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Journal articles on the topic 'Enantiomers'
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1
Zhou, Juan, Qiao Chen, Li-lan Wang, Yong-hua Wang, and Ying-zi Fu. "Chiral Discrimination of Tryptophan Enantiomers via (1R, 2R)-2-Amino-1, 2-Diphenyl Ethanol Modified Interface." International Journal of Electrochemistry 2011 (2011): 1–6. http://dx.doi.org/10.4061/2011/502364.
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The paper reported that a simple chiral selective interface constructed by (1R, 2R)-2-amino-1, 2-diphenyl ethanol had been developed to discriminate tryptophan enantiomers. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the characteristic analysis of the electrode. The results indicated that the interface showed stable and sensitive property to determine the tryptophan enantiomers. Moreover, it exhibited the better stereoselectivity for L-tryptophan than that for D-tryptophan. The discrimination characteristics of the chiral selective interface for discriminating tryptophan enantiomers, including the response time, the effect of tryptophan enantiomers concentration, and the stability, were investigated in detail. In addition, the chiral selective interface was used to determine the enantiomeric composition of L- and D-tryptophan enantiomer mixtures by measuring the relative change of the peak current as well as in pure enantiomeric solutions. These results suggested that the chiral selective interface has the potential for enantiomeric discrimination of tryptophan enantiomers.
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Coles, Simon, David Davies, Michael Hursthouse, Serkan Yeşilot, Bünyemin Çoşut, and Adem Kılıç. "Absolute structure determination as a reference for the enantiomeric resolution of racemic mixtures of cyclophosphazenes via chiral high-performance liquid chromatography." Acta Crystallographica Section B Structural Science 65, no. 3 (May 2, 2009): 355–62. http://dx.doi.org/10.1107/s0108768109006120.
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Reversed-phase chiral high-performance liquid chromatography (HPLC) is a potentially powerful technique for the enantiomeric resolution of racemic mixtures, although the elution order of enantiomers is only relative and it is necessary to fully characterize reference systems for this method to provide absolute configurational information. The enantiomeric resolution of a series of racemic di-spiro cyclotriphosphazene derivatives, N3P3 X 2[O(CH2)3NH]2 (X = Cl, Ph, SPh, NHPh, OPh) [(1)–(5), respectively] was carried out by reversed-phase chiral HPLC on a commercially available Pirkle-type chiral stationary phase (R,R)-Whelk-01 using 85:15 (v/v) hexane–thf as the mobile phase. The absolute configurations of the resulting enantiomers of compounds (3) (X = SPh) and (5) (X = OPh) were determined unambiguously by X-ray crystallography. For both (3) and (5) it was found that the SS enantiomer eluted before the RR enantiomer, indicating a convenient method to determine the absolute configurations of enantiomers of this series of cyclophosphazene derivatives and providing the first set of enantiomeric reference compounds for cyclophosphazene derivatives. These structures demonstrate an interesting anomaly in that the pair of enantiomers of (3) crystallize in enantiomorphically paired space groups whilst, under the same conditions, the solid-state forms of the enantiomers of (5) form structures in Sohncke space groups that are not enantiomorphous.
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Saufi, Ahmad, Cosima B. I. von Heimendahl, A. Wilhelm Alfermann, and Elisabeth Fuss. "Stereochemistry of Lignans in Phaleria macrocarpa (Scheff.) Boerl." Zeitschrift für Naturforschung C 63, no. 1-2 (February 1, 2008): 13–16. http://dx.doi.org/10.1515/znc-2008-1-203.
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Phaleria macrocarpa (Scheff.) Boerl., a member of the Thymelaeaceae, is traditionally used in Indonesia as medicinal plant against cancer. In this context, we isolated the lignans pinoresinol, lariciresinol and matairesinol from different parts of this plant. The enantiomeric composition of these lignans was determined by chiral column analysis. Pinoresinol and lariciresinol were mixtures of both enantiomers with (79 ± 4)% and (55 ± 6)% enantiomeric excess for the (−)-enantiomers, respectively, whereas matairesinol was found as pure (+)-enantiomer.
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Costa, Ana Rita, Virgínia M. F. Gonçalves, Bruno B. Castro, João Soares Carrola, Ivan Langa, Ariana Pereira, Ana Rita Carvalho, Maria Elizabeth Tiritan, and Cláudia Ribeiro. "Toxicity of the 3,4-Methylenedioxymethamphetamine and Its Enantiomers to Daphnia magna after Isolation by Semipreparative Chromatography." Molecules 28, no. 3 (February 2, 2023): 1457. http://dx.doi.org/10.3390/molecules28031457.
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MDMA (3,4-methylenedioxymethamphetamine) is a chiral psychoactive recreational drug sold in illicit markets as racemate. Studies on the impact of MDMA on aquatic organisms are scarce. While enantioselectivity in toxicity in animals and humans has been reported, none is reported on aquatic organisms. This study aimed to investigate the ecotoxicological effects of MDMA and its enantiomers in Daphnia magna. For that, enantiomers (enantiomeric purity > 97%) were separated by liquid chromatography using a homemade semipreparative chiral column. Daphnids were exposed to three concentrations of (R,S)-MDMA (0.1, 1.0 and 10.0 µg L−1) and two concentrations of (R)- and (S)-enantiomers (0.1 and 1.0 µg L−1) over the course of 8 days. Morphophysiological responses were dependent on the substance form and daphnia development stage, and they were overall not affected by the (R)-enantiomer. Changes in swimming behaviour were observed for both the racemate and its enantiomers, but enantioselective effects were not observed. Reproductive or biochemical changes were not observed for enantiomers whereas a significant decrease in acetylcholinesterase and catalase activity was noted at the highest concentration of (R,S)-MDMA (10 µg L−1). Overall, this study showed that sub-chronic exposure to MDMA racemate and its enantiomers can interfere with morphophysiological and swimming behaviour of D. magna. In general, the (R)-enantiomer demonstrated less toxicity than the (S)-enantiomer.
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Dutta, Soham, and Andrew J. Gellman. "2D Ising Model for Enantiomer Adsorption on Achiral Surfaces: L- and D-Aspartic Acid on Cu(111)." Entropy 24, no. 4 (April 18, 2022): 565. http://dx.doi.org/10.3390/e24040565.
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The 2D Ising model is well-formulated to address problems in adsorption thermodynamics. It is particularly well-suited to describing the adsorption isotherms predicting the surface enantiomeric excess, ees, observed during competitive co-adsorption of enantiomers onto achiral surfaces. Herein, we make the direct one-to-one correspondence between the 2D Ising model Hamiltonian and the Hamiltonian used to describe competitive enantiomer adsorption on achiral surfaces. We then demonstrate that adsorption from racemic mixtures of enantiomers and adsorption of prochiral molecules are directly analogous to the Ising model with no applied magnetic field, i.e., the enantiomeric excess on chiral surfaces can be predicted using Onsager’s solution to the 2D Ising model. The implication is that enantiomeric purity on the surface can be achieved during equilibrium exposure of prochiral compounds or racemic mixtures of enantiomers to achiral surfaces.
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Wang, Peng, Donghui Liu, Xu Gu, Shuren Jiang, and Zhiqiang Zhou. "Quantitative Analysis of Three Chiral Pesticide Enantiomers by High-Performance Column Liquid Chromatography." Journal of AOAC INTERNATIONAL 91, no. 5 (September 1, 2008): 1007–12. http://dx.doi.org/10.1093/jaoac/91.5.1007.
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Abstract Methods for the enantiomeric quantitative determination of 3 chiral pesticides, paclobutrazol, myclobutanil, and uniconazole, and their residues in soil and water are reported. An effective chiral high-performance liquid chromatographic (HPLC)-UV method using an amylose-tris(3,5-dimethylphenylcarbamate; AD) column was developed for resolving the enantiomers and quantitative determination. The enantiomers were identified by a circular dichroism detector. Validation involved complete resolution of each of the 2 enantiomers, plus determination of linearity, precision, and limit of detection (LOD). The pesticide enantiomers were isolated by solvent extraction from soil and C18 solid-phase extraction from water. The 2 enantiomers of the 3 pesticides could be completely separated on the AD column using n-hexane isopropanol mobile phase. The linearity and precision results indicated that the method was reliable for the quantitative analysis of the enantiomers. LODs were 0.025, 0.05, and 0.05 mg/kg for each enantiomer of paclobutrazol, myclobutanil, and uniconazole, respectively. Recovery and precision data showed that the pretreatment procedures were satisfactory for enantiomer extraction and cleanup. This method can be used for optical purity determination of technical material and analysis of environmental residues.
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León-González, María Eugenia, and Noelia Rosales-Conrado. "Enantioselective determination of ibuprofen residues by chiral liquid chromatography: a systematic study of enantiomeric transformation in surface water and sediments." Environmental Chemistry 13, no. 4 (2016): 656. http://dx.doi.org/10.1071/en15146.
