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

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

A combination of selective 1D Total Correlation Spectroscopy (TOCSY) and <sup>1</sup>H-<sup>13</sup>C Heteronuclear Multiple Bond Correlation (HMBC) NMR techniques has been employed for the identification of methyl linolenate primary oxidation products without the need for la...

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Main Authors: Raheel Ahmed, Panayiotis C. Varras, Michael G. Siskos, Hina Siddiqui, M. Iqbal Choudhary, Ioannis P. Gerothanassis
Format: Article
Language:English
Published: MDPI AG 2020-10-01
Series:Molecules
Subjects:
polyunsaturated fatty acids
hydroperoxides
<i>endo</i>-hydroperoxides
NMR
chemical shifts
hydrogen bonding
Online Access:https://www.mdpi.com/1420-3049/25/21/4902
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spelling doaj-86f5393db0a54eecafbbdf9c649d4f422020-11-25T03:56:00ZengMDPI AGMolecules1420-30492020-10-01254902490210.3390/molecules25214902NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric <i>Endo</i>-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl LinolenateRaheel Ahmed0Panayiotis C. Varras1Michael G. Siskos2Hina Siddiqui3M. Iqbal Choudhary4Ioannis P. Gerothanassis5H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, PakistanSection of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, GreeceSection of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, GreeceH.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, PakistanH.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, PakistanH.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, PakistanA combination of selective 1D Total Correlation Spectroscopy (TOCSY) and <sup>1</sup>H-<sup>13</sup>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 <i>endo</i>-hydroperoxides were identified and quantified. Strongly deshielded C–O–O–H <sup>1</sup>H-NMR resonances of diastereomeric <i>endo</i>-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 <i>endo</i>-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 <sup>1</sup>H-NMR chemical shifts, Density Functional Theory (DFT), and Our N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) calculations.https://www.mdpi.com/1420-3049/25/21/4902polyunsaturated fatty acidshydroperoxides<i>endo</i>-hydroperoxidesNMRchemical shiftshydrogen bonding
collection DOAJ
language English
format Article
sources DOAJ
author Raheel Ahmed
Panayiotis C. Varras
Michael G. Siskos
Hina Siddiqui
M. Iqbal Choudhary
Ioannis P. Gerothanassis
spellingShingle Raheel Ahmed
Panayiotis C. Varras
Michael G. Siskos
Hina Siddiqui
M. Iqbal Choudhary
Ioannis P. Gerothanassis
NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric <i>Endo</i>-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate
Molecules
polyunsaturated fatty acids
hydroperoxides
<i>endo</i>-hydroperoxides
NMR
chemical shifts
hydrogen bonding
author_facet Raheel Ahmed
Panayiotis C. Varras
Michael G. Siskos
Hina Siddiqui
M. Iqbal Choudhary
Ioannis P. Gerothanassis
author_sort Raheel Ahmed
title NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric <i>Endo</i>-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate
title_short NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric <i>Endo</i>-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate
title_full NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric <i>Endo</i>-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate
title_fullStr NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric <i>Endo</i>-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate
title_full_unstemmed NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric <i>Endo</i>-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate
title_sort nmr and computational studies as analytical and high-resolution structural tool for complex hydroperoxides and diastereomeric <i>endo</i>-hydroperoxides of fatty acids in solution-exemplified by methyl linolenate
publisher MDPI AG
series Molecules
issn 1420-3049
publishDate 2020-10-01
description A combination of selective 1D Total Correlation Spectroscopy (TOCSY) and <sup>1</sup>H-<sup>13</sup>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 <i>endo</i>-hydroperoxides were identified and quantified. Strongly deshielded C–O–O–H <sup>1</sup>H-NMR resonances of diastereomeric <i>endo</i>-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 <i>endo</i>-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 <sup>1</sup>H-NMR chemical shifts, Density Functional Theory (DFT), and Our N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) calculations.
topic polyunsaturated fatty acids
hydroperoxides
<i>endo</i>-hydroperoxides
NMR
chemical shifts
hydrogen bonding
url https://www.mdpi.com/1420-3049/25/21/4902
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