1
|
Low Temperature Dynamic Chromatography for the Separation of the Interconverting Conformational Enantiomers of the Benzodiazepines Clonazolam, Flubromazolam, Diclazepam and Flurazepam. Symmetry (Basel) 2021. [DOI: 10.3390/sym13061012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
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.
Collapse
|
2
|
Sabia R, Ciogli A, Pierini M, Franzini R, Iazzetti A, Villani C. Chromatographic separation of the interconverting enantiomers of imidazo- and triazole-fused benzodiazepines. J Chromatogr A 2021; 1647:462148. [PMID: 33957345 DOI: 10.1016/j.chroma.2021.462148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 03/25/2021] [Accepted: 04/03/2021] [Indexed: 10/21/2022]
Abstract
The toolbox of medicinal chemists includes the 1,4-benzodiazepine scaffold as a "privileged scaffold" in drug discovery. Several biologically active small molecules containing a 1,4-benzodiazepine scaffold have been approved by the FDA for the treatment of various diseases, with most of them being used for their psychotropic effects. The therapeutic potential of 1,4-benzodiazepines has stimulated the interest of synthetic chemists in developing new synthetic strategies to a range of substituted analogues for biological evaluation. A structural variation of the classical benzodiazepine skeleton is observed e.g. in alprazolam, midazolam, and related benzodiazepines, which contain a 1,2,4-triazole or an imidazole ring fused to the benzodiazepine core. Irrespective of the presence of the fused heterocyclic ring, the seven-membered diazepine ring is far from planar, and its shape resembles a twist chair. Then, the unsymmetrical substitution pattern around the seven membered cycle renders these molecules chiral, as they lack any reflection-type symmetry element. However, chirality of this molecules is labile at room temperature, becausea simple ring flipping process converts one enantiomer into the other, and 1,4-benzodiazepines exist as a mixture of rapidly interconverting conformational enantiomers in solution at or near room temperature. Physical separation of the interconverting enantiomers of diazepam and of other related 1,4-benzodiazepin-2-ones can be accomplished by low temperature HPLC on chiral stationary phases (CSPs). If the HPLC column is cooled down to temperatures where the interconversion rate is sufficiently low, compared to the chromatographic separation rate, distinct separated peaks can be observed, provided the CSP is sufficiently enantioselctive. The apparent rate constants for the on-column enantiomerization and the corresponding free energy activation barriers were obtained by simulation of exchange-deformed HPLC profiles using a computer program based on the stochastic model. Here we report on the dynamic HPLC investigations carried out on a set of fused imidazo and triazolo-benzodiazepines (alprazolam, midazolam, triazolam and estazolam) The experimental dynamic chromatograms and the corresponding interconversion barriers reported in this paper show that the third fused heterocyclic ring increase the energy barrier by 2 kcal/mol.
Collapse
Affiliation(s)
- Rocchina Sabia
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy.
| | - Alessia Ciogli
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy
| | - Marco Pierini
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy
| | - Roberta Franzini
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy
| | - Antonia Iazzetti
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy
| | - Claudio Villani
- SapienzaUniversità di Roma, Dipartimento di Chimica e Tecnologie del Farmaco, P.le A. Moro 5, 00185Rome, Italy.
| |
Collapse
|
3
|
Franzini R, Pierini M, Mazzanti A, Iazzetti A, Ciogli A, Villani C. Molecular Recognition of the HPLC Whelk-O1 Selector towards the Conformational Enantiomers of Nevirapine and Oxcarbazepine. Int J Mol Sci 2020; 22:ijms22010144. [PMID: 33375681 PMCID: PMC7796420 DOI: 10.3390/ijms22010144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/16/2020] [Accepted: 12/23/2020] [Indexed: 01/19/2023] Open
Abstract
The presence of stereogenic elements is a common feature in pharmaceutical compounds, and affording optically pure stereoisomers is a frequent issue in drug design. In this context, the study of the chiral molecular recognition mechanism fundamentally supports the understanding and optimization of chromatographic separations with chiral stationary phases. We investigated, with molecular docking, the interactions between the chiral HPLC selector Whelk-O1 and the stereoisomers of two bioactive compounds, the antiviral Nevirapine and the anticonvulsant Oxcarbazepine, both characterized by two stereolabile conformational enantiomers. The presence of fast-exchange enantiomers and the rate of the interconversion process were studied using low temperature enantioselective HPLC and VT-NMR with Whelk-O1 applied as chiral solvating agent. The values of the energetic barriers of interconversion indicate, for the single enantiomers of both compounds, half-lives sufficiently long enough to allow their separation only at critically sub-ambient temperatures. The chiral selector Whelk-O1 performed as a strongly selective discriminating agent both when applied as a chiral stationary phase (CSP) in HPLC and as CSA in NMR spectroscopy.
