bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of hydroxyl and carbonyl groups on long‐range proton—carbon coupling constants
Authors: Parella Teodor , Sánchez‐Ferrando Francisco , Virgili Albert 
Published: May 2005

AbstractLong‐range 1H13C coupling constants were measured for some simple, rigid model compounds containing hydroxyl, bromine or carbonyl groups. These were performed using the recently proposed selective J‐resolved SPININEP and SDEPT‐2D experiments. The geminal and vicinal heteronuclear coupling constant values were analysed in terms of the nature of substituent, the position along the coupling path and the orientation of the substituent relative to the bounds. In some cases, through‐space interactions of the substituent group were also observed. Sizeable substituent effects are associated with the electronegativity and lone pair of the oxygen nucleus in the hydroxyl and carbonyl systems. In addition, the π‐system of the carbonyl group may also be important. Such substituent effects may be as large at ±5 Hz. Since nJCH constants rarely exceed 10 Hz, these effects can produce important deviations in nJCH magnitudes and therefore are essential for applications to stereochemical and conformational analysis.
Molecular symmetry and shielding tensor properties—some illustrative examples
Authors: Klaus Elke , Sebald Angelika 
Published: May 2005

Abstract13C, 29Si, 119Sn and 207Pb cross‐polarization magic angle spinning (CP/MAS) spectra for a series of closely related compounds R4−nM(CCR′)n, (n = 1−4; M = Si, Sn, Pb; R = alkyl; R′ = alkyl, SiMe3) are reported. Shielding tensor components for 29Si, 119Sn and 207Pb as obtained from CP/MAS spectra are discussed in relation to the respective highest possible molecular symmetry group as a function of the degree of substitution n = 1−4. For this class of compounds the orientation of the shielding tensor of M within the molecular frame can sometimes be derived from symmetry considerations. The limitations of such considerations, based on shielding tensor components obtained from polycrystalline powder samples under CP/MAS conditions, are discussed.
13C NMR chemical shift assignments of N‐monosubstituted and N,N‐disubstituted 3‐aminopyrroles
Authors: Rolfs Andreas , Mügge Clemens , Liebscher Jürgen 
Published: May 2005

Abstract13C NMR chemical shift assignments of 47 N‐mono‐ and N,N‐disubstituted 3‐aminopyrroles with hydrogen or methyl in the 5‐position are reported. Substituents in the 2‐position are electron withdrawing such as alkoxycarbonyl, cyano or acyl in most cases and those in the 4‐position are aryl or ethoxycarbonyl.
Substituted methyl 5β‐cholan‐24‐oates II. 13C NMR spectral assignment
Authors: Lappalainen Kari , Kolehmainen Erkki , Kaartinen Mari , Kauppinen Reijo , Seppälä Raimo , Vatanen Virpi 
Published: May 2005

AbstractThe 13C NMR spectra were recorded and assigned for nine derivatives of methyl 5β‐cholan‐24‐oates (esters of bile acids) including hydroxy, oxo and/or acetyloxy groups. Assignments were based on the empirical substituent‐induced chemical shifts (SCS), spectral comparison with compounds of similar structure, distortionless enhancement by polarization transfer (DEPT) and proton coupled 13C NMR measurements.
1H NMR chiral analysis of benzhydrylamine derivatives using β‐cyclodextrin. Solution geometry of host‐guest complexes as determined by 1D NOE and ROESY experiments
Authors: Redondo J. , Frigola J. , Torrens A. , Lupón P. 
Published: May 2005

AbstractThe 1H NMR chiral analysis of a series of benzhydrylamine derivatives was accomplished by means of β‐cyclodextrin as chiral resolving agent, forming the corresponding inclusion complexes in aqueous solution. NOE and ROESY experiments were used in order to establish the most probable host‐guest geometries in solution. In all cases studied, it was found that the phenyl groups of guest molecules preferably binds with the macrocyclic cavity of β‐cyclodextrin, thus forming ternary complexes (2:1, β‐cyclodextrin:guest) when two phenyl groups were present in the guest molecule.
Approach to the conformational behaviour of tetraazamacrocycles in the solution state. NMR and molecular modelling studies
Authors: Boetzel R. , Failla S. , Finocchiaro P. , Hägele G. 
Published: May 2005

