Mukai K, Tsuzuki N, Ishizu K, Ouchi S, Fukuzawa K
Chem Phys Lipids. 1984 Aug;35(3):199-208. doi: 10.1016/0009-3084(84)90046-x.
Electron spin resonance (ESR) and electron nuclear double resonance (ENDOR) measurements were performed for the cation radicals obtained from the model compounds of alpha-, beta-, gamma- and delta-tocopherol (vitamin E) by oxidizing the tocopherol precursors in an AlCl3-CH2Cl2 solution. The proton hyperfine coupling constants and g-values were precisely determined. The ENDOR spectra of the cation radicals of alpha-, beta-, gamma- and delta-tocopherol models in CH2Cl2 at -100 degrees C clearly show 10, 6, 6 and 12 different proton hyperfine couplings, respectively. By varying the temperature, the ESR spectra of the alpha- and delta-tocopherol model cations exhibit line-width alternation phenomena characteristic of the hindered rotation of the OH group. However, neither the beta- nor the gamma-tocopherol model cation radical ESR spectra show any sign of an alternating line-width effect. These results are interpreted by assuming that the beta- and gamma- tocopherol model cations are stabilized in the trans and cis conformations, respectively. On the other hand, both the alpha- and delta-tocopherol model cations exist as cis and trans isomers.
通过在AlCl₃ - CH₂Cl₂溶液中氧化生育酚前体，对从α -、β -、γ - 和δ - 生育酚（维生素E）的模型化合物中获得的阳离子自由基进行了电子自旋共振（ESR）和电子核双共振（ENDOR）测量。精确测定了质子超精细耦合常数和g值。在-100℃下，α -、β -、γ - 和δ - 生育酚模型在CH₂Cl₂中的阳离子自由基的ENDOR光谱分别清楚地显示出10、6、6和12种不同的质子超精细耦合。通过改变温度，α - 和δ - 生育酚模型阳离子的ESR光谱表现出OH基团受阻旋转特征的线宽交替现象。然而，β - 和γ - 生育酚模型阳离子自由基的ESR光谱均未显示出线宽交替效应的任何迹象。通过假设β - 和γ - 生育酚模型阳离子分别稳定在反式和顺式构象中来解释这些结果。另一方面，α - 和δ - 生育酚模型阳离子均以顺式和反式异构体形式存在。
