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101.
Unusually Short Chalcogen Bonds Involving Organoselenium: Insights into the Se–N Bond Cleavage Mechanism of the Antioxidant Ebselen and Analogues
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Dr. Sajesh P. Thomas K. Satheeshkumar Prof. Govindasamy Mugesh Prof. T. N. Guru Row 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6793-6800
Structural studies on the polymorphs of the organoselenium antioxidant ebselen and its derivative show the potential of organic selenium to form unusually short Se???O chalcogen bonds that lead to conserved supramolecular recognition units. Se???O interactions observed in these polymorphs are the shortest such chalcogen bonds known for organoselenium compounds. The FTIR spectral evolution characteristics of this interaction from solution state to solid crystalline state further validates the robustness of this class of supramolecular recognition units. The strength and electronic nature of the Se???O chalcogen bonds were explored using high‐resolution X‐ray charge density analysis and atons‐in‐molecules (AIM) theoretical analysis. A charge density study unravels the strong electrostatic nature of Se???O chalcogen bonding and soft‐metal‐like behavior of organoselenium. An analysis of the charge density around Se?N and Se?C covalent bonds in conjunction with the Se???O chalcogen bonding modes in ebselen and its analogues provides insights into the mechanism of drug action in this class of organoselenium antioxidants. The potential role of the intermolecular Se???O chalcogen bonding in forming the intermediate supramolecular assembly that leads to the bond cleavage mechanism has been proposed in terms of electron density topological parameters in a series of molecular complexes of ebselen with reactive oxygen species (ROS). 相似文献
102.
P. N. Jayaram Gouriprasanna Roy Govindasamy Mugesh 《Journal of Chemical Sciences》2008,120(1):143-154
The keto-enol type tautomerism in anti-thyroid drugs and their selenium analogues are described. The commonly used anti-thyroid
drug methimazole exists predominantly in its thione form, whereas its selenium analogue exists in a zwitterionic form. To
understand the effect of thione/thiol and selone/selenol tautomerism on the inhibition of peroxidase-catalysed reactions,
we have synthesized some thiones and selones in which the formation of thiol/selenol forms are blocked by different substituents.
These compounds were synthesized by a carbene route utilizing an imidazolium salt. The crystal structures of these compounds
reveal that the C=Se bonds in the selones are more polarized than the C=S bonds in the corresponding thiones. The structures
of selones were studied in solution by NMR spectroscopy and the 77Se NMR chemical shifts for the selones show large upfield shifts in the signals, confirming their zwitterionic structures
in solution. The inhibition of lactoperoxidase by the synthetic thiones indicates that the presence of a free N-H moiety is
essential for an efficient inhibition. In contrast, such moiety is not required for an inhibition by the selenium compounds. 相似文献
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Angiotensin converting enzyme (ACE) inhibitors are important for the treatment of hypertension as they can decrease the formation of vasopressor hormone angiotensin II (Ang II) and elevate the levels of vasodilating hormone bradykinin. It is observed that bradykinin contains a Ser-Pro-Phe motif near the site of hydrolysis. The selenium analogues of captopril represent a novel class of ACE inhibitors as they also exhibit significant antioxidant activity. In this study, several di- and tripeptides containing selenocysteine and cysteine residues at the N-terminal were synthesized. Hydrolysis of angiotensin I (Ang I) to Ang II by ACE was studied in the presence of these peptides. It is observed that the introduction of L-Phe to Sec-Pro and Cys-Pro peptides significantly increases the ACE inhibitory activity. On the other hand, the introduction of L-Val or L-Ala decreases the inhibitory potency of the parent compounds. The presence of an L-Pro moiety in captopril analogues appears to be important for ACE inhibition as the replacement of L-Pro by L-piperidine 2-carboxylic acid decreases the ACE inhibition. The synthetic peptides were also tested for their ability to scavenge peroxynitrite (PN) and to exhibit glutathione peroxidase (GPx)-like activity. All the selenium-containing peptides exhibited good PN-scavenging and GPx activities. 相似文献
106.
Krishna P. Bhabak Govindasamy Mugesh Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(38):9846-9854
In this study, a series of secondary‐ and tertiary‐amino‐substituted diaryl diselenides were synthesized and studied for their glutathione peroxidase (GPx) like antioxidant activities with H2O2, cumene hydroperoxide, or tBuOOH as substrates and with PhSH or glutathione (GSH) as thiol cosubstrates. This study reveals that replacement of the tert‐amino groups in benzylamine‐based diselenides by sec‐amino moieties drastically enhances the catalytic activities in both the aromatic thiol (PhSH) and GSH assay systems. Particularly, the N‐propyl‐ and N‐isopropylamino‐substituted diselenides are 8–18 times more active than the corresponding N,N‐dipropyl‐ and N,N‐diisopropylamine‐based compounds in all three peroxide systems when GSH is used as the thiol cosubstrate. Although the catalytic mechanism of sec‐amino‐substituted diselenides is similar to that of the tert‐amine‐based compounds, differences in the stability and reactivity of some of the key intermediates account for the differences in the GPx‐like activities. It is observed that the sec‐amino groups are better than the tert‐amino moieties for generating the catalytically active selenols. This is due to the absence of any significant thiol‐exchange reactions in the selenenyl sulfides derived from sec‐amine‐based diselenides. Furthermore, the seleninic acids (RSeO2H) derived from the sec‐amine‐based compounds are more stable toward further reactions with peroxides than their tert‐amine‐based analogues. 相似文献
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Kálai T Mugesh G Roy G Sies H Berente Z Hideg K 《Organic & biomolecular chemistry》2005,3(19):3564-3569
Benzo[d]isoselenazol-3-ones N-substituted with sterically hindered diamagnetic and paramagnetic five- or six-membered nitroxides or their precursors, including ring-opened diselenides, exhibit synergism in glutathione peroxidase (GPx) activity. 相似文献
110.
Hydroxyl group terminated poly(propyl ether imine) dendrimers of 1 to 5 generations absorb in the region of 260-340 nm, in MeOH and aqueous solutions. Excitation of a solution of the dendrimers at 330 nm led to an emission at approximately 390 nm. The emission intensities increased under acidic pH and in more viscous solvents. The presence of air did not affect the emission profiles, as also aging of a dendrimer solution for prolonged periods. Lifetime measurements show at least two species responsible for the emission. Anions perchlorate, periodate, nitrite, and pyridinium methyliodide quenched the fluorescence efficiently, among several anions tested. 相似文献