bluuebunny/crossref_metadata_2025_split huggingface dataset:
Déplacements Chimiques induits en RMN par un Réactif Lanthanidique: II—Analyse Conformationnelle de Sulfinamates Cycliques: Oxo‐2 Oxathiazannes‐1,2,3 et Oxo‐2 Benzo‐5,6 Dihydro‐3,4 Oxathiazines‐1,2,3
Authors: Tisnès P. , Maroni P. , Cazaux L. 
Published: May 2005

AbstractUn réexamen des résultats récents de la littérature concernant les tert‐butyl‐5‐c oxo‐2‐r dioxaphosphorinanes‐1,3,2 substitués en 2 et le diméthyl‐3,3 oxo‐1 thietanne nous a conduit à choisir, dans les conditions indiquées, le modèle statique d'étude des déplacements induits par le lanthanides (DIL), plus souple d'emploi que le modéle dynamique. Son application à dix‐sept sulfinamates cycliques appartenant à deux séries, les oxo‐2 oxathiazannes‐1,2,3 (I) et les oxo‐2 benzo‐5,6 dihydro‐3,4 oxathiazines‐1,2,3 (II) confirme en présence d'Eu(fod)3, les structures établies en son absence sur les seules bases des déplacements chimiques et des constantes de couplage, et montre leur diversité conformationnelle. Pour la série I, on trouve (i) des chaises standard à SO axial (CA) lorsque la molécule ne comporte pas de substituants en position 4 et 6 ou lorsqu'ils sont équatoriaux, à une exception près; les substituants sur l'atome d'azote RMe, iPr ou tBu sont de préférence axiaux; (ii) des chaises déformées à SO et Me‐4 axiaux (CA); cette conformation permet à RPh une certaine conjugaison et à RMe ou tBu d'occuper la position axiale; (iii) des conformations croisées d'axe‐1,4 à SO axial (COA) pour les deux di‐tert‐butyl‐4‐c‐6‐c, et ‐4‐t‐6‐c phenyl‐3 oxo‐2‐r oxathiazannes‐1,2,3; (iv) la conformation croisée d'axe‐3,6 à SO axial (CNA) pour le méthyl‐4 tert‐butyl‐3 oxo‐2 oxathiazanne‐1,2,3 trans en raison de l'interaction‐1,2 Me‐4‐ ‐tBu‐3. Pour la série II, on retient des formes demi‐chaises à SO axial.
Détermination Directe de la Stéréochimie de l'Addition de Carbènes aux Oléfines Bicycliques par RMN du Carbone‐13
Authors: Brun P. , Casanova J. , Hatem J. , Zahra J. P. , Waegell B. 
Published: May 2005

AbstractLes déplacements chimiques en RMN du 13C d'une série de dérivés tricycliques obtenus par addition de carbènes sur des alcènes bicycliques sont comparés aux déplacements chimiques des oléfines de départ. La measure du déplacement chimique du carbone 7 montre que cette valeur peut être utilisée comme sonde configurationnelle pour la détermination de la stéréochimie de l'addition des carbènes étudiés.
The effects of substituents on the 5J long‐range spin‐spin coupling constants in substituted benzaldehydes
Authors: Contreras R. H. , de Kowalewski D. G. , Osella A. 
Published: May 2005

AbstractProton magnetic resonance spectra of several mono‐ and disubstituted benzaldehydes were studied using CW, INDOR and double resonance techniques. It was verified that substitution in the para position has no effect on the long‐range coupling of the aldehydic proton with the ring protons five bonds away. Substitution in the ortho and meta positions (with the exception of 2,4‐dinitrobenzaldehyde) follows closely the additivity rule effects of the substituents.
Equation de Karplus appliquée à des systèmes sp2–sp3
Authors: Jankowski K. , Bélanger J. , Söler F. , Zamojski A. 
Published: May 2005

