1H Spin-spin Coupling Constants Research Articles

Sesquiterpenes and Flavonoids of Anthemis odontostephana var. odontostephana

Phytochemical investigation of the flowers of Anthemis odontostephana Boiss. var. odontostephana (Asteraceae) resulted in the isolation of a natural cyclohexenone sesquiterpenoid with a bisabolene skeleton, 1-hydroxydelobanone (1), for the first time as a natural product, and a previously reported cyclohexenone derivative, antheminone A (2), along with two known flavonoids, pectolinaringenin (3), and salvigenin (4). The stereochemistry at positions C-4 and C-5 of the cyclohexenone ring of compound 2 was established based on 1H–1H spin-spin coupling constants and ROESY spectra. Compounds 2 and 3 were reported previously as antileishmanial and cytotoxic agents by other authors. The structures of the compounds were elucidated using NMR spectroscopic methods including 1H NMR, 13C NMR, APT, COSY, HSQC, and HMBC, and mass spectrometry.

Experimental and NMR Theoretical Methodology Applied to Geometric Analysis of the Bioactive Clerodanetrans-Dehydrocrotonin

trans-Dehydrocrotonin (t-DCTN) a bioactive 19-nor-diterpenoid clerodane type isolated from Croton cajucara Benth, is one of the most investigated clerodane in the current literature. In this work, a new approach joining X-ray diffraction data, nuclear magnetic resonance (NMR) data and theoretical calculations was applied to the thorough characterization of t-DCTN. For that, the geometry of t-DCTN was reevaluated by X-ray diffraction as well as 1H and 13C NMR data, whose geometrical parameters where compared to those obtained from B3LYP/6-311G++(d,p) level of theory. From the evaluation of both calculated and experimental values of 1H and 13C NMR chemical shifts and spin-spin coupling constants, it was found very good correlations between theoretical and experimental magnetic properties of t-DCTN. Additionally, the delocalization indexes between hydrogen atoms correlated accurately with theoretical and experimental spin-spin coupling constants. An additional topological analysis from quantum theory of atoms in molecules (QTAIM) showed intramolecular interactions for t-DCTN.

Synthesis and NMR spectra of tetrahydrofuran-2-13C

An original method was developed for the synthesis of THF labeled selectively with the 13C isotope at the α-carbon atom. The effective reduction of symmetry brought about by the insertion of the isotopic label removes the excess degeneracy of the spin systems describing the multiplet structure of the 1H and 13C NMR spectra, making it possible to undertake a detailed analysis. Exact values for the 1H–1H spin-spin coupling constants through four bonds and also the 13C–1H and 13C–13C spin-spin coupling constants involving the α-carbon atom were determined for the first time. The isotopic chemical shifts of the protons and 13C nuclei caused by replacement of the 12C nucleus by 13C were determined. These data can be used to construct a quantitative model of the conformational behavior of THF as a molecular system in which pseudorotation in terms of vibrations with large amplitude is realized.

DFT Calculation of 1J(119Sn,13C) and 2J(119Sn,1H) Coupling Constants in Di- and Trimethyltin(IV) Compounds

We have tested several computational protocols, at the nonrelativistic DFT level of theory, for the calculation of 1J(119Sn, 13C) and 2J(119Sn, 1H) spin-spin coupling constants in di- and trimethyltin(IV) derivatives with various ligands. Quite a good agreement with experimental data has been found with several hybrid functionals and a double-zeta basis set for a set of molecules comprising tetra-, penta-, and hexa-coordinated tin(IV). Then, some of the protocols have been applied to the calculation of the 2J(119Sn, 1H) of the aquodimethyltin(IV) ion and dimethyltin(IV) complex with D-ribonic acid and to the calculation of 1J(119Sn, 13C) and 2J(119Sn, 1H) of the dimethyltin(IV)-glycylglycine and glycylhistidine complexes in water solutions. Solvent effects have been considered in these cases by including explicit water molecules and/or the solvent reaction field, resulting in a good agreement with experimental data. The proposed protocols constitute a helpful tool for the structural determination of di- and triorganotin(IV) derivatives.

Conformational study of 2‐arylazo‐1‐vinylpyrroles

Conformational study of 2-phenylazo-1-vinylpyrrole and 2-(4-bromophenyl)azo-5-methyl-1-vinylpyrrole was performed on the basis of the experimental measurements and high-level ab initio calculations of their 13C--13C and 13C--1H spin-spin coupling constants, showing marked stereochemical behaviour upon the internal rotation of the vinyl group and the pyrrolyl moiety. In liquid phase, both compounds were found to adopt predominant s-trans-s-trans conformation with the noticeable population (ca. 30%) of the higher-energy s-cis-s-trans conformation in the latter compound. As follows from the X-ray data, 2-phenylazo-1-vinylpyrrole crystallizes in s-trans-s-trans conformation while the crystalline molecular structure of 2-(4-bromophenyl)azo-5-methyl-1-vinylpyrrole is s-cis-s-trans.