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Environmental context Ibuprofen, a common anti-inflammatory drug and one of many pharmaceuticals sold as a mixture of enantiomers, has recently been found in river and surface waters. There are, however, few analytical methods able to separate and accurately measure ibuprofen enantiomers in environmental matrices. This study reports a method for quantifying ibuprofen enantiomers in sediments and surface water, and applies it to shed light on the degradation and fate of the enantiomers in aquatic systems. Abstract The enantioselective composition of ibuprofen in sediments in contact with surface water was evaluated over 168h in the presence and absence of light. Multivariate techniques applied for the evaluation of enantiomeric fraction (EF) and recoveries of enantiomers in water and sediments show differences in the EF and composition of each enantiomer. In sediments, differences in the EF are a result of the presence or absence of light, whereas in water it is attributable to degradation of the two enantiomers with time. To achieve enantioselective separation of ibuprofen in surface water and sediments, a clean-up and preconcentration procedure using solid phase extraction combined with a direct chiral liquid chromatography–ultraviolet method was developed. Quantitation limits of the proposed method were between 0.12 and 0.15µgg–1 for each enantiomer in sediments, and between 2.4 and 3.0µgL–1 in surface water. Intra- and inter-day precisions were between 5.1 and 8.9%. Multivariate techniques can be useful to identify enantiomeric modifications and to select the variables that should be used for modelling such transformations.
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Tok, Kenan Can, Mehmet Gumustas, Giorgi Jibuti, Halit Sinan Suzen, Sibel A. Ozkan, and Bezhan Chankvetadze. "The Effect of Enantiomer Elution Order on the Determination of Minor Enantiomeric Impurity in Ketoprofen and Enantiomeric Purity Evaluation of Commercially Available Dexketoprofen Formulations." Molecules 25, no. 24 (December 11, 2020): 5865. http://dx.doi.org/10.3390/molecules25245865.
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In a recent study, opposite enantiomer elution order was observed for ketoprofen enantiomers on two amylose-phenylcarbamate-based chiral columns with the same chemical composition of the chiral selector but in one case with coated while in the other with an immobilized chiral selector. In the present study, the influence of this uncommon effect on method validation parameters for the determination of minor enantiomeric impurity in dexketoprofen was studied. The validated methods with two alternative elution orders for enantiomers were applied for the evaluation of enantiomeric impurity in six marketed dexketoprofen formulations from various vendors. In most of these formulations except one the content of enantiomeric impurity exceeded 0.1% (w/w).
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Hocking, Martin B., and Aga Z.-Q. Khan. "Chromatographic enantiomer separation and circular dichroism (CD) spectra of three 4-endosubstituted-3,6-diphenyl-3,6-phenylphosphorylcyclohexenes." Canadian Journal of Chemistry 85, no. 9 (September 1, 2007): 600–602. http://dx.doi.org/10.1139/v07-088.
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Three enantiomeric pairs of Diels–Alder adducts of 2,5-diphenylphosphole-1-oxide have been resolved by elution of each of the enantiomers with 95% ethanol from a swollen microcrystalline triacetylcellulose stationary phase. The degree of separation achieved in each case was confirmed by comparing the absorbance maximum of the UV spectrum of each separated enantiomer with that of a similar concentration of the relevant racemic mixture. The circular dichroism (CD) spectrum of each of the separated enantiomers was recorded, and spectral parameters are listed.Key words: enantiomer separations, three 4-endosubstituted phosphorus-bridged cyclohexenes (phosphanorbornenes), ethanol, microcrystalline triacetylcellulose.
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Kant, Ravi, Ramesh Babu Bodla, Rubina Bhutani, and Garima Kapoor. "Enantioselective Box Behenken Optimized HPLC-DAD Method for the Simultaneous Estimation of Alogliptin Enantiomorphs in Pharmaceutical For mulations and their Pharmacokinetic Study in Rat Plasma." Advanced Pharmaceutical Bulletin 9, no. 1 (February 21, 2019): 147–58. http://dx.doi.org/10.15171/apb.2019.018.
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Purpose: A stereoselective high performance liquid chromatographic analytical method withphotodiode array detector was developed and validated as per the International Conferenceon Harmonization (ICH) guidelines for the determination of alogliptin (ALO) enantiomers informulations and rat plasma.Methods: Enantiomeric separation was performed on a Phenomenex Lux Cellulose-2 chiralcolumn. Box-Behnken design was used to identify the optimum conditions of the threeindependent variables for the desired output responses.Results: The HPLC peaks of ALO enantiomers and the internal standard pioglitazone wereachieved before 8 min with a resolution of 0.77 min between R and S enantiomer and resolutionof more than 2.0 between each enantiomer and pioglitazone (internal) with more than 95%recovery. The linearity range and the limit of quantification of both the enantiomers in rat plasmawere 10-70 ng mL-1 and 1.2 ng mL-1 respectively.Conclusion: The developed method after validation was successfully applied for estimation ofALO enantiomers in formulations. Single oral dose of 25 mg of the ALO racemate tablets wereadministered to a group of 6 healthy rats for a comparative pharmacokinetic study of both theenantiomers.
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Gładkowski, Witold, Aleksandra Włoch, Aleksandra Pawlak, Angelika Sysak, Agata Białońska, Marcelina Mazur, Paweł Mituła, Gabriela Maciejewska, Bożena Obmińska-Mrukowicz, and Halina Kleszczyńska. "Preparation of Enantiomeric β-(2′,5′-Dimethylphenyl)Bromolactones, Their Antiproliferative Activity and Effect on Biological Membranes." Molecules 23, no. 11 (November 20, 2018): 3035. http://dx.doi.org/10.3390/molecules23113035.
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Three novel enantiomeric pairs of bromolactones possesing a 2,5-dimethylphenyl substituent at the β-position of the lactone ring have been synthesized from corresponding enantiomeric (E)-3-(2′,5′-dimethylphenyl)hex-4-enoic acids (4) by kinetically controlled bromolactonization with N-bromosuccinimide (NBS). γ-Bromo-δ-lactones (5) were isolated as the major products. Absolute configurations of stereogenic centers of γ-bromo-δ-lactones (5) were assigned based on X-ray analysis; configurations of cis δ-bromo-γ-lactones (6) and trans δ-bromo-γ-lactones (7) were determined based on mechanism of bromolactonization. Synthesized compounds exhibited significant antiproliferative activity towards the four canine cancer cell lines (D17, CLBL-1, CLB70, and GL-1) and one human cancer line (Jurkat). Classifying the compounds in terms of activity, the most active were enantiomers of trans δ-bromo-γ-lactones (7) followed by enantiomers of cis isomer (6) and enantiomeric γ-bromo-δ-lactones (5). Higher activity was observed for all stereoisomers with S configuration at C-4 in comparison with their enantiomers with 4R configuration. Synthesized compounds did not induce hemolysis of erythrocytes. The results of the interaction of bromolactones with red blood cell membranes suggest that these compounds incorporate into biological membranes, concentrating mainly in the hydrophilic part of the bilayer but have practically no influence on fluidity in the hydrophobic region. The differences in interactions with the membrane between particular enantiomers were observed only for γ-lactones: stronger interactions were found for enantiomer 4R,5R,6S of cis γ-lactone (6) and for enantiomer 4S,5R,6S of trans γ-lactone (7).
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Szabó-Szentjóbi, Hajnalka, Anna Márton, Dávid Pál, Gergő Dargó, Áron Szigetvári, Csaba Szántay, György Tibor Balogh, Tünde Tóth, and Péter Huszthy. "Synthesis, Fluorescence and NMR Spectroscopic Studies of a Novel Phosphinoxido-18-crown-6 Ether Containing an Anthracene Fluorophore Unit." Periodica Polytechnica Chemical Engineering 64, no. 1 (October 17, 2019): 37–45. http://dx.doi.org/10.3311/ppch.14646.
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The synthesis of the (R,R) and (S,S) enantiomers of a new enantiopure monophospha-18-crown-6 ether (1), which contains an anthracene fluorophore unit and methyl groups at its stereogenic centers, was accomplished. The structure of one enantiomer ((S,S)-1) was studied using one-dimensional (1H, 13C{1H}, and 31P{1H}) and two-dimensional NMR spectra. Because (R,R)-1 and (S,S)-1 can act as new fluorescent chemosensors, we examined their enantiomeric differentiation abilities toward the enantiomers of protonated chiral primary amines and amino acid esters (PEA, 1-NEA, PGME, PAME) using UV-Vis and fluorescence spectroscopies. These monophospha-crown ethers showed moderate enantiomeric discrimination abilities.
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Antonsen, Simen, Erling B. Monsen, Kirill Ovchinnikov, Jens M. J. Nolsøe, Dag Ekeberg, Jette E. Kristiansen, Dzung B. Diep, and Yngve Stenstrøm. "Synthesis of the Enantiomers of Thioridazine." SynOpen 04, no. 01 (January 2020): 12–16. http://dx.doi.org/10.1055/s-0039-1690834.
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Thioridazine, a well-known antipsychotic drug, has shown promising effects on several bacterial strains (including Mycobacterium tuberculosis and methicillin-resistant Staphylococcus aureus). Suppressive effects towards selected cancer cell-lines have also been reported. However, due to adverse effects, the compound is no longer in use for the primary indication. More recent research has demonstrated that these side effects are limited to one of the two enantiomers, (+)-thioridazine. The question arises to whether the beneficial effects of thioridazine are limited to one enantiomer, or if (–)-thioridazine can prove itself to be useful in its pure enantiomeric state. The published procedures on the synthesis of the optically pure enantiomers of thioridazine were found to be unsatisfactory, either due to low optical purity, high cost, or problems scaling up. Herein, we have used an auxiliary-based strategy for the total synthesis of both enantiomers in high optical purity and good overall yield. The strategy can easily be scaled up. Both enantiomers were tested against several bacteria. Comparison of the racemic mixture, (–)-thioridazine and its (+)-antipode revealed that they have the same antimicrobial effects. Thus, the non-toxic enantiomer, (–)-thioridazine, can prove useful in this role and should be investigated further.