AbstractOn présente une tentative d'affinage de l'équation de Karplus pour des systèmes sp2‐sp3. L'étude porte sur un total de 68 constantes de couplage vicinal venant de 32 produits différents. On obtient la meilleure équation de Karplus jusqu'à ce jour, avec un facteur d'accord relatif de 31,01%.
Tritium nuclear magnetic resonance spectroscopy. Part 11. Further consideration of referencing, isotope effects and coupling constants: Preparation of [3H]tetramethylsilane
Authors: Bloxsidge James P. , Elvidge John A. , Jones John R. , Mane Ramachandra B. , Saljoughian Manouchehr 
Published: May 2005

AbstractSmall discrepancies between 3H and 1H chemical shifts in organic compounds led to the finding that the ratio of Larmor frequencies ωT/ωH depends on the carbon‐hydrogen bond hybridisation. The ‘best’ ratio for ghost referencing of 3H NMR spectra was then determined from measurements on purified partially tritiated TMS as 1.066639738±2 × 10−9. Some 3H isotope effects on chemical shifts are listed and the 3H isotope effect on the methylene geminal coupling constant in benzyl methyl sulphoxide is measured. Use of 2H in the measurement of 2J(HH) coupling constants has inherent disadvantages, overcome by use of 3H substitution.
Etude RMN 13C d'un Dérivé Uniformément Enrichi en 13C. Signe des Valeurs des Constantes de Couplage Observées
Authors: Gagnaire D. , Reutenauer H. , Taravel F. 
Published: May 2005

AbstractLes paramètres RMN‐13C d'un dérivé statistiquement enrichi en 13C, le 3‐O‐acétyl‐1,2:5,6‐di‐O‐isopropylidène‐α‐D‐glucofuranose utilisé comme produit d'analyse dans des expériences de biosynthèse mettant en jeu un double marquage, ont été mesurés. Des expériences de double résonance homonucléaire 13C{13C} réalisées à 62,8 MHz ont en particulier permis de déterminer les constantes de couplage 13C13C. Par calcul théorique de spectre, grâce aux effets du second ordre qui apparaissent dans les spectres réalisés à 25,2 MHz et à 15,08 MHz, le signe de ces constantes de couplage a été déterminé. La reconstitution théorique totale des spectres tient compte de la présence des isotopoméres et a été effectuée à l'aide d'un programme (dérivé d programme LAOCOON) permettant l'addition pondérée des spectres.
Carbon‐13 NMR investigation of 2,5‐diaryl‐1,4‐dithiins
Authors: Buess C. M. , Narayanan K. S. , O'Donnell D. J. , Arjunan P. , Berlin K. D. 
Published: May 2005

AbstractThe 13C NMR spectra of eight 2,5‐diaryl‐1,4‐dithiins were recorded and signals were assigned. A linear correlation was observed between the electronegativity of the substituent groups on C‐10,10′ and the chemical shifts of C‐10,10′ after applying corrections for the magnetic anisotropic effect of the substituents. A Hammett correlation was found between the 13C chemical shifts of C‐3,6 and C‐7,7′ and the σp+ parameter associated with the substituents on C‐10,10′. Extended electronic interaction between the π system of the aryl group and the π system of the dithiin ring was suggested by the observance of an alternating behavior in the magnitude of the substituent effects on the 13C shifts of C‐2,5 and C‐3,6. An alternating effect was also noted in the magnitude of the long‐range 13CF coupling constants for these same carbon signals in 2,5‐(10,10′‐difluoro)diphenyl‐1,4‐dithiin.
Binding dynamics in biological systems. Interaction of MOPC‐315 with 19F labelled nitrophenyl haptens
Authors: Kooistra Dale A. , Richards John H. , Smallcombe Stephen H. 
Published: May 2005

