1
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Mruc P, Olbrycht M, Korbetskyy M, Antos D. Altering the mobile phase composition to enhance self-disproportionation of enantiomers in achiral chromatography. J Chromatogr A 2024; 1715:464603. [PMID: 38168648 DOI: 10.1016/j.chroma.2023.464603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 12/13/2023] [Accepted: 12/22/2023] [Indexed: 01/05/2024]
Abstract
The influence of mobile phase composition on the efficiency of enantiomer separation by achiral chromatography (ACh) was investigated. The separation was induced by the phenomenon of self-disproportionation of enantiomers (SDE) triggered by their homo and hetero-chiral interactions in an achiral environment. Typically, SDE occurs in apolar mobile phases of weak elution strength, which causes the separation time to extend and the process productivity to deteriorate. To mitigate that effect, we altered the content of a strong solvent (modifier) in the mobile phase by use of a solvent gradient in which the target enantiomer was separated in the presence of the weak solvent, whereas the unresolved mixture of enantiomers was eluted by increasing the modifier content in the mobile phase. This enabled accelerating the solute elution while preserving the separation selectivity. The approach was examined for the separation of nonracemic mixtures of two structurally different compounds that exhibited the SDE effect in ACh, i.e., metalaxyl (MX) and methyl p-tolyl sulfoxide (MTSO). The target compound of the separation was the more abundant enantiomer in the enantiomeric mixture. The process realization was preceded by the determination of the effect of the modifier content on the separation yield for enantiomeric mixtures of MX and MTSO of different enantiomeric excess (ee). In the case of MX, yield of the pure target enantiomer varied from 2 %, for the maximum concentration of the modifier, to 45 % for the minimum modifier concentration and the largest ee used in the experiments. In the case of MTSO, the yield varied from minimum 40 % to maximum 66 %. To predict the process, we employed a dynamic model, in which underlying thermodynamic dependencies were implemented.
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Affiliation(s)
- Patrycja Mruc
- Doctoral School of the Rzeszów University of Technology/PL, Poland
| | - Maksymilian Olbrycht
- Department of Chemical and Process Engineering, Rzeszow University of Technology, Rzeszów, Poland
| | - Markiian Korbetskyy
- Department of Chemical and Process Engineering, Rzeszow University of Technology, Rzeszów, Poland
| | - Dorota Antos
- Department of Chemical and Process Engineering, Rzeszow University of Technology, Rzeszów, Poland.
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2
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Takimoto K, Shimada T, Nagura K, Hill JP, Nakanishi T, Yuge H, Ishihara S, Labuta J, Sato H. Thermo-/Mechano-Chromic Chiral Coordination Dimer: Formation of Switchable and Metastable Discrete Structure through Chiral Self-Sorting. J Am Chem Soc 2023; 145:25160-25169. [PMID: 37943955 DOI: 10.1021/jacs.3c05866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
Although strong chiral self-sorting often emerges in extended covalent or supramolecular polymers, the phenomenon is generally weak in discrete assemblies (e.g., dimers and oligomers) of small molecules due to the lack of a cooperative growth mechanism. Consequently, chiral self-sorting has been overlooked in the design of switchable and metastable discrete supramolecular structures. Here, we report a butyl-benzo[h]quinoline-based iridium(III) complex (Bu-Ir) with helical chirality at its metal center, which forms preferentially a homochiral dimer and exhibits thermo-/mechano-chromism based on a monomer-dimer transformation. While a five-coordinate monomer is formed in a racemic or an enantiopure Bu-Ir solution at 25 °C, a six-coordinate homochiral dimer complex is formed almost exclusively at low temperatures, with a higher degree of dimerization in enantiopure Bu-Ir solution. Estimation of apparent dimerization binding constants (K) and thermodynamic parameters (ΔH and ΔS) based on variable temperature ultraviolet-visible (UV-vis) and 1H NMR spectra reveals a strong preference for homochiral dimerization (largest known value for the coordination complex, Khomo/Khetero > 50). Notably, crystals of the homochiral dimer are metastable, undergoing a distinct color change upon grinding (from yellow to red) due to mechanical cleavage of coordination bonds (i.e., a dimer to monomer transformation). A comparison with control compounds having different substituents (proton, methyl, isopropyl, and phenyl groups) reveals that Bu-Ir dimerization involves both strong homochiral self-sorting preference and connected thermo-/mechano-chromic behavior, which is based on matched propeller-shaped chirality and subtle steric repulsion between alkyl substituents that render the homochiral dimer switchable and metastable. These findings provide substantial insights into the emergence of dynamic functionality based on the rational design of discrete chiral assemblies.
