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de Oliveira DM, de Oliveira DBC, Nunes YRF, de Almeida Alves TM, Kohlhoff M, Andrade AA, Cota BB. Natural Occurring Phenolic Derivatives from Mauritia flexuosa (Buriti) Stems and Their Potential Antibacterial Activity against Methicillin-Resistant Staphylococcus aureus (MRSA). Chem Biodivers 2022; 19:e202100788. [PMID: 35146890 DOI: 10.1002/cbdv.202100788] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 01/13/2022] [Indexed: 11/12/2022]
Abstract
Mauritia flexuosa Linnaeus filius (buriti or aguage; Arecaceae) is a palm used by traditional medicine in Brazil to treat dysentery and diarrhea. Our group showed that the soluble dichloromethane (CH2 Cl2 ) fraction from EtOH extract from M. flexuosa stems inhibited the growth of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) and it is rich in phenolic compounds. This study aimed to isolate new phenolic compounds from CH2 Cl2 fraction from M. flexuosa stems with in vitro antibacterial activity. The crude CH2 Cl2 fraction was fractionated by gel permeation chromatography (GPC) followed by semi-preparative RP-HPLC. The antibacterial activity was evaluated using the broth microdilution method against MSSA (ATCC 29213) and MRSA (clinical isolate 155). All compounds were also tested against Gram-negative (Escherichia coli; ATCC 35218) bacteria and two fungi species (Candida albicans; ATCC 14053 and Trichophyton rubrum; ATCC MYA 4438). The chemical structures of isolated compounds were determined by analysis and comparison with literature data of their NMR and HRMS spectra and optical activity. The chemical investigation yielded seven aromatic compounds, of which four, (2S,15S)-2,15-dimethyl-2,15-dioxa-1,8(1,4)-dibenzenacyclotetradecaphane (1), (2S,5S)-1-(4-hydroxyphenyl)hexane-2,5-diol (3), bruguierol E (4), and buritin (5) were previously unreported and three are known compounds identified as 6-(4'-hydroxyphenyl) hexan-2-one (2), (+)-(2R,3R)-dihydrokaempferol (6), and (+)-(2R)-naringenin (7). Compounds 1 and 7 showed antibacterial activity against MRSA and MSSA with minimum inhibitory concentrations (MICs) of between 62.5 and 31.3 μg/mL, respectively. Our preliminary findings support that CH2 Cl2 fraction from buriti, a typical species of flooded areas of Brazilian savanna, and its aromatic phenolic compounds are active against MSSA and MRSA contributing with understanding about the traditional use of this species.
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Affiliation(s)
- Djalma Menezes de Oliveira
- Department of Science and Technology, State University of Bahia Southwest, José Moreira Sobrinho Avenue, 45206-191, Jequié, Bahia, Brazil
| | - Diego Batista Carneiro de Oliveira
- Laboratory of Microbiology, Federal University of Triângulo Mineiro, Pça Manoel Terra, 330, Abadia, 38025-015, Uberaba, Minas Gerais, Brazil
| | - Yule Roberta Ferreira Nunes
- Ecology Laboratory and Plant Propagation, Department of General Biology, Estadual University of Montes Claros, University Campus Prof. Darcy Ribeiro, 39401-089, Montes Claros, Minas Gerais, Brazil
| | - Tânia Maria de Almeida Alves
- Laboratory of Chemistry Bioactive Natural Products, René Rachou Institute, Oswaldo Cruz Foundation, Augusto de Lima Avenue, 1715, Barro Preto, 30190-002, Belo Horizonte, Minas Gerais, Brazil
| | - Markus Kohlhoff
- Laboratory of Chemistry Bioactive Natural Products, René Rachou Institute, Oswaldo Cruz Foundation, Augusto de Lima Avenue, 1715, Barro Preto, 30190-002, Belo Horizonte, Minas Gerais, Brazil
| | - Anderson Assunção Andrade
- Laboratory of Microbiology, Federal University of Triângulo Mineiro, Pça Manoel Terra, 330, Abadia, 38025-015, Uberaba, Minas Gerais, Brazil
| | - Betania Barros Cota
- Laboratory of Chemistry Bioactive Natural Products, René Rachou Institute, Oswaldo Cruz Foundation, Augusto de Lima Avenue, 1715, Barro Preto, 30190-002, Belo Horizonte, Minas Gerais, Brazil
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Fungal biocatalysts for labdane diterpene hydroxylation. Bioprocess Biosyst Eng 2020; 43:1051-1059. [PMID: 32020446 DOI: 10.1007/s00449-020-02303-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 01/27/2020] [Indexed: 01/23/2023]
Abstract
