1
|
Stereoselective synthesis and investigation of mechanism of trifluoromethylated cyclopropylphosphonate. J Fluor Chem 2022. [DOI: 10.1016/j.jfluchem.2021.109934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
2
|
Du FY, Ju GL, Xiao L, Zhou YM, Wu X. Sesquiterpenes and Cyclodepsipeptides from Marine-Derived Fungus Trichoderma longibrachiatum and Their Antagonistic Activities against Soil-borne Pathogens. Mar Drugs 2020; 18:md18030165. [PMID: 32188169 PMCID: PMC7142749 DOI: 10.3390/md18030165] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 03/05/2020] [Accepted: 03/11/2020] [Indexed: 01/25/2023] Open
Abstract
Soil-borne pathogens, including phytopathogenic fungi and root-knot nematodes, could synergistically invade vegetable roots and result in serious economic losses. The genus of Trichoderma has been proven to be a promising reservoir of biocontrol agents in agriculture. In this study, the search for antagonistic metabolites from a marine-derived fungus, Trichoderma longibrachiatum, obtained two structural series of sesquiterpenes 1-6 and cyclodepsipeptides 7-9. Notably, the novel 1 was a rare norsesquiterpene characterized by an unprecedented tricyclic-6/5/5-[4.3.1.01,6]-decane skeleton. Their structures were elucidated by extensive spectroscopic analyses, while the absolute configuration of novel 1 was determined by the comparison of experimental and calculated ECD spectra. The novel 1 and known 2 and 3 showed significant antifungal activities against Colletotrichum lagrnarium with MIC values of 8, 16, and 16 μg/mL respectively, even better than those of the commonly used synthetic fungicide carbendazim with 32 μg/mL. They also exhibited antifungal potential against carbendazim-resistant Botrytis cinerea. Cyclodepsipeptides 7-9 showed moderate nematicidal activities against the southern root-knot nematode (Meloidogyne incognita). This study constitutes the first report on the antagonistic effects of metabolites from T. Longibrachiatum against soil-borne pathogens, also highlighting the integrated antagonistic potential of marine-derived T. Longibrachiatum as a biocontrol agent.
Collapse
Affiliation(s)
- Feng-Yu Du
- College of Chemistry and Pharmacy, Qingdao Agricultural University, Qingdao 266109, China; (F.-Y.D.); (G.-L.J.); (L.X.)
- Shandong Key Laboratory of Applied Mycology, Qingdao Agricultural University, Qingdao 266109, China
| | - Guang-Lin Ju
- College of Chemistry and Pharmacy, Qingdao Agricultural University, Qingdao 266109, China; (F.-Y.D.); (G.-L.J.); (L.X.)
| | - Lin Xiao
- College of Chemistry and Pharmacy, Qingdao Agricultural University, Qingdao 266109, China; (F.-Y.D.); (G.-L.J.); (L.X.)
