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Journal articles on the topic 'Chiral enrichment'

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Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

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1

Marloie, G., F. Pauzat, Y. Ellinger, A. Markovits, and J. Pilmé. "Homochirality in space – Selective enrichment of chiral molecules on chiral surfaces." BIO Web of Conferences 2 (2014): 04004. http://dx.doi.org/10.1051/bioconf/20140204004.

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2

Yang, Xiaochuan, Shin Yee Wong, David K. Bwambok, Manza B. J. Atkinson, Xi Zhang, George M. Whitesides, and Allan S. Myerson. "Separation and enrichment of enantiopure from racemic compounds using magnetic levitation." Chem. Commun. 50, no. 56 (2014): 7548–51. http://dx.doi.org/10.1039/c4cc02604g.

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3

Lu, Tingting, Liangkui Zhu, Xiaohe Wang, Wenfu Yan, Wei Shi, and Ruren Xu. "Identification of the key factor promoting the enrichment of chiral polymorph A in zeolite beta and the synthesis of chiral polymorph A highly enriched zeolite beta." Inorganic Chemistry Frontiers 5, no. 7 (2018): 1640–45. http://dx.doi.org/10.1039/c8qi00265g.

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4

Mahmoud, Hussein, Ying Han, Brent M. Segal, and Lisheng Cai. "Chiral enrichment of 2-amino-2′-hydroxy-1,1′-binaphthyl." Tetrahedron: Asymmetry 9, no. 12 (June 1998): 2035–42. http://dx.doi.org/10.1016/s0957-4166(98)00203-1.

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5

Pérez, Cristóbal, Amanda L. Steber, Anna Krin, and Melanie Schnell. "State-Specific Enrichment of Chiral Conformers with Microwave Spectroscopy." Journal of Physical Chemistry Letters 9, no. 16 (July 26, 2018): 4539–43. http://dx.doi.org/10.1021/acs.jpclett.8b01815.

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6

Naruse, Yuji, Hidefumi Watanabe, Yasuhiro Ishiyama, and Tomoe Yoshida. "Enantiomeric Enrichment of Allenedicarboxylates by a Chiral Organoeuropium Reagent." Journal of Organic Chemistry 62, no. 12 (June 1997): 3862–66. http://dx.doi.org/10.1021/jo961870v.

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7

Lorenz, Klaus, Eiji Yashima, and Yoshio Okamoto. "Enantiomeric Enrichment of Stereolabile Chiral Spiro Compounds by Dynamic HPLC on Chiral Stationary Phases." Angewandte Chemie International Edition 37, no. 13-14 (August 3, 1998): 1922–25. http://dx.doi.org/10.1002/(sici)1521-3773(19980803)37:13/14<1922::aid-anie1922>3.0.co;2-#.

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8

Borowski, Piotr, Marek Stankevič, Dorota Strzelecka, and Olga Bąk. "Dynamic Kinetic Resolution of Phosphinic Acid Derivatives via Nucleophilic Substitution at Phosphorus Center." Synthesis 50, no. 24 (September 5, 2018): 4922–32. http://dx.doi.org/10.1055/s-0037-1609947.

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Reaction of racemic phosphinic acid derivatives with chiral alcohols proceeds with predominant formation of one diastereomer. The highest level of enrichment has been obtained for transesterfication of racemic methyl benzylphenylphosphinate (64% de). The outcome of the reaction depends on both the structure of chiral alcohol and the starting organophosphorus compound. The results strongly suggest that the nature of the observed phenomena is not a classical equilibration of intermediates found in dynamic kinetic resolution process but is a result of a different reactivity of both enantiomers of racemic substrate towards the same chiral nucleophile.

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9

Osano, Yasuko T., Akira Uchida, and Yuji Ohashi. "Optical enrichment of a racemic chiral crystal by X-ray irradiation." Nature 352, no. 6335 (August 1991): 510–12. http://dx.doi.org/10.1038/352510a0.

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10

Yan, Hailong, Yidong Liu, and Wenling Qin. "Efficient Enrichment of Chiral β-Sulfonyl Ketones through Asymmetric β-Elimination." Synlett 27, no. 20 (October 20, 2016): 2756–60. http://dx.doi.org/10.1055/s-0036-1588632.

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11

Ohashi, Yuji, Takashi Nemoto, and Yasuyuki Takenaka. "Optical Enrichment of Chiral Racemic Crystals on Exposure to Visible Light." Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 242, no. 1 (March 1994): 103–8. http://dx.doi.org/10.1080/10587259408037742.