Labdane diterpenes and their derivatives have shown remarkable biological activities and are useful as chiral building blocks for the synthesis of a variety of bioactive compounds. There is great interest in developing biocatalyst technology to achieve regio- and stereoselective hydroxylation of unactivated C-H bonds in complex natural products, since the functionalization of unactivated C-H bonds generally requires hard reaction conditions and highly reactive oxidizing agents, which are limited regarding the control of regio- and stereoselectivity. Filamentous fungi are efficient biocatalysts capable of catalyzing a wide variety of hydroxylation reactions, and the use of whole cell biocatalysts provides advantages regarding cofactor regeneration and is much less expensive. Therefore, the goal of this study was to select biocatalysts to develop biotransformation processes that can be scalable under mild reaction conditions for hydroxylation of a labdane diterpene, 3β-acetoxy-copalic acid, which contains the trans-decalin moiety and a side chain dienic system appropriate for the preparation of a variety of compounds. Biotransformation processes were carried out and five filamentous fungi were selected as capable of producing hydroxylated diterpenes at positions C-3, C-6, C-7 and C-18 of the trans-decalin moiety and C-13 of the side chain dienic system. Hydroxylation reactions occurred with regio- and stereoselectivity by using some fungi that produced only the 6α, 7α and 13α-hydroxyl derivatives. The chemical structures of the hydroxylated diterpenes were determined from spectrometric and spectroscopic data, and the relative stereochemistry of stereogenic centers was established from coupling constants, by NOE-diff experiments and/or by computational calculations.
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Mari SH, Varras PC, Atia-tul-Wahab, Choudhary IM, Siskos MG, Gerothanassis IP. Solvent-Dependent Structures of Natural Products Based on the Combined Use of DFT Calculations and 1H-NMR Chemical Shifts. Molecules 2019; 24:E2290. [PMID: 31226776 PMCID: PMC6631582 DOI: 10.3390/molecules24122290] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 06/13/2019] [Accepted: 06/18/2019] [Indexed: 01/09/2023] Open
Abstract
Detailed solvent and temperature effects on the experimental 1H-NMR chemical shifts of the natural products chrysophanol (1), emodin (2), and physcion (3) are reported for the investigation of hydrogen bonding, solvation and conformation effects in solution. Very small chemical shift of │Δδ│ < 0.3 ppm and temperature coefficients │Δδ/ΔΤ│ ≤ 2.1 ppb/K were observed in DMSO-d6, acetone-d6 and CDCl3 for the C(1)-OH and C(8)-OH groups which demonstrate that they are involved in a strong intramolecular hydrogen bond. On the contrary, large chemical shift differences of 5.23 ppm at 298 K and Δδ/ΔΤ values in the range of -5.3 to -19.1 ppb/K between DMSO-d6 and CDCl3 were observed for the C(3)-OH group which demonstrate that the solvation state of the hydroxyl proton is a key factor in determining the value of the chemical shift. DFT calculated 1H-NMR chemical shifts, using various functionals and basis sets, the conductor-like polarizable continuum model, and discrete solute-solvent hydrogen bond interactions, were found to be in very good agreement with the experimental 1H-NMR chemical shifts even with computationally less demanding level of theory. The 1H-NMR chemical shifts of the OH groups which participate in intramolecular hydrogen bond are dependent on the conformational state of substituents and, thus, can be used as molecular sensors in conformational analysis. When the X-ray structures of chrysophanol (1), emodin (2), and physcion (3) were used as input geometries, the DFT-calculated 1H-NMR chemical shifts were shown to strongly deviate from the experimental chemical shifts and no functional dependence could be obtained. Comparison of the most important intramolecular data of the DFT calculated and the X-ray structures demonstrate significant differences for distances involving hydrogen atoms, most notably the intramolecular hydrogen bond O-H and C-H bond lengths which deviate by 0.152 tο 0.132 Å and 0.133 to 0.100 Å, respectively, in the two structural methods. Further differences were observed in the conformation of -OH, -CH3, and -OCH3 substituents.