Collapse
Affiliation(s)
- Roberta Franzini
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
- Correspondence: (R.F.); (C.V.)
| | - Marco Pierini
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
| | - Andrea Mazzanti
- Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, V. Risorgimento 4, 40136 Bologna, Italy;
| | - Antonia Iazzetti
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
| | - Alessia Ciogli
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
| | - Claudio Villani
- Department of Chemistry and Technology of Drugs, “Department of Excellence 2018−2022”, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; (M.P.); (A.I.); (A.C.)
- Correspondence: (R.F.); (C.V.)
| |
Collapse
|
4
|
Costil R, Crespi S, Pfeifer L, Feringa BL. Modulation of a Supramolecular Figure-of-Eight Strip Based on a Photoswitchable Stiff-Stilbene. Chemistry 2020; 26:7783-7787. [PMID: 32343010 PMCID: PMC7384132 DOI: 10.1002/chem.202002051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Indexed: 01/18/2023]
Abstract
The preparation, assembly and dynamic properties of photoswitchable bisphosphine ligands based on the stiff-stilbene scaffold are reported. Directional bonding and coordination-induced assembly allow complexation of these ligands with palladium(II), resulting in the formation of discrete metallo-supramolecular entities. While the Z isomer forms a simple bidentate metallo-macrocycle, an intricate double helicate figure-of-eight dimer is observed with the E ligand. Topologically 3D complexes can thus be obtained from 2D ligands. Upon irradiation with UV light, isomerization of the ligands allows control of the architecture of the formed complexes, resulting in a light-triggered modulation of the supramolecular topology. Furthermore, a mechanistic investigation unveiled the dynamic nature of the helicate chirality, where a transmission of motion from the palladium centers yields an "eight-to-eight" inversion.
Collapse
Affiliation(s)
- Romain Costil
- Stratingh Institute for ChemistryZernike Institute for Advanced MaterialsUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
| | - Stefano Crespi
- Stratingh Institute for ChemistryZernike Institute for Advanced MaterialsUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
| | - Lukas Pfeifer
- Stratingh Institute for ChemistryZernike Institute for Advanced MaterialsUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
| | - Ben L. Feringa
- Stratingh Institute for ChemistryZernike Institute for Advanced MaterialsUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
| |
Collapse
|
5
|
Talsi EP, Bryliakova AA, Ottenbacher RV, Rybalova TV, Bryliakov KP. Chiral Autoamplification Meets Dynamic Chirality Control to Suggest Nonautocatalytic Chemical Model of Prebiotic Chirality Amplification. RESEARCH (WASHINGTON, D.C.) 2019; 2019:4756025. [PMID: 31922134 PMCID: PMC6946252 DOI: 10.34133/2019/4756025] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 09/16/2019] [Indexed: 06/10/2023]
Abstract
Oxidative kinetic resolution of 1-phenylethanol in the presence of manganese complexes, bearing conformationally nonrigid achiral bis-amine-bis-pyridine ligands, in the absence of any exogenous chiral additives, is reported. The only driving force for the chiral discrimination is the small initial enantiomeric imbalance of the scalemic (nonracemic) substrate: the latter dynamically controls the chirality of the catalyst, serving itself as the chiral auxiliary. In effect, the ee of 1-phenylethanol increases monotonously over the reaction course. This dynamic control of catalyst chirality by the substrate has been unprecedented; a consistent kinetic model for this process is presented. The reported catalyzed substrate self-enantioenrichment mechanism is discussed in relation to the problem of prebiotic chirality amplification.
Collapse
Affiliation(s)
- Evgenii P. Talsi
- Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
- Boreskov Institute of Catalysis, Pr. Lavrentieva 5, Novosibirsk 630090, Russia
| | - Anna A. Bryliakova
- Boreskov Institute of Catalysis, Pr. Lavrentieva 5, Novosibirsk 630090, Russia
| | - Roman V. Ottenbacher
- Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
- Boreskov Institute of Catalysis, Pr. Lavrentieva 5, Novosibirsk 630090, Russia
| | - Tatyana V. Rybalova
- Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
- Vorozhtsov Novosibirsk Institute of Organic Chemistry, Pr. Lavrentieva 9, Novosibirsk 630090, Russia
| | - Konstantin P. Bryliakov
- Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
- Boreskov Institute of Catalysis, Pr. Lavrentieva 5, Novosibirsk 630090, Russia
| |
Collapse
|
6
|
Chatterjee S, Bhattacharjee P, Butterfoss GL, Achari A, Jaisankar P. Establishment of atropisomerism in 3-indolyl furanoids: a synthetic, experimental and theoretical perspective. RSC Adv 2019; 9:22384-22388. [PMID: 35519481 PMCID: PMC9066644 DOI: 10.1039/c9ra05350f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 07/15/2019] [Indexed: 11/21/2022] Open
Abstract
A number of axially chiral 3-indolyl furanoids have been synthesized and the individual enantiomers are found to be configurationally stable and isolable at room temperature.