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12

Yan, Li, Zhongkui Li, Xue Zhong, Jianxin Du, Yan Xiong, Shaochun Peng, and Hui Li. "Preferential Enrichment of Enantiomer from Amino Acid Schiff Bases by Coordination Interaction and Crystallization." Materials 16, no. 2 (January 5, 2023): 530. http://dx.doi.org/10.3390/ma16020530.

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In this paper, preferential enrichment (PE) is described for three pairs of novel amino acid Schiff base Cu(II)/Cu(I) complexes. Single crystal X-ray diffraction indicated that 1-S/R are one-dimensional coordination polymers (CPs) with helical structures, and 2-S/R and 3-S/R are one-dimensional CPs with auxiliary ligands. By tuning the pH, the solvent and second ligands, the 1-S/R, 3-S/R underwent polymorphic transitions, resulting in enantioselective liberation of excess enantiomers into solution, until the deposited crystals were slightly enriched with the opposite enantiomer, thereby successfully exhibiting PE. However, under the effects of Cu(II), the solvent and low pH, 2-S/R did not exhibit PE and resulted in enrichment of racemic compounds, which was attributed to amino acid Schiff base chiral complex mechanisms of PE. The three pairs of Cu complex structures were characterized by UV-vis, MS and X-ray photoelectron spectroscopy (XPS). All chiral properties were studied by circular dichroism (CD) in the solid and liquid.

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13

Chen, Shuang, Hanmi Xi, Rodger F. Henry, Ian Marsden, and Geoff G. Z. Zhang. "Chiral co-crystal solid solution: structures, melting point phase diagram, and chiral enrichment of (ibuprofen)2(4,4-dipyridyl)." CrystEngComm 12, no. 5 (2010): 1485. http://dx.doi.org/10.1039/b910662f.

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14

Tamura, Rui. "Origin of regular chiral fluctuation or symmetry breaking unique to preferential enrichment." Acta Crystallographica Section A Foundations and Advances 73, a1 (May 26, 2017): a319. http://dx.doi.org/10.1107/s0108767317096878.

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15

Dutta, Debosruti, R. Mohan Sankaran, and Venkat R. Bhethanabotla. "Predicting the Chiral Enrichment of Metallic SWCNTs on Ni–Cu Bimetallic Surfaces." Chemistry of Materials 26, no. 17 (August 15, 2014): 4943–50. http://dx.doi.org/10.1021/cm501167z.

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16

Nicoud, Roger-Marc, Jean-No�l Jaubert, Isabell Rupprecht, and Joachim Kinkel. "Enantiomeric enrichment of non-racemic mixtures of binaphthol with non-chiral packings." Chirality 8, no. 3 (1996): 234–43. http://dx.doi.org/10.1002/(sici)1520-636x(1996)8:3<234::aid-chir2>3.0.co;2-h.

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17

Lu, Tingting, Liangkui Zhu, Xiaohe Wang, Wenfu Yan, Wei Shi, and Ruren Xu. "A green route for the crystallization of a chiral polymorph A-enriched zeolite beta." Inorganic Chemistry Frontiers 5, no. 4 (2018): 802–5. http://dx.doi.org/10.1039/c7qi00709d.

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18

Coquerel, Gérard, and Marine Hoquante. "Spontaneous and Controlled Macroscopic Chiral Symmetry Breaking by Means of Crystallization." Symmetry 12, no. 11 (October 30, 2020): 1796. http://dx.doi.org/10.3390/sym12111796.

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In this paper, macroscopic chiral symmetry breaking refers to as the process in which a mixture of enantiomers departs from 50–50 symmetry to favor one chirality, resulting in either a scalemic mixture or a pure enantiomer. In this domain, crystallization offers various possibilities, from the classical Viedma ripening or Temperature Cycle-Induced Deracemization to the famous Kondepudi experiment and then to so-called Preferential Enrichment. These processes, together with some variants, will be depicted in terms of thermodynamic pathways, departure from equilibrium and operating conditions. Influential parameters on the final state will be reviewed as well as the impact of kinetics of the R ⇔ S equilibrium in solution on chiral symmetry breaking. How one can control the outcome of symmetry breaking is examined. Several open questions are detailed and different interpretations are discussed.

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19

Rybak, Witold K., and Anna Skarżyńska. "Enantiomeric enrichment of a nonracemic conglomerate of a chiral oxo-rhenium(v) complex." New J. Chem. 27, no. 12 (2003): 1687–89. http://dx.doi.org/10.1039/b308170b.

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20

OSANO, Y. T., A. UCHIDA, and Y. OHASHI. "ChemInform Abstract: Optical Enrichment of a Racemic Chiral Crystal by X-Ray Irradiation." ChemInform 22, no. 48 (August 22, 2010): no. http://dx.doi.org/10.1002/chin.199148051.