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Affiliation(s)
- Kazuyoshi Takimoto
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
- Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitazato, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan
| | - Takumi Shimada
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Kazuhiko Nagura
- Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Jonathan P Hill
- Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Takashi Nakanishi
- Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Hidetaka Yuge
- Department of Chemistry, School of Science, Kitasato University, 1-15-1 Kitazato, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan
| | - Shinsuke Ishihara
- Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Jan Labuta
- Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Hisako Sato
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
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Olbrycht M, Gumieniak J, Mruc P, Balawejder M, Piątkowski W, Antos D. Separation of non-racemic mixtures of enantiomers by achiral chromatography. J Chromatogr A 2023; 1693:463877. [PMID: 36854210 DOI: 10.1016/j.chroma.2023.463877] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/15/2023] [Accepted: 02/15/2023] [Indexed: 02/21/2023]
Abstract
The phenomenon of partial separation of enantiomeric mixtures in achiral chromatography (ACh) has already been documented for a wide variety of chiral compounds. It is attributed to the so-called effect of self-disproportionation of enantiomers (SDE). However, quantitative description of the SDE mechanism underlying adsorption of enantiomers on achiral surfaces is still incomplete, which hinders the application of that technique for large-scale separations. In this study, a mechanistic model for description of retention behavior of SDE-phoric compounds in silica-based ACh has been developed along with a procedure for fast determination of the model parameters. The model assumes formation of associates of chiral molecules, which occurs due to homo and hetero-chiral interactions in the adsorbed phase. The ability of the model to reproduce band profiles was verified for enantiomeric mixtures of three structurally different chiral compounds.
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Affiliation(s)
- Maksymilian Olbrycht
- Department of Chemical and Process Engineering, Rzeszow University of Technology, Rzeszów, Poland
| | - Justyna Gumieniak
- Department of Component Manufacturing and Production Organization, Rzeszów University of Technology, Stalowa Wola, Poland
| | - Patrycja Mruc
- Doctoral School of Engineering and Technical Sciences at the Rzeszów University of Technology, Poland
| | - Maciej Balawejder
- Institute of Food Technology and Nutrition, The College of Natural Sciences, University of Rzeszów, Rzeszów, Poland
| | - Wojciech Piątkowski
- Department of Chemical and Process Engineering, Rzeszow University of Technology, Rzeszów, Poland
| | - Dorota Antos
- Department of Chemical and Process Engineering, Rzeszow University of Technology, Rzeszów, Poland.
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Han J, Wzorek A, Klika KD, Soloshonok VA. Recommended Tests for the Self-Disproportionation of Enantiomers (SDE) to Ensure Accurate Reporting of the Stereochemical Outcome of Enantioselective Reactions. MOLECULES (BASEL, SWITZERLAND) 2021; 26:molecules26092757. [PMID: 34067099 PMCID: PMC8124418 DOI: 10.3390/molecules26092757] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 05/04/2021] [Accepted: 05/04/2021] [Indexed: 12/14/2022]
Abstract
The purpose of this review is to highlight the necessity of conducting tests to gauge the magnitude of the self-disproportionation of enantiomers (SDE) phenomenon to ensure the veracity of reported enantiomeric excess (ee) values for scalemic samples obtained from enantioselective reactions, natural products isolation, etc. The SDE always occurs to some degree whenever any scalemic sample is subjected to physicochemical processes concomitant with the fractionation of the sample, thus leading to erroneous reporting of the true ee of the sample if due care is not taken to either preclude the effects of the SDE by measurement of the ee prior to the application of physicochemical processes, suppressing the SDE, or evaluating all obtained fractions of the sample. Or even avoiding fractionation altogether if possible. There is a clear necessity to conduct tests to assess the magnitude of the SDE for the processes applied to samples and the updated and improved recommendations described herein cover chromatography and processes involving gas-phase transformations such as evaporation or sublimation.