Collapse
Affiliation(s)
- Sourav Chatterjee
- Laboratory of Catalysis and Chemical Biology
- Department of Organic and Medicinal Chemistry
- CSIR-Indian Institute of Chemical Biology
- Kolkata-700 032
- India
| | - Pinaki Bhattacharjee
- Laboratory of Catalysis and Chemical Biology
- Department of Organic and Medicinal Chemistry
- CSIR-Indian Institute of Chemical Biology
- Kolkata-700 032
- India
| | - Glenn L. Butterfoss
- Center for Genomics and Systems Biology
- New York University Abu Dhabi
- Abu Dhabi-129188
- United Arab Emirates
| | - Anushree Achari
- Laboratory of Catalysis and Chemical Biology
- Department of Organic and Medicinal Chemistry
- CSIR-Indian Institute of Chemical Biology
- Kolkata-700 032
- India
| | - Parasuraman Jaisankar
- Laboratory of Catalysis and Chemical Biology
- Department of Organic and Medicinal Chemistry
- CSIR-Indian Institute of Chemical Biology
- Kolkata-700 032
- India
| |
Collapse
|
7
|
Sepsey A, Németh DR, Németh G, Felinger A. Rate constant determination of interconverting enantiomers by chiral chromatography using a stochastic model. J Chromatogr A 2018; 1564:155-162. [DOI: 10.1016/j.chroma.2018.06.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 06/03/2018] [Accepted: 06/05/2018] [Indexed: 11/29/2022]
|
8
|
Prati L, Mancinelli M, Ciogli A, Mazzanti A. Tetrasubstituted cyclopentadienones as suitable enantiopure ligands with axial chirality. Org Biomol Chem 2017; 15:8720-8728. [DOI: 10.1039/c7ob01455d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of thermally stable atropisomeric phencyclones has been successfully synthesized as ligands in new ruthenium-based enantioselective hydrogenation catalysts.
Collapse
Affiliation(s)
- L. Prati
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| | - M. Mancinelli
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| | - A. Ciogli
- Department of Chemistry and Technologies of Drug
- Sapienza University of Rome
- I-00185 Rome
- Italy
| | - A. Mazzanti
- Department of Industrial Chemistry “Toso Montanari”
- University of Bologna
- 40136 Bologna
- Italy
| |
Collapse
|
9
|
Moskowitz M, Xu H, Wolf C. Enantiomerization Kinetics of 2,2′‐Disubstituted Biphenyls: A Dynamic Chiral HPLC Investigation. Isr J Chem 2016. [DOI: 10.1002/ijch.201600070] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Max Moskowitz
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 (USA)
| | - Hanhui Xu
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 (USA)
| | - Christian Wolf
- Department of Chemistry Georgetown University 37th and O Streets Washington DC 20057 (USA)
| |
Collapse
|
10
|
Dynamic Behavior of Clobazam on High-Performance Liquid Chromatography Chiral Stationary Phases. Chirality 2015; 28:17-21. [DOI: 10.1002/chir.22542] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 09/03/2015] [Accepted: 09/09/2015] [Indexed: 12/24/2022]
|
11
|
Rizzo S, Menta S, Benincori T, Ferretti R, Pierini M, Cirilli R, Sannicolò F. Determination of the Enantiomerization Barrier of the Residual Enantiomers ofC3-Symmetric Tris[3-(1-Methyl-2-Alkyl)Indolyl]Phosphane Oxides: Case Study of a Multitasking HPLC Investigation Based on an Immobilized Polysaccharide Stationary Phase. Chirality 2015; 27:888-99. [DOI: 10.1002/chir.22525] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 08/03/2015] [Accepted: 08/03/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Simona Rizzo
- Istituto di Scienze e Tecnologie Molecolari; Consiglio Nazionale delle Ricerche; Milano Italy
| | - Sergio Menta
- Dipartimento di Chimica e Tecnologie del Farmaco; Sapienza Università di Roma; Roma Italy
| | - Tiziana Benincori
- Dipartimento di Scienza ed Alta Tecnologia; Università degli Studi dell'Insubria; Como Italy
| | - Rosella Ferretti
- Dipartimento di Chimica del Farmaco; Istituto Superiore di Sanità; Roma Italy
| | - Marco Pierini
- Dipartimento di Chimica e Tecnologie del Farmaco; Sapienza Università di Roma; Roma Italy
| | - Roberto Cirilli
- Dipartimento di Chimica del Farmaco; Istituto Superiore di Sanità; Roma Italy
| | | |
Collapse
|
12
|
Walz S, Weis S, Franz M, Rominger F, Trapp O. Investigation of the enantiomerization barriers of the phthalimidone derivatives EM12 and lenalidomide by dynamic electrokinetic chromatography. Electrophoresis 2015; 36:796-804. [DOI: 10.1002/elps.201400499] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 11/27/2014] [Accepted: 11/29/2014] [Indexed: 01/09/2023]
Affiliation(s)
- Sarah Walz
- Organisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Heidelberg Germany