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21

Singh, Kavita, Wim J. M. Hegeman, Remi W. P. M. Laane, and Hing Man Chan. "Review and evaluation of a chiral enrichment model for chlordane enantiomers in the environment." Environmental Reviews 24, no. 4 (December 2016): 363–76. http://dx.doi.org/10.1139/er-2016-0015.

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Chlordane is an organochlorine pesticide that contains a mixture of components, some of which are chiral. Analysis of enantiomers can provide insights into the mechanisms of their sources, pathway, and fate. The objectives of this work were: (i) to review the published literature that reported chlordane enantiomer concentrations in various environmental compartments; (ii) to evaluate the applicability of a model developed by Hegeman and Laane (2002) for predicting the relative distribution of various chiral pesticides in the environment. This model predicts that enantiomer deviation increases in the following order: air, water, soil, molluscs, fish/birds, marine mammals, specific tissues, and enzymes; (iii) to determine the relative ranking of plants within the model. All data were converted into an enantiomer fraction and aggregated by environmental compartment using bootstrap averaging to compare to model predictions. Enantiomer distributions of cis-chlordane, trans-chlordane, oxychlordane, and heptachlor exo-epoxide were reported in soil, air, water/sediments, plants, and animals. Based on aggregated average estimates for enantiomer fraction, the deviation from racemic increased in the following order for cis-chlordane: water/sediments = lower trophic aquatic organisms < air < fish < soil < plants (all combined) < seal < polar bear < bird < whale; for trans-chlordane: fish < water/sediments < lower trophic aquatic organisms < air < soil < plants (all combined) < seal < whales < bird < polar bear; and for heptachlor exo-epoxide: plants (all combined) < fish < soil = whale < water/sediments < bird < air < seal < polar bear. Depending on the species used to represent marine mammals, the Spearman’s rank-order correlation coefficients of observed data against model predictions were + 0.75 or + 0.84 for cis-chlordane, + 0.41 or + 0.49 for trans-chlordane, and −0.59 or + 0.12 for heptachlor exo-epoxide. This suggests that the model is applicable for cis- and trans-chlordane, but not for heptachlor exo-epoxide. The fundamental mechanisms behind the observed enantiomeric enrichment are of eminent importance in understanding the enantioselective deviations.

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22

Hejl, Ewald, and Friedrich Finger. "Chiral Proportions of Nepheline Originating from Low-Viscosity Alkaline Melts. A Pilot Study." Symmetry 10, no. 9 (September 18, 2018): 410. http://dx.doi.org/10.3390/sym10090410.

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Chromatographic interaction between infiltrating solutions of racemic mixtures of enantiomers and enantiomorphic minerals with chiral excess has been proposed as a scenario for the emergence of biomolecular homochirality. Enantiomer separation is supposed to be produced by different partition coefficients of both enantiomers with regard to crystal faces or walls of capillary tubes in the enantiomorphic mineral. Besides quartz, nepheline is the only common magmatic mineral with enantiomorphic symmetry. It crystallizes from SiO2-undersaturated melts with low viscosity and is a promising candidate for chiral enrichment by autocatalytic secondary nucleation. Under liquidus conditions, the dynamic viscosity of silicate melts is mainly a function of polymerization. Melts with low concentrations of SiO2 (<55 wt%) and rather high concentrations of Na2O (>7 wt%) are only slightly polymerized and hence are characterized by low viscosities. Such melts can ascend, intrude or extrude by turbulent flow. Fourteen volcanic and subvolcanic samples from alkaline provinces in Africa and Sweden were chemically analyzed. Polished thin sections containing fresh nepheline phenocrysts were etched with 1% hydrofluoric acid at 20 °C for 15 to 25 min. Nepheline crystals suitable for a statistical evaluation of their etch figures were found in four samples. Crystals with chiral etch figures are mainly not twinned. Their chiral proportions in grain percentages of single crystals are close to parity in three samples. Only one sample shows a slight chiral excess (41.67% L-type vs. 58.33% D-type) but at a low level of significance (15 vs. 21 crystals, respectively).

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23

Kozyra, Kinga, Magdalena Klimek-Ochab, Małgorzata Brzezińska-Rodak, and Ewa Żymańczyk-Duda. "Direct determination of enantiomeric enrichment of chiral, underivatized aminophosphonic acids — useful for enantioselective bioconversion results evaluation." Open Chemistry 11, no. 9 (September 1, 2013): 1542–47. http://dx.doi.org/10.2478/s11532-013-0277-5.