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Affiliation(s)
- Jianlin Han
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, International Innovation Center for Forest Chemicals and Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China;
| | - Alicja Wzorek
- Institute of Chemistry, Jan Kochanowski University in Kielce, Uniwersytecka 7, 25-406 Kielce, Poland;
| | - Karel D. Klika
- Molecular Structure Analysis, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- Correspondence: (K.D.K.); (V.A.S.)
| | - Vadim A. Soloshonok
- Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel Lardizábal 3, 20018 San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, Alameda Urquijo 36-5, Plaza Bizkaia, 48011 Bilbao, Spain
- Correspondence: (K.D.K.); (V.A.S.)
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5
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Abstract
The optical purity of an enantiomeric mixture deduced from specific rotation measurements was found by Horeau to be different from its enantiomeric excess, which came to be known as the Horeau effect. This observation had important implications in the practical use of specific rotations and has led to investigations on homochiral and heterochiral aggregation processes. In this review, dedicated to the Horeau principle, the theoretical basis for the observance of the Horeau effect and a survey of the specific rotation studies investigating the Horeau effect are provided, and possible future investigations are suggested.
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Han J, Wzorek A, Soloshonok VA, Klika KD. The self-disproportionation of enantiomers (SDE): The effect of scaling down, potential problems versus prospective applications, possible new occurrences, and unrealized opportunities? Electrophoresis 2019; 40:1869-1880. [PMID: 30653701 DOI: 10.1002/elps.201800414] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 12/24/2018] [Accepted: 01/13/2019] [Indexed: 11/10/2022]
Abstract
This commentary discusses an important, though not widely appreciated, chiral phenomenon of molecular chirality that effectively always occurs whenever nonracemic samples are subjected to practically any physicochemical process (e.g., force field, recrystallization, sublimation, even distillation, etc.) under totally achiral conditions external to the sample itself. The phenomenon is termed as the self-disproportionation of enantiomers (SDE) and though ubiquitous, its presence may not always be readily apparent, or workers may be otherwise oblivious to its effects. In the particular case of chromatography, when the SDE is apparent, the enantiomeric excess (ee) of the chiral compound is observed to vary across an eluted peak, with anterior eluted portions either enantioenriched or enantiodepleted relative to the ee of the starting material, and conversely for the posterior eluted portions. Herein, we highlight various aspects of the SDE phenomenon as it pertains to chromatography and, in particular, the effect of scaling down chromatographic systems, the potential risk of problems that the SDE can cause, as well as opportunities for practical applications of the phenomenon, possible new occurrences of the SDE phenomenon to be searched for, and unrealized opportunities.
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Affiliation(s)
- Jianlin Han
- College of Chemical Engineering, Nanjing Forestry University, Nanjing, P. R. China
| | - Alicja Wzorek
- Institute of Chemistry, Jan Kochanowski University in Kielce, Kielce, Poland.,Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country UPV/EHU, San Sebastián, Spain
| | - Vadim A Soloshonok
- Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country UPV/EHU, San Sebastián, Spain.,Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Karel D Klika
- Molecular Structure Analysis, German Cancer Research Center (DKFZ), Heidelberg, Germany
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7
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Self-induced recognition of enantiomers (SIRE) and its application in chiral NMR analysis. Trends Analyt Chem 2018. [DOI: 10.1016/j.trac.2018.07.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Han J, Kitagawa O, Wzorek A, Klika KD, Soloshonok VA. The self-disproportionation of enantiomers (SDE): a menace or an opportunity? Chem Sci 2018; 9:1718-1739. [PMID: 29675218 PMCID: PMC5892310 DOI: 10.1039/c7sc05138g] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Accepted: 01/12/2018] [Indexed: 01/05/2023] Open
Abstract
Herein we report on the well-documented, yet not widely known, phenomenon of the self-disproportionation of enantiomers (SDE): the spontaneous fractionation of scalemic material into enantioenriched and -depleted fractions when any physicochemical process is applied.