| | - Yuan-Ming Zhou
- Analytical and Testing Center, Qingdao Agricultural University, Qingdao 266109, China;
| | - Xia Wu
- Key Lab of Integrated Crop Pest Management of Shandong Province, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China
- Correspondence:
| |
Collapse
|
3
|
Sousa JLC, Silva AMS, Alkorta I, Elguero J. Assignment of 1 H and 13 C NMR data for three pairs of diastereomers of 4'-X benzo[1,3]cyclopropa[1,2-b]chromene-4,5-diones (X = H, OCH 3 , and Cl). MAGNETIC RESONANCE IN CHEMISTRY : MRC 2019; 57:512-521. [PMID: 31134669 DOI: 10.1002/mrc.4892] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 05/08/2019] [Accepted: 05/09/2019] [Indexed: 06/09/2023]
Affiliation(s)
- Joana L C Sousa
- Department of Chemistry & QOPNA, University of Aveiro, 3810-193, Aveiro, Portugal
| | - Artur M S Silva
- Department of Chemistry & QOPNA, University of Aveiro, 3810-193, Aveiro, Portugal
| | - Ibon Alkorta
- Instituto de Química Médica (IQM-CSIC), Juan de la Cierva, 3, E-28006, Madrid, Spain
| | - José Elguero
- Instituto de Química Médica (IQM-CSIC), Juan de la Cierva, 3, E-28006, Madrid, Spain
| |
Collapse
|
4
|
Rahaman M, Hussein IA, Aldalbahi A, Parvez A, Soares JBP. Synthesis of Metallocene Catalyzed Ethylene 1,7-Octadiene Copolymer: Effect of Copolymerization on Polymer Properties. Macromol Res 2018. [DOI: 10.1007/s13233-018-6049-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
5
|
García-Vázquez JB, Bañuelos-Hernández AE, Trujillo-Serrato JJ, Suárez-Castillo OR, Ariza-Castolo A, Morales-Ríos MS. Structure-selectivity relationship in the cleavage of spirocyclopropyl oxindoles: An experimental and theoretical investigation. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2017.05.099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
6
|
Abraham RJ, Ashley Cooper M. A molecular mechanics and ab initio prediction of the 1 H chemical shifts of pinanes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2017; 55:837-845. [PMID: 28422317 DOI: 10.1002/mrc.4598] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 04/06/2017] [Accepted: 04/09/2017] [Indexed: 06/07/2023]
Abstract
Molecular mechanics calculations plus the application of a refined Karplus equation gave the conformations of 19 pinanes. These range from a Y-shaped geometry in the apopinene and α-pinene series to a pseudo chair conformation in β-pinene, nopinone and verbanone, a flattened chair in pinocarvone and the pinocarveols and a distorted Y shape for iso-verbanone. These structures were then used as input to predict the 1 H chemical shifts of these compounds by semi-empirical (1 H-NMR spectra (HSPEC)) and ab initio gauge-invariant atomic orbital (GIAO) calculations, the latter at the B3LYP hybrid density functional theory level using 6-31++G** basis set. The two methods gave generally good agreement with the 184 observed shifts with root mean square (RMS) errors 0.07 ppm (HSPEC) and 0.10 ppm (GIAO), but the GIAO calculations gave several significant (>0.25 ppm) errors. One was for the H3 proton in apopinenone and other α,β unsaturated ketones; the others occurred for protons in close proximity to hydroxyl groups. To provide more information, smaller analogues of known geometry and chemical shifts were subject to the same analysis. In cyclopentenone, the Gaussian geometry gave good agreement with the observed shifts, but the MMFF94, MMX and MM3 geometries all gave errors for different protons. These results show clearly that the molecular geometries of the α,β unsaturated ketones are responsible for the errors. The errors for the alcohols were examined using ethanol as model and were shown to be due to the different possible conformations of the OH group. Similar GIAO calculations on substituted methanes gave good agreement for the methyl compounds but poor agreement for di and tri halosubstituted methanes. The aforementioned method of molecular mechanics plus GIAO calculations is shown to be a very useful tool for the investigation of molecular geometries and conformations. However, multihalogen compounds may require different basis sets for accurate calculations. Copyright © 2017 John Wiley & Sons, Ltd.
Collapse
Affiliation(s)
- Raymond J Abraham
- Chemistry Department, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK
| | - M Ashley Cooper
- Chemistry Department, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK
| |
Collapse
|
7
|
Zeng J, Zhang DB, Zhou PP, Zhang QL, Zhao L, Chen JJ, Gao K. Rauvomines A and B, Two Monoterpenoid Indole Alkaloids from Rauvolfia vomitoria. Org Lett 2017; 19:3998-4001. [PMID: 28718654 DOI: 10.1021/acs.orglett.7b01723] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Two unusual normonoterpenoid indole alkaloids rauvomine A (1) and rauvomine B (2), together with two known compounds peraksine (3) and alstoyunine A (4), were isolated from the aerial parts of Rauvolfia vomitoria. The structures with absolute configurations of 1 and 2 were elucidated by spectroscopic analysis, single-crystal X-ray diffraction, and electronic circular dichroism (ECD) calculations. Compound 2 is a novel C18 normonoterpenoid indole alkaloid with a substituted cyclopropane ring that forms an unusual 6/5/6/6/3/5 hexcyclic rearranged ring system. The plausible biogenetic pathways of 1 and 2 were proposed. Compound 2 exhibited significant anti-inflammatory activity.