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AbstractAbstract The possibility of applying 31P NMR spectroscopy for the determination of the enantiomeric excess of the racemic mixture of non-derivatized aminophosphonic acids with small side chains has been investigated. It is proven, that the effectiveness of the application of a chiral solvating agent strongly depends on the concentration of applied shift reagent and on the pH of the particular experiment. Effectual resolution protocols are elaborated for following phosphonic acids: 1-aminoethanephosphonic acid, 1-amino-2-methylpropanephosphonic acid, 1-aminophenylmethanephosphonic acid, 1-aminophenylmethane-phosphonic acid and 1-amino-2-phenylethanephosphonic acid. Graphical abstract

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24

Kołodziejska, Renata, Renata Studzińska, Agnieszka Tafelska-Kaczmarek, Hanna Pawluk, Dominika Mlicka, and Alina Woźniak. "Microbial Synthesis of (S)- and (R)-Benzoin in Enantioselective Desymmetrization and Deracemization Catalyzed by Aureobasidium pullulans Included in the Blossom Protect™ Agent." Molecules 26, no. 6 (March 12, 2021): 1578. http://dx.doi.org/10.3390/molecules26061578.

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In this study, we examined the Aureobasidium pullulans strains DSM 14940 and DSM 14941 included in the Blossom Protect™ agent to be used in the bioreduction reaction of a symmetrical dicarbonyl compound. Both chiral 2-hydroxy-1,2-diphenylethanone antipodes were obtained with a high enantiomeric purity. Mild conditions (phosphate buffer [pH 7.0, 7.2], 30 °C) were successfully employed in the synthesis of (S)-benzoin using two different methodologies: benzyl desymmetrization and rac-benzoin deracemization. Bioreduction carried out with higher reagent concentrations, lower pH values and prolonged reaction time, and in the presence of additives, enabled enrichment of the reaction mixture with (R)-benzoin. The described procedure is a potentially useful tool in the synthesis of chiral building blocks with a defined configuration in a simple and economical process with a lower environmental impact, enabling one-pot biotransformation.

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25

Jávor, Bálint, Panna Vezse, Ádám Golcs, Péter Huszthy, and Tünde Tóth. "Enantiodiscriminating Lipophilic Liquid Membrane-Based Assay for High-Throughput Nanomolar Enantioenrichment of Chiral Building Blocks." Membranes 13, no. 1 (January 11, 2023): 94. http://dx.doi.org/10.3390/membranes13010094.

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The reported optical resolution method was designed to support high-throughput enantioseparation of molecular building blocks obtained by automated small-scale synthetic methods. Lipophilic esters of common resolving agents were prepared and used as liquid membranes on the indifferent polymer surface of a microtiter assay. Chiral model compounds were enriched in one of the enantiomers starting from the aqueous solutions of their racemic mixture. Enantiodiscrimination was provided by forming diastereomeric coordination complexes of lipophilic enantiopure esters with the enantiomers of the chiral building blocks inside the liquid membranes. This enantiomeric recognition resulted in a greater distribution ratio of the preferred isomer in the membrane phase, thus the process enables a simultaneous enantioenrichment of the solutions outside the membrane. This paper reports a novel microplate-integrated stereoselective membrane enrichment technique satisfying the need for automatable enantioseparation on a subpreparative scale.

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26

Xue, Pengfei, Xiaowei Liu, Hao Jia, Haiyue Yuan, Bingjie Liu, Jingran Zhang, and Zeying He. "Environmental behavior of the chiral fungicide epoxiconazole in earthworm-soil system: Enantioselective enrichment, degradation kinetics, chiral metabolite identification, and biotransformation mechanism." Environment International 167 (September 2022): 107442. http://dx.doi.org/10.1016/j.envint.2022.107442.

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27

Berger, Urs, Walter Vetter, Arntraut Götsch, and Roland Kallenborn. "Chromatographic enrichment and enantiomer separation of axially chiral polybrominated biphenyls in a technical mixture." Journal of Chromatography A 973, no. 1-2 (October 2002): 123–33. http://dx.doi.org/10.1016/s0021-9673(02)01112-3.

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28

Hasegawa, Tomokuni, Masaaki Omote, Kazuyuki Sato, Akira Ando, and Itsumaro Kumadaki. "New Approach to a Novel Axially Chiral Ligand Showing Spontaneous Enrichment of Axial Chirality." CHEMICAL & PHARMACEUTICAL BULLETIN 51, no. 3 (2003): 265–67. http://dx.doi.org/10.1248/cpb.51.265.

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29

Nanita, Sergio C., Zoltan Takats, R. Graham Cooks, Sunnie Myung, and David E. Clemmer. "Chiral enrichment of serine via formation, dissociation, and soft-landing of octameric cluster ions." Journal of the American Society for Mass Spectrometry 15, no. 9 (September 2004): 1360–65. http://dx.doi.org/10.1016/j.jasms.2004.06.010.

