Chiral NMR Solvating Additives for Differentiation of Enantiomers

Uccello‐Barretta, Gloria; Balzano, Federica

doi:10.1007/128_2013_445

Cited by 52 publications

(52 citation statements)

References 263 publications

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“…Among them the most popular are chromatographic [1][2][3][4][5][6] and spectroscopic methods, and, particularly, nuclear magnetic resonance (NMR). [6][7][8][9][10] The easy commercial accessibility of chiral stationary phases for high-performance liquid chromatography / gas chromatography (HPLC/GC) and of chiral auxiliaries for NMR spectroscopy has made these analytical methods very popular and has led to the recognition, especially in chromatography, of the critical dependence of the reproducibility of analytical separations from the presence of intentional additives or unintentional impurities. 11,12 A source of irreproducible chromatographic separation consists of the traces of water or moisture, the content of which is very difficult to control and, in general, constitutes an undesired presence.…”

Section: Introductionmentioning

confidence: 99%

Synergistic Effects of Trace Amounts of Water in the Enantiodiscrimination Processes by Lipodex E: A Spectroscopic and Computational Investigation

et al. 2014

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Nuclear magnetic resonance (NMR) investigations on mixtures containing octakis(3-O-butanoyl-2,6-di-O-pentyl)-γ-cyclodextrin (Lipodex E) and each enantiomer of methyl-2-chloropropionate (MCP) ascertained the role of trace amounts of water in the enantiodiscrimination processes. Water is deeply included into the cyclodextrin and favors the formation of the inclusion complex with (S)-MCP, whereas (R)-MCP is only slightly affected, thus causing a significant increase of NMR differentiation. Molecular dynamics simulations were performed to shed light on the possible behavior of Lipodex E in different conditions (i.e., solvent, inclusion complexes), providing energetic and atomistic details that are in agreement with NMR observations.

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Section: Introductionmentioning

confidence: 99%

Synergistic Effects of Trace Amounts of Water in the Enantiodiscrimination Processes by Lipodex E: A Spectroscopic and Computational Investigation

et al. 2014

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“…Among these methods, NMR spectroscopy using chiral solvating agents (CSAs) to form diastereomeric complexes with samples via noncovalent interactions might be one of the most facile methods without chiral derivatization of the analyte or using special equipment apart from the common NMR spectrometers, which has the advantages of easy performance and accessibility. 5 As soon as there is a large enough chemical shift nonequivalence to give clear baseline separation of the NMR signals of probe groups in two diastereomeric complexes formed between CSAs and samples, the enantiomeric purities of samples can be measured.…”

Section: ■ Introductionmentioning

confidence: 99%

A Chiral Bisthiourea as a Chiral Solvating Agent for Carboxylic Acids in the Presence of DMAP

et al. 2013

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A simple chiral bisthiourea has been used as a highly effective and practical chemical solvating agent (CSA) for diverse α-carboxylic acids in the presence of DMAP. Excellent enantiodiscrimination based on well-resolved α-H NMR signals of the enantiomers of carboxylic acids can be obtained without interference from the chiral bisthiourea and DMAP. To check the practicality of the chiral bisthiourea/ DMAP for enantiomeric determination, the ee values of mandelic acid (MA) samples over a wide ee range were determined by integration of the α-H signal of MA in 1 H NMR. A discrimination mechanism is proposed, that the formation of two diasteromeric ternary complexes between the chiral bisthiourea and two in situ formed enantiomeric carboxylate-DMAPH + ion pairs discriminates the enantiomers of carboxylic acids. Computational modeling studies show that the chemical shift value of α-H of (S)-MA is greater than that of (R)-MA in ternary complexes, which is consistent with experimental observation. 1D and 2D NOESY spectra demonstrate the intermolecular noncovalent interactions between the protons on the aromatic rings of chiral bisthiourea and α-H of the enantiomers of racemic α-methoxy phenylacetic acids in the complexes.

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“…In some cases, these compounds cause reproducible perturbations in chemical shifts that can be used in the assignment of the absolute stereochemistry [1–7]. Since chiral solvating agents associate with the compound being studied through non-covalent interactions, they are easy to use and involve merely mixing the reagent with the compound in an NMR tube.…”

Section: Introductionmentioning

confidence: 99%

Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds

Puentes¹,

Wenzel²

2017

Beilstein J. Org. Chem.

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The utility of phosphated α-, β- and γ-cyclodextrins as water-soluble chiral NMR solvating agents for cationic substrates is described. Two sets of phosphated cyclodextrins, one with degrees of substitution in the 2–6 range, the other with degrees of substitution in the 6–10 range, are examined. Results with 33 water-soluble cationic substrates are reported. We also explored the possibility that the addition of paramagnetic lanthanide ions such as praseodymium(III) and ytterbium(III) further enhances the enantiomeric differentiation in the NMR spectra. The chiral differentiation with the phosphated cyclodextrins is compared to prior results obtained with anionic carboxymethylated cyclodextrins. There are a number of examples where a larger differentiation is observed with the phosphated cyclodextrins.

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Chiral NMR Solvating Additives for Differentiation of Enantiomers

Cited by 52 publications

References 263 publications

Synergistic Effects of Trace Amounts of Water in the Enantiodiscrimination Processes by Lipodex E: A Spectroscopic and Computational Investigation

Synergistic Effects of Trace Amounts of Water in the Enantiodiscrimination Processes by Lipodex E: A Spectroscopic and Computational Investigation

A Chiral Bisthiourea as a Chiral Solvating Agent for Carboxylic Acids in the Presence of DMAP

Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds

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