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Affiliation(s)
- Saima H. Mari
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
| | - Panayiotis C. Varras
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
| | - Atia-tul-Wahab
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
| | - Iqbal M. Choudhary
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
| | - Michael G. Siskos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
| | - Ioannis P. Gerothanassis
- H.E.J. Research Institute of chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan; Saimahassanmari123@gmail (S.H.M.); (I.M.C.)
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece; (P.C.V.); (M.G.S.)
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 7527, Pakistan
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Kunikawa S, Tanaka A, Takasuna Y, Tasaki M, Chida N. Discovery of 2,4-diamino-5-cyanopyrimidine derivatives as protein kinase C theta inhibitors with mitigated time-dependent drug-drug interactions. Bioorg Med Chem 2019; 27:790-799. [PMID: 30704835 DOI: 10.1016/j.bmc.2019.01.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/14/2019] [Accepted: 01/18/2019] [Indexed: 10/27/2022]
Abstract
Protein kinase C theta (PKCθ) plays a critical role in T cell signaling and has therapeutic potential for T cell-mediated diseases such as transplant rejection and rheumatoid arthritis. PKCθ inhibitors have emerged as effective immunomodulative agents for the prevention of transplant rejection. We previously reported that the 2,4-diamino-5-cyanopyrimidine derivative 2 was a potent PKCθ inhibitor; however, it exhibited CYP3A4 time-dependent inhibition (TDI). Here, we report the structural modification of compound 2 into 34 focusing on mitigating CYP3A4 TDI. Compound 34 exhibited potent in vitro activity with mitigated CYP3A4 TDI and efficacy in vivo transplant model.
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Affiliation(s)
- Shigeki Kunikawa
- Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan.
| | - Akira Tanaka
- Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
| | - Yuji Takasuna
- Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
| | - Mamoru Tasaki
- Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
| | - Noboru Chida
- Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
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DFT-calculated structures based on 1H NMR chemical shifts in solution vs. structures solved by single-crystal X-ray and crystalline-sponge methods: Assessing specific sources of discrepancies. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.07.038] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Dutta S, Maity B, Thirumalai D, Koley D. Computational Investigation of Carbene–Phosphinidenes: Correlation between 31P Chemical Shifts and Bonding Features to Estimate the π-Backdonation of Carbenes. Inorg Chem 2018. [DOI: 10.1021/acs.inorgchem.8b00174] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sayan Dutta
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741 246, India
| | - Bholanath Maity
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741 246, India
| | - D. Thirumalai
- Department of Chemistry, Thiruvalluvar University, Serkkadu, Vellore 632 115, India
| | - Debasis Koley
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741 246, India
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Siskos MG, Choudhary MI, Gerothanassis IP. Refinement of labile hydrogen positions based on DFT calculations of 1H NMR chemical shifts: comparison with X-ray and neutron diffraction methods. Org Biomol Chem 2018; 15:4655-4666. [PMID: 28513720 DOI: 10.1039/c7ob01019b] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Numerous gas phase electron diffraction, ultra-fast electron diffraction, X-ray and neutron diffraction experiments on β-dicarbonyl compounds exhibiting enol-enol tautomeric equilibrium, with emphasis on acetylacetone and dibenzoylmethane, have so far been reported with conflicting results on the structural details of the O-HO intramolecular hydrogen bond and resulted in alternative hypotheses on the intramolecular hydrogen bond potential function either a double minimum potential corresponding to two tautomeric forms in equilibrium or a single symmetrical one. We demonstrate herein, firstly, that the DFT calculated OH 1H NMR chemical shifts of acetylacetone and dibenzoylmethane exhibit a strong linear dependence on the computed OO hydrogen bond length of ∼-50 ppm Å-1 and as a function of the O-HO bond angle of ∼1 ppm per degree, upon the transfer of the hydrogen atom from the ground state toward the transition state. Secondly, the refinement of labile hydrogen atomic positions in intramolecular hydrogen bonds based on the root-mean-square deviation between experimentally determined and DFT calculated 1H NMR chemical shifts in solution can provide high resolution structures of O-H and O(H)O bond lengths and O-HO bond angles with an accuracy of ∼10-2 Å and ∼0.5°, respectively. Thirdly, the calculated 1H NMR chemical shifts in solution of the two ground state tautomers in equilibrium of acetylacetone and dibenzoylmethane are in excellent agreement with the experimental value, even for moderate basis sets for energy minimization. In contrast, the single symmetrical structure in a strongly delocalized system is a transition state with calculated 1H NMR chemical shifts which strongly deviate from the experimental value. Fourth, the DFT calculated ground state O-H bond lengths of acetylacetone and dibenzoylmethane are in quantitative agreement with the literature data which take into account the effect of quantum nuclear motion. The DFT structural results are critically discussed with respect to the state-of-the-art variable temperature X-ray and neutron diffraction methods.