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30

Peng, Xiaobin, Naoki Komatsu, Takahide Kimura, and Atsuhiro Osuka. "Improved Optical Enrichment of SWNTs through Extraction with Chiral Nanotweezers of 2,6-Pyridylene-Bridged Diporphyrins." Journal of the American Chemical Society 129, no. 51 (December 2007): 15947–53. http://dx.doi.org/10.1021/ja075094s.

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31

Shan, Zixing, Ying Xiong, Jing Yi, and Xiaoyun Hu. "Heterocomplexation of a Chiral Dipeptide and Quantitative Enantiomeric Enrichment of Nonracemic 1,1′-Bi-2-naphthol." Journal of Organic Chemistry 73, no. 22 (November 21, 2008): 9158–60. http://dx.doi.org/10.1021/jo801547j.

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32

Uchida, Yoshiaki, Sekai Iwama, Gérard Coquerel, and Rui Tamura. "A Kinetic/Thermodynamic Origin of Regular Chiral Fluctuation or Symmetry Breaking Unique to Preferential Enrichment." Chemistry - A European Journal 22, no. 33 (July 13, 2016): 11660–66. http://dx.doi.org/10.1002/chem.201601550.

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33

Iwama, Sekai, Kazunori Kuyama, Yuko Mori, Kochunnoonny Manoj, Rajesh G. Gonnade, Katsuaki Suzuki, Colan E. Hughes, et al. "Highly Efficient Chiral Resolution ofdl-Arginine by Cocrystal Formation Followed by Recrystallization under Preferential-Enrichment Conditions." Chemistry - A European Journal 20, no. 33 (July 15, 2014): 10343–50. http://dx.doi.org/10.1002/chem.201402446.

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34

Bidleman, Terry F., Andi D. Leone, Renee L. Falconer, Tom Harner, Liisa M. M. Jantunen, Karin Wiberg, Paul A. Helm, Miriam L. Diamond, and Binh Loo. "Chiral Pesticides in Soil and Water and Exchange with the Atmosphere." Scientific World JOURNAL 2 (2002): 357–73. http://dx.doi.org/10.1100/tsw.2002.109.

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The enantiomers of chiral pesticides are often metabolised at different rates in soil and water, leading to nonracemic residues. This paper reviews enantioselective metabolism of organochlorine pesticides (OCPs) in soil and water, and the use of enantiomers to follow transport and fate processes. Residues of chiral OCPs and their metabolites are frequently nonracemic in soil, although exceptions occur in which the OCPs are racemic. In soils where enantioselective degradation and/or metabolite formation has taken place, some OCPs usually show the same degradation preference — e.g., depletion of (+)trans-chlordane (TC) and (–)cis-chlordane (CC), and enrichment of the metabolite (+)heptachlor exo-epoxide (HEPX). The selectivity is ambivalent for other chemicals; preferential loss of either (+) or (–)o,p’-DDT and enrichment of either (+) or (–)oxychlordane (OXY) occurs in different soils. Nonracemic OCPs are found in air samples collected above soil which contains nonracemic residues. The enantiomer profiles of chlordanes in ambient air suggests that most chlordane in northern Alabama air comes from racemic sources (e.g., termiticide emissions), whereas a mixture of racemic and nonracemic (volatilisation from soil) sources supplies chlordane to air in the Great Lakes region. Chlordanes and HEPX are also nonracemic in arctic air, probably the result of soil emissions from lower latitudes. The (+) enantiomer ofα-hexachlorocyclohexane (α-HCH) is preferentially metabolised in the Arctic Ocean, arctic lakes and watersheds, the North American Great Lakes, and the Baltic Sea. In some marine regions (the Bering and Chukchi Seas, parts of the North Sea) the preference is reversed and (–)α-HCH is depleted. Volatilisation from seas and large lakes can be traced by the appearance of nonracemicα-HCH in the air boundary layer above the water. Estimates of microbial degradation rates forα-HCH in the eastern Arctic Ocean and an arctic lake have been made from the enantiomer fractions (EFs) and mass balance in the water column. Apparent pseudo first-order rate constants in the eastern Arctic Ocean are 0.12 year-1for (+)α-HCH, 0.030 year-1 for (–)α-HCH, and 0.037 year-1for achiralΥ-HCH. These rate constants are 3–10 times greater than those for basic hydrolysis in seawater. Microbial breakdown may compete with advective outflow for long-term removal of HCHs from the Arctic Ocean. Rate constants estimated for the arctic lake are about 3–8 times greater than those in the ocean.