Herein we report on the well-documented, yet not widely known, phenomenon of the self-disproportionation of enantiomers (SDE): the spontaneous fractionation of scalemic material into enantioenriched and -depleted fractions when any physicochemical process is applied. The SDE has implications ranging from the origins of prebiotic homochirality to unconventional enantiopurification methods, though the risks of altering the enantiomeric excess (ee) unintentionally, regrettably, remain greatly unappreciated. While recrystallization is well known as an SDE process, occurrences of the SDE in other processes are much less recognized, e.g. sublimation and even distillation. But the most common process that many workers seem to be completely ignorant of is SDE via chromatography and reports have included all manner of structures, all types of interactions, and all forms of chromatography, including GC. The SDE can be either a blessing – as a means to obtain enantiopure samples from scalemates – or a curse, as unwitting alteration of the ee leads to errors in the reporting of results and/or misinterpretation of the system under study. Thus the ramifications of the SDE are relevant to any area involving chirality – natural products, asymmetric synthesis, etc. Moreover, there is grave concern regarding errors in the literature, in addition to the possible occurrence of valid results which may have been overlooked and thus remain unreported, as well as the potential for the SDE to alter the ee, particularly via chromatography, and the following concepts will be conveyed: (1) the SDE occurs under totally achiral conditions of (a) precipitation, (b) centrifugation, (c) evaporation, (d) distillation, (e) crystallization, (f) sublimation, and (g) achiral chromatography (e.g. column, flash, MPLC, HPLC, SEC, GC, etc.). (2) The SDE cannot be controlled simply by experimental accuracy and ignorance of the SDE unavoidably leads to mistakes in the recorded and reported stereochemical outcome of enantioselective transformations. (3) The magnitude of the SDE (the difference between the extremes of enantioenrichment and -depletion) can be controlled and used to: (a) minimize mistakes in the recorded experimental values and (b) to develop unconventional and preparatively superior methods for enantiopurification. (4) The magnitude of the SDE cannot be predicted but can be expected for compounds possessing SDE-phoric groups or which have a general tendency for strong hydrogen or halogen bonds or dipole–dipole or aromatic π–π interactions. (5) An SDE test and the rigorous reporting and description of applied physicochemical processes should become part of standard experimental practice to prevent the erroneous reporting of the stereochemical outcome of enantioselective catalytic reactions and the chirooptical properties of scalemates. New directions in the study of the SDE, including halogen bonding-based interactions and novel, unconventional enantiopurification methods such as pseudo-SDE (chiral selector-assisted SDE resolution of racemates), are also reported.
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Affiliation(s)
- Jianlin Han
- School of Chemistry and Chemical Engineering , State Key Laboratory of Coordination Chemistry , Jiangsu Key Laboratory of Advanced Organic Materials , Nanjing University , 210093 Nanjing , China .
| | - Osamu Kitagawa
- Department of Applied Chemistry , Shibaura Institute of Technology , 3-7-5 Toyosu, Kohto-ku , Tokyo 135-8548 , Japan
| | - Alicja Wzorek
- Institute of Chemistry , Jan Kochanowski University in Kielce , Świętokrzyska 15G , 25-406 Kielce , Poland.,Department of Organic Chemistry I , Faculty of Chemistry , University of the Basque Country UPV/EHU , Paseo Manuel Lardizábal 3 , 20018 San Sebastián , Spain .
| | - Karel D Klika
- Molecular Structure Analysis , German Cancer Research Center (DKFZ) , Im Neuenheimer Feld 280 , D-69009 Heidelberg , Germany .
| | - Vadim A Soloshonok
- Department of Organic Chemistry I , Faculty of Chemistry , University of the Basque Country UPV/EHU , Paseo Manuel Lardizábal 3 , 20018 San Sebastián , Spain . .,IKERBASQUE, Basque Foundation for Science , Alameda Urquijo 36-5, Plaza, Bizkaia , 48011 Bilbao , Spain
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9
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Martens J, Bhushan R. Enantioseparations in Achiral Environments and Chromatographic Systems. Isr J Chem 2016. [DOI: 10.1002/ijch.201600086] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jürgen Martens
- Institute of Chemistry; Carl von Ossietzky University Oldenburg; Carl-von-Ossietzky-Strasse 9-11, DE- 26129 Oldenburg Germany
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Covington CL, Polavarapu PL. Solvation dependence observed in the electronic dissymmetry factor spectra: how much information are we missing by analyzing the circular dichroism spectra alone? Phys Chem Chem Phys 2016; 18:13912-7. [DOI: 10.1039/c6cp01247g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electronic dissymmetry factor (EDF) spectra reveal that for [1,1′-binaphthalene]-2,2′-diol the experimental EDF spectra show solvent polarity dependent effects that are not apparent in the electronic circular dichroism or absorption spectra.
