bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic field dependence of internal interactions in nuclear spin systems
Authors: Ding Shangwu , Ye Chaohui 
Published: May 2005

AbstractThe internal interactions in spin systems depend on the magnetic field strength, since the latter perturbs the electronic wave functions. The changes in the interaction tensors are approximately proportional to the applied magnetic field. This effect is experimentally most significant for quadrupolar spin systems, since the quadrupolar interaction is usually the strongest. This field dependence of internal interactions, seldom considered before, may lead to an ambiguity in the explanation of nuclear magnetic resonance (NMR) experiments of quadrupolar spin systems.
1H and 13C NMR spectral assignment of the prenylflavanones sigmoidins A, B and C, by two‐dimensional NMR techniques
Authors: Ndom Jean‐Claude , Mbafor J. Tanyi , Fomum Z. Tanee , Martin Marie‐Thérèse , Bodo Bernard 
Published: May 2005

AbstractThree prenylflavanones, sigmoidins A, B and C, were studied using one‐ and two‐dimensional NMR techniques. The interpretation of these spectra led to the definitive assignments of all carbon and hydrogen chemical shifts.
Simple solutions to resolve extreme NMR spectral overcrowding using shaped pulses
Authors: Berthault Patrick , Desvaux Hervé , Perly Bruno 
Published: May 2005

AbstractImproved two‐dimensional 1H NMR sequences including shaped pulses are proposed for increasing the separation of cross peaks in the case of severe spectral overcrowding. Ways around limitations in soft 2D experiments are proposed for increasing the resolution and the apparent peak separation in both dimensions. Modulated shaped pulses leading to multi‐selective excitation are proposed for reducing the size of data matrices at a given F2 resolution and for simplifying coherence transfer pathways. Separation of the signals in F1 is achieved by either introduction of refocusing soft pulses or constant‐time experiments. These methods were applied to inclusion complexes of cyclodextrin derivatives where, although of considerable value in deriving the 3D structure of the complex, a total assignment of NMR spectra is not, at first glance, a simple task. It is demonstrated that the proposed solutions overcome the apparently discouraging complexity of the 1D NMR spectra and yield a wealth of important data for further structural determination.
Solasodine and diosgenin: 1H and 13C assignments by two‐dimensional NMR spectroscopy
Authors: Puri Raman , Wong Tuck C. , Puri Ravi K. 
Published: May 2005

AbstractSolasodine and diosgenin have been widely used as starting materials for the partial synthesis of cortisone, progresterone and C21 steroidal derivatives (oral contraceptives). This study involved the total 1H and 13C spectral assignments of these two important compounds by using two‐dimensional NMR techniques (COSY, CSCM and HMBC), and resulted in unambiguous spectral assignments, especially in the convoluted regions of the spectra (1H, 0.7–2.0 ppm; 13C, 28–35 ppm).
Complete proton and carbon nuclear magnetic resonance spectral assignments of some morphinan‐6‐one alkaloids by two‐dimensional NMR techniques
Authors: Caldwell Gary W. , Gauthier A. Diane , Mills John E. , Greco Michael N. 
Published: May 2005

AbstractThe 1H (400 MHz) and carbon 13C (100 MHz) NMR peak assignments of two oxymorphone alkaloids including the free base and the hydrochloride (HCl) salt and four oxycodone alkaloids including the free base, the HCl salt, the N‐oxide and the methyl iodide quaternary salt were assigned using a variety of two‐dimensional NMR techniques. Proton coupling constants provide evidence that the cyclohexanone (D) and the piperidine (E) rings adopt slightly distorted chair conformations. Nuclear Overhauser enhancement difference experiments indicate that the conformation of the N‐methyl group is equatorial and the O‐methyl group prefers a cis orientation relative to C‐2. The minor component observed in aqueous 1H and 13C NMR spectra of each HCl salt and the N‐oxide is produced by the reaction of the alkaloid with water at the C‐6 carbonyl, forming a gem‐diol, and is not due to the presence of the axial isomer. The first complete solution and solid conformational analyses of oxycodone N‐oxide by NMR and x‐ray crystallography have been investigated. The data indicate that the C‐14‐OH proton is intramolecularly hydrogen bonded to the NO oxygen.
Heavy atom solid‐state NMR. Mercury‐199 spectral simulation and effects of off‐magic angle spinning
Authors: Groombridge Christopher J. 
Published: May 2005