AbstractThe differences in complexation behaviour of two diastereomeric tetraazamacrocycles, meso (1) and racemic (2) 5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane, are explained by different conformations in solution, 1 being one stable conformer of almost rigid structure while 2 shows higher conformational flexibility to avoid steric strain. The methods used were 1H and 13C NMR and molecular modelling.
Use of cross‐polarization in lithium‐6 solid‐state NMR
Authors: Harris Robin K. , Minoja Anna P. 
Published: May 2005

AbstractCross‐polarization (CP) magic angle spinning (MAS) 6Li{1H} spectra were acquired for three different inorganic lithium compounds. Spectra with a good signal‐to‐noise ratio can be obtained in reasonable times. The poorer signal‐to‐noise ratios shown by spectra acquired in the same experimental time by means of a single pulse experiment are explained by the longer values of T1(6Li) in comparison with T1(1H). The determination of these values allows the acquisition parameters to be optimized. In particular, the optimum experimental conditions are discussed, taking into account the pulse delay, the number of transients and the total time of the experiment. Finally, a standard for 6Li1H CP matching is proposed.
19F NMR investigations of cobalt(II) complexes with cysteine‐containing peptide ligands
Authors: Sun Wei‐Yin , Ueno Takafumi , Ueyama Norikazu , Nakamura Akira 
Published: May 2005

AbstractIsotropically shifted 19F NMR signals were observed for novel mononuclear Co(II) complexes, (Et4N)2[Co(Z‐Cys‐Pro‐Leu‐Cys‐Gly‐X)2] (Z = benzyloxycarbonyl, X = NHC6H4‐p = F, NHC6H4‐m‐F and NHCH2CH2C6H4‐p‐F). Such isotropically shifted signals show very short 19F spin‐lattice relaxation times (T1) in the range 20–150 ms compared with the corresponding SH‐free peptide ligands, Z‐Cys(SH)‐Pro‐Leu‐Cys(SH)‐Gly‐X, which revealed signals with 19F T1 values in the range 1600–3200 ms. The observed 19F NMR isotropic shifts and short 19F T1 values in the Co(II)‐cysteine‐peptide complexes are ascribed to the formation of NH—S hydrogen bonds and the presence of interactions of aromatic groups with the sulphur atom of the coordinated cysteine residue.
Complete spin dynamics of the AX, AX2 and AX3 spin systems. Application to BIRD pulses
Authors: Bain Alex D. , Burton Ian W. , Carpenter Katharine A. , Yang Ji‐Ping , Reynolds William F. 
Published: May 2005

AbstractThe BIRD pulse sequence is widely used to distinguish between protons that are directly bonded to a 13C nucleus and those that are not. It consists of a proton 90° pulse, a delay of 1/(21JCH), simultaneous carbon and proton 180° pulses, a further delay of 1/2J and a final proton 90° pulse. For two spins at equilibrium, the effect of this sequence can be easily understood, but for complex systems the behaviour can be counter‐intuitive. This paper explains the general behaviour of the BIRD sequence using theoretical equations and numerical simulations, and discusses some practical applications of the BIRD pulse train. The theoretical equations are derived using tables of general behaviour for the spin systems AX, AX2 and AX3. The tables allow the exact calculation of the effect of any pulse sequence on these spin systems, including all multiple quantum effects. The simulations show that the sequence is usually robust with respect to pulse imperfections and non‐ideal spin systems. In other cases, particularly when signals should be suppressed, small errors can have dramatic consequences. The results derived here are for a BIRD sequence inserted into an INEPT experiment, but many of the conclusions can be applied to all of the more standard applications of the BIRD.
Two‐dimensional 1H1H and 13C1H maximum‐quantum correlation NMR spectroscopy with application to the assignment of the NMR spectra of the bile salt sodium taurocholate
Authors: Liu Maili , Farrant R. Duncan , Lindon John C. , Nicholson Jeremy K. 
Published: May 2005

AbstractFollowing earlier studies on the development of one‐ and two‐dimensional NMR methods based on selection of coherences via maximum‐quantum pathways and using inverse 1H detection, a pulse sequence is now described for analogous direct heteronuclear detection for use in laboratories which do not have access to inverse detection technology. The method has been applied to the assignment of all of the 1H and 13C NMR resonances of sodium taurocholate, an important component of bile. The assignment of the resonances of major bile salts is important for the assignments of NMR resonances in bile itself to yield understanding of altered biochemistry in disease states. The effect of deliberately missetting the refocusing delay in the pulse sequence is shown to be beneficial in the assignment process.
1H and 13C NMR spectra of spiramycin I in organic and aqueous solutions
Authors: Alam Perwaiz , Barber Jill , Brennan Richard J. , Kennedy Karen , Tehrani M. Hassan H. 
Published: May 2005

