Synthesis of the tetraethyl substituted pH-sensitive nitroxides of imidazole series with enhanced stability towards reduction
作者:Igor A. Kirilyuk、Andrey A. Bobko、Igor A. Grigor'ev、Valery V. Khramtsov
DOI:10.1039/b400252k
日期:——
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.
本文介绍了从 3-乙基戊-2-烯合成 2,2,5,5-四乙基咪唑亚硝基化合物的方法。新合成的硝基化合物,即 4-甲基-2,2,5,5-四乙基-2,5-二氢-1H-咪唑-1-基氧基(1)、3,4-二甲基-2,2,5,5-四乙基过氢咪唑-1-基氧基(2)和 2、2,5,5-四乙基-4-吡咯烷-1-基-2,5-二氢-1H-咪唑-1-氧基(3)是 pH 敏感的自旋探针,pK 值分别为 1.2、4.95 和 7.4。最重要的发现是,与 2,2,5,5-四甲基类似物相比,这些新的亚硝基化合物在抗坏血酸存在下的稳定性提高了 20-30 倍,在大鼠血液中的半衰期也明显延长。后一项观察结果为四乙基取代的咪唑亚硝基化合物作为功能性 EPR 探针的应用提供了独特的优势。