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Formen JSSK, Wolf C. Optical Enantiodifferentiation of Chiral Nitriles. Org Lett 2024. [PMID: 39229874 DOI: 10.1021/acs.orglett.4c02758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
Chiroptical sensing of nitriles is achieved with excellent functional group tolerance by hydrozirconation and subsequent transmetalation of the corresponding iminate to a chromophoric palladium complex. A one-pot workflow that uses the Schwartz reagent and [(η3-1-tert-butylindenyl)(μ-Cl)Pd]2 as sensor generates a palladium complex displaying red-shifted CD inductions and characteristic UV changes. These chiroptical responses are accurately correlated to the enantiomeric ratio and total concentration of the original nitrile.
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Affiliation(s)
- Jeffrey S S K Formen
- Chemistry Department, Georgetown University, Washington D.C. 20057, United States
| | - Christian Wolf
- Chemistry Department, Georgetown University, Washington D.C. 20057, United States
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2
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Formen JSSK, Wolf C. Optical Relay Sensing of Cryptochiral Alcohols Displaying α-, β-, γ- and δ-Stereocenters or Chirality by Virtue of Isotopic Substitution. Angew Chem Int Ed Engl 2024; 63:e202409790. [PMID: 38880778 DOI: 10.1002/anie.202409790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Accepted: 06/11/2024] [Indexed: 06/18/2024]
Abstract
A reaction-based optical relay sensing strategy that enables accurate determination of the concentration and enantiomeric ratio (er) of challenging chiral alcohols exhibiting stereocenters at the α-, β-, γ- or even δ-position or hard-to-detect cryptochirality arising from H/D substitution is described. This unmatched application scope is achieved with a conceptually new sensing approach by which the alcohol moiety is replaced with an optimized achiral sulfonamide chromophore to minimize the distance between the covalently attached chiroptical reporter unit and the stereogenic center in the substrate. The result is a remarkably strong, red-shifted CD induction that increases linearly with the sample er. The CD sensing part of the tandem assay is seamlessly coupled to a redox reaction with a quinone molecule to generate a characteristic UV response that is independent of the enantiopurity of the alcohol and thus allows determination of the total analyte concentration. The robustness and utility of the CD/UV relay are further verified by chromatography-free asymmetric reaction analysis with small aliquots of crude product mixtures, paving the way toward high-throughput chiral compound screening workflows which is a highly sought-after goal in the pharmaceutical industry.
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Affiliation(s)
| | - Christian Wolf
- Department of Chemistry, Georgetown University, Washington, DC-20057, USA
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3
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Nelson E, Bertke JA, Thanzeel FY, Wolf C. Organometallic Chirality Sensing via "Click"-Like η 6-Arene Coordination with an Achiral Cp*Ru(II) Piano Stool Complex. Angew Chem Int Ed Engl 2024; 63:e202404594. [PMID: 38634562 DOI: 10.1002/anie.202404594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 04/09/2024] [Accepted: 04/18/2024] [Indexed: 04/19/2024]
Abstract
Piano stool complexes have been studied over many years and found widespread applications in organic synthesis, catalysis, materials and drug development. We now report the first examples of quantitative chiroptical molecular recognition of chiral compounds through click-like η6-arene coordination with readily available half sandwich complexes. This conceptually new approach to chirality sensing is based on irreversible acetonitrile displacement of [Cp*Ru(CH3CN)3]PF6 by an aromatic target molecule, a process that is fast and complete within a few minutes at room temperature. The metal coordination coincides with characteristic circular dichroism inductions that can be easily correlated to the absolute configuration and enantiomeric ratio of the bound molecule. A relay assay that decouples the determination of the enantiomeric composition and of the total sample amount by a practical CD/UV measurement protocol was developed and successfully tested. The introduction of piano stool complexes to the chiroptical sensing realm is mechanistically unique and extends the scope of currently known methods with small-molecule probes that require the presence of amino, alcohol, carboxylate or other privileged functional groups for binding of the target compound. A broad application range including pharmaceutically relevant multifunctional molecules and the use in chromatography-free asymmetric reaction analysis are also demonstrated.