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Gal, Joseph. "Single-Isomer Science: The Phenomenon and Its Terminology." CNS Spectrums 7, S1 (April 2002): 8–13. http://dx.doi.org/10.1017/s1092852900028546.
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ABSTRACTSingle-isomer drugs are of great importance in modern therapeutics. In this article, the basics of the underlying phenomenon are explained. Some molecules are chiral, ie, their mirror image is not superposable on the original. The most common element producing molecular chirality is a chiral center, typically a carbon atom carrying four different groups. The mirror-image molecules are termed enantiomers, but the less specific terms stereoisomers and isomers are also used. A substance consisting of only one of the two enantiomers is a single enantiomer or single isomer, and the 1:1 mixture of the enantiomers is the racemic mixture or racemate. A graphical convention that conveys the three-dimensional aspects of chiral molecules drawn in two dimensions, as well as two nongraphical conventions, based on optical rotation and configuration, are used to identify enantiomers. Optical rotation is a physical property of single enantiomers and involves rotation of the plane of plane-polarized light, each pure enantiomer rotating with equal magnitude but in the opposite direction (dextro and levo). Configuration is the actual arrangement in space of the atoms of chiral molecules. Two systems of indicating configuration are in use. One employs D and L to denote the respective enantiomers, and is applicable only to α-amino acids and carbohydrates. The other is a universal system using R and S as descriptors for the two possible arrangements, respectively, of the atoms around the chiral center. Interest in chiral drugs stems from the frequently observed biological differences between enantiomers. Such enantioselectivity is the result of different interactions of the drug enantiomers with target receptors that are themselves chiral and single-enantiomeric.
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Almeida, Ana Sofia, Bárbara Silva, João Pedro Silva, José Augusto Pereira, Fernando Remião, and Carla Fernandes. "Semi-Preparative Separation, Absolute Configuration, Stereochemical Stability and Effects on Human Neuronal Cells of MDPV Enantiomers." Molecules 28, no. 5 (February 24, 2023): 2121. http://dx.doi.org/10.3390/molecules28052121.
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Synthetic cathinones, such as 3,4-methylenedioxypyrovalerone (MDPV), are widely abused due to their psychostimulant effects. As they are chiral molecules, studies of their stereochemical stability (racemization can occur in certain temperatures and acidic/basic environments) and of their biological and/or toxicity effects (enantiomers might display different properties) are of great relevance. In this study, the liquid chromatography (LC) semi-preparative enantioresolution of MDPV was optimized to collect both enantiomers with high recovery rates and enantiomeric ratio (e.r.) values. The absolute configuration of the MDPV enantiomers was determined by electronic circular dichroism (ECD) with the aid of theoretical calculations. The first eluted enantiomer was identified as S-(-)-MDPV and the second eluted enantiomer was identified as R-(+)-MDPV. A racemization study was performed by LC-UV, showing enantiomers’ stability up to 48 h at room temperature and 24 h at 37 °C. Racemization was only affected by higher temperatures. The potential enantioselectivity of MDPV in cytotoxicity and in the expression of neuroplasticity-involved proteins—brain-derived neurotrophic factor (BDNF) and cyclin-dependent kinase 5 (Cdk5)—was also evaluated using SH-SY5Y neuroblastoma cells. No enantioselectivity was observed.
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Buchcic-Szychowska, Aleksandra, Stanisław Leśniak, and Michał Rachwalski. "Chiral Aziridine Phosphines as Highly Effective Promoters of Asymmetric Rauhut–Currier Reaction." Symmetry 14, no. 8 (August 8, 2022): 1631. http://dx.doi.org/10.3390/sym14081631.
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A series of chiral enantiomerically pure aziridines containing a phosphine moiety were synthesized and successfully applied as organocatalysts in asymmetric intramolecular Rauhut–Currier reactions of p-quinone derivatives. The desired chiral phenols were achieved in high chemical yields and with satisfactory values of enantiomeric excess (up to 98% ee, in some cases). The stereochemical course of the title reaction may be controlled by the use of an appropriate enantiomer of the catalyst. The individual enantiomers of the organocatalyst led to the formation of specific enantiomers of the chiral product.
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Song, Mei, Claudio Fuentes, and Elizabeth Tomasino. "Chemo-diversity of chiral monoterpenes in different styles of Riesling wine from different regions." OENO One 56, no. 3 (July 22, 2022): 155–65. http://dx.doi.org/10.20870/oeno-one.2022.56.3.4834.
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Monoterpenes are important characteristic compounds for aromatic white wines, including Riesling, but their enantiomer composition has been little explored in wine. Enantiomers can differ depending on region and style, as they are sensitive to environmental factors, and thus could be used for wine authentication. Thirteen monoterpene isomers were quantified by HS-SPME-MDGC-MS in fifty-four commercial Riesling wines from three wine styles (dry, medium dry and medium sweet) and four well-established wine-growing regions in Germany, France (Alsace) and the USA (New York and Oregon). Significant differences were found for nine out of the 13 enantiomers among different regions and eight enantiomers among styles. X-Y scatterplots of enantiomer pair concentrations, with excellent fitted lines, implies low variation of enantiomeric ratios from each region. The study suggests that wines from different regions and styles were differentiated by chiral monoterpene profiles. Chiral monoterpene analyses could provide supporting information in Riesling wine authentication by offering an objective measure of flavour quality, as these compounds are key compounds for Riesling aroma and flavor.
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Mostafa, Gamal A. E., Mohammed M. Hefnawy, and Abdulrahman El-Majed. "Separation and Determination of Clenbuterol by HPLC Using a Vancomycin Chiral Stationary Phase." Journal of AOAC INTERNATIONAL 92, no. 3 (May 1, 2009): 824–29. http://dx.doi.org/10.1093/jaoac/92.3.824.
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Abstract Enantiomers of clenbuterol were separated by a new HPLC method on a chiral column. Enantiomeric resolution was achieved on a vancomycyin macrocyclic antibiotic chiral stationary phase known as chirobiotic V with UV detection at 247 nm. The polar ionic mobile phase consisting of methanoltriethylamineglacial acetic acid (100 + 0.05 + 0.025, v/v/v), was used at a flow rate of 1.0 mL/min. The method was validated for linearity, accuracy, precision, and robustness. Standard linear calibration curves were established for the R-() and S-(+) enantiomers over the range of 0.220 g/mL, and an average recovery of 98.0 and a mean relative standard deviation of 1.5 were obtained at 5.0 g/mL. The lower limit of detection was 0.05 g/mL for each enantiomer. The mean recovery for R-() and S-(+)-clenbuterol enantiomers from plasma was 91.097.0 at 0.2020 g/mL. The method was successfully used to identify and quantify the clenbuterol enantiomers in human plasma.
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VS, PRAGADHEESH, ANJU YADAV, and CHANDAN S. CHANOTIYA. "Chiral differentiation of terpenoids in bergamot mint (Mentha citrata) cultivar Kiran: A non-menthol mint essential oil." Journal of Medicinal and Aromatic Plant Sciences 42, no. 2 (July 1, 2020): 138–44. http://dx.doi.org/10.62029/jmaps.v42i2.vs.
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Mentha citrata, popularly known as bergamot mint,is one of the mint species which does not possess menthol, a terpenoid chemical constituent that gives the name Mentha to the genus. CSIR-CIMAP has developed a cultivar cv. Kiran by induced mutagenesis. Gas chromatographic (GC) analysis of the essential oil of this cultivar shows linalool (44.9 %) and linalyl acetate (28.7%) as the major constituents. Further, the enantioselective GC analysis of the essential oil to determine the enantiomeric ratio of linalool and linalyl acetate indicate that (R)-(-)-linalool is in 78.8% excess over its enantiomer, whereas (R)-(-)-linalyl acetate is present as a single enantiomer. Other chiral terpenoids resolved in the enantioselective GC analysis are (1S)-(-)-ß-pinene as the major exclusive enantiomer with 93.0% enantiomeric excess and (-)-sabinene with 60.2% enantiomeric excess than its enantiomers. The significance of enantiomer separation and enantiomeric excess of chiral terpenoids in the essential oil of M. citrata cv. Kiran is of great importance in ascertaining the authenticity of this essential oil.
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Wu, Xiuli, Yange Zhang, Wenzhen Li, Tingmei Liu, Yu Yang, Yijie Wang, and Yiwen Zhang. "A Validated LC Method for the Enantiomeric Separation of EAI045 on Chiral Stationary Phase." Journal of Chromatographic Science 58, no. 6 (April 18, 2020): 562–68. http://dx.doi.org/10.1093/chromsci/bmz125.
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Abstract A simple and accurate chiral liquid chromatographic method was developed for enantiomeric resolution and determination of 2-(5-fluoro-2-hydroxyphenyl)-2-(1-oxo-2,3-dihydro-1H-isoindol-2-yl)-N-(1,3-thiazol-2-yl)acetamide (EAI045). The enantiomers of EAI045 were baseline resolved on a Chiralpak AD-H (250 mm × 4.6 mm, 5 μm) column using a mobile phase system containing n-hexane: 2-propanol (75: 25 v/v) at a flow rate of 1 mL min−1 at 30°C. The eluted analytes were subsequently detected with an ultraviolet detector at 254 nm. The effects of organic modifiers and temperature on the enantioselectivity and resolution of the enantiomers were evaluated. The calibration curves were plotted within the concentration range between 2 and 600 μg mL−1 (n = 11), and recoveries between 98.74% and 101.52% were obtained, with relative standard deviation < 1.4%. The limit of detection and limit of quantitation for R-enantiomer were 0.94 and 3.07 μg mL−1 and for S-enantiomer were 0.86 and 2.84 μg mL−1, respectively. The validated method was found to be suitable for enantiomeric separation and sufficiently accurate for the determination of enantiomeric purity of EAI045 in bulk drugs.
