- Differences in the Mechanisms of MnO2Oxidation between Lignin Model Compounds with the p-Hydroxyphenyl, Guaiacyl, and Syringyl Nuclei
-
The purpose of this study was to examine how the rate and mechanism of MnO2 oxidation differ between the p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) types of simple nonphenolic lignin model compounds as well as the p-ethylphenyl (E) type compounds. The oxidation was conducted using an excess amount of MnO2 in a sulfate buffer solution at a pH value of 1.5 at room temperature. MnO2 oxidized at least the G and S nuclei, although it commonly oxidizes alcohols present at the benzyl position. The oxidation rates of the benzyl alcohol derivatives were in the order of G- > S- ? H- > E-type, which suggests that the rates are determined by the electronic effects of their methoxy and ethyl functional groups on not only their benzyl positions but also their aromatic π-electron systems. The kinetic isotope effect was observed in the MnO2 oxidations of the same derivatives deuterated at their benzyl hydroxymethyl groups. The observed magnitudes were in the order of E- ? H- > G- ? S-type, suggesting that the contribution of oxidation of their aromatic nuclei, which is another reaction mode of the oxidation of their benzyl positions, increases in the reverse order.
- Sun, Shirong,Akiyama, Takuya,Yokoyama, Tomoya,Matsumoto, Yuji
-
p. 6819 - 6825
(2020/07/02)
-
- Synthesis of deuterium-labelled coenzyme Q10
-
Deuterium-labelled coenzyme Q10 ([2-CD3-1′-CD2]coenzyme Q10, coenzyme Q10-d5) was synthesized by condensation of 2,3-dimethoxy-[5-CD3]methyl-1, 4-hydroquinone with [1-CD2]decaprenol. Five positions were selected for deuteration as replacement at these positions allowed examination of every step of the synthesis. This examination was carried out by a combination of 1H- and 13C-nuclear magnetic spectrometry and mass spectrometry. Further, these positions have been proved to be metabolically stable. This reagent makes simultaneous quantification of the source of coenzyme Q10 (exogenously supplied or endogenously supplied) possible in biological samples by measurements on gas chromatography-mass spectrometry. Copyright
- Hamamura, Kimio,Yamagishi, Yoji,Kijima, Shizumasa,Suzuki, Takeshi,Mori, Yutaka,Nakamura, Tetsuya
-
p. 831 - 839
(2007/10/03)
-