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11
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Covington CL, Polavarapu PL. Specific Optical Rotations and the Horeau Effect. Chirality 2015; 28:181-5. [DOI: 10.1002/chir.22565] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Revised: 11/12/2015] [Accepted: 11/18/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Cody L. Covington
- Department of Chemistry; Vanderbilt University; Nashville Tennessee USA
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12
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Polavarapu PL, Covington CL. Wavelength resolved specific optical rotations and homochiral equilibria. Phys Chem Chem Phys 2015; 17:21630-3. [DOI: 10.1039/c5cp01834j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Wavelength resolved specific optical rotations in homochiral monomer–dimer equilibria.
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13
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Self-disproportionation of Enantiomers of Enantiomerically Enriched Compounds. Top Curr Chem (Cham) 2013; 341:301-39. [PMID: 23605252 DOI: 10.1007/128_2013_434] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
This review describes self-disproportionation of enantiomers (SDE) of non-racemic mixtures, subjected to distillation, sublimation, or chromatography on achiral stationary phase using achiral eluent, which leads to the substantial enantiomeric enrichment and corresponding depletion in different fractions, as compared to the enantiomeric composition of the starting material. This phenomenon is of a very general nature as SDE has been reported for different classes of chiral organic compounds bearing various functional groups and possessing diverse elements of chirality. The literature data discussed in this review clearly suggests that SDE is typical for enantiomerically enriched chiral organic compounds and special care should always be taken in evaluation of the stereochemical outcome of enantioselective reactions as well as determination of enantiomeric ratios of non-racemic mixtures of natural products after any purification process. The role of molecular association of enantiomers on the magnitude and preparative efficiency of SDE, as a new, nonconventional method for enantiomerc purifications, is emphasized and discussed.
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14
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Soloshonok VA, Roussel C, Kitagawa O, Sorochinsky AE. Self-disproportionation of enantiomers via achiral chromatography: a warning and an extra dimension in optical purifications. Chem Soc Rev 2012; 41:4180-8. [PMID: 22517405 DOI: 10.1039/c2cs35006h] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This tutorial review describes the self-disproportionation of enantiomers (SDE) of chiral, non-racemic compounds, subjected to chromatography on an achiral stationary phase using an achiral eluent, which leads to the substantial enantiomeric enrichment and the corresponding depletion in different fractions, as compared to the enantiomeric composition of the starting material. The physicochemical background of SDE is a dynamic formation of homo- or heterochiral dimeric or oligomeric aggregates of different chromatographic behavior. This phenomenon is of a very general nature as the SDE has been reported for different classes of organic compounds bearing various functional groups and possessing diverse elements of chirality (central, axial and helical chirality). The literature data discussed in this review clearly suggest that SDE via achiral chromatography might be expected for any given chiral enantiomerically enriched compound. This presents two very important issues for organic chemists. First, chromatographic purification of reaction products can lead to erroneous determination of the stereochemical outcome of catalytic asymmetric reactions and second, achiral chromatography can be used as a new, nonconventional method for optical purifications. The latter has tremendous practical potential as the currently available techniques are limited to crystallization or chiral chromatography. However, a further systematic study of SDE is needed to develop understanding of this phenomenon and to design practical chromatographic separation techniques for optical purification of non-racemic mixtures by achiral-phase chromatography.
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Affiliation(s)
- Vadim A Soloshonok
- Department of Organic Chemistry I, Faculty of Chemistry, University of the Basque Country UPV/EHU, 20018 San Sebastian, Spain.
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15
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Atencio A. Separation of chiral molecules: a way to homochirality. ORIGINS LIFE EVOL B 2012; 42:55-73. [PMID: 22373602 DOI: 10.1007/s11084-012-9265-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Accepted: 12/05/2011] [Indexed: 10/28/2022]
Abstract
A mechanism for separating chiral molecules is proposed. The separation of two enantiomers in an aquifer is considered. The molecules are dragged in the aquifer porous medium by a flow of water or of another liquid. The molecule velocity is u=v/R, where v is the liquid velocity, and R is the retardation factor. The aquifer consists of two one-dimensional layers disposed in series. The layers differ by the retardation factor or by the liquid velocity. The enantiomer velocity is a function of the enantiomer concentrations. This function is different in the two layers. For certain values of the model parameters and when the molecules entering the aquifer are enantiomerically enriched or when the medium is chiral, the concentration of one enantiomer increases around the interface between the two layers and in one layer, whereas the concentration of the other enantiomer decreases. Enantiomer synthesis and decay are not taken into account. The needed values of the parameters can be obtained when the enantiomers are moved by an alternating liquid flow, and the retardation factor oscillates in synchronism with the alternating liquid flow. The parameters of the model are then understood as quantities averaged over one oscillation period. The equations that give the values of the stationary concentrations of the enantiomers are found. The evolution of the enantiomer concentrations is determined by numerically solving a system of two nonlinear advection-dispersion equations. The proposed mechanism may have played a role in the emergence of biomolecular homochirality.