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Affiliation(s)
- Eryn Nelson
- Chemistry Department, Georgetown University, 3700 O St NW, Washington, DC-20057
| | - Jeffery A Bertke
- Chemistry Department, Georgetown University, 3700 O St NW, Washington, DC-20057
| | - F Yushra Thanzeel
- Chemistry Department, Georgetown University, 3700 O St NW, Washington, DC-20057
| | - Christian Wolf
- Chemistry Department, Georgetown University, 3700 O St NW, Washington, DC-20057
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4
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Formen JSSK, Howard JR, Anslyn EV, Wolf C. Circular Dichroism Sensing: Strategies and Applications. Angew Chem Int Ed Engl 2024; 63:e202400767. [PMID: 38421186 DOI: 10.1002/anie.202400767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 02/23/2024] [Accepted: 02/28/2024] [Indexed: 03/02/2024]
Abstract
The analysis of the absolute configuration, enantiomeric composition, and concentration of chiral compounds are frequently encountered tasks across the chemical and health sciences. Chiroptical sensing methods can streamline this work and allow high-throughput screening with remarkable reduction of operational time and cost. During the last few years, significant methodological advances with innovative chirality sensing systems, the use of computer-generated calibration curves, machine learning assistance, and chemometric data processing, to name a few, have emerged and are now matched with commercially available multi-well plate CD readers. These developments have reframed the chirality sensing space and provide new opportunities that are of interest to a large group of chemists. This review will discuss chirality sensing strategies and applications with representative small-molecule CD sensors. Emphasis will be given to important milestones and recent advances that accelerate chiral compound analysis by outperforming traditional methods, conquer new directions, and pioneering efforts that lie at the forefront of chiroptical high-throughput screening developments. The goal is to provide the reader with a thorough understanding of the current state and a perspective of future directions of this rapidly emerging field.
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Affiliation(s)
| | - James R Howard
- Chemistry Department, University of Texas at Austin, Austin TX, USA
| | - Eric V Anslyn
- Chemistry Department, University of Texas at Austin, Austin TX, USA
| | - Christian Wolf
- Chemistry Department, Georgetown University, Washington DC, USA
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5
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Formen JSSK, Hassan DS, Wolf C. Chemometric sensing of stereoisomeric compound mixtures with a redox-responsive optical probe. Chem Sci 2024; 15:1498-1504. [PMID: 38274061 PMCID: PMC10806675 DOI: 10.1039/d3sc05706b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 12/20/2023] [Indexed: 01/27/2024] Open
Abstract
The analysis of mixtures of chiral compounds is a common task in academic and industrial laboratories typically achieved by laborious and time-consuming physical separation of the individual stereoisomers to allow interference-free quantification, for example using chiral chromatography coupled with UV detection. Current practice thus impedes high-throughput and slows down progress in countless chiral compound development projects. Here we describe a chemometric solution to this problem using a redox-responsive naphthoquinone that enables chromatography-free click chemistry sensing of challenging mixtures. The achiral probe covalently binds amino alcohols within a few minutes at room temperature and generates characteristic UVA and CDA spectra that are intentionally altered via sodium borohydride reduction to provide a second, strikingly different chiroptical data set (UVB and CDB). Chemometric partial least squares processing of the chiroptical outputs then enables spectral deconvolution and accurate determination of individual analyte concentrations. The success of this approach is demonstrated with 35 samples covering considerably varied total analyte amounts and stereoisomeric ratios. All chemicals and machine learning algorithms are readily available and can be immediately adapted by any laboratory.
