Molecules, Vol. 25, Pages 4902: NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate

Molecules, Vol. 25, Pages 4902: NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate
Molecules doi: 10.3390/molecules25214902
Authors:
Raheel Ahmed
Panayiotis C. Varras
Michael G. Siskos
Hina Siddiqui
M. Iqbal Choudhary
Ioannis P. Gerothanassis

A combination of selective 1D Total Correlation Spectroscopy (TOCSY) and 1H-13C 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 endo-hydroperoxides were identified and quantified. Strongly deshielded C–O–O–H 1H-NMR resonances of diastereomeric endo-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 endo-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 1H-NMR chemical shifts, Density Functional Theory (DFT), and Our N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) calculations.

Source: Molecules - October 23, 2020 Category: Chemistry Authors: Raheel Ahmed Panayiotis C. Varras Michael G. Siskos Hina Siddiqui M. Iqbal Choudhary Ioannis P. Gerothanassis Tags: Article Source Type: research