Collapse
Affiliation(s)
- Jun Zeng
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University , Lanzhou 730000, China
| | - Dong-Bo Zhang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University , Lanzhou 730000, China
| | - Pan-Pan Zhou
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University , Lanzhou 730000, China
| | - Qi-Li Zhang
- Gansu University of Chinese Medicine , Lanzhou 730000, China
| | - Lei Zhao
- Gansu University of Chinese Medicine , Lanzhou 730000, China
| | - Jian-Jun Chen
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University , Lanzhou 730000, China
| | - Kun Gao
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University , Lanzhou 730000, China
| |
Collapse
|
8
|
García-Vázquez JB, González-Juárez DE, Morales-Ríos MS, Suárez-Castillo OR, Mora-Pérez Y. Structure elucidation of configurational isomers of nitrile-substituted spirocyclopropyloxindoles by NMR spectroscopy, molecular modeling, and X-ray crystallography. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2015; 53:1061-1070. [PMID: 26768305 DOI: 10.1002/mrc.4293] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 06/11/2015] [Accepted: 06/15/2015] [Indexed: 06/05/2023]
Affiliation(s)
- J Benjamín García-Vázquez
- Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000, Mexico
- Programa de Posgrado en Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000, Mexico
| | - Daphne E González-Juárez
- Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000, Mexico
| | - Martha S Morales-Ríos
- Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000, Mexico
- Programa de Posgrado en Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000, Mexico
| | - Oscar R Suárez-Castillo
- Área Académica de Química, Universidad Autónoma del Estado de Hidalgo, Mineral de la Reforma, Hidalgo, 42184, Mexico
| | - Yolanda Mora-Pérez
- Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000, Mexico
| |
Collapse
|
9
|
Senthil Raj P, Shoba D, Ramalingam S, Periandy S. Spectroscopic (FT-IR/FT-Raman) and computational (HF/DFT) investigation and HOMO/LUMO/MEP analysis on 1,1-difluoro-2-vinyl-cyclopropane. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2015; 147:293-302. [PMID: 25854609 DOI: 10.1016/j.saa.2015.03.084] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Revised: 03/07/2015] [Accepted: 03/10/2015] [Indexed: 06/04/2023]
Abstract
All the computational calculations were made in the ground state using the HF and DFT (B3LYP) methods with 6-31++G (d,p) and 6-311++G (d,p) basis sets. Making use of the recorded data, the complete vibrational assignments were made and analysis of the observed fundamental bands of molecule was carried out. The shifting of the frequencies in the vibrational pattern of the title molecule due to the substitutions; CHCH₂ and F were deeply investigated by the vibrational analysis. Moreover, (13)C NMR and (1)H NMR chemical shifts were calculated by using the gauge independent atomic orbital (GIAO) method with HF/B3LYP methods with 6-311++G (d,p). A study on the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. Mulliken charges of the 1DF2VCP were also calculated and interpreted. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures were calculated in gas phase.
Collapse
Affiliation(s)
| | - D Shoba
- Periyar Maniammai University, Thanjavur, India
| | - S Ramalingam
- Department of Physics, A.V.C. College, Mayiladuthurai, Tamilnadu, India
| | - S Periandy
- Department of Physics, Tagore Arts College, Puducherry, India
| |
Collapse
|
10
|
Kleinpeter E, Krüger S, Koch A. Anisotropy Effect of Three-Membered Rings in 1H NMR Spectra: Quantification by TSNMRS and Assignment of the Stereochemistry. J Phys Chem A 2015; 119:4268-76. [DOI: 10.1021/acs.jpca.5b03078] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Erich Kleinpeter
- Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam (Golm), Germany
| | - Stefanie Krüger
- Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam (Golm), Germany
| | - Andreas Koch
- Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam (Golm), Germany
| |
Collapse
|
11
|
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.