| | - Sylvia Weis
- Organisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Heidelberg Germany
| | - Mareike Franz
- Organisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Heidelberg Germany
| | - Frank Rominger
- Organisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Heidelberg Germany
| | - Oliver Trapp
- Organisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; Heidelberg Germany
| |
Collapse
|
13
|
Sabia R, Ciogli A, Pierini M, Gasparrini F, Villani C. Dynamic high performance liquid chromatography on chiral stationary phases. Low temperature separation of the interconverting enantiomers of diazepam, flunitrazepam, prazepam and tetrazepam. J Chromatogr A 2014; 1363:144-9. [DOI: 10.1016/j.chroma.2014.07.097] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 07/25/2014] [Accepted: 07/28/2014] [Indexed: 10/24/2022]
|
14
|
Vanthuyne N, Roussel C. Chiroptical Detectors for the Study of Unusual Phenomena in Chiral Chromatography. Top Curr Chem (Cham) 2013; 340:107-51. [DOI: 10.1007/128_2013_441] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
|
15
|
Reddy G. N. M, Ballesteros-Garrido R, Lacour J, Caldarelli S. Determination of Labile Chiral Supramolecular Ion Pairs by Chromatographic NMR Spectroscopy. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201209616] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
16
|
Reddy G. N. M, Ballesteros-Garrido R, Lacour J, Caldarelli S. Determination of Labile Chiral Supramolecular Ion Pairs by Chromatographic NMR Spectroscopy. Angew Chem Int Ed Engl 2013; 52:3255-8. [DOI: 10.1002/anie.201209616] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Indexed: 11/07/2022]
|
17
|
He X, Lin R, He H, Sun M, Xiao D. Chiral Separation of Ketoprofen on a Chirobiotic T Column and Its Chiral Recognition Mechanisms. Chromatographia 2012. [DOI: 10.1007/s10337-012-2352-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
18
|
Levi Mortera S, Sabia R, Pierini M, Gasparrini F, Villani C. The dynamic chromatographic behavior of tri-o-thymotide on HPLC chiral stationary phases. Chem Commun (Camb) 2012; 48:3167-9. [DOI: 10.1039/c2cc00021k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
19
|
Affiliation(s)
- Timothy J. Ward
- Millsaps College, 1701 N. State Street, Box 150306, Jackson, Mississippi 39210
| | - Karen D. Ward
- Millsaps College, 1701 N. State Street, Box 150306, Jackson, Mississippi 39210
| |
Collapse
|
20
|
Piron F, Vanthuyne N, Joulin B, Naubron JV, Cismaş C, Terec A, Varga RA, Roussel C, Roncali J, Grosu I. Synthesis, structural analysis, and chiral investigations of some atropisomers with EE-tetrahalogeno-1,3-butadiene core. J Org Chem 2010; 74:9062-70. [PMID: 19886632 DOI: 10.1021/jo901762j] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The atropenantiomers of stable 1,2,3,4-tetrahalo-1,3-butadiene derivatives (where halogeno stands for bromine or iodine) were separated with use of chiral HPLC. The barriers for the enantiomerization process were determined on-line by dynamic HPLC (DHPLC) or off-line by classical kinetic measurements. In the case of the tetrachloro compound, the barrier was too low for DHPLC and its value was obtained by dynamic NMR experiments. The obtained barriers for chloro, bromo, and iodo derivatives correlate with the van der Waals radii of the halogens. The absolute configuration of the isolated enantiomers of the tetraiodo and tetrabromo compounds was assigned by comparison of the experimental and conformations averaged calculated VCD spectra. The identification of a signature band of the absolute configuration of the butadiene core, the sign and location of which are independent from the different conformations and substituents, allowing the safe assignment of the absolute configuration of the enantiomers of chiral 1,3-butadienes, is also reported.
Collapse
Affiliation(s)
- Flavia Piron
- Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, Cluj-Napoca, 11 Arany Janos str., 400028, Cluj-Napoca, Romania
| | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Cancelliere G, Ciogli A, D’Acquarica I, Gasparrini F, Kocergin J, Misiti D, Pierini M, Ritchie H, Simone P, Villani C. Transition from enantioselective high performance to ultra-high performance liquid chromatography: A case study of a brush-type chiral stationary phase based on sub-5-micron to sub-2-micron silica particles. J Chromatogr A 2010; 1217:990-9. [DOI: 10.1016/j.chroma.2009.10.021] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 10/01/2009] [Accepted: 10/07/2009] [Indexed: 10/20/2022]
|