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Affiliation(s)
- Michael G Siskos
- Section of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina, GR 45110, Greece.
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Siskos MG, Choudhary MI, Gerothanassis IP. Hydrogen Atomic Positions of O-H···O Hydrogen Bonds in Solution and in the Solid State: The Synergy of Quantum Chemical Calculations with ¹H-NMR Chemical Shifts and X-ray Diffraction Methods. Molecules 2017; 22:E415. [PMID: 28272366 PMCID: PMC6155303 DOI: 10.3390/molecules22030415] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 02/27/2017] [Accepted: 03/03/2017] [Indexed: 12/21/2022] Open
Abstract
The exact knowledge of hydrogen atomic positions of O-H···O hydrogen bonds in solution and in the solid state has been a major challenge in structural and physical organic chemistry. The objective of this review article is to summarize recent developments in the refinement of labile hydrogen positions with the use of: (i) density functional theory (DFT) calculations after a structure has been determined by X-ray from single crystals or from powders; (ii) ¹H-NMR chemical shifts as constraints in DFT calculations, and (iii) use of root-mean-square deviation between experimentally determined and DFT calculated ¹H-NMR chemical shifts considering the great sensitivity of ¹H-NMR shielding to hydrogen bonding properties.
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Affiliation(s)
- Michael G Siskos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | - M Iqbal Choudhary
- H.E.J. Research Institute of Chemistry, International Center for Biological and Chemical Sciences, University of Karachi, Karachi 75270, Pakistan.
| | - Ioannis P Gerothanassis
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
- H.E.J. Research Institute of Chemistry, International Center for Biological and Chemical Sciences, University of Karachi, Karachi 75270, Pakistan.
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Lonardi A, Oborský P, Hünenberger PH. Solvent-Modulated Influence of Intramolecular Hydrogen-Bonding on the Conformational Properties of the Hydroxymethyl Group in Glucose and Galactose: A Molecular Dynamics Simulation Study. Helv Chim Acta 2016. [DOI: 10.1002/hlca.201600158] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Alice Lonardi
- Laboratory of Physical Chemistry; ETH Hönggerberg; HCI; CH-8093 Zürich Switzerland
| | - Pavel Oborský
- Laboratory of Physical Chemistry; ETH Hönggerberg; HCI; CH-8093 Zürich Switzerland
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Lomas JS, Joubert L, Maurel F. Association of symmetrical alkane diols with pyridine: DFT/GIAO calculation of 1 H NMR chemical shifts. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2016; 54:805-814. [PMID: 27247256 DOI: 10.1002/mrc.4457] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 05/04/2016] [Accepted: 05/05/2016] [Indexed: 06/05/2023]
Abstract
Proton nuclear magnetic resonance (NMR) shifts of the free diol and of its 1 : 1 and 1 : 2 hydrogen-bonded complexes with pyridine have been computed for five symmetrical alkane diols on the basis of density functional theory, by applying the gauge-including atomic orbital method to geometry-optimized conformers. For certain conformers, intramolecular OH···OH interactions, evidenced by high NMR OH proton shifts, are further enhanced on going from the free diol to the corresponding 1 : 1 diol/pyridine complex. This is confirmed by atoms-in-molecules and non-covalent interaction plots. The computed OH and CH proton shifts for the diol and the two complexes correlate well with values obtained by analysing data from the NMR titration of the diols in benzene against pyridine. Shift values for the diols in neat pyridine are calculated by weighting the shifts of the various protons in the three forms (free diol, 1 : 1 and 1 : 2 diol/pyridine complexes) according to the experimentally determined association constants. The results are in good agreement with those observed, and after empirical scaling, the root mean square difference is 0.18 ppm. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- John S Lomas
- ITODYS (UMR 7086), Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Laurent Joubert
- Normandy Univ., COBRA UMR 6014 & FR 3038, Université de Rouen, INSA Rouen, CNRS, France
| | - François Maurel
- ITODYS (UMR 7086), Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