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35

Ghiasvand, Alireza, Zikai Feng, and Joselito P. Quirino. "Enrichment and Separation of Cationic, Neutral, and Chiral Analytes by Micelle to Cyclodextrin Stacking–Micellar Electrokinetic Chromatography." Analytical Chemistry 91, no. 3 (December 24, 2018): 1752–57. http://dx.doi.org/10.1021/acs.analchem.8b03542.

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36

Valković, Vlado, and Jasmina Obhođaš. "Origins of Chiral Life in Interstellar Molecular Clouds." Astronomical Journal 163, no. 6 (May 17, 2022): 270. http://dx.doi.org/10.3847/1538-3881/ac63d0.

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Abstract The exploring of galactic chemical composition across the the Milky Way, and specifically across the solar neighborhood, provides insights into the chemical evolution of the universe. Since the formation of the first stars some hundred million years after the big bang (BB), heavier elements are synthesized in different stellar production processes at the expense of lighter elements. When the relative abundances of the life-forming elements evaluated for the Last Universal Common Ancestor (LUCA) are compared with the solar neighborhood stellar abundances, a striking similarity occurs. In this study, we tested the hypothesis that in some particular regions and at some particular time, the abundance curve of the first living matter and the universe coincided. Indeed, the best agreement between the two curves was obtained for (4 ± 1)× 109 yr after the BB, indicating the time of the origin of life. All organisms evolved on the Earth independently of place and time are leading to the LUCA and involve chiral molecules such as L amino acids and D sugars in fundamental life processes. The growing evidence from carbonaceous meteorites analysis shows an excess of L-type amino acids and D-type sugars, suggesting that the increase in L-type or D-type molecular chirality is the process that takes place in planetary and stellar forming systems, thus the life emerging from interstellar molecular clouds (IMCs) had to be chiral. Here we propose the spin-polarized proton–proton scattering as a potential physical process that takes place in IMCs environments and could lead to enrichment of L-type amino acids and D-type sugars.

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37

Bayer, Ernst, Hartmut Frank, Jürgen Gerhardt, and Graeme Nicholson. "Capillary Gas Chromatographic Analysis of Amino Acids by Enantiomer Labeling." Journal of AOAC INTERNATIONAL 70, no. 2 (March 1, 1987): 234–40. http://dx.doi.org/10.1093/jaoac/70.2.234.

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Abstract The optical isomers of amino acids can be easily separated by gas chromatography using capillary columns coated with the chiral polysiloxane peptide, Chirasil-Val. Quantitative trace amino acid analysis in complex mixtures such as biological fluids, sea water, or protein hydrolysates can be achieved by enantiomer labeling: The D-amino acid enantiomers, which do not occur naturally, are added to the sample prior to analysis as internal standards. Because the D-enantiomers show the same physical and chemical properties as the natural L-enantiomers, they are ideal standard references. In routine analysis, the derivatization is achieved with a new automated derivatization robot. The D-standard serves as overall internal standard for the whole analytical procedure from sample enrichment to derivatization, chromatography, and response of the detector.

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38

Franzini, Roberta, Alessia Rosetti, and Claudio Villani. "Low Temperature Dynamic Chromatography for the Separation of the Interconverting Conformational Enantiomers of the Benzodiazepines Clonazolam, Flubromazolam, Diclazepam and Flurazepam." Symmetry 13, no. 6 (June 4, 2021): 1012. http://dx.doi.org/10.3390/sym13061012.

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Benzodiazepines (BZDs) are an important class of psychoactive drugs with hypnotic-sedative, myorelaxant, anxiolytic and anticonvulsant properties due to interaction with the GABAa receptor in the central nervous system of mammals. BZDs are interesting both in clinical and forensic toxicology for their pharmacological characteristics and potential of abuse. The presence of a non-planar diazepine ring generates chiral conformational stereoisomers, even in the absence of stereogenic centers. A conformational enrichment of BZD at the binding sites has been reported in the literature, thus making interesting a stereodynamic screening of a wide range of BZDs. Herein, we report the investigation of three stereolabile 1,4-benzodiazepine included in the class of “designer benzodiazepines” (e.g., diclazepam, a chloro-derivative of diazepam, and two triazolo-benzodiazepines, flubromazolam and clonazolam) and a commercially available BZD known as flurazepam, in order to study the kinetic of the “ring-flip” process that allows two conformational enantiomers to interconvert at high rate at room temperature. A combination of low temperature enantioselective dynamic chromatography on chiral stationary phase and computer simulations of the experimental chromatograms allowed us to measure activation energies of enantiomerization (ΔG‡) lower than 18.5 kcal/mol. The differences between compounds have been correlated to the pattern of substitutions on the 1,4-benzodiazepinic core.

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39

Meierhenrich, Uwe J. "Amino Acids and the Asymmetry of Life." European Review 21, no. 2 (April 30, 2013): 190–99. http://dx.doi.org/10.1017/s106279871200035x.

