1
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Kemper M, Drost DA, Engelage E, Merten C. Stereochemistry Controls Dihydrogen Bonding Strengths in Chiral Amine Boranes Adducts. Angew Chem Int Ed Engl 2022; 61:e202213859. [PMID: 36245340 PMCID: PMC10099978 DOI: 10.1002/anie.202213859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Indexed: 11/07/2022]
Abstract
The growing interest in exploiting novel concepts of non-covalent interactions in catalysts and supramolecular chemistry made us revisit a special kind of hydrogen bonding: the dihydrogen bond (DHB), formed between a classical hydrogen bond donor and a hydridic hydrogen as acceptor. Herein, we investigate how the strength of the N-Hδ+ ⋅⋅⋅δ- H-B interaction and hence the DHB-driven self-aggregation of amine-borane adducts is governed by steric effects by comparing the structures and binding enthalpies of various chiral derivatives. For a diastereomeric pair of amine-boranes prepared from a chiral secondary amine, we show that the stereochemistry at the nitrogen has significant influence on the interaction enthalpy. Based on this finding, N-chiral amine boranes can be envisioned to become interesting building blocks in supramolecular chemistry to fine-tune the formation dynamics of assemblies.
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Affiliation(s)
- Michael Kemper
- Ruhr Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraße 150, 44801, Bochum, Germany
| | - Deborah A Drost
- Ruhr Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraße 150, 44801, Bochum, Germany
| | - Elric Engelage
- Ruhr Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraße 150, 44801, Bochum, Germany
| | - Christian Merten
- Ruhr Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraße 150, 44801, Bochum, Germany
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2
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Scholten K, Merten C. Solvation of the Boc-Val-Phe- nPr peptide characterized by VCD spectroscopy and DFT calculations. Phys Chem Chem Phys 2022; 24:3611-3617. [PMID: 35103263 DOI: 10.1039/d1cp05457k] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The conformational preferences of peptides are strongly determined by hydrogen bonding interactions. Intermolecular solute-solvent interactions compete with intramolecular interactions, which typically stabilize the secondary structure of the peptide. The analysis of vibrational circular dichroism (VCD) spectra can give insights into solvation-induced changes in the conformational distribution of small peptides. Here we describe the VCD spectroscopic characterization of the model peptide Boc-Val-Phe-nPr in chloroform as representative for a weakly interacting solvent and dimethyl sulfoxide (DMSO-d6) as a strongly hydrogen bonding solvent. We show that the conformational preferences of the peptide in chloroform are well-described by the computationally predicted distribution of the isolated molecule assuming only implicit solvation effects through a continuum solvation model. In order to simulate the spectra recorded in DMSO-d6, solvation was accounted for explicitly by computed microsolvated structures containing one to three solvent molecules. A good match of the computed spectra with the experimental data is obtained by this method. Comparing the conformational distributions in deuterated chloroform-d1 and DMSO-d6, structures with intramolecular hydrogen bonds such as the (δ,δ)-conformer family contribute to the conformational distribution only when there is no strong interaction with the solvent. This is in contrast to the results for the related Boc-Pro-Phe-nPr studied before, for which the intramolecular interaction was found to persist in DMSO-d6. Furthermore, we discuss the influence of hydrogen bonding to different numbers of solvent molecules on the spectral signatures and show that the structure of the peptide in DMSO-d6 is best described as a mixture of twofold-solvated (δ,β)- and threefold-solvated (β,β)-conformers.
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Affiliation(s)
- Kevin Scholten
- Ruhr-Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraße 150, 44801 Bochum, Germany.
| | - Christian Merten
- Ruhr-Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraße 150, 44801 Bochum, Germany.
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3
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Scholten K, Merten C. Anion-binding of a chiral tris(2-aminoethyl)amine-based tripodal thiourea: A spectroscopic and computational study. Phys Chem Chem Phys 2022; 24:4042-4050. [DOI: 10.1039/d1cp05688c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thioureas are well-known structural motifs in supramolecular anion recognition. Their conformational preferences are typically characterized by detailed NMR spectroscopy and crystallography, which are often complemented with computational results from geometry...
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4
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Weirich L, Merten C. Induced VCD and conformational chirality in host-guest complexes of a chiral ammonium salt with crown ethers. Phys Chem Chem Phys 2021; 23:18300-18307. [PMID: 34114592 DOI: 10.1039/d1cp01846a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The hydrogen bonded complexes of the chiral ammonium salt α-methylbenzyl ammonium chloride (MBA-H+Cl-) and the achiral crown ethers 18c6 and 15c5 serve as model systems to investigate the effect of host-guest complex formation on the conformational preferences of the macrocycles. We demonstrate that the intermolecular interactions result in new VCD signatures, that can be assigned to vibrational modes of the crown ethers. Based on a detailed conformational analysis, we investigate the origin of these signatures and discuss induced VCD (iVCD) and conformational chirality as possible sources of VCD intensity. The macrocycle in the MBA-H+/18c6 complex prefers either an achiral D3d-symmetric conformation, which gives rise to iVCD, or chiral conformations, that feature individual contributions to the VCD spectrum. For the MBA-H+/15c5 complex, the contributions of the macrocycle to the VCD signatures are less pronounced and found to arise solely from conformational chirality. Therefore, analysis of the VCD signatures confirms that the small chiral guest molecule is able to affect the conformational preferences of a macrocyclic host. The study thus demonstrates the suitability of VCD spectroscopy for the characterization of analogous supramolecular host-guest complexes.