AbstractThe effects of small deviations from the magic angle on 199Hg solid‐state NMR spectra with large chemical shift anisotropy are shown by computation and illustrated with spectra of mercury(II) acetate. These are shown to give the false appearance of multiple species, and place great importance on very precise angle setting (much better than ± 0.1°) for heavy atom solid‐state NMR. Chemical shift tensor principal components have been derived from spinning sideband analysis, and the difficulties of this are discussed; revised values for the anisotropy and asymmetry of mercury(II) acetate are −1732 ppm and 0.08, respectively. 199Hg spectra are also given for mercury(II) lactate and citrate.
Substituent‐induced chemical shifts (SCS) by the phenyl group in sterically congested styrene derivatives
Authors: Knorr Rudolf , Stephenson David S. , Böhrer Petra , Hoang Thi‐Phung 
Published: May 2005

AbstractThe two 13C NMR methyl signals of the sterically congested 9‐benzylidene‐1,8‐dimethylfluorene (1a) have the surprisingly small separation of only 0.37 ppm; for 9‐benzylidene‐2,7‐dimethylfluorene the corresponding methyl separation is 0.04 ppm. An alternative analysis of 1a with respect to 1,8‐dimethylfluorene shows that the perturbing syn‐phenyl substituent has caused a downfield ( + 0.47 ppm) 13C shift but an upfield 1H shift ( − 0.97 ppm) of the compressed 1‐CH3 group. For further comparisons, NMR assignments were also made for 2,7‐dimethylfluorene, 1,8‐dimethylfluoren‐9‐one and 2‐(1,1‐dimethylethyl)‐3,3‐dimethyl‐1‐phenylbut‐1‐ene.
Simplification of 13C NMR spectra by selective excitation of subspectra
Authors: Schraml Jan , Pelnař Jan , Blechta Vratislav 
Published: May 2005

AbstractA new combination of 1D HOHAHA and INEPT pulse sequences is proposed and tested on an antibiotic, amikacin disulphate. The sequence provides 13C NMR spectra of chosen structural subunits and thus facilitates the NMR analysis of oligomers.
1H and 13C chemical shifts of (E)‐ and (Z)‐stilbenes and of phenanthrenes di‐substituted by oxygenated side‐chains
Authors: Touillaux R. , Weiler J. , Soumillion J.‐Ph. , Motte F. 
Published: May 2005

AbstractThe assignment of the 13C and 1H resonances of phenanthrenes and stilbenes di‐substituted with oxygenated side‐chains is presented based on chemical shifts, multiplicities and proton‐selective irradiation.
True spatial mapping of 14N by 3D NMR imaging
Authors: Kinchesh Paul , Randall Edward W. , Williams Steve C. R. 
Published: May 2005

AbstractThree‐dimensional NMR imaging was used to create true maps of the 14N distribution in aqueous phantoms containing ammonium nitrate and sodium azide. The technique allowed for the creation of separate images from each nitrogen chemical environment and a total nitrogen image devoid of any appreciable artefacts.
Nuclear magnetic resonance study of sulphur diimides bearing the Di‐tert‐butylphosphinyl substituent—application of Hahn‐echo extended pulse sequences
Authors: Wrackmeyer Bernd , Gerstmann Silke , Herberhold Max 
Published: May 2005