Collapse
Affiliation(s)
- John S Lomas
- Univ Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086, F-75205, Paris, France
| |
Collapse
|
12
|
Abraham RJ, Griffiths L, Perez M. 1H NMR spectra part 31: 1H chemical shifts of amides in DMSO solvent. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2014; 52:395-408. [PMID: 24824670 DOI: 10.1002/mrc.4079] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 04/02/2014] [Accepted: 04/04/2014] [Indexed: 06/03/2023]
Abstract
The (1)H chemical shifts of 48 amides in DMSO solvent are assigned and presented. The solvent shifts Δδ (DMSO-CDCl3 ) are large (1-2 ppm) for the NH protons but smaller and negative (-0.1 to -0.2 ppm) for close range protons. A selection of the observed solvent shifts is compared with calculated shifts from the present model and from GIAO calculations. Those for the NH protons agree with both calculations, but other solvent shifts such as Δδ(CHO) are not well reproduced by the GIAO calculations. The (1)H chemical shifts of the amides in DMSO were analysed using a functional approach for near ( ≤ 3 bonds removed) protons and the electric field, magnetic anisotropy and steric effect of the amide group for more distant protons. The chemical shifts of the NH protons of acetanilide and benzamide vary linearly with the π density on the αN and βC atoms, respectively. The C=O anisotropy and steric effect are in general little changed from the values in CDCl3. The effects of substituents F, Cl, Me on the NH proton shifts are reproduced. The electric field coefficient for the protons in DMSO is 90% of that in CDCl3. There is no steric effect of the C=O oxygen on the NH proton in an NH…O=C hydrogen bond. The observed deshielding is due to the electric field effect. The calculated chemical shifts agree well with the observed shifts (RMS error of 0.106 ppm for the data set of 257 entries).
Collapse
Affiliation(s)
- Raymond J Abraham
- The Chemistry Department, University of Liverpool, Crown St., Liverpool, L69 7ZD, UK
| | | | | |
Collapse
|
13
|
Barbosa LR, Vieira YW, Lacerda V, de Oliveira KT, dos Santos RB, Greco SJ, Neto AC, de Castro EVR, Brocksom TJ. Unequivocal structural assignments of three cycloheptenoid intermediates for guaiane sesquiterpenes: an experimental and theoretical approach. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2014; 52:318-328. [PMID: 24723362 DOI: 10.1002/mrc.4057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 02/07/2014] [Accepted: 02/11/2014] [Indexed: 06/03/2023]
Affiliation(s)
- Layla R Barbosa
- Departamento de Química, Centro de Ciências Exatas, Universidade Federal do Espírito Santo, Av. Fernando Ferrari 514, 29.075-910, Vitória, ES, Brazil
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Affiliation(s)
- Guglielmo Monaco
- Dipartimento
di Chimica e
Biologia, Universitá degli Studi di Salerno, Via Giovanni
Paolo II, 132, Fisciano 84084 Salerno, Italy
| | - Riccardo Zanasi
- Dipartimento
di Chimica e
Biologia, Universitá degli Studi di Salerno, Via Giovanni
Paolo II, 132, Fisciano 84084 Salerno, Italy
| |
Collapse
|
15
|
Baranac-Stojanović M. New insight into the anisotropic effects in solution-state NMR spectroscopy. RSC Adv 2014. [DOI: 10.1039/c3ra45512b] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
|
16
|
Abraham RJ, Griffiths L, Perez M. 1H NMR spectra. Part 30(+): 1H chemical shifts in amides and the magnetic anisotropy, electric field and steric effects of the amide group. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2013; 51:143-55. [PMID: 23354811 DOI: 10.1002/mrc.3920] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 12/09/2012] [Accepted: 12/09/2012] [Indexed: 05/13/2023]
Abstract