AbstractWe have studied the dynamics of binding of 19F labelled haptens by mouse plasmacytoma antibody MOPC‐315, a protein which shows specificity for nitrophenyl haptens. The off‐rates for the dissociation of hapten from MOPC‐315 proteins (7S, Fab′ and Fv) were determined by the application of several methods including a technique which, in certain cases, allows the direct determination of the rate of exchange of nuclei between magnetically non‐equivalent sites without requiring prior knowledge of intrinsic line widths. Used in conjunction with independently determined data on line widths, chemical shifts, and binding affinities, these studies show that the rates for hapten association to, or dissociation from, the intact 7S antibody, the Fab′ fragment, and the Fv fragment of MOPC‐315 are essentially the same. They also indicate the presence, probably in the Fv region, of a low affinity (K∼ 103 M−1) site(s) for hapten binding. The mobility of the hapten combining site decreases as the size of the protein increases. These rate data, which were determined at relatively high protein concentrations (up to 40 mg ml−1), agree with on‐rates determined at much lower protein concentrations (≤1 mg ml−1); we therefore conclude that protein aggregation, if it does occur, does not significantly affect binding in these systems.
NMR spectra, MO calculations of spin–spin coupling constants and conformational analysis of substituted 1,3‐dioxolanes
Authors: Benassi Rois , Schenetti Luisa , Taddei Ferdinando , Villa Luigi , Ferri Vincenzo 
Published: May 2005

AbstractThe NMR spectra of a number of 2,4‐disubstituted 1,3‐dioxolanes have been recorded and the proton chemical shifts and coupling constants derived from complete spectral analysis. Vicinal coupling constants were found to be dependent on the substituent at C‐4 and this effect is more pronounced for J(trans) of the C‐4‐C‐5 fragment. These coupling constants also indicate a homogeneous behaviour within a series with either a cis or trans configuration, although the cis behaviour differs from that of trans isomers. This has been interpreted in terms of definite ring conformations in substituted derivatives, while the unsubstituted 1,3‐dioxolane undergoes free pesudorotation. Calculations of coupling constants were performed by semi‐empirical MO methods, both for unsubstituted 1,3‐dioxolane and for C‐4 substituted derivatives in a large number of conformations, in order to compare calculated and experimental values; the correct order of J(cis) and J(trans) for 1,3‐dioxolane is obtained only by employing energies from ab‐initio MO calculations averaged over the pseudorotation circuit. For the C‐4 substituted compounds calculated coupling constants were employed in a ‘trial and error’ process for the identification of the preferred conformations of these compounds; a set of two torsional angles for each compound was derived which allows a tentative description of the geometry of each molecule. A criticism of these geometries is given according to the evidence available on the structure of substituted 1,3‐dioxolanes.
Use of 13C isotope shifts to assign carbon atoms α and β (and para) to a hydroxy group in alkyl substituted phenols and alcohols
Authors: Newmark Richard A. , Hill James R. 
Published: May 2005

AbstractDoublets can be observed for carbons α and β to the hydroxyl in aliphatic alcohols containing equimolar amounts of OH and OD dissolved in (CH3)2SO containing CaSO4 desiccant. Isotopic doublets are also observed for the ipso and ortho carbons in alkyl substituted phenols. Para isotopic doublets are observable in para‐substituted phenols containing a large 2‐substituent. The isotope shift is positive (low field) for the para carbon, opposite to the negative shifts usually observed.
On the assignment of the carbon‐13 NMR spectrum of bilirubin
Authors: Kaplan Doron , Navon Gil 
Published: May 2005

AbstractAn individual assignment of certain peaks in the proton and 13C NMR spectra of bilirubin and of bilirubin dimethyl ester is described. The assignment was achieved through the spectra of vinylneoxanthobilirubinic acid and by off‐resonance decoupled 13C spectra of bilirubin dimethyl ester. The signals due to the endo and exo vinyl groups were separately assigned. This assignment allows a rational interpretation of previously obtained spin‐lattice relaxation times of the vinyl carbon peaks. The two vinyl groups are found to differ considerably in their motional correlation time.
Proton magnetic resonance studies of compounds with bridgehead nitrogen. 37–a comparison of the positions of conformational equilibria in 1‐methylperhydro‐oxazolo[3,4‐a]pyridines and in 1‐methylperhydrothiazolo [3,4‐a]pyridines
Authors: Crabb Trevor A. , Jupp Philip A. 
Published: May 2005