AbstractSulphur diimides of the type BuP(NSN)R′ [R′ = PBu (1), But (2), SiMe3 (3), SiPh2Me (4), SiMe2But (5), SiPh2But (6), SiBuH (7), Si2Me5 (8), GeMe3 (9), SnMe3 (10), SnBu3 (11), SnPh3 (12)] and Bu(E)P(NSN)R′ [R′ = But, E = S, Se [2(S), 2(Se)]; R′ = SiPh2But, E = S, Se [6(S), 6(Se)]] were studied by solution‐state 15N and 31P NMR in order to obtain information on their preferred configuration in solution. Hahn‐echo extended (HEED) pulse sequences served for measuring coupling constants 1J(31P 15N) from 31P NMR spectra, giving at the same time isotope‐induced chemical shifts 1Δ 15/14N(31P) with 15N at natural abundance. Chemical shifts δ 15N are sensitive towards substituents in E‐ (deshielding) and Z‐positions (shielding). All NMR data indicate that most compounds are fluxional, at least at room temperature, with respect to interconversion of configurational isomers (E/E, E/Z, Z/E). The consistent NMR data suggest that the BuP group prefers the E‐position. Solid‐state 31P and 15N cross‐polarization magic angle spinning NMR spectra of 1 and 7 support the assumption of different structures in solution and in the solid state, in accord with the assumed fluxional behaviour in solution.
13C NMR assignments of 1‐oxaspiro[4.5]decan‐2‐ones and 1‐oxaspiro[4.5] decanes
Authors: Alonso Daniel , Font Josep , Ortuño Rosa M. 
Published: May 2005

Abstract13C NMR studies of a series of lactones and ethers containing the spiro[4.5] decenering system were carried out. Complete 13C chemical shift assignments were achieved.
Heteronuclear long‐range coupling constant 4J(31P, C, S, C, 1H) in diethyl α‐methylthio‐substituted phosphonates and related compounds
Authors: Balczewski P. 
Published: May 2005

AbstractThe long‐range coupling constant 4J(31P, C, S, C, 1H) was measured in several diethyl α‐methylthio‐substituted phosphonates and their analogues. A dependence of the 4J coupling on the substituent electronegativity was observed.
Nitramino, NRNO2 (R = H, CH3), as a substituent. 13C and 15N NMR spectroscopic study of nitraminobenzenes and ‐pyridines
Authors: Kolehmainen Erkki , Laihia Katri , Kauppinen Reijo , Gawinecki Ryszard , Rasala Danuta 
Published: May 2005

AbstractIn order to clarify the special properties of the aryl‐bound nitramino substituent NRNO2 (R = H, CH3), 13C and 15N NMR spectra of six nitraminobenzenes and nine nitraminopyridines were measured in DMSO‐d6 and their chemical shifts assigned. 1H NMR chemical shifts and spin‐spin coupling constants of all the compounds were also determined. In contrast to the behaviour of nitropyridines or ‐benzenes studied previously, most of the present compounds gave very broad 17O NMR lines even at elevated temperatures and their 17O NMR data were not useful for any reliable conclusions.
NMR study of some dihydrobenzofuran lignans
Authors: Pieters Luc , De Bruyne Tess , De Groot Alex , Mei Gao , Dommisse Roger , Lemière Guy , Vlietinck Arnold 
Published: May 2005

AbstractA detailed NMR analysis of 3′,4‐O‐dimethylcedrusin and 4‐O‐methylcedrusin using two‐dimensional COSY, HETCOR and long‐range HETCOR techniques showed that some 13C NMR spectral assignments reported previously for related dihydrobenzofuran lignans such as dihydrodehydrodiconiferyl alcohol and dihydrocarinatinol must be revised.
New bitter saponins from the bark of Colubrina elliptica: 1H and 13C assignments by 2D NMR spectroscopy
Authors: Tinto Winston F. , Reynolds William F. , Seaforth Compton E. , Mohammed Shaliza , Maxwell Anderson 
Published: May 2005

