Synthesis of the tetraethyl substituted pH-sensitive nitroxides of imidazole series with enhanced stability towards reduction.
The synthesis of 2,2,5,5-tetraethylimidazole nitroxides from 3-ethylpent-2-ene is described. The newly synthesized nitroxides, namely 4-methyl-2,2,5,5-tetraethyl-2,5-dihydro-1H-imidazol-1-yloxy (1), 3,4-dimethyl-2,2,5,5-tetraethylperhydroimidazol-1-yloxy (2) and 2,2,5,5-tetraethyl-4-pyrrolidin-1-yl-2,5-dihydro-1H-imidazol-1-oxyl (3), were found to be pH sensitive spin probes, with pK values of 1.2, 4.95 and 7.4, respectively. The most important finding was the fact that these new nitroxides were 20-30 times more stable in the presence of ascorbate and had significantly longer halflifes in rat blood as compared to 2,2,5,5-tetramethyl analogs. The latter observation provides a unique advantage for the application of tetraethyl substituted imidazole nitroxides as functional EPR probes.
Kirilyuk
Igor A
IA
N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, pr. Acad. Lavrentjeva 9, Novosibirsk 630090, Russia. kirilyuk@nioch.nsc.ru
Bobko
Andrey A
AA
Grigor'ev
Igor A
IA
Khramtsov
Valery V
VV
D000818:Animals; D001205:Ascorbic Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000138:chemical synthesis*; D007700:Kinetics; D015394:Molecular Structure; D009589:Nitrogen Oxides / Q000737:chemistry*; D010084:Oxidation-Reduction; D051381:Rats
D007093:Imidazoles; D009589:Nitrogen Oxides; D001205:Ascorbic Acid