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Published on: August 18, 2012
Development of novel nitroxyl radicals for controlling reactivity with ascorbic acid
Yuichi Kinoshita1, Ken-Ichi Yamada, Toshihide Yamasaki
1Department of Bio-function Science, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Free Radical Research
|April 23, 2009
Summary
Researchers developed stable nitroxyl radicals, enhancing their antioxidant and radical polymerization functions. These new compounds resist reduction by ascorbic acid (AsA), offering improved performance as antioxidants and contrast agents.
Area of Science:
- Organic Chemistry
- Polymer Chemistry
- Biochemistry
Background:
- Piperidine and pyrrolidine nitroxyl radicals are versatile compounds used as antioxidants, contrast agents, spin probes, and polymerization mediators.
- Their reactivity and paramagnetic properties are crucial for their function, but they are susceptible to reduction by reductants like ascorbic acid (AsA).
Purpose of the Study:
- To synthesize novel functional nitroxyl radicals with enhanced stability against reduction, particularly by ascorbic acid (AsA).
- To improve the synthetic route for 2,6-substituted nitroxyl radicals to achieve greater stability and tailored reactivity.
Main Methods:
- Synthesis of a series of 2,6-substituted nitroxyl radicals.
- Evaluation of the stability of synthesized radicals towards reduction by ascorbic acid (AsA).
- Kinetic studies to determine rate constants for reactions with reductants.
Main Results:
- Tetraethyl-substituted piperidine nitroxyl radical (compound 8) demonstrated significant resistance to AsA reduction.
- 2,6-dispiro-4',4''-dipyrane-piperidin-4-one-N-oxyl (compound 5) exhibited a second-order rate constant 10 times greater than hydroxyl-TEMPO and oxo-TEMPO in reactions with AsA.
- The 2,6-substituted compounds displayed varied reactivities towards AsA.
Conclusions:
- The developed 2,6-substituted nitroxyl radicals offer improved stability against ascorbic acid reduction.
- These novel compounds present potential applications as enhanced antioxidants, contrast agents, and radical polymerization mediators.
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