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Yang, S. K., M. Mushtaq, H. B. Weems, D. W. Miller, and P. P. Fu. "Stereoselective formation and hydration of 12-methylbenz[a]anthracene 5,6-epoxide enantiomers by rat liver microsomal enzymes." Biochemical Journal 245, no. 1 (July 1, 1987): 191–204. http://dx.doi.org/10.1042/bj2450191.
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The K-region trans-5,6-dihydrodiols formed in the metabolism of 12-methylbenz[a]anthracene (12-MBA) by liver microsomal preparations from untreated, phenobarbital-treated and 3-methylcholanthrene-treated male Sprague-Dawley rats were found by chiral stationary-phase h.p.l.c. (c.s.p.-h.p.l.c.) analyses to contain (5S,6S)/(5R,6R) enantiomer ratios of 93:7, 88:12 and 97:3 respectively. The absolute stereochemistry of a 12-MBA trans-5,6-dihydrodiol enantiomer was elucidated by the exciton-chirality c.d. method. The 5,6-epoxides formed in the metabolism of 12-MBA by liver microsomal preparations from untreated, phenobarbital-treated and 3-methylcholanthrene-treated male Sprague-Dawley rats in the presence of the epoxide hydrolase inhibitor 3,3,3-trichloropropylene 1,2-oxide were isolated from a mixture of metabolites by normal-phase h.p.l.c., and their (5S,6R)/(5R,6S) enantiomer ratios were found by c.s.p.-h.p.l.c. analyses to be 73:27, 78:22 and 99:1 respectively. The absolute configurations of 12-MBA 5,6-epoxide enantiomers, resolved by c.s.p.-h.p.l.c., were determined via high-resolution (500 MHz) proton-n.m.r. and c.d. spectral analyses of the two isomeric methoxylation products derived from each of the 12-MBA 5,6-epoxide enantiomers. Enantiomeric pairs of the two methoxylation products were resolved by c.s.p.-h.p.l.c. The results indicate that enantiomeric 5S,6R-epoxide and 5S,6S-dihydrodiol were the major enantiomers preferentially formed in the metabolism at the K-region 5,6-double bond of 12-MBA by all three rat liver microsomal preparations. Optically pure 12-MBA 5S,6R-epoxide was hydrated predominantly at the C(6) position (R centre) to form 12-MBA trans-5,6-dihydrodiol with a (5S,6S)/(5R,6R) enantiomer ratio of 97:3. However, optically pure 12-MBA 5R,6S-epoxide was hydrated nearly equally at both C(5) and C(6) positions to form 12-MBA trans-5,6-dihydrodiol with a (5S,6S)/(5R,6R) enantiomer ratio of 57:43.
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Li, Zhi Wei, Xing Jia, Chun Mei Xu, Lei Liu, and De Cai Fu. "Chiral Separation of Amlodipine and its Enantiomer on a Molecularly Imprinted Polymer-Based Stationary Phase." Advanced Materials Research 706-708 (June 2013): 36–39. http://dx.doi.org/10.4028/www.scientific.net/amr.706-708.36.
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A new chiral stationary phase for amlodipine (3-ethyl 5-methyl-2 -[(-2-(aminoethoxymethyl)-4-(2-chlorophenyl)-1,4-dihydro-6-methyl-3,5-pyridinedicarboxylate) based on a molecularly imprinted polymer has been prepared by radiation polymerization method and used for chromatographic separation of the chiral enantiomers. The effects on the separation of mobile phase and flow rate were investigated, and the optimum conditions for HPLC were shown to be: mobile phase, chloroform; flow rate, 0.3 ml min-1; at room temperature. The results has shown that the amlodipine-imprinted polymer was capable of recognizing the enantiomeric difference between the template and its R-enantiomer, whereas the non-imprinted and thermal polymerization polymer have no chiral recognition ability for the enantiomers.
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Hefnawy, Mohammed M., Mona M. Al-Shehri, Mohammed A. Abounassif, and Gamal A. E. Mostafa. "Enantioselective Quantification of Atenolol in Mouse Plasma by High Performance Liquid Chromatography Using a Chiral Stationary Phase: Application to a Pharmacokinetic Study." Journal of AOAC INTERNATIONAL 96, no. 5 (September 1, 2013): 976–80. http://dx.doi.org/10.5740/jaoacint.11-191.
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Abstract Enantiomeric resolution of atenolol was achieved on the HPLC vancomycin macrocyclic antibiotic chiral stationary phase Chirobiotic V. The polar ionic mobile phase consisted of methanol–glacial acetic acid–triethylamine (100 + 0.025 + 0.75, v/v/v) at a flow rate of 0.8 mL/min. Fluorescence detection at 275/305 nm for excitation and emission, respectively, was used. Plasma samples were purified using SPE on Oasis HLB cartridges. The calibration curves in plasma were linear over the range of 5–400 ng/mL (r = 0.999) for each enantiomer with an LOD of 1.0 ng/mL. The proposed method was validated in compliance with International Conference of Harmonization guidelines in terms of linearity, accuracy, precision, LOD, LOQ, and selectivity. The overall recoveries for S-(–)- and R-(+)-atenolol enantiomers from plasma were 95.0–99.5%; RSD ranged from 2.5 to 3.3%. The developed method was applied for the trace analysis of atenolol enantiomers in plasma and for the pharmacokinetic investigation of atenolol enantiomers in mouse plasma.
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Gandhi, Karan, Umang Shah, and Sandip Patel. "Drug Stereochemistry: A Prodigy For Pharmacology and Drug Development." Current Drug Discovery Technologies 17, no. 5 (December 23, 2020): 565–73. http://dx.doi.org/10.2174/1570163816666190502101803.
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Stereochemistry has evinced the importance of many chiral drugs with respect to drug designing and development. A literature review was conducted for several chiral drugs involving pharmacokinetic and pharmacodynamic parameters of their enantiomers along with their uses in certain diseased conditions. This article mainly includes the pharmacological profile review of some chiral drugs and the aspects due to which the single enantiomer is of importance as compared to the racemic mixture of the drug. This was achieved by moderating the side effects or toxic effects; or by the potentiated activity of the single enantiomer. Resolution deals with the separation of racemic compounds which shows up the credibility to obtain the desired enantiomeric properties. As isomers vary in their pharmacokinetic and pharmacodynamic profiles, chiral drugs have showcased considerable importance in the drug development process. Both the enantiomers have a different pharmacological profile in the treatment of a disease, which differentiates them from drug racemates.
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Červinka, Otakar, and Vladimír Stružka. "Preparation of both enantiomers of (1R*, 2S*)-1-cyclohexyl-1,2-propanediol from the commercial Neuberg's ketol." Collection of Czechoslovak Chemical Communications 55, no. 11 (1990): 2685–91. http://dx.doi.org/10.1135/cccc19902685.
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Both the optically pure enantiomers of (1R*, 2S*)-1-cyclohexyl-1,2-propanediol (II) were prepared from commercial (R)-(-)-1-phenyl-1-hydroxy-2-propanone (I; Neuberg's ketol). (1R, 2S)-(+)-1-Cyclohexyl-1,2-propanediol ((+)-II) was obtained in 19% total yield, its (1S, 2R)-enantiomer ((-)-II) in 8% yield. Both diols, as well as their precursors, enantiomeric (1R*, 2S*)-1-phenyl-1,2-propanediols (IIIa), are suitable chiral synthons.
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Zhang, Ping, Sheng Wang, Dongmei Shi, Yangyang Xu, Furong Yang, Xile Deng, Yuhan He, and Lin He. "Direct Enantiomeric Separation and Determination of Hexythiazox Enantiomers in Environment and Vegetable by Reverse-Phase High-Performance Liquid Chromatography." International Journal of Environmental Research and Public Health 17, no. 10 (May 15, 2020): 3453. http://dx.doi.org/10.3390/ijerph17103453.
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In the present study, the direct enantiomeric separation of hexythiazox enantiomers on Lux cellulose-1, Lux cellulose-2, Lux cellulose-3, Lux cellulose-4, Lux amylose-1 and Chirapak IC chiral columns were carefully investigated by reverse-phase high-performance liquid chromatography (RP-HPLC). Acetonitrile/water and methanol/water were used as mobile phase at a flow rate of 0.8 mL·min−1. The effects of chiral stationary phase, temperature, thermodynamic parameters, mobile phase component and mobile phase ratio on hexythiazox enantiomers separation were fully evaluated. Hexythiazox enantiomers received a baseline separation on the Lux cellulose-3 column with a maximum resolution of Rs = 2.09 (methanol/water) and Rs = 2.74 (acetonitrile/water), respectively. Partial separations were achieved on other five chiral columns. Furthermore, Lux amylose-1 and Chirapak IC had no separation ability for hexythiazox enantiomers when methanol/water was used as mobile phase. Temperature study indicated that the capacity factor (k) and resolution factor (Rs) decreased with column temperature increasing from 10 °C to 40 °C. The enthalpy (ΔH) and entropy (ΔS) involved in hexythiazox separation were also calculated and demonstrated the lower temperature contributed to better separation resolution. Moreover, the residue analytical method for hexythiazox enantiomers in the environment (soil and water) and vegetable (cucumber, cabbage and tomato) were also established with reliable accuracy and precision under reverse-phase HPLC condition. Such results provided a baseline separation method for hexythiazox enantiomers under reverse-phase conditions and contributed to an environmental and health risk assessment of hexythiazox at enantiomer level.