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‘How did life start on Earth?’ and ‘Why were left-handed amino acids selected for the architecture of proteins?’ A new attempt to answer these questions of high public and interdisciplinary scientific interest will be provided by this review. It will describe most recent experimental data on how the basic and molecular building blocks of life, amino acids, formed in a prebiotic setting. Most amino acids are chiral, that is that they cannot be superimposed with their mirror image molecules (enantiomers). In processes triggering the origin of life on Earth, the equal occurrence, i.e. the parity between left-handed amino acids and their right-handed mirror images, was violated. In the case of amino acids, the balance was tipped to the left – as a result of which life's proteins today exclusively implement the left-handed form of amino acids, called l-amino acid enantiomers. Neither plants, nor animals, including humans, make use of d-amino acids for the molecular architecture of their proteins (enzymes). This review addresses the molecular asymmetry of amino acids in living organisms, namely the preference for left-handedness. What was the cause for the violation of molecular parity of amino acids in the emergence of life on Earth? All the fascinating models proposed by physicists, chemists, and biologists will be vividly presented including the scientific conflicts. Special emphasis will be given to amino acid enantiomers that were subjected to chiral photons. The interaction between racemic molecules and chiral photons was shown to produce an enantiomeric enrichment that will be discussed in the context of absolute asymmetric synthesis. The concluding paragraphs will describe the attempt to verify any of those models with the chirality-module of the Rosetta mission. This European space mission contains probe Philae that was launched on board the Rosetta spacecraft with the aim of landing on the icy surface of comet 67P/Churyumov-Gerasimenko and analysing whether chiral organic compounds are present that could have been brought to the Earth by comet impacts.

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Manoj, Kochunnoonny, Hiroki Takahashi, Sekai Iwama, Rajesh G. Gonnade, Hirohito Tsue, and Rui Tamura. "Crystal structure analysis of highly efficient chiral resolution of (RS)-arginine-fumaric acid cocrystal under preferential enrichment conditions." Journal of Molecular Structure 1245 (December 2021): 131073. http://dx.doi.org/10.1016/j.molstruc.2021.131073.

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41

Raudino, Antonio, and Martina Pannuzzo. "Hydrodynamic-induced enantiomeric enrichment of self-assemblies: Role of the solid-liquid interface in chiral nucleation and seeding." Journal of Chemical Physics 137, no. 13 (October 7, 2012): 134902. http://dx.doi.org/10.1063/1.4754434.

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42

Tamura, Rui, Hiroki Takahashi, Hideyuki Miura, Zsolt Lepp, Yoshitaka Nakajima, Ken Hirotsu, and Takanori Ushio. "Comparison of Crystal Structures of New Racemic Chiral Compounds Showing and Not Showing the Phenomenon of Preferential Enrichment." Supramolecular Chemistry 13, no. 1 (January 1, 2001): 71–78. http://dx.doi.org/10.1080/10610270108034884.

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43

Kumar, Vijay Bhooshan, Yael Steinberg, Ze'ev Porat, Molhm Nassir, Abed Saady, Alfred Hassner, and Aharon Gedanken. "A New Approach to Chiral Enrichment by Exposure of Racemates of Amino Acids to Sonochemically-Prepared BSA Microspheres." ChemistrySelect 2, no. 27 (September 21, 2017): 8234–38. http://dx.doi.org/10.1002/slct.201701525.

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44

De Saint Jores, Clément, Clément Brandel, Marie Vaccaro, Najla Gharbi, Isabelle Schmitz-Afonso, Pascal Cardinael, Rui Tamura, and Gérard Coquerel. "Reinvestigating the Preferential Enrichment of DL-Arginine Fumarate: New Thoughts on the Mechanism of This Far from Equilibrium Crystallization Phenomenon." Molecules 27, no. 24 (December 7, 2022): 8652. http://dx.doi.org/10.3390/molecules27248652.

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Preferential enrichment (PE) is a crystallization process, starting from either a racemic of slightly enantio-enriched solution (ca. +5%) that results in a high enantiomeric excess in the liquid phase (>+90%ee) and a slight opposite excess in the deposited crystals (−2 to −5%ee). The mechanism(s) of this symmetry-breaking phenomenon is (are) still a matter of debate since it eludes rationalization by phase diagram formalism. In this publication, we thoroughly reinvestigate the PE phenomenon of arginine fumarate by using a new approach: the process is monitored by introducing isotopically labeled arginine enantiomers into the crystallization medium to better understand the mass exchanges during crystallization. These experiments are supported by chiral HPLC-MS/MS. This study permits re-evaluating the criteria that were thought mandatory to perform PE. In particular, we show that PE occurs by a continuous exchange between the solution and the crystals and does not require the occurrence of a solvent-mediated solid–solid phase transition.