AbstractThree new bitter saponins, designated mabioside A, B and C, were isolated from the bark of Colubrina elliptica and were determined to be 3‐O‐[α‐JL‐rhamnopyranosy]‐(1 → 6)‐β‐D‐glucopyranosyl‐15‐O‐[β‐D‐ glucopyranosyl] mabiogenin, 3‐O‐[α‐L‐rhamnopyranosy]‐(1 → 6)‐[β‐D‐glucopyranosyl‐(1 → 2)]‐β‐D‐glucopyranosyl}mabiogenin and 3‐O‐[α‐L‐rhamnopyranosyl‐(1 → 6)‐β‐D‐glucopyranosyl] mabiogenin, respectively. The structures were elucidated by using a combination of 2D NMR techniques (H‐H COSY, H‐H DQF‐COSY, RCT‐COSY, C‐H COSY, FLOCK, NOESY).
Assignments of the 1H and 13C NMR spectra of trans‐4‐hydroxy‐N‐9‐fluorenylmethoxycarbonyl‐L‐proline using one‐ and two‐dimensional NMR spectroscopy
Authors: Aksnes Dagfinn W. , Francis George W. , Papaioannou Dionissios 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of trans‐4‐hydroxy‐N‐9‐fluorenylmethoxycarbonyl‐L‐proline show a 56:44 mixture of two conformers due to hindered rotation around the partial CN double bond. A combination of homo‐ and heteronuclear 1 D and 2D NMR techniques provided the assignments of the 1H and 13C resonances.
Application of two‐dimensional NMR to the structure determination of an unsymmetrical monosubstituted bisporphyrin
Authors: Sala R. Costa i , Latour J.‐M. , Bardet M. 
Published: May 2005

AbstractThe complete assignment of 1H and 13C data of an unsymmetrical monosubstitute bisporphyrin based on an extensive application of two‐dimensional 1H1H, 1H13C and 13C‐13C shift spectroscopy is described. The 1H1H shift correlation through dipolar interaction (2D NOESY) was essential to prove the connection of the alkyl fragments and to distinguish protons spatially close but belonging to different units. The additive structural increments method allowed the assignment of the quatenary carbons of tolyl residues.
NMR‐invisible nucleosides in adducts formed from carcinogenic nitrobenzo[a]pyrenes
Authors: Evans Frederick E. , Deck Joanna , Herreno‐Saenz Diogenes , Fu Peter P. 
Published: May 2005

AbstractAnomalous 1H NMR spectra have been obtained for two related carcinogen‐nucleoside adducts in which a 1‐ or 3‐aminobenzo[a]pyrene ring is bound from its C‐6 position to the N−2 position of 2′‐deoxyguanosine. NOESY and COSY measurements at low temperature in methanol‐d4 revealed chemical exchange between at least two forms. Large chemical shift differences exist between subspectra for all corresponding protons of the nucleoside moiety, whereas all such chemical shift differences are small for the protons of the benzo[a]pyrene moiety. Thus, at intermediate rates of exchange, the nucleoside resonances are broadened beyond recognition, whereas the aminobenzo[a]pyrene resonances appear normal. This is linked with the large anisotropic ring‐current field from the carcinogen ring system, and restricted internal rotation at the site of attachment of the carcinogen to the nucleic acid base. The possibility of an absence of resonances from a nucleoside moiety can complicate structure elucidation of unknown carcinogen‐nucleoside adducts and related compounds, especially in trace analysis.
Molecular modeling and NMR spectroscopic examination of (E)‐cyclodec‐5‐enone and its 2 ‐and 10‐methyl analogs
Authors: Chu Yongliang , Colclough David , White James B. , Smith William B. 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of (E)‐cyclodec‐5‐enone and its 2‐ and 10‐methyl analogs were determined. The 1H NMR spectrum of the former was determined over the temperature range −60 to 20°C. Information from the 2‐D INADEQUATE spectrum of the parent compound was combined with that derived from the homonuclear and heteronuclear correlation spectra to assign the olefinic proton at C‐6. In all three proton spectra, this was the only set of resonances sufficiently well defined to allow conformational information to be deduced. Molecular modeling by molecular mechanics, semi‐empirical and ab initio molecular orbital methods were used to predict conformational preferences. These results were then compared with the NMR data.
Structural assignment of (σ‐π)palladium complexes
Authors: Gogoll Adolf , Grennberg Helena 
Published: May 2005

AbstractA series of (σ‐π)palladium complexes derived from cyclooctadiene were investigated by 1H, 13C and 19F NMR. The stereochemical assignment was based on intramolecular NOEs in conjunction with molecular modelling and semi‐empirical methods, and confirmed by interligand NOEs in nitrogen chelate complexes derived from the title compounds. The nitrogen chelating ligands are involved in a rotation with respect to the ligand‐palladium axis.
19F NMR study of 1‐halo‐F‐adamantanes
Authors: Adcock James L. , Luo Huimin , Dai Sheng 
Published: May 2005