AbstractFull assignments of the 1H and 13C NMR spectra of spiramycin l in CDCl3 and buffered D2O were carried out unambiguously using a range of 1D and 2D NMR methods.
Assignment of the 1H NMR resonances of D‐glycero‐D‐ido‐ and D‐glycero‐D‐altro‐octulose mono‐ and bisphosphates
Authors: Flanigan Ian L. , Collins J. Grant , Graham Kirstin L. , Macleod John K. , Williams John F. 
Published: May 2005

AbstractThe 1H NMR chemical shifts of the various contributing forms of the mono‐ and bisphosphates of D‐glycero‐D‐ido‐ and D‐glycero‐D‐altro‐octuloses were determined by two‐dimensional NMR spectroscopy.
17O NMR study of p‐π conjugation in methoxybutadienes and related compounds
Authors: Taskinen Esko 
Published: May 2005

AbstractThe 17O NMR spectra of some monomethoxy and dimethoxy derivatives of buta‐1,3‐diene, hexa‐2,4‐diene, cyclohexa‐1,3‐diene and cyclohexa‐1,4‐diene were recorded in CDCl3. The δ(17O) values show that in 2‐methoxybuta‐1,3‐diene the efficiency of p‐π conjugation in the OCC moeity is significantly lowered by cross‐conjugation of the CC bond with the other olefinic linkage. In the related system of 2‐methoxycyclohexa‐1,3‐diene, however, the corresponding effect is much smaller, apparently because of weak conjugative π‐π interaction in the olefinic system. On the other hand, the strength of p‐π conjugation appears to be the same in the OCCCC moieties of both 1‐methoxybuta‐1,3‐diene and 1‐methoxycyclohexa‐1,3‐diene. Moreover, as a transmitter of substituent effects, the unsaturated system of cyclohexa‐1,3‐diene is comparable to that of the benzene nucleus.
NMR of terminal oxygen. 1517O NMR spectra of the N+O− group: tert‐Amine oxides R3N+O−, nitrones HC  N+(O−), azoxy derivatives N  N+(O−), nitrile oxides  C  N+O− and related compounds. Shielding anisotropy in linear heteroatomar π‐systems
Authors: Dahn Hans , Péchy Péter , Van Toan Vien , Carrupt Pierre‐Alain 
Published: May 2005

AbstractThe 17O NMR signals of trimethylamine oxide and of six (para‐substituted) N‐aryldimethylamine oxides appear at 240–260 ppm, ca. 200 ppm more deshielded than hydroxylamines. The influence of the arene group and its substituents is small, confirming the absence of resonance interaction between the ring and the N+O− group. XN+(O−)Ar compounds (X =; R2C, nitrones; X = RN, azoxy compounds; X = ArN(O), azodioxy compounds = C‐nitroso dimers) are more deshielded, δo 350–450 ppm, due to resonance participation of NOtype structures (true nitroso compounds XNO appear at 650–1500 ppm). Carbonitrile oxides RCN+O− and NN+O− show high shielding, δo ca. 140 and 115 ppm respectively, higher than amine oxides; their C and N atoms also are significantly shielded. The increase in shielding, relative to sp2‐type π‐systems, is explained by the shielding anisotropy in linear (sp‐type) π‐systems. The shift values observed for four classes of NO compounds are in excellent agreement with predictions by IGLO calculations.
ESR study of the tricyclohexylmethyl radical
Authors: Luff Stefan , Morton John R. , Negri Fabrizia , Sharifi Mamood , Sutcliffe Leslie H. 
Published: May 2005