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Xu, Hao, Yifeng Dai, Shuyi Qiu, Baoguo Sun, and Xiangyong Zeng. "Distribution and Quantification of 1,2-Propylene Glycol Enantiomers in Baijiu." Foods 10, no. 12 (December 7, 2021): 3039. http://dx.doi.org/10.3390/foods10123039.
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Enantiomers of 1,2-Propylene glycol (1,2-PG) were investigated in 64 commercial Chinese Baijiu including soy sauce aroma-type Baijiu (SSB), strong aroma-type Baijiu (STB), and light aroma-type Baijiu (LTB), via chiral gas chromatography (β-cyclodextrin). The natural enantiomeric distribution and concentration of 1,2-PG in various baijiu were studied to evaluate whether the distribution and content of the two isomers of 1,2-PG were correlated with the aroma type and storage year. The results showed that 1,2-PG has a high enantiomeric ratio and the (S)-configuration predominated in SSB. The average S/R enantiomeric ratio of this compound in SSB was approximately 87:13 (±3.17), with an average concentration of 52.77 (±23.70) mg/L for the (S)-configuration and 8.72 (±3.63) mg/L for the (R)-enantiomer. The (R)-configuration was predominant in the STB, whereas neither (S) nor (R)-form of 1,2-PG were detected in LTB. The content of the two configurations of 1,2-PG in the JSHSJ vintage of SSB showed a wave variation, with an average S/R enantiomeric ratio of 89:11 (±1.15). The concentration of (R)-1,2-PG in XJCTJ vintage liquors showed an upward and then downward trend with aging time, with an overall downward trend, and the concentration of (S)-form showed a wavy change with an overall upward trend. Except for the LZLJ-2019 vintage where both (R) and (S)-1,2-PG were present, all other samples only existed (R)-form, and a decreasing trend of (R)-enantiomer with aging time was observed. The enantiomeric ratio of 1,2-PG might be one of the potential markers for adulteration control of Baijiu as industrial 1,2-PG usually presented in the racemic mixture. Sensory analysis revealed olfactory thresholds of 4.66 mg/L and 23.92 mg/L for the (R)- and (S)-configurations in pure water respectively. GC-O showed both enantiomers exhibited different aromatic nuances.
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Ritter, Kevin, Nikolaus Jork, Anne-Sophie Unmüßig, Maja Köhn, and Henning J. Jessen. "Assigning the Absolute Configuration of Inositol Poly- and Pyrophosphates by NMR Using a Single Chiral Solvating Agent." Biomolecules 13, no. 7 (July 19, 2023): 1150. http://dx.doi.org/10.3390/biom13071150.
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Inositol phosphates constitute a family of highly charged messenger molecules that play diverse roles in cellular processes. The various phosphorylation patterns they exhibit give rise to a vast array of different compounds. To fully comprehend the biological interconnections, the precise molecular identification of each compound is crucial. Since the myo-inositol scaffold possesses an internal mirror plane, enantiomeric pairs can be formed. Most commonly employed methods for analyzing InsPs have been geared towards resolving regioisomers, but they have not been capable of resolving enantiomers. In this study, we present a general approach for enantiomer assignment using NMR measurements. To achieve this goal, we used 31P-NMR in the presence of L-arginine amide as a chiral solvating agent, which enables the differentiation of enantiomers. Using chemically synthesized standard compounds allows for an unambiguous assignment of the enantiomers. This method was applied to highly phosphorylated inositol pyrophosphates, as well as to lowly phosphorylated inositol phosphates and bisphosphonate analogs. Our method will facilitate the assignment of biologically relevant isomers when isolating naturally occurring compounds from biological specimens.
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Suraj Koorpet R, Akshay N, Nishanth G, Chandan R S, and Anand Kumar Tengli. "A Review on Chiral Columns/Stationary Phases for HPLC." International Journal of Research in Pharmaceutical Sciences 11, no. 2 (May 15, 2020): 2466–80. http://dx.doi.org/10.26452/ijrps.v11i2.2240.
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The chiral separation of pharmaceutical molecules and their precursors is one of the important areas of application of HPLC in pharmaceutical analysis for obtaining enantiomerically pure drug. The latter procedures include the use of so-called chiral selectors to enantio-selectively recognise and isolate the enantiomer. The direct approaches, i.e. those which do not derivate the compound of interest before separation, are addressed in detail, since they are now the most common approaches. The role of stereochemistry in medicinal products is being given greater emphasis to medical practice. For physicians to make conscious choice about the use of single-enantiomered medicinal products, basic knowledge is required. For few treatments single-enantiomer formulations can provide more selectivity than a combination of enantiomers in their biological purposes, enhanced therapeutic indexes and/or better pharmacokinetics. This highlights the possible biological and pharmacological variations between the two drug enantiomers and underlines the clinical experience of individual enantiomers. Particular emphases have been put on chiral separation by HPLC on chiral stationary phases (CSPs). Chiral derivatization reagents (CDRs) are optically pure reagent on reaction with drugs forms a pair of diastereoisomers that can be separated on conventional achiral phase. In Chiral mobile phase additive (CMPA) method, the stationary phase is achiral and the chiral selector is dissolved during the mobile phase. Interaction with the analyte’s enantiomer leads to the formation of transient diastereomeric complexes that are separated by their affinity towards mobile/stationary phase. Separation mechanisms and method development for chiral molecules using these phases are discussed in this review.
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Oz, Murat, Yuliya Tchugunova, and Meral Dinç. "Effects of (+) and (-) enantiomers of calcium channel agonist, Bay K 8644, on mechanical and electrical responses of frog skeletal muscle." Canadian Journal of Physiology and Pharmacology 78, no. 8 (August 1, 2000): 649–55. http://dx.doi.org/10.1139/y00-035.
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The effects of (+) and (-) enantiomers of Bay K 8644, a Ca2+ channel agonist, on the mechanical and electrical properties of frog skeletal muscle fibers were investigated. In the concentration range of 10-6 to 10-5 M, both (+) and (-) enantiomers of Bay K 8644 significantly increased the maximum amplitudes of twitch responses. Both (+) and (-) enantiomers of Bay K 8644, at higher concentrations such as 10-4 M, greatly depressed the amplitudes of twitches. Potentiating and depressing effects of (-) enantiomer of Bay K 8644 on twitch responses were significantly greater than those of the (+) enantiomer. At all concentrations used, both (+) and (-) enantiomers of Bay K 8644 significantly decreased the area under the tetanic force × time curve. In intracellular recordings, it was found that the depressing effects of both (+) and (-)-Bay K 8644 on tetanic contractions and twitch responses were due to the inhibition of action potentials. The inhibitory effect of (-) enantiomer of Bay K 8644 on action potentials also was significantly greater than that of the (+) enantiomer. In conclusion, present results suggest that, in contrast with cardiac muscle fibers, (+) and (-) enantiomers of Bay K 8644 have similar inhibitory effects on the electrical and mechanical properties of frog skeletal muscle fibers.Key words: Bay K 8644, calcium channels, sodium channels, skeletal muscle.
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Harman, Christine A., Melissa V. Turman, Kevin R. Kozak, Lawrence J. Marnett, William L. Smith, and R. Michael Garavito. "Structural Basis of Enantioselective Inhibition of Cyclooxygenase-1 by S-α-Substituted Indomethacin Ethanolamides." Journal of Biological Chemistry 282, no. 38 (July 26, 2007): 28096–105. http://dx.doi.org/10.1074/jbc.m701335200.
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The modification of the nonselective nonsteroidal anti-inflammatory drug, indomethacin, by amidation presents a promising strategy for designing novel cyclooxygenase (COX)-2-selective inhibitors. A series of α-substituted indomethacin ethanolamides, which exist as R/S-enantiomeric pairs, provides a means to study the impact of stereochemistry on COX inhibition. Comparative studies revealed that the R- and S-enantiomers of the α-substituted analogs inhibit COX-2 with almost equal efficacy, whereas COX-1 is selectively inhibited by the S-enantiomers. Mutagenesis studies have not been able to identify residues that manifest the enantioselectivity in COX-1. In an effort to understand the structural impact of chirality on COX-1 selectivity, the crystal structures of ovine COX-1 in complexes with an enantiomeric pair of these indomethacin ethanolamides were determined at resolutions between 2.75 and 2.85Å. These structures reveal unique, enantiomer-selective interactions within the COX-1 side pocket region that stabilize drug binding and account for the chiral selectivity observed with the (S)-α-substituted indomethacin ethanolamides. Kinetic analysis of binding demonstrates that both inhibitors bind quickly utilizing a two-step mechanism. However, the second binding step is readily reversible for the R-enantiomer, whereas for the S-enantiomer, it is not. These studies establish for the first time the structural and kinetic basis of high affinity binding of a neutral inhibitor to COX-1 and demonstrate that the side pocket of COX-1, previously thought to be sterically inaccessible, can serve as a binding pocket for inhibitor association.
