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Yang Y, Alshalalfeh M, Xu Y. Conformational distributions of tetrahydro-2-turoic acid in water at different pH values by their IR and vibrational circular dichroism spectra. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 307:123634. [PMID: 37976578 DOI: 10.1016/j.saa.2023.123634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 11/01/2023] [Accepted: 11/07/2023] [Indexed: 11/19/2023]
Abstract
Infrared (IR) and vibrational circular dichroism (VCD) spectra of tetrahydro-2-furoic acid (THFA) in aqueous solutions under several different pH conditions were recorded. To interpret the IR and VCD spectra of THFA obtained in highly acidic and basic aqueous solutions, extensive and systematic conformational searches were conducted to acquire the low-energy minima for both the neutral and deprotonated forms of THFA species, as well as their hydrated clusters. This was accomplished by using the conformer-rotamer ensemble sampling tool (CREST) with an implicit solvation model for water. The CREST candidates were further optimized at the B3LYP-D3BJ/def2-TZVP level of theory. The simulated VCD spectra of the neutral THFA conformers in the polarizable continuum model (PCM) of water alone exhibit little agreement with the experimental data under highly acidic conditions. Applying the clusters-in-a-liquid solvation model by considering the monohydrate THFA conformers in the PCM of water, significantly improved agreement with the experimental data. Similarly, the deprotonated THFA species solvated with one to four explicit water molecules in the PCM of water were considered. While the IR and VCD spectra of the deprotonated THFA monohydrate conformers offer the best agreement with the experimental data, other larger hydrated clusters, particularly the dihydrates, also contribute to the spectra. Through the synergistic combined experimental and theoretical approach used in the study, comprehensive conformational distributions of the predominant THFA species across various pH conditions were extracted.
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Affiliation(s)
- Yanqing Yang
- Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada
| | - Mutasem Alshalalfeh
- Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada
| | - Yunjie Xu
- Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada.
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Vang ZP, Sonstrom RE, Scolati HN, Clark JR, Pate BH. Assignment of the absolute configuration of molecules that are chiral by virtue of deuterium substitution using chiral tag molecular rotational resonance spectroscopy. Chirality 2023; 35:856-883. [PMID: 37277968 PMCID: PMC11102577 DOI: 10.1002/chir.23596] [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: 03/11/2023] [Revised: 05/10/2023] [Accepted: 05/16/2023] [Indexed: 06/07/2023]
Abstract
Chiral tag molecular rotational resonance (MRR) spectroscopy is used to assign the absolute configuration of molecules that are chiral by virtue of deuterium substitution. Interest in the improved performance of deuterated active pharmaceutical ingredients has led to the development of precision deuteration reactions. These reactions often generate enantioisotopomer reaction products that pose challenges for chiral analysis. Chiral tag rotational spectroscopy uses noncovalent derivatization of the enantioisotopomer to create the diastereomers of the 1:1 molecular complexes of the analyte and a small, chiral molecule. Assignment of the absolute configuration requires high-confidence determinations of the structures of these weakly bound complexes. A general search method, CREST, is used to identify candidate geometries. Subsequent geometry optimization using dispersion corrected density functional theory gives equilibrium geometries with sufficient accuracy to identify the isomers of the chiral tag complexes produced in the pulsed jet expansion used to introduce the sample into the MRR spectrometer. Rotational constant scaling based on the fact that the diastereomers have the same equilibrium geometry gives accurate predictions allowing identification of the homochiral and heterochiral tag complexes and, therefore, assignment of absolute configuration. The method is successfully applied to three oxygenated substrates from enantioselective Cu-catalyzed alkene transfer hydrodeuteration reaction chemistry.