The (1)H spectra of 37 amides in CDCl(3) solvent were analysed and the chemical shifts obtained. The molecular geometries and conformational analysis of these amides were considered in detail. The NMR spectral assignments are of interest, e.g. the assignments of the formamide NH(2) protons reverse in going from CDCl(3) to more polar solvents. The substituent chemical shifts of the amide group in both aliphatic and aromatic amides were analysed using an approach based on neural network data for near (≤3 bonds removed) protons and the electric field, magnetic anisotropy, steric and for aromatic systems π effects of the amide group for more distant protons. The electric field is calculated from the partial atomic charges on the N.C═O atoms of the amide group. The magnetic anisotropy of the carbonyl group was reproduced with the asymmetric magnetic anisotropy acting at the midpoint of the carbonyl bond. The values of the anisotropies Δχ(parl) and Δχ(perp) were for the aliphatic amides 10.53 and -23.67 (×10(-6) Å(3)/molecule) and for the aromatic amides 2.12 and -10.43 (×10(-6) Å(3)/molecule). The nitrogen anisotropy was 7.62 (×10(-6) Å(3)/molecule). These values are compared with previous literature values. The (1)H chemical shifts were calculated from the semi-empirical approach and also by gauge-independent atomic orbital calculations with the density functional theory method and B3LYP/6-31G(++) (d,p) basis set. The semi-empirical approach gave good agreement with root mean square error of 0.081 ppm for the data set of 280 entries. The gauge-independent atomic orbital approach was generally acceptable, but significant errors (ca. 1 ppm) were found for the NH and CHO protons and also for some other protons.
Collapse
Affiliation(s)
- Raymond J Abraham
- The Chemistry Department, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK.
| | | | | |
Collapse
|
17
|
Cai Z, Harmata M. Benzothiazines in organic synthesis: formation of a cyclopropane via neighboring group participation. Tetrahedron Lett 2013. [DOI: 10.1016/j.tetlet.2012.11.066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
18
|
Abraham RJ, Leonard P. 1H NMR spectra. Part 29§: Proton chemical shifts and couplings in esters--the conformational analysis of methyl γ-butyrolactones. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2013; 51:9-15. [PMID: 23125038 DOI: 10.1002/mrc.3896] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 10/08/2012] [Accepted: 10/08/2012] [Indexed: 06/01/2023]
Abstract
The (1)H NMR spectra of 35 cyclic and acyclic esters are analysed to give the (1)H chemical shifts and couplings. The substituent chemical shifts of the ester group were analysed using three-bond (γ) effects for near protons and the electric field, magnetic anisotropy and steric effect of the ester group for more distant protons. The electric field is calculated from the partial atomic charges on the O⋅C = O atoms, and the asymmetric magnetic anisotropy of the carbonyl group acts at the midpoint of the C = O bond. The values of the anisotropies Δχ(parl) and Δχ(perp) were for the aliphatic esters 10.35 and -18.84 and for the conjugated esters 7.33 and -15.75 (×10(-6) Å(3)/molecule). The oxygen steric coefficients found were 104.4 (aliphatic C = O), 45.5 (aromatic C = O) and 16.0 (C-O) (×10(-6) Å(6)/molecule). After parameterisation, the overall RMS error for the data set of 280 entries was 0.079 ppm. The strongly coupled (1) H NMR spectra of the 2-methyl, 3-methyl and 4-methyl γ-butyrolactones were analysed and the methyl conformational equilibrium obtained from the observed couplings. The observed versus calculated density functional theory (DFT) ΔG(ax-eq) was 1.0 (1.01), 0.34 (0.54) and 0.65 (0.71) kcal/mol res. The shielding effect of a methyl cis to a proton in the five-membered lactone rings is -0.40 ±0.05 ppm and deshielding trans effect 0.12 ±0.05 ppm, which is common to both five and six membered rings. The cis/trans isomerism in the vinyl esters methyl acrylate, crotonate and methacrylate and methyl furoate was examined using the (1)H chemical shifts. The calculated shifts of both the cis and trans isomers were in good agreement with the observed shifts.
Collapse
Affiliation(s)
- Raymond J Abraham
- The Chemistry Department, University of Liverpool, Crown St, Liverpool, L69 7ZD, UK.
| | | |
Collapse
|