AbstractAn ‘anomalous’ variation of β‐fluorine chemical shifts with respect to the inductive effect in the 19F NMR of a series of 1‐halo‐F‐adamantanes is reported. These fluorine chemical shifts are similar to the hydrogen chemical shift anomaly found in the corresponding hydrocarbon halides. Whereas the γ‐hydrogen chemical shifts can be rationalized by the inductive effect, the γ‐fluorine chemical shifts have the same ‘anomalous’ variation as found in the β‐fluorine chemical shifts.
15N NMR study of dialkyl, N‐alkyl‐N′‐phenyl and diphenyl sulphur diimides: Assignment of configuration in solution
Authors: Wrackmeyer Bernd , Köhler Christian , Herberhold Max 
Published: May 2005

Abstract15N NMR spectra of dialkyl sulphur diimides (1) [R1(NSN)R2; R1 = R2 = Me (a), Et (b), nPr (c), iPr (d), nBu (e), tBu (f), tOct (g)], N‐alkyl‐N′‐phenyl sulphur diimides (2) [R1(NSN)R2; R1 = Me (a), Et (b); R2 = Ph] and diphenyl sulphur diimide (3) were measured at variable temperature. The assignment is based on the comparison with data for the corresponding N‐sulphinylamines R1(NSO). The Z/E configuration is always preferred at low temperature, whereas the minor isomer adopts the Z/Z configuration. In the presence of bulky substituents (If and g), only the isomer with Z/E configuration is observed. At room temperature, 15N NMR signals were not observed for symmetrically substituted sulphur diimides, but a single averaged 14N resonance can be measured. The unsymmetrically substituted sulphur diimides 2a and b adopt the Z/E configuration with the alkyl group Z and the phenyl group E. There are no indications of other isomers at low temperature. 14N NMR spectra at room temperature prove that the (Z)‐phenyl/(E)‐alkyl isomer contributes little to the equilibrium.
Applications of Raman magnetic resonance to heteronuclear spin systems
Authors: Yang Daiwen , Ye Chaohui 
Published: May 2005

AbstractRaman magnetic resonance (RMR) with direct and indirect detection schemes features 1D display of multiple quantum (MQ) transitions. Consequently, useful information such as couplings and correlations can be easily extracted from the RMR approach. In this paper, RMR experiments are demonstrated to determine heteronuclear chemical shift correlations, homonuclear and heteronuclear long‐range coupling constant values and their relative signs, with typical samples. It is shown that this approach is useful for the study of small molecules and groups of special interest in a complex molecule.
Solvation and metal ion effects on structure and reactivity of phosphoryl compounds. Part 3—conformational analysis of 2‐substituted alkylphosphonates by phosphorus‐31‐carbon‐13 coupling constants
Authors: Belciug Marie‐ P. , Wessels Philippus L. , Modro Tomasz A. 
Published: May 2005

AbstractOne‐ and three‐bond P,C coupling constants in the phosphonate skeleton of dimethyl esters of 2‐hydroxy (or 2‐methoxy) alkylphosphonic acids were determined from 13C NMR spectra recorded in various solvents and in the presence of metal ions. The results confirmed earlier conclusions about the intramolecular attractive interactions between the OH (OMe) and the phosphoryl groups, enhanced by the complexation with Na+ or Mg2+ ions. Reasonable correlation between the 3J(P,C) values and the population of the conformer involving the trans orientation of the phosphonate group and the C‐3 carbon atom was obtained.
Detection of NOE interaction between components of organic π‐complexes
Authors: Hoffman Roy E. , Rabinovitz Mordecai 
Published: May 2005

AbstractHomonuclear 1H, 1H NOE effects were observed for π charge‐transfer complexes of 2,4,6‐trinitrotoluene (TNT) with aromatic hydrocarbons using a 1D‐NOESY experiment. The intensity of the NOEs indicates that the structure in solution is analogous to that in the solid state as determined by x‐ray crystallography.
Solution and solid phase 13C NMR studies of cyclic and acyclic 1,2‐dialkoxybenzenes and their mononitro derivatives
Authors: Buchanan G. W. , Driega A. B. , Ratcliffe C. I. 
Published: May 2005