AbstractThe ESR spectrum of the tricyclohexylmethyl radical was obtained from tricyclohexylmethyl chloride and was studied in solution in the range 275–455 K. It has a half‐life of about 30 min at room temperature. The complex hyperfine structure of the radical was analysed with the help of MNDO/UHF calculations. Hyperfine interactions with three beta protons, twelve gamma protons and six delta protons were resolved. The alpha and the three beta carbon atoms are coplanar. The temperature dependence of the beta and six of the gamma proton hyperfine interactions was ascribed to torsional motions of the cyclohexyl rings about the CαCβ bond. The radical has C3h symmetry, the Cα and Cβ atoms being coplanar. Evidence for the existence of hexacyclohexylethane at about 200 K was obtained for the first time.
Preparation and steric structure of partially saturated isoindolo[1,3]‐ and ‐[3,1]benzoxazinones and ‐[2,4]benzoxazepinones
Authors: Sohár Pál , Stájer Géza , Nagy Katalin , Bernáth Gábor 
Published: May 2005

AbstractFrom cis‐2‐(p‐methylbenzoyl)cyclohexanecarboxylic acid (1), diendo‐3‐(p‐methylbenzoyl)bicyclo[2.2.1]heptane‐2‐carboxylic acid (2) or 2‐(p‐methylbenzoyl)benzoic acid (3) with stereoisomeric 1,3‐ or 1,4‐amino alcohols with cyclohexane/ene or norbornane/ene skeletons, various partially or fully saturated isoindolo[1,2‐b] [1,3]‐ and ‐[2,1‐a] [3,1]benzoxazinones methylene‐bridged derivatives and [1,2‐c] [2,4]benzoxazepinones were prepared. For these compounds, containing two hetero rings and two or three cycloalkane rings, the stereostructures (the annelation of the terminal rings and aryl group) were established by 1H and 13C NMR spectroscopy, including DNOE, DEPT and 2D‐HSC measurements.
Structural investigation and conformational analysis of helianthosid 2, a saponin from Helianthus annuus L
Authors: Hiegemann Monika , Duddeck Helmut , Bader Gerd , Hiller Karl 
Published: May 2005

AbstractThe structure of helianthosid 2 was re‐examined by a spectroscopic investigation using one‐ and two‐dimensional NMR spectroscopy and all 1H and 13C signals of the saccharide part were assigned. NOE difference and ROESY experiments allowed a conformational analysis of the orientation of the monosaccharide units with respect to each other.
Complete 1H and 13C resonance assignment of 27‐norurs‐13‐en‐3β‐acetyloxy‐28‐oic acid by NMR spectroscopy
Authors: Jimeno M. L. , Rumbero A. , Vázquez P. 
Published: May 2005

AbstractThe first NMR study of a 27‐nortriterpene of the α‐amyrin type is described. In addition to conventional 1D NMR methods, 2D shift‐correlated NMR techniques (DQF COSY, TOCSY, HMQC and HMBC) were used for the complete 1H and 13C NMR resonance assignments of 27‐norurs‐13‐en‐3‐acetyloxy‐28‐oic acid.
Conformation of peptide T in aqueous solution. Determination of homonuclear coupling constants by selective HOHAHA techniques
Authors: Zangger Klaus , Sterk Heinz 
Published: May 2005

AbstractThe conformation of Peptide T in aqueous solution was investigated by means of 1H NMR spectroscopy in one and two dimensions. The data were compared with those obtained previously for the peptide in DMSO solution. While Peptide T forms a β‐turn in DMSO, no evidence was found for such a structure in water. Instead, Peptide T exists in aqueous medium in a random coil conformation with an increased tendency to form a stretched chain at the ends of the peptide backbone. This partly populated β‐strand was identified mostly by the analysis of atomic distances and coupling constants. To evaluate NMR parameters such as chemical shift and scalar coupling constants in the heavily overcrowded spectral regions, selective homonuclear Hartmann‐Hahn transfer was employed, which allows the observation of a distinct multiplet through the excitation of its scalar coupling partner, and subsequent magnetization transfer.
Ab initio study of the 13C nuclear shieldings for some polyenals and their schiff bases using LORG theory
Authors: Wada Mitsuhito , Sakurai Minoru , Inoue Yoshio , Tamura Yusuke , Watanabe Yoichi 
Published: May 2005

AbstractAb initio LORG (localized orbital/local origin) shielding calculations were applied to some polyenes and their Schiff bases. Computations were performed as a function of basis set quality. The use of polarization functions in the shielding calculations for these highly polarizable compounds gives good agreement with the experimental values even for the carbonyl and the imine carbons.
13C NMR of acyclic sulphonated compounds including some fluorosulphonic acids: A chemical shift study
Authors: Canselier J. P. , Boyer J. L. , Castro V. , Card G. L. , Mohtasham J. , Peyton D. H. , Behr F. E. 
Published: May 2005

