Disentangling Complex Mixtures of Compounds with Near‐Identical <sup>1</sup>H and <sup>13</sup>C NMR Spectra using Pure Shift NMR Spectroscopy

Castañar, Laura; Roldán, Raquel; Clapés, Pere; Virgili, Albert; Parella, Teodor

doi:10.1002/chem.201500521

Cited by 25 publications

(26 citation statements)

References 27 publications

(49 reference statements)

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“…Although our use of Eu(hfc) 3 as a shift reagent for the NMR assignment of achiral alkene-containing structure has precedent in the use of chiral shift reagent analysis of racemic alkene-containing structures, 17 we emphasize (as have others 18, 19 ) that optimization of the choice of chiral-shift reagent, its stoichiometry, and of solvent can disperse effectively resonances with minimal line broadening. As both pure 1 H shift-pulse sequences 20 and computer-assisted methods for NMR spectra interpretation 21 require a difference in chemical shifts , our decisive NMR differentiation of the two undecaprenol stereoisomers—one from bacteria, and one from plants—affirms the argument 18 of a continuing relevance of the shift reagent to the de novo NMR assignment of complex chemical structure. The ability to prepare these valuable synthetic lipids with full spectral characterization opens opportunities for the exploration of their roles in the intricate biochemical pathways of living organisms.…”

supporting

confidence: 53%

Synthesis and shift-reagent-assisted full NMR assignment of bacterial (Z₈,E₂,ω)-undecaprenol

et al. 2017

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The repeating isoprene unit is a fundamental biosynthetic motif. Repetitive structure presents challenges both for synthesis and for structural characterization. In this synthesis of the (Z8, E2, ω)-undecaprenol of prokaryotic glycobiology, we exemplify solutions to these challenges. Allylation of sulfone-derived carbanions controlled the stereochemistry, and its proof-of-structure was secured with Eu(hfc)3 complexation to disperse the overlayed resonances of its 1H NMR spectrum.

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confidence: 53%

Synthesis and shift-reagent-assisted full NMR assignment of bacterial (Z₈,E₂,ω)-undecaprenol

et al. 2017

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“…All earlier F 1 ‐PSYCHE‐TOCSY (or pure‐shift TOCSY) applications have focused on either a single challenging molecule or an artificial complex mixture of few molecules . In the present work, we go one step further by including F 1 ‐PSYCHE TOCSY in the NMR toolbox of various 1D and 2D correlation experiments ( J ‐resolved, TOCSY, and heteronuclear single quantum coherence sensitivity enhanced [HSQCSE]) to perform identification of the small molecule metabolites present in the coriander seed extract (in aqueous‐acetonitrile) in a snapshot.…”

Section: Introductionmentioning

confidence: 76%

Identification of metabolites in coriander seeds (Coriandrum Sativum L.) aided by ultrahigh resolution total correlation NMR spectroscopy

Verma

Parihar

Baishya

2019

Magnetic Reson in Chemistry

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NMR is a fast method for obtaining a holistic snapshot of the metabolome and also offers quantitative information without separating the compounds present in a complex mixture. Identification of the metabolites present in a plant extract sample is a crucial step for all plant metabolomics studies. In the present work, we used various two dimensional (2D) NMR methods such as J‐resolved NMR, total correlation spectroscopy (TOCSY), and heteronuclear single quantum coherence sensitivity enhanced NMR spectroscopy for the identification of 36 common metabolites present in Coriandrum sativum L. seed extract. The identified metabolites belong to the following classes: organic acids, amino acids, and carbohydrates. 1H NMR spectra of such complex mixtures in general display tremendous signal overlap due to the presence of a large number of metabolites with closely resonating multiplet signals. This signal overlapping leads to ambiguity in an assignment, and hence, identification of metabolites becomes tedious or impossible in many cases. Therefore, the utility of pure‐shift proton spectrum along the indirect (F1) dimension of the F1‐PSYCHE‐TOCSY spectrum is demonstrated for overcoming ambiguity in assignment of metabolites in crowded spectral regions from Coriandrum sativum L. seed extract sample. Because pure‐shift NMR methods yield ultrahigh resolution spectrum (i.e., a singlet peak per chemical site) along one or more dimensions, such spectra provide better identification of metabolites compared with regular 2D TOCSY where signal overlap and peak distortions lead to ambiguity in the assignment. Nine metabolites were unambiguously assigned by pure‐shift F1‐PSYCHE‐TOCSY spectrum, which was unresolved in regular TOCSY spectrum.