Abstractcis(1‐H, 8a‐H)‐1‐Methylperhydro‐oxazolo[3,4‐a]pyridine and cis(1‐H, 8a‐H)‐1‐methylperhydrothiazolo[3,4‐a]pyridine both adopt exclusively the trans‐fused conformation in carbon tetrachloride solution at room temperature. Both parent unsubstituted systems exist under similar conditions as equilibria containing c. 67% (oxazolo compound) and 64% (thiazolo compound) of the trans‐fused conformation. In marked contrast to these similar positions of conformational equilibria in both systems the trans(1‐H,8a‐H)‐1‐methylperhydrooxazolo[3,4‐a]pyridine exists as c. 73% trans‐fused in equilibrium with a cis‐fused conformation whereas the trans(1‐H, 8a‐H)‐1‐methylperhydrothiazolo[3,4‐a]pyridine exists almost exclusively in a cis‐fused ring conformation. These differences in conformational equilibria are explained in terms of changes in non‐bonded interactions.
31P and 13C NMR study of tribenzolyphosphine (CC6H5)3 Oriented in a Liquid Crystal
Authors: Cogne A. , Wiesenfeld L. , Robert J. B. , Tyka R. 
Published: May 2005

AbstractThe 13C and 31P NMR spectra of the triply 13C labelled tribenzoylphosphine [] oriented in a nematic phase have been recorded. From the spectral analysis one obtains the average CPC valence bond angle value (95.9°± 0.2), and the phosphorus chemical shift anisotropy Δσ(σ∥︁ – σ ⊥) which is equal to 75 ± 15 ppm.
Proton magnetic resonance study of rotational isomerism in vinylcycloalkanes
Authors: De Maré George R. , Lapaille Serge 
Published: May 2005

AbstractThe vicinal coupling constant, J(12), between the vinyl CH and the ring CH protons in vinylcyclohexane was calculated from a ‘partial molecule’ six‐spin system. The 100 and 270 MHz results are in good agreement; those at 60 MHz were, however, still inaccurate in this approximation. J(12) increases with increasing solvent polarity and decreasing temperature. The energy difference between the s‐trans and gauche conformers in both C2Cl4 and perdeuterioacetone solvents is 879 ± 167 J mol−1 (210±40 cal mole−1). The s‐trans conformer is the most stable, in contrast to the isoelectronic cyclohexylcarboxyaldehyde where the gauche rotamers are lower in energy.
13C NMR spectra of 2,3‐dihydro‐1H‐pyrrolo[1,2‐c]imidazol‐1,3‐dione and its thione analogues
Authors: Budhram Ronald S. , Uff Barrie C. , Jones R. Alan , Jones Richard O. 
Published: May 2005

AbstractAnalysis of the 13C NMR spectra of a series of 2,3‐dihydro‐1H‐pyrrolo[1,2‐c]imidazole derivatives has provided chemical shift data for (˜184 ppm), (˜173.5 ppm), (˜158 ppm) and (˜148 ppm) groups. A full analysis of the 13C chemical shifts of the C atoms of the pyrrole ring and of an N‐phenyl substituent is described.
Zero‐field‐splitting of some aromatic charge‐transfer complexes in their lowest excited triplet states—an ESR study
Authors: Krzystek Jerzy 
Published: May 2005

AbstractThe ESR spectra of some aromatic charge‐transfer complexes in the lowest excited triplet states were measured. From the extracted zero‐field‐splitting parameters it was found that in each case the lowest excited triplet state was localized on the donor, with a variable contribution of charge‐transfer configuration.
Coupling of HPLC and NMR 1—analysis of flowing liquid chromatographic fractions by proton magnetic resonance
Authors: Buddrus Joachim , Herzog Helmut 
Published: May 2005

AbstractA procedure is described which allows the recording of 1H NMR spectra from high performance liquid chromatography (HPLC) fractions flowing through the magnetic field with a velocity of either 0.05 or 0.25 cm/s. The NMR spectra are obtained by the pulse Fourier transform technique; the beginning and the termination of the pulse sequence is timed according either to the chromatogram from a UV detector or to the free induction decay of the appropriate HPLC fraction. The linewidth of the signals in the NMR spectra is between 1.5 and 2.0 Hz.
Partial orientation of nitroxide biradicals in the plastic phase of cyclohexane and in frozen toluene solution
Authors: Chiarelli Robert , Jeunet André , Michon Josette , Michon Pierre , Morat Claude , Rassat André , Sieveking Hans Ulrich 
Published: May 2005