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Lomas JS. 1H NMR spectra of alcohols and diols in chloroform: DFT/GIAO calculation of chemical shifts. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2014; 52:745-754. [PMID: 25199903 DOI: 10.1002/mrc.4130] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 07/10/2014] [Accepted: 07/29/2014] [Indexed: 06/03/2023]
Abstract
Proton nuclear magnetic resonance (NMR) shifts of aliphatic alcohols in chloroform have been computed on the basis of density functional theory, the solvent being included by the integral-equation-formalism polarisable continuum model of Gaussian 09. Relative energies of all conformers are calculated at the Perdew, Burke and Ernzerhof (PBE)0/6-311+G(d,p) level, and NMR shifts by the gauge-including atomic orbital method with the PBE0/6-311+G(d,p) geometry and the cc-pVTZ basis set. The 208 computed CH proton NMR shifts for 34 alcohols correlate very well with the experimental values, with a gradient of 1.00 ± 0.01 and intercept close to zero; the overall root mean square difference (RMSD) is 0.08 ppm. Shifts for CH protons of diols in chloroform are well correlated with the theoretical values for (isotropic) benzene, with similar gradient and intercept (1.02 ± 0.01, -0.13 ppm), but the overall RMSD is slightly higher, 0.12 ppm. This approach generally gives slightly better results than the CHARGE model of Abraham et al. The shifts of unsaturated alcohols in benzene have been re-examined with Gaussian 09, but the overall fit for CH protons is not improved, and OH proton shifts are worse. Shifts of vinyl protons in alkenols are systematically overestimated, and the correlation of computed shifts against the experimental data for unsaturated alcohols follows a quadratic equation. Splitting the 20 compounds studied into two sets, and applying empirical scaling based on the quadratic for the first set to the second set, gives an RMSD of 0.10 ppm. A multi-standard approach gives a similar result.
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Affiliation(s)
- John S Lomas
- Univ Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086, F-75205, Paris, France
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Charisiadis P, Kontogianni VG, Tsiafoulis CG, Tzakos AG, Siskos M, Gerothanassis IP. 1H-NMR as a structural and analytical tool of intra- and intermolecular hydrogen bonds of phenol-containing natural products and model compounds. Molecules 2014; 19:13643-82. [PMID: 25185070 PMCID: PMC6271058 DOI: 10.3390/molecules190913643] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 11/23/2022] Open
Abstract
Experimental parameters that influence the resolution of 1H-NMR phenol OH signals are critically evaluated with emphasis on the effects of pH, temperature and nature of the solvents. Extremely sharp peaks (Δν1/2≤2 Hz) can be obtained under optimized experimental conditions which allow the application of 1H-13C HMBC-NMR experiments to reveal long range coupling constants of hydroxyl protons and, thus, to provide unequivocal assignment of the OH signals even in cases of complex polyphenol natural products. Intramolecular and intermolecular hydrogen bonds have a very significant effect on 1H OH chemical shifts which cover a region from 4.5 up to 19 ppm. Solvent effects on -OH proton chemical shifts, temperature coefficients (Δδ/ΔT), OH diffusion coefficients, and nJ(13C, O1H) coupling constants are evaluated as indicators of hydrogen bonding and solvation state of phenol -OH groups. Accurate 1H chemical shifts of the OH groups can be calculated using a combination of DFT and discrete solute-solvent hydrogen bond interaction at relatively inexpensive levels of theory, namely, DFT/B3LYP/6-311++G (2d,p). Excellent correlations between experimental 1H chemical shifts and those calculated at the ab initio level can provide a method of primary interest in order to obtain structural and conformational description of solute-solvent interactions at a molecular level. The use of the high resolution phenol hydroxyl group 1H-NMR spectral region provides a general method for the analysis of complex plant extracts without the need for the isolation of the individual components.
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Affiliation(s)
- Pantelis Charisiadis
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | - Vassiliki G Kontogianni
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | | | - Andreas G Tzakos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | - Michael Siskos
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
| | - Ioannis P Gerothanassis
- Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Ioannina GR-45110, Greece.
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