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J Am Chem Soc. 2007 May 2;129(17):5503-14. Epub 2007 Apr 10.

4-Aryl-1,3,2-oxathiazolylium-5-olates as pH-controlled NO-donors: the next generation of S-nitrosothiols.

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  • 1Department of Biochemistry, The Davis Heart and Lung Research Institute, Division of Cardiovascular Medicine, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA.


S-Nitrosothiols (RSNOs) are important exogenous and endogenous sources of nitric oxide (NO) in biological systems. A series of 4-aryl-1,3,2-oxathiazolylium-5-olates derivatives with varying aryl para-substituents (-CF3, -H, -Cl, and -OCH3) were synthesized. These compounds were found to release NO under acidic condition (pH = 5). The decomposition pathway of the aryloxathiazolyliumolates proceeded via an acid-catalyzed ring-opening mechanism after which NO was released and an S-centered radical was generated. Electron paramagnetic resonance (EPR) spin trapping studies were performed to detect NO and the S-centered radical using the spin traps of iron(II) N-methyl-D-glucamine dithiocarbamate [(MGD)2-FeII] and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Also, EPR spin trapping and UV-vis spectrophotometry were used to analyze the effect of aryl para substitution on the NO-releasing property of aryloxathiazolyliumolates. The results showed that the presence of an electron-withdrawing substituent such as -CF3 enhanced the NO-releasing capability of the aryloxathiazolyliumolates, whereas an electron-donating substituent like methoxy (-OCH3) diminished it. Computational studies using density functional theory (DFT) at the PCM/B3LYP/6-31+G**//B3LYP/6-31G* level were used to rationalize the experimental observations. The aryloxathiazolyliumolates diminished susceptibility to reduction by ascorbate or gluthathione, and their capacity to cause vasodilation as compared to other S-nitrosothiols suggests potential application in biological systems.

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