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Ruiz-Rodríguez, L., A. Aguilar, A. N. Díaz, and F. G. Sánchez. "Enantioseparation of the fungicide imazalil in orange juice by chiral HPLC. Study on degradation rates and extractive/enrichment techniques." Food Chemistry 178 (July 2015): 179–85. http://dx.doi.org/10.1016/j.foodchem.2015.01.004.

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46

Hashizume, Daisuke, and Yuji Ohashi. "Optical enrichment in chiral crystal environment of [(R,S)-1-cyanoethyl][methyl (S)-alaninate]cobaloxime complex only by photoirradiation." Journal of Physical Organic Chemistry 13, no. 7 (2000): 415–21. http://dx.doi.org/10.1002/1099-1395(200007)13:7<415::aid-poc286>3.0.co;2-z.

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47

Ruddell, Stuart, Elena Sugrue, Sarah Memarzadeh, Lorna Mae Hellam, Sam J. Wilson, and David J. France. "Synthesis, Enantiomeric Resolution and Biological Evaluation of HIV Capsid Inhibition Activity for Racemic, (S)- and (R)-PF74." Molecules 26, no. 13 (June 26, 2021): 3919. http://dx.doi.org/10.3390/molecules26133919.

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PF74 is a capsid-targeting inhibitor of HIV replication that effectively perturbs the highly sensitive viral uncoating process. A lack of information regarding the optical purity (enantiomeric excess) of the single stereogenic centre of PF74 has resulted in ambiguity as to the potency of different samples of this compound. Herein is described the synthesis of enantiomerically enriched (S)- and (R)-PF74 and further enrichment of the samples (≥98%) using chiral HPLC resolution. The biological activities of each enantiomer were then evaluated, which determined (S)-PF74 (IC50 1.5 µM) to be significantly more active than (R)-PF74 (IC50 19 µM). Computational docking studies were then conducted to rationalise this large discrepancy in activity, which indicated different binding conformations for each enantiomer. The binding energy of the conformation adopted by the more active (S)-PF74 (ΔG = −73.8 kcal/mol) was calculated to be more favourable than the conformation adopted by the less active (R)-enantiomer (ΔG = −55.8 kcal/mol) in agreement with experimental observations.

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Hermansson, Jörgen, Inger Hermansson, and Jan Nordin. "Characterization of a Chiral-AGP capillary column coupled to a micro sample-enrichment system with UV and electrospray mass spectrometric detection." Journal of Chromatography A 631, no. 1-2 (February 1993): 79–90. http://dx.doi.org/10.1016/0021-9673(93)80508-6.

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Brand, Stephen K., Joel E. Schmidt, Michael W. Deem, Frits Daeyaert, Yanhang Ma, Osamu Terasaki, Marat Orazov, and Mark E. Davis. "Enantiomerically enriched, polycrystalline molecular sieves." Proceedings of the National Academy of Sciences 114, no. 20 (May 1, 2017): 5101–6. http://dx.doi.org/10.1073/pnas.1704638114.

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Zeolite and zeolite-like molecular sieves are being used in a large number of applications such as adsorption and catalysis. Achievement of the long-standing goal of creating a chiral, polycrystalline molecular sieve with bulk enantioenrichment would enable these materials to perform enantioselective functions. Here, we report the synthesis of enantiomerically enriched samples of a molecular sieve. Enantiopure organic structure directing agents are designed with the assistance of computational methods and used to synthesize enantioenriched, polycrystalline molecular sieve samples of either enantiomer. Computational results correctly predicted which enantiomer is obtained, and enantiomeric enrichment is proven by high-resolution transmission electron microscopy. The enantioenriched and racemic samples of the molecular sieves are tested as adsorbents and heterogeneous catalysts. The enantioenriched molecular sieves show enantioselectivity for the ring opening reaction of epoxides and enantioselective adsorption of 2-butanol (the R enantiomer of the molecular sieve shows opposite and approximately equal enantioselectivity compared with the S enantiomer of the molecular sieve, whereas the racemic sample of the molecular sieve shows no enantioselectivity).

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Peng, Xiaobin, Feng Wang, Takahide Kimura, Naoki Komatsu, and Atsuhiro Osuka. "Optical Resolution and Diameter-Based Enrichment of Single-Walled Carbon Nanotubes through Simultaneous Recognition of Their Helicity and Diameter with Chiral Monoporphyrin." Journal of Physical Chemistry C 113, no. 21 (May 4, 2009): 9108–13. http://dx.doi.org/10.1021/jp810952g.

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