Results 171 to 180 of about 10,075 (214)
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Enantiomeric Excesses in Meteoritic Amino Acids
Science, 1997Gas chromatographic-mass spectral analyses of the four stereoisomers of 2-amino-2,3-dimethylpentanoic acid (DL-α-methylisoleucine and DL-α-methylalloisoleucine) obtained from the Murchison meteorite show that the L enantiomer occurs in excess (7.0 and 9.1%, respectively) in both of the enantiomeric pairs.
J R, Cronin, S, Pizzarello
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Determination of enantiomeric excess by capillary electrophoresis
Electrophoresis, 2000Capillary electrophoresis (CE) is becoming an established method for the determination of chiral trace impurities. This paper provides an overview of the state of the art of CE for such determinations. Detection limits of 0.1% impurity is widely accepted as a minimum requirement for chiral trace impurity determinations.
L G, Blomberg, H, Wan
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Sensing of enantiomeric excess in chiral carboxylic acids
Chemical Communications, 2015Cinchona-derived fluorescent molecules are used in a cross-reactive sensor array for the sensing of enantiomeric excess (ee) in carboxylate drugs analysis.
Ali, Akdeniz +3 more
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Recent Advances in the Measurement of Enantiomeric Excesses
ChemInform, 2002AbstractFor Abstract see ChemInform Abstract in Full Text.
Masaki Tsukamoto, Henri B. Kagan
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Enantiomeric Excess of Amino Acids in Hydrothermal Environments
Origins of Life and Evolution of Biospheres, 2005In a simulated hydrothermal environment allowing fluid circulation between hot and cold regions repeatedly, D- and L-alanine molecules were racemized differently depending upon the concentration of alanine, whether D or L, present in the solution. In particular, the relative population of L-alanine was slightly more enhanced compared to that of D ...
Atsushi, Nemoto +5 more
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Optical purity, enantiomeric excess and the Horeau effect
Organic & Biomolecular Chemistry, 2020Optical purity (op) and enantiomeric excess (ee) become equal when either heterochiral dimerization constant is twice that of homochiral dimerization constant or specific rotations of monomer and dimer are equal.
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Direct 1H NMR determination of the enantiomeric excess of carnitine
The Analyst, 1988The 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
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Rapid determination of enantiomeric excess: a focus on optical approaches
Chem. Soc. Rev., 2012High-throughput screening (HTS) methods are becoming increasingly essential in discovering chiral catalysts or auxiliaries for asymmetric transformations due to the advent of parallel synthesis and combinatorial chemistry. Both parallel synthesis and combinatorial chemistry can lead to the exploration of a range of structural candidates and reaction ...
Diana, Leung +2 more
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Measurement of Enantiomeric Excess Using Molecularly Imprinted Polymers
Organic Letters, 2002[reaction: see text] A new method is presented for the measurement of enantiomeric excess (ee) utilizing molecularly imprinted polymers (MIPs). The method is demonstrated to be accurate and rapid, as the ee values can be calculated from straightforward concentration measurements.
Yizhao, Chen, Ken D, Shimizu
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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 +5 more
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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 +5 more
openaire +2 more sources