NBO) and atoms in molecules (AIM) calculations. Glutathione peroxidase-like (GPx) antioxidant activities of 15, 18, 21, 22, and related heterocycles such as 7-nitro-1,2-benzisoselenol(2H)-3-one selenium oxide (4b), 7-nitro-1,2-benzisoselenol(2H)-3-one (8), and 29 have been determined by the coupled reductase assay.

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“…The 77 Se NMR signal at 1069 ppm may correspond to NictSeOH, as reported in case of o-nitrobenzeneselenenic acid (δ 1066 ppm). 20 NictSeSG formed during the GPx cycle can either react with GSH to form NictCvSe (eqn (6)) or with H 2 O 2 to form Nict-SeOH (eqn (7)). The relative reactivity of NictSeSG with the two substrates i.e.…”

Section: A Gpx Activity By Nadph Assaymentioning

confidence: 99%

Stable selones in glutathione-peroxidase-like catalytic cycle of selenonicotinamide derivative

et al. 2014

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Selenonicotinamide, 2,2'-diselenobis[3-amidopyridine] (NictSeSeNict) exhibits glutathione-peroxidase (GPx)-like activity, catalyzing the reduction of hydrogen peroxide (H2O2) by glutathione (GSH). Estimated reactivity parameters for the reaction of selenium species, according to the Dalziel kinetic model, towards GSH (ϕGSH) and H2O2 (ϕH2O2), indicated that the rate constant for the reaction of NictSeSeNict with GSH is higher as compared to that with H2O2, indicating that the activity is initiated by reduction. (77)Se NMR spectroscopy, HPLC analysis, mass spectrometry (MS) and absorption spectroscopy were employed to understand the nature of selenium intermediates responsible for the activity. The (77)Se NMR resonance at 525 ppm due to NictSeSeNict disappeared in the presence of GSH with the initial appearance of signals at δ 364 and 600 ppm, assigned to selone (NictC=Se) and selenenyl sulfide (NictSeSG), respectively. Reaction of H2O2 with NictSeSeNict produced a mixture of selenenic acid (NictSeOH) and seleninic acid (NictSeO2H) with (77)Se NMR resonances appearing at 1069 and 1165 ppm, respectively. Addition of three equivalents of GSH to this mixture produced a characteristic (77)Se NMR signal of NictSeSG. HPLC analysis of the product formed by the reaction of NictSeSeNict with GSH confirmed the formation of NictC=Se absorbing at 375 nm. Stopped-flow kinetic studies with global analysis revealed a bimolecular rate constant of 4.8 ± 0.5 × 10(3) M(-1) s(-1) and 1.7 ± 0.6 × 10(2) M(-1) s(-1) for the formation of NictC=Se produced in two consecutive reactions of NictSeSeNict and NictSeSG with GSH, respectively. Similarly the rate constant for the reaction of NictC=Se with H2O2 was estimated to be 18 ± 1.8 M(-1) s(-1). These studies clearly indicated that the GPx activity of NictSeSeNict is initiated by reduction to form NictSeSG and a stable selone, which is responsible for its efficient GPx activity.

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“Stable” selenenic acids

Cited by 52 publications

References 12 publications

Stable Selenenium Cations: Unusual Reactivity and Excellent Glutathione Peroxidase‐Like Activity

Stable Selenenium Cations: Unusual Reactivity and Excellent Glutathione Peroxidase‐Like Activity

Synthesis of Cyclic Selenenate/Seleninate Esters Stabilized byortho‐Nitro Coordination: Their Glutathione Peroxidase‐Like Activities

Stable selones in glutathione-peroxidase-like catalytic cycle of selenonicotinamide derivative

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