AbstractSeveral nitroxide biradicals have been studied by electron spin resonance, in cyclohexane solution at −10°C and in toluene solution at −150°C. The ESR spectra change when the sample orientation in the spectrometer cavity is changed: under favourable circumstances oriented spectra are obtained.
13C NMR investigation of flavonoid C‐β‐D‐glucosides. Detection of a conformational equilibrium
Authors: Davoust Daniel , Massias Marcel , Molho Darius 
Published: May 2005

AbstractEvidence of a slow conformational equilibrium in some flavonoid 6‒C‒β‒D‒glucosides is deduced from examination of their 13C NMR spectra run at room temperature.
The rα‐structure of partially oriented 1,2,3,5‐tetrachlorobenzene determined from its 1H NMR spectra with natural‐abundance 13C‐satellites. A Demonstration of the Combined Use of Spectra Obtained from Molecules Dissolved in Several Different Liquid Crystals as Solvents for Spin Systems not having enough Dipolar Coupling Constants to Determine the Molecular Structure
Authors: Dombi G. , Amrein J. , Diehl P. 
Published: May 2005

AbstractIt is demonstrated that in a case where neither the proton nor the natural‐abundance 13C‐satellite spectra of a partially oriented molecule carry enough structural information, one can determine the entire molecular geometry by the combined use of several liquid crystals as solvents. As an example, the spectrum of 1,2,3,5‐tetrachlorobenzene is analysed and the rα‐structure is computed after vibration corrections of the dipolar coupling constants obtained in two different liquid crystals. The carbon‐hydrogen, carbon‐carbon internuclear distance ratios as well as bond lengths and angles are determined. The solvent effect of the two different nematic phases on the molecular structure is investigated and found to be negligible. Indirect proton‐proton and proton‐carbon couplings, as well as one‐bond and two‐bond 13C isotope effects on the proton chemical shifts, are measured in an isotropic solvent.
Carbon‐13 NMR of 1,2‐indandione and heterocyclic analogues. A reappraisal
Authors: Galasso V. , Pellizer G. , Pappalardo G. C. 
Published: May 2005

Abstract13C NMR chemical shifts previously reported for 1,2‐indandione and thionaphthenequinone have been found to be erroneous; the correct results have now been established.
Some INDO calculations of fluorine‐nitrogen spin–spin coupling constants
Authors: Khin Tun , Duangthai S. , Webb G. A. 
Published: May 2005

AbstractINDO parameterized calculations of nJ(19F15N) are reported where n=1, 2, 3, 4 and 5. The calculations are performed within the sum‐over‐states perturbation and self‐consistent perturbation frameworks. In general, satisfactory agreement between both sets of calculated results and the available experimental data is obtained. All of the 1 J(19F15N) and 4J(19F15N) couplings can be of either sign. Most of the couplings considered are dominated by the contact contribution but the non‐contact interactions can be very important in certain cases.
Conformational equilibria in isomeric methylcyclohexanols studied by 13C NMR spectroscopy
Authors: Subbotin O. A. , Sergeyev N. M. , Chlopkov V. N. , Nikishova N. G. , Bundel Yu. G. 
Published: May 2005

AbstractThe conformational equilibrium constants for isomeric methylcyclohexanols (cis‐ and trans‐1,2‐, 1,3‐ and 1,4‐methylcyclohexanols) have been determined from peak area measurements in the completely proton decoupled low temperature 13C NMR spectra of the individual conformers. The 13C chemical shifts are discussed in terms of the additive model.
The 13C NMR spectra of tallysomycin and its zinc(II) complex
Authors: Greenaway Frederick T. , Dabrowiak James C. , Grulich Robert , Crooke Stanley T. 
Published: May 2005

AbstractUsing the carbon assignments of bleomycin A2 as well as those of a series of model compounds, the 13C NMR assignments of the antitumor antibiotic tallysomycin (TLM) have been made. With the aid of the carbon assignments the metal binding properties of the new antibiotic toward Zn(II) have been investigated.
13C chemical shifts and conformational analysis of methyl substituted thiacyclopentanes
Authors: Barbarella G. , Dembech P. 
Published: May 2005