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“…Another high‐resolution 2D experiment, HSQC‐TOCSY, also utilizes the proton spins attached to natural abundant 13 C spins to generate a proton–proton total correlation map analogous to the DS‐ F 1 ‐BIRD‐TOCSY presented here. In the HSQC‐TOCSY spectrum, 2D TOCSY has been resolved into the 13 C dimension . This is helpful where the proton signals are overlapped because of chemical shift degeneracy.…”

Section: Resultsmentioning

confidence: 99%

Analyses of Complex Mixtures by F₁ Homo‐Decoupled Diagonal Suppressed Total Correlation Spectroscopy

et al. 2017

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A diagonal suppressed F decoupled total correlation spectroscopy(TOCSY) experiment is developed for analyses of complex mixtures. In 2D homonuclear correlation, assignment of the cross peaks is crucial for structure elucidation. However, when cross peaks are close to the diagonal peaks in overcrowded spectral regions, their assignment becomes tedious. In complex mixtures, the presence of multiple spectra along with broad and complex proton multiplets owing to homonuclear scalar couplings degrade the resolution to the extent that assignment of various cross peaks becomes tedious or impossible. Herein, a diagonal suppressed total correlation technique with F decoupling is presented to improve the resolution of the cross peaks. The resolution of the cross peaks is improved by both diagonal suppression as well as the collapse of the multiplets to singlets. Application of the method to a few mixtures of organic compounds reveals better identification of the cross peaks relative to other TOCSY variants.

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Disentangling Complex Mixtures of Compounds with Near‐Identical ¹H and ¹³C NMR Spectra using Pure Shift NMR Spectroscopy

Cited by 25 publications

References 27 publications

Synthesis and shift-reagent-assisted full NMR assignment of bacterial (Z₈,E₂,ω)-undecaprenol

Synthesis and shift-reagent-assisted full NMR assignment of bacterial (Z₈,E₂,ω)-undecaprenol

Identification of metabolites in coriander seeds (Coriandrum Sativum L.) aided by ultrahigh resolution total correlation NMR spectroscopy

Analyses of Complex Mixtures by F₁ Homo‐Decoupled Diagonal Suppressed Total Correlation Spectroscopy

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Disentangling Complex Mixtures of Compounds with Near‐Identical 1H and 13C NMR Spectra using Pure Shift NMR Spectroscopy

Cited by 25 publications

References 27 publications

Synthesis and shift-reagent-assisted full NMR assignment of bacterial (Z8,E2,ω)-undecaprenol

Synthesis and shift-reagent-assisted full NMR assignment of bacterial (Z8,E2,ω)-undecaprenol

Identification of metabolites in coriander seeds (Coriandrum Sativum L.) aided by ultrahigh resolution total correlation NMR spectroscopy

Analyses of Complex Mixtures by F1 Homo‐Decoupled Diagonal Suppressed Total Correlation Spectroscopy

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Product

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Disentangling Complex Mixtures of Compounds with Near‐Identical ¹H and ¹³C NMR Spectra using Pure Shift NMR Spectroscopy

Synthesis and shift-reagent-assisted full NMR assignment of bacterial (Z₈,E₂,ω)-undecaprenol

Synthesis and shift-reagent-assisted full NMR assignment of bacterial (Z₈,E₂,ω)-undecaprenol

Analyses of Complex Mixtures by F₁ Homo‐Decoupled Diagonal Suppressed Total Correlation Spectroscopy