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Affiliation(s)
- Zoua Pa Vang
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin, USA
| | - Reilly E. Sonstrom
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
- BrightSpec Inc, Charlottesville, Virginia, USA
| | - Haley N. Scolati
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
| | - Joseph R. Clark
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin, USA
| | - Brooks H. Pate
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
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Sonstrom RE, Vang ZP, Scolati HN, Neill JL, Pate BH, Clark JR. Rapid Enantiomeric Excess Measurements of Enantioisotopomers by Molecular Rotational Resonance Spectroscopy. Org Process Res Dev 2023; 27:1185-1197. [PMID: 38046274 PMCID: PMC10691865 DOI: 10.1021/acs.oprd.3c00028] [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: 03/19/2023]
Abstract
Recent work in drug discovery has shown that selectively deuterated small molecules can improve the safety and efficacy for active pharmaceutical ingredients. The advantages derive from changes in metabolism resulting from the kinetic isotope effect when deuterium is substituted for a hydrogen atom at a structural position where rate limiting C-H bond breaking occurs. This application has pushed the development of precision deuteration strategies in synthetic chemistry that can install deuterium atoms with high regioselectivity and with stereocontrol. Copper-catalyzed alkene transfer hydrodeuteration chemistry has recently been shown to have high stereoselectivity for deuteration at the metabolically important benzyl C-H position. In this case, stereocontrol results in the creation of enantioisotopomers-molecules that are chiral solely by virtue of the deuterium substitution-and chiral analysis techniques are needed to assess the reaction selectivity. It was recently shown that chiral tag molecular rotational resonance (MRR) spectroscopy provides a routine way to measure the enantiomeric excess and establish the absolute configuration of enantioisotopomers. High-throughput implementations of chiral tag MRR spectroscopy are needed to support optimization of the chemical synthesis. A measurement methodology for high-throughput chiral analysis is demonstrated in this work. The high-throughput ee measurements are performed using cavity-enhanced MRR spectroscopy, which reduces measurement times and sample consumption by more than an order-of-magnitude compared to the previous enantioisotopomer analysis using a broadband MRR spectrometer. It is also shown that transitions for monitoring the enantiomers can be selected from a broadband rotational spectrum without the need for spectroscopic analysis. The general applicability of chiral tag MRR spectroscopy is illustrated by performing chiral analysis on six enantioisotopomer reaction products using a single molecule as the tag for chiral discrimination.
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Affiliation(s)
| | - Zoua Pa Vang
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233-1881, United States
| | - Haley N Scolati
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, United States
| | - Justin L Neill
- BrightSpec Inc., Charlottesville, Virginia 22903, United States
| | - Brooks H Pate
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, United States
| | - Joseph R Clark
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53233-1881, United States
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Melosso M, Jiang N, Gauss J, Puzzarini C. Hyperfine-resolved spectra of HDS together with a global ro-vibrational analysis. J Chem Phys 2023; 158:2888208. [PMID: 37139997 DOI: 10.1063/5.0148810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 04/17/2023] [Indexed: 05/05/2023] Open
Abstract
Despite their chemical simplicity, the spectroscopic investigation of light hydrides, such as hydrogen sulfide, is challenging due to strong hyperfine interactions and/or anomalous centrifugal-distortion effects. Several hydrides have already been detected in the interstellar medium, and the list includes H2S and some of its isotopologues. Astronomical observation of isotopic species and, in particular, those bearing deuterium is important to gain insights into the evolutionary stage of astronomical objects and to shed light on interstellar chemistry. These observations require a very accurate knowledge of the rotational spectrum, which is so far limited for mono-deuterated hydrogen sulfide, HDS. To fill this gap, high-level quantum-chemical calculations and sub-Doppler measurements have been combined for the investigation of the hyperfine structure of the rotational spectrum in the millimeter- and submillimeter-wave region. In addition to the determination of accurate hyperfine parameters, these new measurements together with the available literature data allowed us to extend the centrifugal analysis using a Watson-type Hamiltonian and a Hamiltonian-independent approach based on the Measured Active Ro-Vibrational Energy Levels (MARVEL) procedure. The present study thus permits to model the rotational spectrum of HDS from the microwave to far-infrared region with great accuracy, thereby accounting for the effect of the electric and magnetic interactions due to the deuterium and hydrogen nuclei.