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Affiliation(s)
- A Atencio
- Institute of Spectroscopy, Russian Academy of Science, 142190, Troitsk, Moscow Region, Russia.
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16
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Thoß M, Seidel RW, Oppel IM, Feigel M. Structural characterization of racemic 1,1′-bi-(2-naphthol) monopivalate and its 6-nitro derivative. J Mol Struct 2010. [DOI: 10.1016/j.molstruc.2010.07.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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17
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Trapp O, Schurig V. Nonlinear effects in enantioselective chromatography: prediction of unusual elution profiles of enantiomers in non-racemic mixtures on an achiral stationary phase doped with small amounts of a chiral selector. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.tetasy.2010.04.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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18
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Enantiodifferentiation of phytoalexin spirobrassinin derivatives using the chiral solvating agent (R)-(+)-1,1′-bi-2-naphthol in conjunction with molecular modeling. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.tetasy.2010.03.035] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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19
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Self-disproportionation of enantiomers of heterocyclic compounds having a tertiary trifluoromethyl alcohol center on chromatography with a non-chiral system. J Fluor Chem 2010. [DOI: 10.1016/j.jfluchem.2009.12.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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20
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Marcelo G, de Francisco R, González-Álvarez MJ, Mendicuti F. Fluorescence properties of (R)- and (S)-[1,1′-binaphthalene]-2,2′-diols solutions and their complexes with cyclodextrins in aqueous medium. J Photochem Photobiol A Chem 2008. [DOI: 10.1016/j.jphotochem.2008.06.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Nieminen V, Murzin DY, Klika KD. NMR and molecular modeling of the dimeric self-association of the enantiomers of 1,1'-bi-2-naphthol and 1-phenyl-2,2,2-trifluoroethanol in the solution state and their relevance to enantiomer self-disproportionation on achiral-phase chromatography (ESDAC). Org Biomol Chem 2008; 7:537-42. [PMID: 19156320 DOI: 10.1039/b814905d] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecular modeling of the homo- and heterochiral dimeric self-associates of the enantiomers of 1,1'-bi-2-naphthol and 1-phenyl-2,2,2-trifluoroethanol in solution has been performed in order to understand their NMR behavior and in light of the phenomenon of "enantiomer self-disproportionation on achiral-phase chromatography" (ESDAC). For 1,1'-bi-2-naphthol in C(6)D(6), distinct NMR signals for each enantiomer arise for some spins in non-racemic mixtures-the phenomenon of self-induced diastereomeric anisochronism (SIDA). The linear divergence of these split signals across an enantiomeric titration (a series of samples in which the percentage of one enantiomer is varied from 50-100% whilst maintaining a constant total concentration), as well as the near linear migration of certain signals in CDCl(3) across a similar enantiomeric titration, where signals were not observed to be split, is consistent with the calculated small energy differences between the homo- and heterochiral associates. For an enantiomeric titration of 1-phenyl-2,2,2-trifluoroethanol in n-hexane, NMR signals also remained unsplit but the noticeable migration of some revealed a skew indicative of a preference for the heterochiral associate. This was duly reflected in the calculations which provided a DeltaG value favoring the heterochiral associate by 2.4 kJ mol(-1). The relevance of these results to evaluating the likely occurrence of ESDAC is considered.