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Tomlin, Sarah L., Andrew Jenkins, William R. Lieb, and Nicholas P. Franks. "Preparation of Barbiturate Optical Isomers and Their Effects on GABA (A) Receptors." Anesthesiology 90, no. 6 (June 1, 1999): 1714–22. http://dx.doi.org/10.1097/00000542-199906000-00029.
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Background Barbiturate anesthetics are optically active and usually exist in two mirror-image enantiomeric forms. Their stereoselective effects in mammals are well known, but remarkably few data are available concerning their effects on anesthetic targets in vitro. This is in part because of the lack of availability of pure barbiturate enantiomers. Such in vitro data could be used to test the relevance of putative molecular targets. Methods A high-performance liquid chromatography technique using a permethylated beta-cyclodextrin column was used to separate the optical isomers of three barbiturates in preparative quantities. The effects of the isomers on GABA-induced currents in stably transfected mouse fibroblast cells were investigated using the whole-cell patch-clamp technique. Results Highly purified optical isomers of hexobarbital, pentobarbital, and thiopental were prepared, and their effects were studied on a gamma-aminobutyric acid type A receptor of defined subunit composition. For each of the three barbiturates, both enantiomers potentiated gamma-aminobutyric acid-induced currents at pharmacologically relevant concentrations, with the S-enantiomer being more potent than the R-enantiomer by a factor of between 1.7 and 3.5. The degree of stereoselectivity did not vary greatly with anesthetic concentration. Conclusions The rank order and degree of stereoselectivity that we have observed for the enantiomers of hexobarbital, pentobarbital, and thiopental acting on the gamma-aminobutyric acid type A receptor are entirely consistent with this receptor playing a central role in the anesthetic actions of barbiturates.
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Williams, J., N. Yassaa, S. Bartenbach, and J. Lelieveld. "Mirror image hydrocarbons from Tropical and Boreal forests." Atmospheric Chemistry and Physics Discussions 6, no. 5 (September 29, 2006): 9583–602. http://dx.doi.org/10.5194/acpd-6-9583-2006.
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Abstract. Monoterpenes, emitted in large quantities by trees to attract pollinators and repel herbivores, can exist in mirror image forms called enantiomers. In this study such enantiomeric pairs have been measured in ambient air over extensive forest ecosystems in South America and northern Europe. For the dominant monoterpene, α-pinene, the (–)-form was measured in large excess over the (+)-form over the Tropical rainforest, whereas the reverse was observed over the Boreal forest. Interestingly, over the Tropical forest (–)-α-pinene did not correlate with its own enantiomer, but correlated well with isoprene. The results indicate a remarkable ecosystem scale enantiomeric fingerprint and a nexus between the biosphere and atmosphere.
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Williams, J., N. Yassaa, S. Bartenbach, and J. Lelieveld. "Mirror image hydrocarbons from Tropical and Boreal forests." Atmospheric Chemistry and Physics 7, no. 3 (February 22, 2007): 973–80. http://dx.doi.org/10.5194/acp-7-973-2007.
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Abstract. Monoterpenes, emitted in large quantities by trees to attract pollinators and repel herbivores, can exist in mirror image forms called enantiomers. In this study such enantiomeric pairs have been measured in ambient air over extensive forest ecosystems in South America and northern Europe. For the dominant monoterpene, α-pinene, the (−)-form was measured in large excess over the (+)-form over the Tropical rainforest, whereas the reverse was observed over the Boreal forest. Interestingly, over the Tropical forest (−)-α-pinene did not correlate with its own enantiomer, but correlated well with isoprene. The results indicate a remarkable ecosystem scale enantiomeric fingerprint and a nexus between the biosphere and atmosphere.
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Šaman, David, Martina Wimmerová, and Zdeněk Wimmer. "Synthesis and Structure Assignment of 2-(4-Methoxybenzyl)cyclohexyl β-D-Galactopyranoside Stereoisomers." Collection of Czechoslovak Chemical Communications 71, no. 8 (2006): 1186–98. http://dx.doi.org/10.1135/cccc20061186.
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Several promoters were used in the Koenigs-Knorr synthesis of the title alkyl β-D-galactopyranosides, both in their diastereoisomeric forms (5a/5b and 6a/6b), resulting from the synthesis performed with the respective racemic cis and trans isomers of 2-(4-methoxybenzyl)cyclohexan-1-ol, and in their enantiomerically pure forms 5a and 6a, starting only from the (1S,2S)- and (1S,2R)-enantiomers of 2-(4-methoxybenzyl)cyclohexan-1-ol. The aim of the study was to find convenient modification(s) of the Koenigs-Knorr synthesis of alkyl β-D-galactopyranosides from more hindered and more complex 2-substituted cycloalkanols. Separation of the diastereoisomeric compounds using HPLC on a chiral Nucleodex-β-OH column was used to obtain small quantities of all possibly existing enantiomerically pure products for unambiguous structure assignment by NMR analysis. The (1S,2S)- and (1S,2R)- enantiomers of 2-(4-methoxybenzyl)cyclohexan-1-ol (1a and 2a) were prepared by a reduction of 2-(4-methoxybenzyl)cyclohexan-1-one with Saccharomyces cerevisiae in enantiomeric purities: ee = 98.5% ((1S,2S)-enantiomer (1a)), and ee ≥ 99% ((1S,2R)-enantiomer (2a)).
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Dickinson, Robert, Ian White, William R. Lieb, and Nicholas P. Franks. "Stereoselective Loss of Righting Reflex in Rats by Isoflurane." Anesthesiology 93, no. 3 (September 1, 2000): 837–43. http://dx.doi.org/10.1097/00000542-200009000-00035.
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Background Although it is accepted widely that optically active intravenous general anesthetics produce stereoselective effects in animals, the situation regarding volatile agents is confused. Conventional studies with scarce isoflurane enantiomers have been limited to small numbers of animals and produced conflicting results. By injecting these volatile enantiomers intravenously, however, it is possible to study large numbers of animals and obtain reliable results that can help to identify the molecular targets for isoflurane. Methods Pure isoflurane enantiomers were administered intravenously to rats after solubilization in a lipid emulsion. The ability of each enantiomer to produce a loss of righting reflex was determined as a function of dose, and quantal dose-response curves were constructed. In addition, sleep times were recorded with each enantiomer. Chiral gas chromatography was used to measure relative enantiomer concentrations in the brains of rats injected with racemic isoflurane. Results The S(+)-enantiomer was 40 +/- 8% more potent than the R(-)-enantiomer at producing a loss of righting reflex. The S(+)-enantiomer induced longer sleep times (by about 50%) than did the R(-)-enantiomer. Rats anesthetized by a dose of racemic isoflurane sufficient to achieve a half-maximal effect had essentially identical brain concentrations of the two enantiomers. Conclusions The S(+)-enantiomer of the general anesthetic isoflurane is significantly (P < 0.001) more potent than the R(-)-enantiomer at causing a loss of righting reflex in rats. This confirms the view that isoflurane acts by binding to chiral sites. The observed degree of stereoselectivity provides a useful guide for ascertaining from in vitro experiments which molecular targets are most likely to play major roles in the loss of righting reflex caused by isoflurane.
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García-Cansino, Laura, María Ángeles García, and María Luisa Marina. "Simultaneous Enantiomeric Separation of Carfentrazone-Ethyl Herbicide and Its Hydrolysis Metabolite Carfentrazone by Cyclodextrin Electrokinetic Chromatography. Analysis of Agrochemical Products and a Degradation Study." Molecules 26, no. 17 (September 2, 2021): 5350. http://dx.doi.org/10.3390/molecules26175350.
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The different activity and toxicity that the enantiomers of agrochemicals may have requires the development of stereoselective analytical methodologies enabling the individual determination of each enantiomer. The aim of this work was to develop the first Electrokinetic Chromatography methodology enabling the simultaneous enantiomeric separation of carfentrazone-ethyl herbicide and its hydrolysis metabolite carfentrazone. The use of an anionic cyclodextrin as chiral selector (captisol at 2.5% (w/v)) in a 25 mM acetate buffer, at a temperature of 30 °C, and an applied voltage (reverse polarity) of −30 kV, allowed the simultaneous separation of the four enantiomers of the two compounds studied in 6.8 min with enantiomeric resolutions of 5.0 for carfentrazone-ethyl and 5.1 for carfentrazone. Analytical characteristics of the developed method were evaluated and found adequate to achieve the quantitation of carfentrazone-ethyl and carfentrazone. Analysis of a commercial herbicide formulation showed the potential of the method for the quality control of these agrochemical products. Degradation studies for carfentrazone-ethyl revealed that no significant degradation took place in cleaned sand samples while a significant but not stereoselective degradation took place in soils for the whole period of time considered (seven days).
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Bystrická, Zuzana, and Jozef Lehotay. "In Vitro Investigation of D- and Lenantiomer Synergistic Efects of Some Amino Acids." Nova Biotechnologica et Chimica 15, no. 1 (June 1, 2016): 47–54. http://dx.doi.org/10.1515/nbec-2016-0005.
