title: Development of novel nitroxyl radicals for controlling reactivity with ascorbic acid.
abstract: 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.
authors.affiliation: Department of Bio-function Science, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kinoshita
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Yamada
authors.forename: Toshihide
authors.initials: T
authors.lastname: Yamasaki
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sadasue
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Sakai
authors.forename: Hideo
authors.initials: H
authors.lastname: Utsumi
mesh_terms: D000975:Antioxidants / Q000737:chemistry; D001205:Ascorbic Acid / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D009589:Nitrogen Oxides / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D009589:Nitrogen Oxides; C039900:nitroxyl; D001205:Ascorbic Acid