AbstractThe 13C NMR spectra of thiacyclopentane (thiolane) and its mono‐ and dimethyl derivatives at positions other than the heteroatom are reported. The 13C shieldings are found to be consistent with a description of these compounds in terms of equilibria between half‐chair conformers. An attempt has been made to establish the axial or equatorial preference of methyl groups adjacent to, or removed from, the sulphur atom in these systems. In agreement with previous observations on thiacyclohexanes (thianes), the conformational preference of a methyl group for the equatorial orientation is greater at the β than at the α position.
NMR study of 2‐alkoxy‐1,3,2‐dioxaphospholanes. II—molecular conformation of alkoxy substituents
Authors: Besserre D. , Coffi‐Nketsia S. 
Published: May 2005

AbstractThe conformation of some 2‐σ‐1,3,2‐dioxaphospholanes (σ=OAlkyl, CI) is studied. The determination of the 2J(POC) and 3J(POCC) coupling constants, which are influenced by the bulk of the alkoxy group, is a means of obtaining information about the rotation around the POR bond, which is dependent on steric interactions between the phosphorus lone pair, the alkoxy group and the substituents on the ring. When σ is a tert‐butoxy group, a direct ‘through‐space’ interaction is found between the phosphorus atom and one of the primary carbons of the OR group. If there is no substituent on the ring, the 31P chemical shifts are little affected by changes in OR; a diamagnetic effect is observed, however, in the case of the tert‐butoxy group which is enhanced for the 4,4,5,5‐tetramethyl derivatives.
1H NMR study of the reaction of ornithine and lysine with pyridoxal‐5′‐phosphate
Authors: Arcelli Antonio , Bongini Alessandro , Budini Rolando 
Published: May 2005

AbstractThe composition of the mixture from the reaction of the basic amino acids ornithine or lysine with pyridoxal‐5′‐phosphate was investigated in D2O by 1H NMR and was found to be dependent on pH, α attack being favoured at acid pH and ω attack in basic solutions.
13C NMR spectra of s‐triazolo‐as‐triazinones: Application to isomeric and tautomeric structure determination
Authors: Daunis Jacques , Follet Michel , Marzin Claude 
Published: May 2005

Abstract13C NMR spectroscopic data are reported for the s‐triazolo‐as‐triazinones of five isomeric series. Comparison of their 13C chemical shifts and CH coupling constants allows the determination of the type of ring junction of the two heterocycles, as well as the predominant tautomeric form in each system.
15N NMR spectroscopy. 23—Shift effects of protecting groups in oligopeptides of glycine and alanine
Authors: Kricheldorf Hans R. , Hull William E. 
Published: May 2005

AbstractThe natural abundance 15N NMR spectra of glycylglycine and alanylalanine derivatives with various N‐ or O‐protecting groups were measured in dimethyl sulphoxide, pyridine and fornic acid. The nitrogens directly attached to the protecting group have chemical shifts relative to NO3− in the range −220 to −358 ppm. The influence of the amino end group on the next peptide nitrogen (Gly‐Gly bond) amounts to, at most, 1.7 ppm. The influence of the O‐protecting group is also weak (Δ δ⩽2 ppm), but strongly dependent on the solvent.
Substituent effects on meta‐proton chemical shifts in substituted benzenes
Authors: Batts B. D. , Pallos G. 
Published: May 2005

AbstractThe chemical shifts at infinite dilution and coupling constants of some meta‐substituted nitrobenzenes (C6H4NO2X) were determined in CDCI3 solutions (X = CHO, OCH3, CI, Br, NH2, NO2) and in CCI4 solutions (X = OCH3, CI, Br). Substituent effects on the chemical shift of the meta‐hydrogen are analysed in terms of existing theories.
Substituent effects on 13C NMR chemical shifts in the saturated framework of primary aliphatic derivatives
Authors: Ejchart Andrzej 
Published: May 2005

AbstractA general equation describing the effect of substituents on α‐carbons in a saturated framework was developed from 13C chemical shifts obtained under uniform conditions for selected aliphatic compounds. Experimental correlations for β‐ and γ‐carbons and a discussion of the results are presented.