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Abstract D-amino acids can arise from endogenous microbial flora, from ingestion with the diet or from spontaneous racemization of L-amino acids during ageing. In this work, the behavior of methionine, homocysteine and cysteine enantiomers was investigated in human serum in vitro during 0-72 h at incubation temperature 37°C. The separation of enantiomers was realized in two dimensional on-line system (the connection of an achiral column Purospher RP-18 endcapped and a chiral column Chirobiotic TAG). This system allowed simultaneous monitoring all tested amino acids and their enantiomers. The possible effect D-enantiomer on the behavior of its L-enantiomer (the synergistic effect) was evaluated during incubation time. The first results have showed that no synergistic effect of D-enantiomer on its Lisomer has been observed in our experimental conditions in vitro.
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Jacques, Vincent, Anthony W. Czarnik, Thomas M. Judge, Lex H. T. Van der Ploeg, and Sheila H. DeWitt. "Differentiation of antiinflammatory and antitumorigenic properties of stabilized enantiomers of thalidomide analogs." Proceedings of the National Academy of Sciences 112, no. 12 (March 9, 2015): E1471—E1479. http://dx.doi.org/10.1073/pnas.1417832112.
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Therapeutics developed and sold as racemates can exhibit a limited therapeutic index because of side effects resulting from the undesired enantiomer (distomer) and/or its metabolites, which at times, forces researchers to abandon valuable scaffolds. Therefore, most chiral drugs are developed as single enantiomers. Unfortunately, the development of some chirally pure drug molecules is hampered by rapid in vivo racemization. The class of compounds known as immunomodulatory drugs derived from thalidomide is developed and sold as racemates because of racemization at the chiral center of the 3-aminoglutarimide moiety. Herein, we show that replacement of the exchangeable hydrogen at the chiral center with deuterium allows the stabilization and testing of individual enantiomers for two thalidomide analogs, including CC-122, a compound currently in human clinical trials for hematological cancers and solid tumors. Using “deuterium-enabled chiral switching” (DECS), in vitro antiinflammatory differences of up to 20-fold are observed between the deuterium-stabilized enantiomers. In vivo, the exposure is dramatically increased for each enantiomer while they retain similar pharmacokinetics. Furthermore, the single deuterated enantiomers related to CC-122 exhibit profoundly different in vivo responses in an NCI-H929 myeloma xenograft model. The (−)-deuterated enantiomer is antitumorigenic, whereas the (+)-deuterated enantiomer has little to no effect on tumor growth. The ability to stabilize and differentiate enantiomers by DECS opens up a vast window of opportunity to characterize the class effects of thalidomide analogs and improve on the therapeutic promise of other racemic compounds, including the development of safer therapeutics and the discovery of new mechanisms and clinical applications for existing therapeutics.
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Valentová, Jindra, Lucia Lintnerová, Natalia Miklášová, Bianka Oboňová, and Ladislav Habala. "Analogues of Anticancer Natural Products: Chiral Aspects." International Journal of Molecular Sciences 24, no. 6 (March 16, 2023): 5679. http://dx.doi.org/10.3390/ijms24065679.
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Life is chiral, as its constituents consist, to a large degree, of optically active molecules, be they macromolecules (proteins, nucleic acids) or small biomolecules. Hence, these molecules interact disparately with different enantiomers of chiral compounds, creating a preference for a particular enantiomer. This chiral discrimination is of special importance in medicinal chemistry, since many pharmacologically active compounds are used as racemates—equimolar mixtures of two enantiomers. Each of these enantiomers may express different behaviour in terms of pharmacodynamics, pharmacokinetics, and toxicity. The application of only one enantiomer may improve the bioactivity of a drug, as well as reduce the incidence and intensity of adverse effects. This is of special significance regarding the structure of natural products since the great majority of these compounds contain one or several chiral centres. In the present survey, we discuss the impact of chirality on anticancer chemotherapy and highlight the recent developments in this area. Particular attention has been given to synthetic derivatives of drugs of natural origin, as naturally occurring compounds constitute a major pool of new pharmacological leads. Studies have been selected which report the differential activity of the enantiomers or the activities of a single enantiomer and the racemate.
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Sonstrom, Reilly E., Donald M. Cannon, and Justin L. Neill. "Chiral Analysis of Linalool, an Important Natural Fragrance and Flavor Compound, by Molecular Rotational Resonance Spectroscopy." Symmetry 14, no. 5 (April 30, 2022): 917. http://dx.doi.org/10.3390/sym14050917.
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The chiral analysis of terpenes in complex mixtures of essential oils, necessary for authentication, has been further developed using chiral tagging molecular rotational resonance (MRR) spectroscopy. One analyte that is of particular interest is linalool (3,7-dimethyl-1,6-octadien-3-ol), a common natural chiral terpene found in botanicals with its enantiomers having unique flavor, fragrance, and aromatherapy characteristics. In this MRR demonstration, resolution of the enantiomers is achieved through the addition of a chiral tag, which creates non-covalent diastereomeric complexes with distinct spectral signatures. The relative stereochemistry of the complexes is identified by the comparison of calculated spectroscopic parameters with experimentally determined parameters of the chiral complexes with high accuracy. The diastereomeric complex intensities are analyzed to determine the absolute configuration (AC) and enantiomeric excess (EE) in each sample. Here, we demonstrate the use of chiral tagging MRR spectroscopy to perform a quantitative routine enantiomer analysis of linalool in complex essential oil mixtures, without the need for reference samples or chromatographic separation.
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Bai, Hui. "Research progress of chiral ligand exchange stationary phases in the enantiomer resolution." E3S Web of Conferences 271 (2021): 04020. http://dx.doi.org/10.1051/e3sconf/202127104020.
Full textAbstract:
The structure of chiral drugs contains at least one asymmetric center. When the enantiomers act on the human body, they are recognized by chiral receptors and enzymes in vivo, which will show different physiological effects and even adverse reactions. Therefore, it is very important for the development of chiral pharmacy to obtain chiral enantiomers with a single configuration by racemic resolution. Some general impurities will be introduced in the production of chiral drugs, thus the detection of impurities is also a crucial step in the quality control of chiral medicines. The chiral ligand exchange stationary phase has a strong recognition effect on enantiomer analytes with multiple chelating sites, and is very suitable for the separation and control of biological samples such as amino acids. In this work, the development of chiral ligand exchange stationary phases in enantiomeric resolution is reviewed, which is expected to provide a basis for the quality control of complex chiral drug components.
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Schulz, Saskia, Wenbo Dong, Ulrich Groth, and Alasdair M. Cook. "Enantiomeric Degradation of 2-(4-Sulfophenyl)Butyrate via 4-Sulfocatechol in Delftia acidovorans SPB1." Applied and Environmental Microbiology 66, no. 5 (May 1, 2000): 1905–10. http://dx.doi.org/10.1128/aem.66.5.1905-1910.2000.
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ABSTRACT Enrichment cultures with enantiomeric 2-(4-sulfophenyl)butyrate (SPB) as the sole added source(s) of carbon and energy for growth yielded a pure culture of a degradative bacterium, which was identified as Delftia acidovorans SPB1. The organism utilized the enantiomers sequentially. R-SPB was utilized first (specific growth rate [μ] = 0.28 h−1), with transient excretion of an unknown intermediate, which was identified as 4-sulfocatechol (4SC). Utilization of S-SPB was slower (μ = 0.016 h−1) and was initiated only after the first enantiomer was exhausted. Suspensions of cells grown inS-SPB excreted 4SC, so metabolism of the two enantiomers converged at 4SC. The latter was degraded by ortho cleavage via 3-sulfo-cis,cis-muconate. Strain SPB1 grew with 4SC and with 1-(4-sulfophenyl)octane (referred to herein as model LAS) but not with commercial linear alkylbenzenesulfonate (LAS) surfactant, which is subterminally substituted but nontoxic. It would appear that metabolism of the model LAS does not represent metabolism of commercial LAS.
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Langa, Ivan, Maria Elizabeth Tiritan, Diana Silva, and Cláudia Ribeiro. "Gas Chromatography Multiresidue Method for Enantiomeric Fraction Determination of Psychoactive Substances in Effluents and River Surface Waters." Chemosensors 9, no. 8 (August 13, 2021): 224. http://dx.doi.org/10.3390/chemosensors9080224.
Full textAbstract:
Determination of psychoactive substances (PAS) and/or their metabolites in surface waters is crucial for environmental risk assessment, and disclosure of their enantiomeric fractions (EF) allows discrimination between consumption, direct disposal, and synthesis pathways. The aim of this study was to develop and validate an indirect method by gas chromatography coupled to mass spectrometry (GC–MS) based on derivatization using (R)-(−)-α-methoxy-α-(trifluoromethyl) phenylacetyl chloride as chiral derivatization reagent, for enantiomeric quantification of amphetamine (AMP), methamphetamine (MAMP), 3,4-methylenedioxymethamphetamine (MDMA), norketamine, buphedrone (BPD), butylone, 3,4-dimethylmethcathinone (3,4-DMMC), 3-methylmethcathinone, and quantification of 1-benzylpiperazine and 1-(4-metoxyphenyl)-piperazine. The method allowed to evaluate the occurrence, spatial distribution, and the EF of the target chiral PAS in Portuguese surface waters and in effluents from 2 wastewater treatment plants (WWTP). For that, water samples were pre-concentrated by solid phase extraction using OASIS® MCX cartridges, derivatized and further analyzed by GC–MS. Both enantiomers of AMP, (R)-MDMA, (S)-MAMP, and the first eluted enantiomer of BPD (configuration not assigned) were found in surface waters, while effluent samples showed both enantiomers of MDMA, (S)-MAMP, (R)-AMP, and the first eluted enantiomer of BPD and 3,4-DMMC. According to our knowledge, this is the first multiresidue analytical method by CG–MS enrolling cathinones, amphetamines, and piperazines. The presence of illicit synthetic cathinones in Douro River estuary is here reported for the first time, along with other amphetamine derivatives. The potential of the method to monitor consumption of the target PAS was demonstrated.
