Results 231 to 240 of about 667,303 (272)

Determination of enantiomeric excess by chiral liquid chromatography without enantiomerically pure starting standards

Biomedical Chromatography, 2012
ABSTRACTA facile approach for the enantiomeric excess determination of enantiomeric mixtures without the necessity of pure enantiomer standards is presented. Promethazine and trimeprazine commercial nonracemic mixtures were used as cases study to probe the validity of the method.
F G, Sánchez, A, Navas Díaz, E, Sánchez Torreño, A, Aguilar, I, Medina Lama, M, Algarra   +5 more
openaire   +2 more sources

Asymmetric Synthesis. Kinetic Amplification of Enantiomeric Excess

Comments on Inorganic Chemistry, 1987
Abstract The efficiency of an asymmetric synthetic reaction is measured by what is called the enantiomeric excess (e.e.). It is commonly assumed that this is a unique quantity for a given asymmetric reaction under specified conditions. The purpose of this Comment is to show that this is not necessxily so, and that, under certain circumstances, e.e.
Steven Bergens, B. Bosnich
openaire   +1 more source

ChemInform Abstract: Rapid Enantiomeric Excess Determination

ChemInform, 2013
AbstractReview: 29 refs.
openaire   +1 more source

Recent Advances in the Measurement of Enantiomeric Excesses

Advanced Synthesis & Catalysis, 2002
The elaboration of an ever increasing number of chiral catalysts or reagents demands fast and sensitive methods to measure enantiomeric excesses of the products. This review discusses the various ways to solve these problems. Mass spectrom- etry, chromatographic or chiroptical methodologies, fluorescence, liquid crystals, enzymatic methods, and ...
Masaki Tsukamoto, Henri B. Kagan
openaire   +2 more sources

Rapid Determination of Enantiomeric Excess Using Infrared Thermography

Organic Process Research & Development, 2002
Infrared thermography (IRT) is presented as a novel technique to screen a potentially large number of asymmetric catalysts or substrates in a high-throughput fashion.
Nicolas Millot, Phil Borman, Mike S. Anson, Ian B. Campbell, Simon J. F. Macdonald, Mahmoud Mahmoudian   +5 more
openaire   +1 more source

Determination of enantiomeric excess using Raman optical activity

Journal of Raman Spectroscopy, 1995
AbstractA simple method for the determination of enantiomeric excess is described. It is based on depolarized Raman optical activity (ROA) measurements in right‐angle scattering employing the incident ciruclar polarization (ICP) modulation approach. The accuracy of this method was assessed utilizing α‐pinene as a chiral test compound. The four α‐pinene
Lutz Hecht, Anthony L. Phillips, Laurence D. Barron   +2 more
openaire   +1 more source

Direct 1H NMR determination of the enantiomeric excess of carnitine

The Analyst, 1988
The enantiomeric purity of carnitine may be determined without any derivatisation of the molecule. Preparations of aqueous mixtures containing stereochemically pure L-malic acid, carnitine and europium trichloride lead to the formation of a complex in which the trimethylammonium groups of D- and L-carnitine are diastereotopic.
J, Bounoure, J, Souppe
openaire   +2 more sources

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
openaire   +2 more sources

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
openaire   +1 more source

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
openaire   +2 more sources