Abstract13C NMR chemical shifts are reported for 1,2‐dimethoxybenzene (veratrole) and related benzodioxane, benzodioxepane and benzodioxenane systems and their 4‐nitro derivatives in solution and in the solid state. Results are discussed in terms of the stereoelectronic influence of substituents.
1H 2D‐NMR characterization of Ni(II)‐substituted azurin from Pseudomonas aeruginosa
Authors: Moratal José‐María , Salgado Jesús , Donaire Antonio , Jiménez Hermas R. , Castells Josep , Martínez‐ferrer María‐josé 
Published: May 2005

Abstract1H two‐dimensional NMR experiments on nickel(II)‐substituted azurin have been successfully applied. Despite the short relaxation times of the hyperfine‐shifted resonances, the combined use of NOESY and COSY spectra allowed the assignment of 15 resonances belonging to the metal‐coordinated residues Gly‐45, His‐46, His‐117 and Met‐121. Even in the case of the two broad and furthest downfield resonances, the NOESY spectra were successful in assigning these signals to the β‐CH2 protons of Cys‐112. The protons of the non‐coordinated residues Met‐13, Phe‐15 and Trp‐48 were also assigned via NOESY, COSY and TOCSY experiments.
Determination of the methionine haem ligand conformation in cytochrome cH from Methylophilus methylotrophus by two‐dimensional 1H NMR
Authors: Santos Helena , Turner David L. 
Published: May 2005

AbstractA complete relaxation matrix approach was used to determine the conformation of the Met ligand to the haem in Methylophilus methylotrophus cytochrome cH, including the configuration at the sulphur; the pattern of NOEs is shown to be dominated by spin diffusion at mixing times as short as 25 ms, rendering the two‐spin approximation unreliable. The Met conformation, together with an analysis of aromatic proton resonances, indicates a structure almost identical with that found by x‐ray crystallography for Pseudomonas aeruginosa cytochrome c551, which has a 45% similarity in sequence. The paramagnetic shifts of the haem methyl proton resonances in the oxidized protein support the view that the asymmetry in the electronic structure of the haem is dominated by the orientation of the Met ligand.
Assignment of the 1H and 13C NMR spectra of 132(R)‐methoxychlorophyll a using the two‐dimensional HMQC and HMBC techniques
Authors: Kilpeläinen Ilkka , Kaltia Seppo , Kuronen Pirjo , Hyvärinen Kristiina , Hynninen Paavo H. 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of 132(R)‐methoxychlorophyll a were assigned utilizing the two‐dimensional 1H‐detected heteronuclear one‐bond (HMQC) and multiple‐bond (HMBC) correlation techniques. The protons and carbons of the macrocycle and its short side‐chains could be completely assigned using the HMQC and HMBC data in concert. These techniques were also valuable in achieving assignments for the phytyl chain, which were previously incomplete. The proton and carbon assignments of the P1‐CH2, P2‐CH, P4‐CH2 and P15‐CH groups and those of all methyl groups of the phytyl chain could be established by the coupling patterns and by the combined information obtained from the HMQC and HMBC connectivities. Fairly unambiguous proton and carbon assignments were also obtained for the P6‐CH2, P7‐CH, P9‐CH2, P11‐CH and P14‐CH2 groups. The sensitivity of the HMQC and HMBC techniques is good, making it possible to achieve the spectral assignments under high dilution and monomeric conditions. This was considered to be of paramount importance in the structural analysis of chlorophylls and related compounds, which are difficult to prepare in adequate amounts and purity because of their lability and which show a strong aggregation tendency at higher concentrations and lower temperatures.
Application of modified selective polarization transfer experiments to the structural analysis of β‐silylated silyl enol ethers by 1H, 13C and 29Si NMR
Authors: Baudrillard Vincent , Davoust Daniel , Ple Gerard 
Published: May 2005

AbstractThe 1H, 13C and 29Si NMR spectral characteristics of β‐silylated silyl enol ethers were determined. nJ(Si, H) measurements (2 < n < 4) were achieved from selective polarization transfer experiments with selective decoupling during acquisition. 1H,29Si two‐dimensional heteronuclear correlation confirmed the positions of the silylated groups in the molecules.