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Affiliation(s)
| | - Diandra S Hassan
- Department of Chemistry, Georgetown University Washington DC 20057 USA
| | - Christian Wolf
- Department of Chemistry, Georgetown University Washington DC 20057 USA
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6
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Lim J, Guo M, Choi S, Miller SJ, Anslyn EV. High-throughput determination of enantiopurity in atroposelective synthesis of aryl triazoles. Chem Sci 2023; 14:5992-5999. [PMID: 37293656 PMCID: PMC10246677 DOI: 10.1039/d3sc01559a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 05/11/2023] [Indexed: 06/10/2023] Open
Abstract
Atropisomeric scaffolds are a common design element found in pharmaceuticals, many deriving from an N-C axis of chirality. The handedness associated with atropisomeric drugs is oftentimes crucial for their efficacy and/or safety. With the increased use of high-throughput screening (HTS) for drug discovery, the need for rapid enantiomeric excess (ee) analysis is needed to keep up with the fast workflow. Here, we describe a circular dichroism (CD) based assay that could be applied to the ee determination of N-C axially chiral triazole derivatives. Analytical samples for CD were prepared from crude mixtures by three sequential steps: liquid-liquid extraction (LLE), a wash-elute, and complexation with Cu(ii) triflate. The initial ee measurement of five samples of atropisomer 2 was conducted by the use of a CD spectropolarimeter with a 6-position cell changer, resulting in errors of less than 1% ee. High-throughput ee determination was performed on a CD plate reader using a 96-well plate. A total of 28 atropisomeric samples (14 for 2 and 14 for 3) were screened for ee. The CD readings were completed in 60 seconds with average absolute errors of ±7.2% and 5.7% ee for 2 and 3, respectively.
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Affiliation(s)
- Jongdoo Lim
- Department of Chemistry, The University of Texas at Austin Austin Texas 78712 USA
| | - Melody Guo
- Department of Chemistry, Yale University New Haven Connecticut 06520-8107 USA
| | - Sooyun Choi
- Department of Chemistry, Yale University New Haven Connecticut 06520-8107 USA
| | - Scott J Miller
- Department of Chemistry, Yale University New Haven Connecticut 06520-8107 USA
| | - Eric V Anslyn
- Department of Chemistry, The University of Texas at Austin Austin Texas 78712 USA
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Jávor B, Vezse P, Golcs Á, Huszthy P, Tóth T. Enantiodiscriminating Lipophilic Liquid Membrane-Based Assay for High-Throughput Nanomolar Enantioenrichment of Chiral Building Blocks. MEMBRANES 2023; 13:94. [PMID: 36676901 PMCID: PMC9862411 DOI: 10.3390/membranes13010094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Revised: 01/01/2023] [Accepted: 01/09/2023] [Indexed: 06/17/2023]
Abstract
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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Affiliation(s)
- Bálint Jávor
- Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary
| | - Panna Vezse
- Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary
| | - Ádám Golcs
- Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary
| | - Péter Huszthy
- Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary
| | - Tünde Tóth
- Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary
- Centre for Energy Research, Konkoly-Thege Miklós út 29-33, H-1121 Budapest, Hungary
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Balaraman K, Kyriazakos S, Palmer R, Thanzeel FY, Wolf C. Selective Csp 3-F Bond Functionalization with Lithium Iodide. SYNTHESIS-STUTTGART 2022; 54:4320-4328. [PMID: 36330045 PMCID: PMC9624501 DOI: 10.1055/s-0041-1738383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A highly efficient method for C-F bond functionalization of a broad variety of activated and unactivated aliphatic substrates with inexpensive lithium iodide is presented. Primary, secondary, tertiary, benzylic, propargylic and α-functionalized alkyl fluorides react in chlorinated or aromatic solvents at room temperature or upon heating to the corresponding iodides which are isolated in 91-99% yield. The reaction is selective for aliphatic monofluorides and can be coupled with in situ nucleophilic iodide replacements to install carbon-carbon, carbon-nitrogen and carbon-sulfur bonds with high yields. Alkyl difluorides, trifluorides, even in activated benzylic positions, are inert under the same conditions and aryl fluoride bonds are also tolerated.
