NMR 和计算研究作为分析和高分辨率结构工具，用于溶液中复杂的脂肪酸过氧化物和非对映异构 - 过氧化物-以亚麻酸甲酯为例。 - Suppr

NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric -Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate.

机构信息

H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan.

Section of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece.

出版信息

Molecules. 2020 Oct 23;25(21):4902. doi: 10.3390/molecules25214902.

A combination of selective 1D Total Correlation Spectroscopy (TOCSY) and H-C Heteronuclear Multiple Bond Correlation (HMBC) NMR techniques has been employed for the identification of methyl linolenate primary oxidation products without the need for laborious isolation of the individual compounds. Complex hydroperoxides and diastereomeric -hydroperoxides were identified and quantified. Strongly deshielded C-O-O-H H-NMR resonances of diastereomeric -hydroperoxides in the region of 8.8 to 9.6 ppm were shown to be due to intramolecular hydrogen bonding interactions of the hydroperoxide proton with an oxygen atom of the five-member -peroxide ring. These strongly deshielded resonances were utilized as a new method to derive, for the first time, three-dimensional structures with an assignment of pairs of diastereomers in solution with the combined use of H-NMR chemical shifts, Density Functional Theory (DFT), and Our N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) calculations.

采用选择性一维总相关光谱（TOCSY）和 H-C 异核多键相关（HMBC）NMR 技术的组合，无需费力分离各个化合物，即可鉴定亚麻木酸甲酯的初级氧化产物。鉴定并定量了复杂的氢过氧化物和非对映异构的 -氢过氧化物。在 8.8 至 9.6 ppm 区域中，非对映异构的 -氢过氧化物的强烈去屏蔽 C-O-O-H H-NMR 共振归因于过氧化物质子与五元 -过氧化物环的氧原子之间的分子内氢键相互作用。这些强烈去屏蔽的共振可用作一种新方法，首次利用 H-NMR 化学位移、密度泛函理论（DFT）和我们的分层综合分子轨道和分子力学（ONIOM）计算的组合，在溶液中推导具有对映异构体对分配的三维结构。