Pattern recognition of the multiplet structure of NMR spectra

A new method of analysis of high-resolution NMR spectra was suggested, and an algorithm and the PAREMUS program package for assignment of patterns of the spectral components based on pattern recognition theory were developed. High effectiveness of the method has been exemplified by determination of the values and relative signs of the interring1H−1H and13C−1H spin-spin coupling constants in 1,2,3-trichloronaphthalene.

Study of stereochemical dependences of the direct13C−1H spin-spin coupling constants in vinylpyridines by the quantum-chemical INDO-RPA method

The stereochemical dependences of the direct13C−1H spin-spin coupling constants (SSCC) in the vinyl group of vinylpyridines studied by the quantum-chemical INDO-RPA method indicate that the steric closeness of the hydrogen atom to the nitrogen atom causes an increase in the corresponding direct13C−1H SSCC and a decrease in the analogous constant of the geminal hydrogen atom. The results obtained qualitatively agree with the data ofab initio calculations for the simplest systems and the experiment. At the same time, an essential quantitative overestimation of the real effect takes place.

Analysis of effect of specific C-H ...X interaction on the direct13C-1H spin-spin coupling constants based onab initio quantum-chemical calculations

Anab initio quantum-chemical calculation of the direct13C−1H spin-spin coupling constants in the CH4−H2O system was carried out and experimental data obtained for a series ofN-vinyl compounds were analyzed. The specific C-H ....X (X = O, N) intramolecular interactions result in increasing the direct13C−1H spin-spin coupling constant of the hydrogen involved in bonding and decreasing the direct13C-1H spin-spin coupling constant for the hydrogen atom that takes no part in the interaction.

Simple Approaches for Estimating Vicinal 1H- 1H Coupling-Constants and for Obtaining Stereospecific Resonance Assignments in Leucine Side Chains

An approach for deriving stereospecific δ-methyl assignments and χ 2 dihedral angle constraints for leucine residues, based on easily recognized patterns of 1H- 1H spin-spin coupling constants and intraresidue nuclear-Overhauser-effect spectroscopy (NOESY) cross-peak intensities, is described. The approach depends on resolved H γ and/or δ-methyl resonances and on initially obtaining stereospecific assignments for H β2 and H β3. As part of the overall strategy, a method is presented for obtaining qualitative or, in favorable cases, semiquantitative estimates of vicinal 1H- 1H coupling constants from peak intensities measured in a short-mixing-time 1H- 1H total correlation spectroscopy (TOCSY) experiment. This method of estimating 1H- 1H spin-spin coupling constants is generally applicable to all side-chain types. The approach is illustrated for several leucine residues within uniformly 15N-labeled and 15N/ 13C-double-labeled isolated light-chain variable domain of the anti-digoxin antibody 26-10. Estimates of 3 J αβ and 3 J βγ coupling constants are derived from a three-dimensional (3D) 13C-edited TOCSY-heteronuclear multiple-quantum coherence (HMQC) spectrum. These data are combined with information from 3D 15N-edited NOESY and 3D 13C-edited NOESY spectra to yield stereospecific H β2, H β3, and δ-methyl assignments, as well as constraints on χ (1) and χ 2 dihedral angles. Although the overall approach is illustrated using 3D 15N-edited and 13C-edited data, it is equally applicable to analysis of two-dimensional 1H- 1H NOESY and TOCSY spectra.

17O, 1H coupling constants in intramolecular hydrogen bonds

17O, 1H spin-spin coupling constants in systems with intramolecular hydrogen bonds are reported. The 17O NMR spectra, proton decoupling and the special DECOMPOSITION program were used. In asymmetrical systems, 17O, 1H coupling constants of about 80 Hz were found for one of the oxygen nuclei while for symmetrical systems 17O, 1H coupling constants of about 30 Hz were observed for both equivalent oxygen nuclei. The data on 17O, 1H coupling constants can be used to estimate the state of the proton in the hydrogen bond.

Heteroorganic derivatives of furan. 65. Effect of substituents on shielding of 1H, 13C, and 29Si and 29Si-13C spin-spin coupling constants in NMR spectra of 2-substituted furans and 5-trimethylsilylfurans

The results of an investigation of 2-substituted furans and 5-trimethylsilylfurans by NMR spectroscopy and the CNDO/2 method showed that the chemical shifts of the different nuclei do not correlate sufficiently clearly with the calculated charges because of an additional change in the electron density under the influence of a π-d interaction. The 13C-29Si direct spin-spin coupling constants (SSCC) are less sensitive to this interaction, since they depend primarily on the inductive effects of the substituents.

ChemInform Abstract: Stereospecifity of the 1H, 15N, and 19F Spin‐Spin Coupling Constants in Substituted 2,2‐Bis(trifluoromethyl)aziridines.