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Affiliation(s)
- Kaluvu Balaraman
- Georgetown University, Chemistry Department, Washington, DC 20057, USA
| | | | - Rachel Palmer
- Georgetown University, Chemistry Department, Washington, DC 20057, USA
| | - F Yushra Thanzeel
- Georgetown University, Chemistry Department, Washington, DC 20057, USA
| | - Christian Wolf
- Georgetown University, Chemistry Department, Washington, DC 20057, USA
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Howard JR, Bhakare A, Akhtar Z, Wolf C, Anslyn EV. Data-Driven Prediction of Circular Dichroism-Based Calibration Curves for the Rapid Screening of Chiral Primary Amine Enantiomeric Excess Values. J Am Chem Soc 2022; 144:17269-17276. [PMID: 36067375 DOI: 10.1021/jacs.2c08127] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Here, we describe the prediction of the circular dichroism (CD) response of a three-component chiroptical sensor for enantiomeric excess (ee) determination of chiral amines using a multivariate fit to electronic and steric parameters. These computationally derived parameters can be computed for nearly any amine and correlate well with the CD response of the 12 amines comprising the training set. The resulting model was used to accurately predict the CD response of a test set of chiral amines. Theoretical calibration curves were then created and used to determine the ee of solutions of unknown ee. Using this method, the error in ee determination differed by less than 10% compared to experimentally generated calibration curves.
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Affiliation(s)
- James R Howard
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Arya Bhakare
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Zara Akhtar
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Christian Wolf
- Department of Chemistry, Georgetown University, Washington, D.C. 20057, United States
| | - Eric V Anslyn
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
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10
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De los Santos ZA, Lynch CC, Wolf C. Dynamic Covalent Optical Chirality Sensing with a Sterically Encumbered Aminoborane. Chemistry 2022; 28:e202202028. [DOI: 10.1002/chem.202202028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Indexed: 11/07/2022]
Affiliation(s)
| | - Ciarán C. Lynch
- Department of Chemistry Georgetown University Washington DC 20057 USA
| | - Christian Wolf
- Department of Chemistry Georgetown University Washington DC 20057 USA
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11
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Ramos De Dios SM, Tiwari VK, McCune CD, Dhokale RA, Berkowitz DB. Biomacromolecule-Assisted Screening for Reaction Discovery and Catalyst Optimization. Chem Rev 2022; 122:13800-13880. [PMID: 35904776 DOI: 10.1021/acs.chemrev.2c00213] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reaction discovery and catalyst screening lie at the heart of synthetic organic chemistry. While there are efforts at de novo catalyst design using computation/artificial intelligence, at its core, synthetic chemistry is an experimental science. This review overviews biomacromolecule-assisted screening methods and the follow-on elaboration of chemistry so discovered. All three types of biomacromolecules discussed─enzymes, antibodies, and nucleic acids─have been used as "sensors" to provide a readout on product chirality exploiting their native chirality. Enzymatic sensing methods yield both UV-spectrophotometric and visible, colorimetric readouts. Antibody sensors provide direct fluorescent readout upon analyte binding in some cases or provide for cat-ELISA (Enzyme-Linked ImmunoSorbent Assay)-type readouts. DNA biomacromolecule-assisted screening allows for templation to facilitate reaction discovery, driving bimolecular reactions into a pseudo-unimolecular format. In addition, the ability to use DNA-encoded libraries permits the barcoding of reactants. All three types of biomacromolecule-based screens afford high sensitivity and selectivity. Among the chemical transformations discovered by enzymatic screening methods are the first Ni(0)-mediated asymmetric allylic amination and a new thiocyanopalladation/carbocyclization transformation in which both C-SCN and C-C bonds are fashioned sequentially. Cat-ELISA screening has identified new classes of sydnone-alkyne cycloadditions, and DNA-encoded screening has been exploited to uncover interesting oxidative Pd-mediated amido-alkyne/alkene coupling reactions.
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Affiliation(s)
| | - Virendra K Tiwari
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Christopher D McCune
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Ranjeet A Dhokale
- Higuchi Biosciences Center, University of Kansas, Lawrence, Kansas 66047, United States
| | - David B Berkowitz
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
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