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Affiliation(s)
- Luisa Weirich
- Ruhr-Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraße 150, 44801 Bochum, Germany.
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Kemper M, Engelage E, Merten C. Chirale molekulare Propeller basierend auf Triarylboran‐Ammoniak‐Addukten. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202014130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Michael Kemper
- Ruhr Universität Bochum Fakultät für Chemie und Biochemie, Organische Chemie II Universitätsstraße 150 44801 Bochum Deutschland
| | - Elric Engelage
- Ruhr Universität Bochum Fakultät für Chemie und Biochemie, Organische Chemie II Universitätsstraße 150 44801 Bochum Deutschland
| | - Christian Merten
- Ruhr Universität Bochum Fakultät für Chemie und Biochemie, Organische Chemie II Universitätsstraße 150 44801 Bochum Deutschland
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Kemper M, Engelage E, Merten C. Chiral Molecular Propellers of Triarylborane Ammonia Adducts. Angew Chem Int Ed Engl 2021; 60:2958-2962. [PMID: 33197119 PMCID: PMC7898383 DOI: 10.1002/anie.202014130] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Indexed: 11/19/2022]
Abstract
Chiral molecular propeller conformations have been induced to various triaryl structures including trityl derivatives and triaryl boranes. For borane-amine adducts, such induced propeller chirality has not been reported yet due to the low energy barrier for racemization in common triarylboranes such as B(C6 H5 )3 or B(C6 F5 )3 . Herein, we demonstrate that point chirality in side chains of chiral triarylborane-ammonia adducts, which feature intramolecular hydrogen bonds in addition to the dative N→B bond, can efficiently be transferred to triarylborane propeller chirality. Employing X-ray crystallography and ECD/VCD spectroscopy for structural characterizations, we investigate three examples with different steric demands of the incorporated chiral alkoxy side groups. We elucidate the conformational preferences of the molecular propellers. Furthermore, we show that computationally predicted conformational preferences obtained for the isolated, only implicitly solvated molecules are actually opposite to the experimentally observed ones.
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Affiliation(s)
- Michael Kemper
- Ruhr Universität BochumFakultät für Chemie und Biochemie, Organische Chemie IIUniversitätsstrasse 15044801BochumGermany
| | - Elric Engelage
- Ruhr Universität BochumFakultät für Chemie und Biochemie, Organische Chemie IIUniversitätsstrasse 15044801BochumGermany
| | - Christian Merten
- Ruhr Universität BochumFakultät für Chemie und Biochemie, Organische Chemie IIUniversitätsstrasse 15044801BochumGermany
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7
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Bünnemann K, Pollok CH, Merten C. Explicit Solvation of Carboxylic Acids for Vibrational Circular Dichroism Studies: Limiting the Computational Efforts without Losing Accuracy. J Phys Chem B 2018; 122:8056-8064. [DOI: 10.1021/acs.jpcb.8b05928] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Karoline Bünnemann
- Ruhr Universität Bochum, Lehrstuhl für Organische Chemie II, Universitätsstraße 150, 44801 Bochum, Germany
| | - Corina H. Pollok
- Ruhr Universität Bochum, Lehrstuhl für Organische Chemie II, Universitätsstraße 150, 44801 Bochum, Germany
| | - Christian Merten
- Ruhr Universität Bochum, Lehrstuhl für Organische Chemie II, Universitätsstraße 150, 44801 Bochum, Germany
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Rode JE, Dobrowolski JC, Lyczko K, Wasiewicz A, Kaczorek D, Kawęcki R, Zając G, Baranska M. Chiral Thiophene Sulfonamide—A Challenge for VOA Calculations. J Phys Chem A 2017; 121:6713-6726. [DOI: 10.1021/acs.jpca.6b11015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Joanna E. Rode
- Institute of Nuclear Chemistry and Technology, 16 Dorodna Street, 03-195 Warsaw, Poland
| | - Jan Cz. Dobrowolski
- Institute of Nuclear Chemistry and Technology, 16 Dorodna Street, 03-195 Warsaw, Poland
| | - Krzysztof Lyczko
- Institute of Nuclear Chemistry and Technology, 16 Dorodna Street, 03-195 Warsaw, Poland
| | - Aleksandra Wasiewicz
- Siedlce University, Faculty of Science, 3 Maja Street No 54, 80-110 Siedlce, Poland
| | - Dorota Kaczorek
- Siedlce University, Faculty of Science, 3 Maja Street No 54, 80-110 Siedlce, Poland
| | - Robert Kawęcki
- Siedlce University, Faculty of Science, 3 Maja Street No 54, 80-110 Siedlce, Poland
| | - Grzegorz Zając
- Faculty of Chemistry, Jagiellonian University, 3 Ingardena
Street, 30-060 Krakow, Poland
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, 14 Bobrzynskiego Street, 30-348 Krakow, Poland
| | - Malgorzata Baranska
- Faculty of Chemistry, Jagiellonian University, 3 Ingardena
Street, 30-060 Krakow, Poland
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, 14 Bobrzynskiego Street, 30-348 Krakow, Poland