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Affiliation(s)
- Ville Nieminen
- Laboratory of Industrial Chemistry, Process Chemistry Centre, Abo Akademi University, FIN-20500 Abo, Finland
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22
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Schurig V. Elaborate treatment of retention in chemoselective chromatography--the retention increment approach and non-linear effects. J Chromatogr A 2008; 1216:1723-36. [PMID: 19070865 DOI: 10.1016/j.chroma.2008.11.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 11/07/2008] [Accepted: 11/10/2008] [Indexed: 11/27/2022]
Abstract
The retention increment approach is described which quantifies the association equilibria of a selectand and a selector in complexation and inclusion chromatography. A thermodynamic treatment of enantioselectivity based on retention phenomena in chromatography including entropy/enthalpy compensation and the isoenantioselective temperature is advanced. Kinetic parameters of enantiomerization are discussed. Non-linear effects, both existent and elusive, are described and proposed, respectively. The enantioselectivity pertaining to catalysis vs. chromatography is compared and a unified nomenclature is proposed. Through an educational effort, this account is aimed at providing a deeper insight into chemoselective aspects of chromatography thereby stimulating further research of both established and speculative phenomena of the most intriguing manifestation of chemoselectivity, that is, of enantioselectivity.
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Affiliation(s)
- Volker Schurig
- Institute of Organic Chemistry, University of Tübingen, 72076 Tübingen, Germany.
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23
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Cozzolino S, Sanna MG, Valentini M. Probing interactions by means of pulsed field gradient nuclear magnetic resonance spectroscopy. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46 Suppl 1:S16-S23. [PMID: 18855336 DOI: 10.1002/mrc.2345] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Molecular self-diffusion coefficients (D) of species in solution are related to size and shape and can be used for studying association phenomena. Pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy has been revealed to be a powerful analytical tool for D measurement in different research fields. The present work briefly illustrates the use of PFG-NMR for assessing the existence of interactions in very different chemical systems: organic and organometallic compounds, colloidal materials and biological aggregates. The application of PFG-NMR is remarkable for understanding the role of anions in homogenous transition metal catalysis and for assessing the aggregation behaviour of biopolymers in material science.
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Affiliation(s)
- Sara Cozzolino
- Agricultural Research Council, Research Centre for Plant Soil System, Instrumental Centre of Tor Mancina, S. P. Pascolarese-Strada della Neve Km 1, 00015 Monterotondo, Rome, Italy
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24
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Rossi S, Lo Nostro P, Lagi M, Ninham BW, Baglioni P. Specific Anion Effects on the Optical Rotation of α-Amino Acids. J Phys Chem B 2007; 111:10510-9. [PMID: 17691834 DOI: 10.1021/jp0721806] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Changes in optical rotation of some alpha-amino acids are induced by electrolytes. Such effects on l- and d-enantiomers of a range of amino acids are explored for sodium salts with varying anion. The amino acids studied were alanine, aspartic acid, glutamic acid, glutamine, proline, threonine, and tryptophan. The anion's polarizability in solution accounts for the change in [alpha] only for the halides. Self-association of amino acids in solution and pH changes due to the presence of the electrolytes do not account for the observed variations in optical activity. Specific interactions of anions with the chiral amino acids (Hofmeister effects) and salt-induced perturbations of the amino acid hydration shell appear to be responsible for the effects, and conformational changes in the chiral solutes due to the presence of ionic species are discussed.
