Results 261 to 270 of about 691,764 (293)

Determination of Enantiomeric Excess via ³¹P‐NMR

Chirality
ABSTRACT31P is a very attractive nucleus for nuclear magnetic resonance (NMR) analysis because of the large chemical dispersion and the simplicity of the spectra when compared with other nuclei (other than 19F). The ability to rapidly and quantitatively assay for enantiomeric excess (ee) measurements of alcohols, amines, thiols, and other chiral ...
Ellis Guernsey, Jean‐Luc Montchamp
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Diporphyrin tweezer for multichannel spectroscopic analysis of enantiomeric excess

Frontiers of Chemical Science and Engineering, 2020
Chiral 1,1’-binaphthyl-linked diporphyrin ‘tweezers’ (R)-1/(S)-1 and the corresponding zinc(II) complexes (R)-2/(S)-2 were prepared as chiral host molecules, and their utility for chiral analyses (especially enantiomeric excess (ee) determinations) were evaluated. Tris(1-n-dodecyl)porphyrins were used for the first time as the interacting units.
Daniel T. Payne, Mandeep K. Chahal, Václav Březina, Whitney A. Webre, Katsuhiko Ariga, Francis D’Souza, Jan Labuta, Jonathan P. Hill   +7 more
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NMR Spectroscopic Determination of Enantiomeric Excess Using Small Prochiral Molecules

The Journal of Physical Chemistry B, 2018
The use of chiral auxiliaries, which derivatize enantiomers to diastereomers, is an established technique for NMR spectroscopic analysis of chirality and enantiomeric excess ( ee). Here we report that some small prochiral molecules exhibit ee-dependent splitting of 1H NMR signals at room temperature based on acid/base interactions with chiral analytes,
Shinsuke Ishihara, Jan Labuta, Zdeněk Futera, Shigeki Mori, Hisako Sato, Katsuhiko Ariga, Jonathan P. Hill   +6 more
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Measurement of Enantiomeric Excess by Kinetic Resolution and Mass Spectrometry

Angewandte Chemie International Edition, 1999
New applications for your mass spectrometer-use it to measure enantiomeric excess! The enantiomeric content of very small quantities of chiral alcohols and amines has been determined by derivatization with chiral acylating agents in which mass is correlated to absolute configuration.
Jianhua, Guo, Jiangyue, Wu, Gary, Siuzdak, M G, Finn   +3 more
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Catalyst–substrate helical character matching determines enantiomeric excess

Tetrahedron, 2005
Abstract In the framework of a helix theory recently developed for molecular chiralities and chiral interactions, it is further proposed that for an asymmetric reaction to be highly enantioselective, the helical characters, that is, the local energies of electrons on the helices, of the catalyst and the substrate complexed with it in the ...
openaire   +1 more source

π-Stacking Induced NMR Spectrum Splitting in Enantiomerically Enriched Ru(II) Complexes:  Evaluation of Enantiomeric Excess

Inorganic Chemistry, 2005
Several chiral octahedral complexes of the general formula [Ru(bpy)2 (Lig)][PF6]2 (Lig = a ligand that can participate in pi-stacking interactions such as eilatin, isoeilatin, and tpphz) were synthesized in both the racemic and enantiomerically pure/enriched forms.
Sheba D, Bergman, Moshe, Kol
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Enantiomeric Excess of a Cruciferous Phytoalexin, Spirobrassinin, and Its Enantiomeric Enrichment in an Achiral HPLC System

Journal of Natural Products, 2000
Enantiomeric purity of a cruciferous phytoalexin, spirobrassinin (1), was determined by chiral HPLC analysis. The enantiomeric excesses of two natural spirobrassinin fractions separated by nonchiral chromatography were considerably different. A significant enantiomeric enrichment was observed during the nonchiral chromatographic separation of an ...
K, Monde, N, Harada, M, Takasugi, P, Kutschy, M, Suchy, M, Dzurilla   +5 more
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High-throughput assay for determining enantiomeric excess of chiral diols, amino alcohols, and amines and for direct asymmetric reaction screening

Nature Protocols, 2020
E. Shcherbakova, T. James, P. Anzenbacher   +2 more
semanticscholar   +1 more source

NMR methods for determination of enantiomeric excess.

Enantiomer, 2002
With the dramatic recent growth in importance of asymmetric syntheses, new applications or approaches for analyses of enantiomeric excess (% e.e.) of samples continue to become more essential. Nuclear magnetic resonance (NMR) spectroscopy provides a wide range of powerful methods which are complementary to chromatographic or electrophoretic-based ...
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Enhancement of Enantiomeric Excess by Ligand Distortion

Journal of the American Chemical Society, 2001
K B, Lipkowitz, S, Schefzick, D, Avnir
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