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Smyrniotopoulos V, Merten C, Kaiser M, Tasdemir D. Bifurcatriol, a New Antiprotozoal Acyclic Diterpene from the Brown Alga Bifurcaria bifurcata. Mar Drugs 2017; 15:E245. [PMID: 28767061 PMCID: PMC5577600 DOI: 10.3390/md15080245] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 07/24/2017] [Accepted: 07/27/2017] [Indexed: 11/18/2022] Open
Abstract
Linear diterpenes that are commonly found in brown algae are of high chemotaxonomic and ecological importance. This study reports bifurcatriol (1), a new linear diterpene featuring two stereogenic centers isolated from the Irish brown alga Bifurcariabifurcata. The gross structure of this new natural product was elucidated based on its spectroscopic data (IR, 1D and 2D-NMR, HRMS). Its absolute configuration was identified by experimental and computational vibrational circular dichroism (VCD) spectroscopy, combined with the calculation of 13C-NMR chemical shielding constants. Bifurcatriol (1) was tested for in vitro antiprotozoal activity towards a small panel of parasites (Plasmodium falciparum, Trypanosoma brucei rhodesiense, T. cruzi, and Leishmania donovani) and cytotoxicity against mammalian primary cells. The highest activity was exerted against the malaria parasite P. falciparum (IC50 value 0.65 μg/mL) with low cytotoxicity (IC50 value 56.6 μg/mL). To our knowledge, this is the first successful application of VCD and DP4 probability analysis of the calculated 13C-NMR chemical shifts for the simultaneous assignment of the absolute configuration of multiple stereogenic centers in a long-chain acyclic natural product.
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Affiliation(s)
| | - Christian Merten
- Lehrstuhl für Organische Chemie 2, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum, Germany.
| | - Marcel Kaiser
- Swiss Tropical and Public Health Institute, 4051 Basel, Switzerland.
- University of Basel, 4003 Basel, Switzerland.
| | - Deniz Tasdemir
- School of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland.
- GEOMAR Centre for Marine Biotechnology (GEOMAR-Biotech), Research Unit Marine Natural Product Chemistry, Research Division Marine Ecology, GEOMAR Helmholtz Centre for Ocean Research Kiel, Am Kiel-Kanal 44, 24106 Kiel, Germany.
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10
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Pollok CH, Riesebeck T, Merten C. Photoisomerisierung eines Schalters auf Basis eines chiralen Imins: Verfolgung durch Matrixisolations-VCD-Spektroskopie. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201610918] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Corina H. Pollok
- Ruhr-Universität Bochum; Fakultät für Chemie und Biochemie, Organische Chemie 2; Universitätsstraße 150 44801 Bochum Deutschland
| | - Tim Riesebeck
- Ruhr-Universität Bochum; Fakultät für Chemie und Biochemie, Organische Chemie 2; Universitätsstraße 150 44801 Bochum Deutschland
| | - Christian Merten
- Ruhr-Universität Bochum; Fakultät für Chemie und Biochemie, Organische Chemie 2; Universitätsstraße 150 44801 Bochum Deutschland
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Pollok CH, Riesebeck T, Merten C. Photoisomerization of a Chiral Imine Molecular Switch Followed by Matrix-Isolation VCD Spectroscopy. Angew Chem Int Ed Engl 2017; 56:1925-1928. [DOI: 10.1002/anie.201610918] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Corina H. Pollok
- Ruhr-Universität Bochum; Fakultät für Chemie und Biochemie, Organische Chemie 2; Universitätsstrasse 150 44801 Bochum Germany
| | - Tim Riesebeck
- Ruhr-Universität Bochum; Fakultät für Chemie und Biochemie, Organische Chemie 2; Universitätsstrasse 150 44801 Bochum Germany
| | - Christian Merten
- Ruhr-Universität Bochum; Fakultät für Chemie und Biochemie, Organische Chemie 2; Universitätsstrasse 150 44801 Bochum Germany
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12
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Bünnemann K, Merten C. Solvation of a chiral carboxylic acid: effects of hydrogen bonding on the IR and VCD spectra of α-methoxyphenylacetic acid. Phys Chem Chem Phys 2017. [DOI: 10.1039/c7cp02049j] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Taking the title compound as a representative example of a chiral carboxylic acid, we investigate how its VCD spectral pattern is affected by hydrogen bonding of different solvents.
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13
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Merten C. Vibrational optical activity as probe for intermolecular interactions. Phys Chem Chem Phys 2017; 19:18803-18812. [DOI: 10.1039/c7cp02544k] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A detailed VCD spectroscopic analysis of well-selected chiral model systems can give valuable and unprecedented insights into intermolecular interactions such as solvation or reactant–substrate binding in catalysis.
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