ChemInformVolume 19, Issue 48 Heterocyclic Compounds ChemInform Abstract: Stereospecifity of the 1H, 15N, and 19F Spin-Spin Coupling Constants in Substituted 2,2-Bis(trifluoromethyl)aziridines. R. G. KOSTYANOVSKII, R. G. KOSTYANOVSKII Inst. khim. fiz. AN SSSR, Moskva 117334Search for more papers by this authorG. K. KADORKINA, G. K. KADORKINA Inst. khim. fiz. AN SSSR, Moskva 117334Search for more papers by this authorI. I. CHERVIN, I. I. CHERVIN Inst. khim. fiz. AN SSSR, Moskva 117334Search for more papers by this authorI. K. A. ROMERO MALDONADO, I. K. A. ROMERO MALDONADO Inst. khim. fiz. AN SSSR, Moskva 117334Search for more papers by this author R. G. KOSTYANOVSKII, R. G. KOSTYANOVSKII Inst. khim. fiz. AN SSSR, Moskva 117334Search for more papers by this authorG. K. KADORKINA, G. K. KADORKINA Inst. khim. fiz. AN SSSR, Moskva 117334Search for more papers by this authorI. I. CHERVIN, I. I. CHERVIN Inst. khim. fiz. AN SSSR, Moskva 117334Search for more papers by this authorI. K. A. ROMERO MALDONADO, I. K. A. ROMERO MALDONADO Inst. khim. fiz. AN SSSR, Moskva 117334Search for more papers by this author First published: November 29, 1988 https://doi.org/10.1002/chin.198848150Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue48November 29, 1988 RelatedInformation

Scalar relaxation of homonuclear multiple-quantum coherences and relative signs of 14N- 1H spin-spin coupling constants in E- N-phenylformamide

Homonuclear multiple-quantum NMR relaxation rates for E- N-phenylformamide, whose interesting part consists of two protons A and M differently coupled to a rapidly relaxing 14N nucleus are reported. The zero- and double-quantum linewidths depend on the cross correlation spectral densities and allow the determination of 1 J and 2 J 14N- 1H spin-spin coupling constants and their relative signs. We show that the two coupling constants have the same signs and are likely to be positive. Note that only one of the resonances of the AM pair needs to be significantly broadened due to scalar interactions in order for the cross correlation spectral density to become important for the multiple-quantum relaxation rates.

Influence of paramagnetic shift reagents on the spin-lattice relaxation times of13C nuclei and the13C?1H spin-spin coupling constants

Influence of paramagnetic shift reagents on the spin-lattice relaxation times of13C nuclei and the13C?1H spin-spin coupling constants

Application of phase sensitive two-dimensional correlated spectroscopy (COSY) for measurements of 1H- 1H spin-spin coupling constants in proteins

Two-dimensional correlated spectroscopy (COSY) is used for measurements of proton-proton spin-spin coupling constants in protein 1H NMR spectra. High digital resolution along the frequency axis ω 2 is achieved by placing the carrier frequency in the center of the spectrum, using quadrature detection in both dimensions and presenting the spectrum in the phase sensitive mode. Compared to other techniques for studies of spin-spin coupling constants, COSY provides greatly improved spectral resolution. This is illustrated by experiments with H 2O solutions of the small globular protein BUSI IIA (bull seminal inhibitor IIA).

Correlation of 13C- 1H spin-spin coupling constants and the sum of internuclear angle distortions in saturated hydrocarbons

An empirical relationship between one bond carbon-hydrogen spin-spin coupling constants, 1J CH and the sum of internuclear angle distortions, ΣΔθ has been found. The proposed formula gives 1J CH values with a 3.22 Hz average deviation from the experimental values (30 data points, s.d. = 2.74) and useable for both the methylene and methine carbons of saturated hydrocarbons.

Multinuclear NMR studies on ZnCl 2-, CdCl 2- and HgCl 2-interaction with adenosin and guanosin and other nitrogen-heterocycles

13C NMR investigation of nitrogen heterocycles have been established as a useful tool for the detection of protonation sites [1]. The 13C, 1H spin-spin interactions are particularly sensitive parameters for this purpose, as was shown recently for purine [2]. Even more direct information is available from 15N NMR studies, where chemical shifts are strongly affected by protonation [3, 4]. An extension of such studies to interaction between metal salts and nitrogen heterocycles seemed interest. The present communication deals with results of 13C, 15N, 199Hg, and 13Cd NMR investigations of adenosin and guanosin in the presence of ZnCl 2, CdCl 2, and HgCl 2 in DMSO-d 6. The information extracted from the various NMR parameters, in particular, 13C, 1H spin-spin coupling constants and 15N as well as 199Hg and 113Cd chemical shifts is compared, and the contact sites as well as the strength of the interaction are discussed. Similar studies with imidazole and 1-methyl imidazole as well as with purine and its methyl derivatives are described.

Tautomerism in OH-, SH-, and NH 2-substituted pyrazines - a carbon-13 and nitrogen-15 NMR study -

It is shown that 13C, 1H spin-spin coupling constants can be used to study heteroaromatic tautomerism. Results for the title compounds are supported by 15N-NMR data.

Negative reduced three-bond 15N 1H spin-spin coupling constants

Negative reduced three-bond 15N 1H spin-spin coupling constants

A method for the accurate measurement of 1H spin-spin coupling constants in large molecules

A method for the accurate measurement of 1H spin-spin coupling constants in large molecules