Development of novel nitroxyl radicals for controlling reactivity with ascorbic acid.
Piperidine and pyrrolidine nitroxyl radicals (nitroxide) contain unpaired electrons and have been widely recognized as antioxidants, contrast agents, spin probes, radiation protective agents and polymerization mediators. Nitroxyl radicals can react with free radicals and reductants and their reactivities depend on the basic structure of the nitroxyl radicals themselves. However, reductants easily reduce these radicals and they lose their paramagnetic nature and function. Therefore, the aim of this study was to develop various functional nitroxyl radicals, particularly focusing on stability towards AsA through the improvement of the synthetic route for a series of 2,6-substituted nitroxyl radicals. Tetraethyl-substituted piperidine nitroxyl radical 8 exhibited resistance to AsA reduction and 2,6-dispiro-4',4''-dipyrane-piperidin-4-one-N-oxyl 5 had a second-order rate constant 10-times greater than those of hydroxyl-TEMPO and oxo-TEMPO. The 2,6-substituted compound offers various reactivities towards AsA and the possibility to be used as a new antioxidant, contrast agent and radical polymerizer.
Kinoshita
Yuichi
Y
Department of Bio-function Science, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Yamada
Ken-Ichi
K
Yamasaki
Toshihide
T
Sadasue
Hiromi
H
Sakai
Kiyoshi
K
Utsumi
Hideo
H
D000975:Antioxidants / Q000737:chemistry; D001205:Ascorbic Acid / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D009589:Nitrogen Oxides / Q000138:chemical synthesis* / Q000737:chemistry*
D000975:Antioxidants; D009589:Nitrogen Oxides; C039900:nitroxyl; D001205:Ascorbic Acid