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Affiliation(s)
- Simona Rossi
- Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze), Italy
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25
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Forrat VJ, Ramón DJ, Yus M. First catalytic enantioselective synthesis of the cocaine abuse therapeutic agent (S)-(+)-1-(4-{2-[bis(4-fluorophenyl)methoxy]ethyl}piperazin-1-yl)-2-phenyl-2-propanol. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.tetasy.2006.12.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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26
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Mihlbachler K, De Jesús MA, Kaczmarski K, Sepaniak MJ, Seidel-Morgenstern A, Guiochon G. Adsorption behavior of the (+/-)-Tröger's base enantiomers in the phase system of a silica-based packing coated with amylose tri(3,5-dimethyl carbamate) and 2-propanol and molecular modeling interpretation. J Chromatogr A 2006; 1113:148-61. [PMID: 16516901 DOI: 10.1016/j.chroma.2006.02.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2004] [Revised: 01/26/2006] [Accepted: 02/01/2006] [Indexed: 11/29/2022]
Abstract
The binary adsorption isotherms of the enantiomers of Tröger's base in the phase system made of Chiral Technologies ChiralPak AD [a silica-based packing coated with amylose tri(3,5-dimethyl carbamate)] as the chiral stationary phase (CSP) and 2-propanol as the mobile phase were measured by the perturbation method. The more retained enantiomer exhibits a S-shaped adsorption isotherm with a clear inflection point, the concentration of the less retained enantiomer having practically no competitive influence on this isotherm: In the entire range of concentrations studied, dq2/dC1 approximately 0. By contrast, the less retained enantiomer has a Langmuir adsorption isotherm when pure. At constant mobile phase concentrations, however, its equilibrium concentration in the adsorbed phase increases with increasing concentration of the more retained enantiomer and dq1/dC2 > 0. This cooperative adsorption behavior, opposed to the classical competitive behavior, is exceedingly rare but was clearly demonstrated in this case. Two adsorption isotherm equations that account for these physical observations were derived. They are based on the formation of an adsorbed multi-layer, as suggested by the isotherm data. The excellent agreement between the experimental overloaded elution profiles of binary mixtures and the profiles calculated with the equilibrium-dispersive model validates this binary isotherm model. The adsorption energies calculated by molecular mechanics (MM) and by molecular dynamics (MD) indicate that the chiral recognition arising from the different interactions between the functional groups of the CSP and the molecules of the Tröger's base enantiomers are mainly driven by their Van der Waals interactions. The MD data suggest that the interactions of the (-)-Tröger's base with the CSP are more favored by 8+/-(5) kJ/mol than those of (+)-Tröger's base. This difference seems to be a contributing factor to the increased retention of the - enantiomer on this chromatographic system. The modeling of the data also indicates that both enantiomers can form high stoichiometry complexes while binding onto the stationary phase, in agreement with the results of the equilibrium isotherm studies.
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27
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Chiral recognition and behavior of [1,1′-binaphthalene]-2,2′-diol in aqueous solution by fluorescence spectroscopy. J Photochem Photobiol A Chem 2006. [DOI: 10.1016/j.jphotochem.2005.06.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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28
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Costero AM, Colera M, Gaviña P, Gil S, Ochando LE. Experimental evidence for the homochiral aggregation of ammonium salts in solution. NEW J CHEM 2006. [DOI: 10.1039/b607100g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Baciocchi R, Mazzotti M, Morbidelli MC. General model for the achiral chromatography of enantiomers forming dimers: application to binaphthol. J Chromatogr A 2004; 1024:15-20. [PMID: 14753702 DOI: 10.1016/j.chroma.2003.10.071] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
This works deals with the development of a model for the description of the chromatographic behavior of enantiomers forming dimers on achiral stationary phases. The model describes the formation of both homochiral and heterochiral dimers by introducing two equilibrium constants, K(homo) and K(hetero), which have to be independently estimated. The adsorption of both monomeric and dimeric species is described by a bi-Langmuir isotherm. Both adsorption and dimerization equilibrium models are implemented in a standard equilibrium-dispersive model of the chromatographic column. The isotherm parameters are determined by fitting of pulses constituted either of the pure enantiomers or of non racemic mixtures of both enantiomers. The validity of the model is then assessed by application to the binaphthol case.
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Affiliation(s)
- Renato Baciocchi
- Department of Civil Engineering, University of Rome "Tor Vergata", via del Politecnico, I-00133 Rome, Italy
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Goldsmith MR, Jayasuriya N, Beratan DN, Wipf P. Optical rotation of noncovalent aggregates. J Am Chem Soc 2004; 125:15696-7. [PMID: 14677931 DOI: 10.1021/ja0376893] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dilute solutions of (R)-(-)-pantolactone in CCl4 were studied by polarimetry in conjunction with theoretical calculations of [alpha]D. Our data demonstrate that the self-association of a chiral solute results in a change in [alpha]D that can be accounted for by the presence of hydrogen-bonded dimeric species. The theoretical analysis predicts a concentration-dependent specific rotation in good agreement with experiment. Further exploration of monomer and dimer [alpha]D differences, through atomic map analysis, reveals large contributions to [alpha]D from the hydrogen-bonded hydroxyl groups in the tightly-coupled dimer. This study extends the computation of chiroptical properties to the accurate concentration-dependent prediction of [alpha]D for noncovalently interacting self-associating species.
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Affiliation(s)
- Michael-Rock Goldsmith
- Departments of Chemistry and Biochemistry, Duke University, Durham, North Carolina 27708, USA
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