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Affiliation(s)
- Mattia Melosso
- Dipartimento di Chimica "Giacomo Ciamician," Università di Bologna, via F. Selmi 2, 40126 Bologna, Italy
| | - Ningjing Jiang
- Dipartimento di Chimica "Giacomo Ciamician," Università di Bologna, via F. Selmi 2, 40126 Bologna, Italy
| | - Jürgen Gauss
- Department Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Cristina Puzzarini
- Dipartimento di Chimica "Giacomo Ciamician," Università di Bologna, via F. Selmi 2, 40126 Bologna, Italy
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Chiral Analysis of Linalool, an Important Natural Fragrance and Flavor Compound, by Molecular Rotational Resonance Spectroscopy. Symmetry (Basel) 2022. [DOI: 10.3390/sym14050917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The chiral analysis of terpenes in complex mixtures of essential oils, necessary for authentication, has been further developed using chiral tagging molecular rotational resonance (MRR) spectroscopy. One analyte that is of particular interest is linalool (3,7-dimethyl-1,6-octadien-3-ol), a common natural chiral terpene found in botanicals with its enantiomers having unique flavor, fragrance, and aromatherapy characteristics. In this MRR demonstration, resolution of the enantiomers is achieved through the addition of a chiral tag, which creates non-covalent diastereomeric complexes with distinct spectral signatures. The relative stereochemistry of the complexes is identified by the comparison of calculated spectroscopic parameters with experimentally determined parameters of the chiral complexes with high accuracy. The diastereomeric complex intensities are analyzed to determine the absolute configuration (AC) and enantiomeric excess (EE) in each sample. Here, we demonstrate the use of chiral tagging MRR spectroscopy to perform a quantitative routine enantiomer analysis of linalool in complex essential oil mixtures, without the need for reference samples or chromatographic separation.
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Assignment-free chirality detection in unknown samples via microwave three-wave mixing. Commun Chem 2022; 5:31. [PMID: 36697786 PMCID: PMC9814651 DOI: 10.1038/s42004-022-00641-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 02/03/2022] [Indexed: 01/28/2023] Open
Abstract
Straightforward identification of chiral molecules in multi-component mixtures of unknown composition is extremely challenging. Current spectrometric and chromatographic methods cannot unambiguously identify components while the state of the art spectroscopic methods are limited by the difficult and time-consuming task of spectral assignment. Here, we introduce a highly sensitive generalized version of microwave three-wave mixing that uses broad-spectrum fields to detect chiral molecules in enantiomeric excess without any prior chemical knowledge of the sample. This method does not require spectral assignment as a necessary step to extract information out of a spectrum. We demonstrate our method by recording three-wave mixing spectra of multi-component samples that provide direct evidence of enantiomeric excess. Our method opens up new capabilities in ultrasensitive phase-coherent spectroscopic detection that can be applied for chiral detection in real-life mixtures, raw products of chemical reactions and difficult to assign novel exotic species.
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Xie F, Mahendiran S, Seifert NA, Xu Y. Modifying conformational distribution of chiral tetrahydro-2-furoic acid through its interaction with water: a rotational spectroscopic and theoretical investigation. Phys Chem Chem Phys 2021; 23:3820-3825. [PMID: 33533340 DOI: 10.1039/d0cp06265k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Rotational spectrum of a binary complex formed between tetrahydro-2-furoic acid (THFA) and water was measured using a chirped pulse Fourier transform microwave spectrometer. A comprehensive theoretical conformational search procedure was carried out using CREST, a conformational searching tool, and DFT calculations to aid the spectral assignment and interpretation. The final conformer ensemble is classified into two structural groups: Type 1 conformers showing a classic carboxylic acid monohydrate structure with two strong hydrogen-bonds formed between the COOH group of cis-THFA and water, and the much less stable Type 2 conformers with trans-THFA and weaker intermolecular interactions with water. The 'cis-' and 'trans-' labels refer to the configurations where the carboxylic C[double bond, length as m-dash]O and OH functional groups are on the same or opposite side, respectively. Only the two most stable Type 2 conformers containing trans-THFA I and II were observed experimentally in a neon jet expansion with an abundance ratio of 1 : 1. This relative abundance observation differs greatly from that of the THFA monomer, i.e. with trans-THFA I : trans-THFA II : cis-THFA III of 10 : 1 : 1 in a neon jet expansion, reported previously. The observation indicates a kinetically controlled formation process of different types of the monohydrates in a jet expansion, whereas a thermodynamically controlled process dominates within each type of structures. The relative stability of the THFA ring conformations is altered by interaction with water, showing a noticeable water induced conformational preference.
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Affiliation(s)
- Fan Xie
- Chemistry Department, The University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | | | - Nathan A Seifert
- Chemistry Department, The University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | - Yunjie Xu
- Chemistry Department, The University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
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