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Szabó, Zoltán-István, Beáta-Mária Benkő, Ágnes Bartalis-Fábián, Róbert Iványi, Erzsébet Varga, Levente Szőcs, and Gergő Tóth. "Chiral Separation of Apremilast by Capillary Electrophoresis Using Succinyl-β-Cyclodextrin—Reversal of Enantiomer Elution Order by Cationic Capillary Coating." Molecules 28, no. 8 (April 8, 2023): 3310. http://dx.doi.org/10.3390/molecules28083310.
Full textAbstract:
A stereospecific capillary electrophoresis method was developed for the separation of the novel, antipsoriatic agent, apremilast (APR). Six anionic cyclodextrin (CD) derivatives were screened for their ability to discriminate between the uncharged enantiomers. Only succinyl-β-CD (Succ-β-CD) presented chiral interactions; however, the enantiomer migration order (EMO) was unfavorable, and the eutomer, S-APR, migrated faster. Despite the optimization of all possible parameters (pH, cyclodextrin concentration, temperature, and degree of substitution of CD), the method was unsuccessful for purity control due to the low resolution and the unfavorable enantiomer migration order. Changing the direction of electroosmotic flow (EOF) by the dynamic coating of the inner surface of the capillary with poly(diallyldimethylammonium) chloride or polybrene resulted in EMO reversal, and the developed method could be applied for the determination of R-APR as the enantiomeric purity. Thus, the application of the dynamic capillary coating offers a general opportunity for enantiomeric migration order reversal in particular cases when the chiral selector is a weak acid.
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MacDonald, Stacy A., and Gary M. Hieftje. "Use of Shift Reagents to Determine Enantiomers by Near-Infrared Analysis." Applied Spectroscopy 50, no. 9 (September 1996): 1161–64. http://dx.doi.org/10.1366/0003702963905213.
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A method is described that utilizes β-cyclodextrin and silica gel as shift reagents to distinguish between enantiomers by means of near-infrared transmission spectroscopy. The premise is that the spectrum of the (+)-enantiomer bound to the shift reagent will be different from that of the (−)-enantiomer bound to the same reagent. With the use of principal component analysis, the difference between the enantiomers can be distinguished. The resulting method is fast, simple, and of potential application in pharmaceutical process control.
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Zhu, Y. L., S. B. Pai, S. H. Liu, K. L. Grove, B. C. Jones, C. Simons, J. Zemlicka, and Y. C. Cheng. "Inhibition of replication of hepatitis B virus by cytallene in vitro." Antimicrobial Agents and Chemotherapy 41, no. 8 (August 1997): 1755–60. http://dx.doi.org/10.1128/aac.41.8.1755.
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The acyclic cytosine nucleoside analog cytallene [1-(4'-hydroxy-1',2'-butadienyl)cytosine], which has both (+)- and (-)-enantiomers, was evaluated for its anti-hepatitis B virus (HBV) activity in 2.2.15 cells and was found to have potent activity against HBV DNA synthesis. The R-(-)-enantiomer was found to be the more active of the cytallene enantiomers, with a 50% inhibition concentration against HBV synthesis (HBIC50) of 0.08 microM. Its antiviral activity could be reversed by deoxycytidine (dC) and less efficiently by cytidine. Upon removal of the R-(-)-enantiomer from culture medium, the synthesis of HBV DNA could reinitiate, which suggested that the antiviral action is reversible. The R-(-)-enantiomer was also found to be more cytotoxic than the S-(+)-enantiomer. The degree of cytotoxicity varied among the cell lines, with a 50% inhibition of cell growth at greater than 10 microM. The R-(-)-enantiomer had no effect on HBV RNA synthesis and mitochondrial DNA synthesis at a concentration of 10 times or more than the HBIC50. The two enantiomers cannot be deaminated by dC deaminase, and they can be phosphorylated by cytoplasmic dC kinase. The R-(-)-enantiomer of cytallene is the first acyclic cytosine analog with potent inhibitory activity against HBV similar to those of other L-(-)-ddC analogs.
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Alembik, Marc C., and Irving W. Wainer. "Resolution and Analysis of Enantiomers of Amphetamines by Liquid Chromatography on a Chiral Stationary Phase: Collaborative Study." Journal of AOAC INTERNATIONAL 71, no. 3 (May 1, 1988): 530–33. http://dx.doi.org/10.1093/jaoac/71.3.530.
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Abstract A rapid, accurate method for separating and determining the enantiomeric composition of amphetamine bulk drug and commercial preparations was developed and subjected to collaborative study. Amide derivatives of the amphetamine enantiomers are formed by using achiral 2-naphthoyl chloride. The resulting enantiomeric amides are then chromatographed on a commercially available chiral stationary phase with hexane-isopropyl alcohol-acetonitrile (97 + 3 + 0.5) mobile phase, with detection at 254 nm. Seven collaborators received bulk drug and commercial samples of amphetamine. The collaborators and authors determined the mean percent /- and rf-amphetamine from 2 injections of each sample. The method can detect the presence of as little as 0.5% of the /-enantiomer in ^-amphetamine, with reproducibility between laboratories of ±71.3%. The method has been adopted official first action for determination of the enantiomeric composition of amphetamine bulk drug and preparations
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Pragadheesh, VPPalayam S., Anju Yadav, Manju Singh, and Chandan S. Chanotiya. "Characterization of Volatile Components of Zingiber roseum Essential Oil Using Capillary GC on Modified Cyclodextrins." Natural Product Communications 8, no. 2 (February 2013): 1934578X1300800. http://dx.doi.org/10.1177/1934578x1300800223.
Full textAbstract:
The essential oil from different parts of Zingiber roseum plants was extracted by hydrodistillation, and analyzed using enantio-GC, capillary-GC and GC-MS. Two chiral selectors, 6- tert-butyldimethylsilyl-2,3-diethyl-β-cyclodextrin (TBDE-β-CD), and 2,3,6-methyl-β-cyclodextrin (PM-β-CD) doped into 14% cyanopropylphenyl/ 86% dimethylpolysiloxane, and 35% diphenyl/ 65% dimethylpolysiloxane, respectively were compared in order to clarify the stereochemistry and enantioselectivity of terpenoids using chiral gas chromatography. The enantiomeric excess for (1R)-(+)-α-pinene, (1R)-(+)-β-pinene, and (R)-(+)-limonene were characteristic for the rhizome. In TBDE-β-cyclodextrin coated chiral columns, a significant increase in separation factor (a) for β-pinene, limonene, linalool and α-terpineol enantiomers was observed when compared with methyl substituted β-cyclodextrin. The increase in chain length of the alkyl substituents may be the possible cause for enantiomer separation in β-cyclodextrin cavity. In addition, enantioreversal of α-pinene enantiomers in 6-tert-butyldimethylsilyl-2,3-diethyl-β-cyclodextrin was noticed as a unique feature. The enantiomeric compositions of Z. roseum fruit and flower essential oils were similar, but, in contrast, the rhizome oil contained an entirely different composition. Therefore, these results aid in the authentication of the natural origin of Z. roseum essential oils.
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Cook, J. I., S. Majeed, R. Ignell, J. A. Pickett, M. A. Birkett, and J. G. Logan. "Enantiomeric selectivity in behavioural and electrophysiological responses of Aedes aegypti and Culex quinquefasciatus mosquitoes." Bulletin of Entomological Research 101, no. 5 (May 18, 2011): 541–50. http://dx.doi.org/10.1017/s0007485311000162.
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Abstract1-Octen-3-ol is a kairomone for many haematophagous insects including mosquitoes. Numerous studies have examined the effects of racemic 1-octen-3-ol; however, few studies have investigated the role of individual enantiomers in relation to mosquito attraction. In the present study, we investigated the behavioural and electrophysiological responses of two mosquito species, Aedes aegypti and Culex quinquefasciatus, to individual enantiomers and mixtures of 1-octen-3-ol, employing a laboratory Y-tube olfactometer and single sensillum recordings. The olfactory receptor neurons of both Ae. aegypti and Cx. quinquefasciatus had a significantly higher response to the (R)-1-octen-3-ol enantiomer compared to the (S)-1-octen-3-ol enantiomer at 10−9 g μl−1 to 10−6 g μl−1. Behaviourally, Ae. aegypti was more responsive to the (R)-1-octen-3-ol enantiomer, showing an increase in flight activity and relative attraction compared to Cx. quinquefasciatus. The (R)-1-octen-3-ol enantiomer caused an increase in activation for Cx. quinquefasciatus. However, the most notable effect was from an (R:S)-1-octen-3-ol mixture (84:16) that caused significantly more mosquitoes to sustain their flight and reach the capture chambers (demonstrated by a reduced non-sustained flight activity), suggesting that it may have a behaviourally excitatory effect. For Cx. quinquefasciatus, a reduced relative attraction response was also observed for all treatments containing the (R)-1-octen-3-ol enantiomer, either on its own or as part of a mixture, but not with the (S)-1-octen-3-ol enantiomer. This is the first time enantiomeric selectivity has been shown for Ae. aegypti using electrophysiology in vivo. The implications of these results for exploitation in mosquito traps are discussed.