AbstractA chemical shift analysis of the 13C NMR spectra of more than 50 acyclic sulphonic acids, alkali metal sulphonates and methyl esters was carried out. Chemical shift increment systems with n‐alkanes as reference molecules were established for linear alkanesulphonates and alk‐2‐enesulphonates. Some short‐chain fluorinated sulphonic acids were also studied, especially pentafluorothio derivatives. CF spin‐spin coupling constants were determined. Pauling electronegativity values for SO3H and SF5 groups were derived from α chemical shift increments.
Characterization of new methyl‐substituted tetralins and indans by 13C NMR spectroscopy
Authors: Laurens T. , Schmit‐Quilès F. , Nicole D. 
Published: May 2005

AbstractIn order to perform the analysis of the components contained in fossil fuels, carbon assignments of new methylated derivatives of tetralin and indan were obtained. Their chemical shifts were calculated by applying additivity rules.
1H and 13C NMR assignment of theaflavin, theaflavin monogallate and theaflavin digallate
Authors: Davis Adrienne L. , Cai Ya , Davies Alan P. 
Published: May 2005

AbstractTheaflavin, theaflavin monogallate and theaflavin digallate were isolated from black tea leaves and studied by 1D and 2D NMR techniques, thus allowing unambiguous assignment of the 1H and 13C resonances of these complexes. Earlier studies have not yielded 13C data of equal reliability, especially for the benzotropolone moiety of these molecules, and consequently the data given here will be of use in future studies of natural products isolated from tea. The utility of the 2D proton detected long‐range 13C1H correlation experiment (HMBC) in the study of polyphenolic complexes is demonstrated by these results.
Analysis of ABX spin systems in some 1,4‐dihydro‐1λ5, 4λ5‐diphosphinines: Signs of 31P13C coupling constants and isotope effects
Authors: Heckmann Gernot , Fluck Ekkehard 
Published: May 2005

AbstractThe ABX spin systems of the [mono‐13C]isotopomers with vinylic and phenyl ipso‐13C atoms of a number of symmetrical 1,4‐dihydro‐1,4‐diphenyl‐1λ5,4λ5‐diphosphinines were analysed. The substituent dependence of the absolute signs and magnitudes of 2J(PC) between the two 31P nuclei and two vinylic 13C atoms and of the 4J(PC) and 3J(PP) are reported. 13C isotope effects on δ(31P) and 3J(PP) are discussed.
Semi‐selective two‐dimensional homonuclear and heteronuclear NMR experiments recorded with pulsed field gradients
Authors: Dalvit Claudio 
Published: May 2005

AbstractNew two‐dimensional ω, and ω1, ω2 semi‐selective homonuclear and heteronuclear NMR experiments recorded with pulsed field gradients (PFGs) were designed and tested on two peptides. The use of PFGs improves dramatically the performance of the semi‐soft experiments. The complete absence of t1 modulations allows the observation of cross peaks which are buried in the noise. The same principle as described here can also be implemented for recording three‐dimensional and four‐dimensional semi‐soft experiments.
Structure elucidation of two diphenylhydantoin derivatives via 1H and 13C NMR spectroscopy
Authors: Ciechanowicz‐Rutkowska M. , Ragona L. , Greco F. , Zetta L. , Pegna M. 
Published: May 2005

AbstractThe solution conformations of 1‐benzyl‐5,5‐diphenyl‐2,4‐dioxo‐3‐imidazolidineacetic acid (AC) and 3‐(2,4‐dichlorobenzyl)‐5,5‐diphenyl‐2,4‐dioxo‐1‐imidazolidine acetic acid (AD) were studied by proton and carbon NMR spectroscopy. The two drugs have different pharmacological activities, AC having anticonvulsant and AD having antidepressant but no anticonvulsant properties. The relative orientations of the hydantoin ring substituents were investigated and are discussed in terms of amphipathic distribution of polar and apolar domains.
Hadamard long‐range proton‐carbon coupling constant measurements with band‐selective proton decoupling
Authors: Nishida T. , Widmalm G. , Sandor P. 
Published: May 2005

AbstractLong‐range 13C1H coupling constants were measured by using multiple‐site selective excitation followed by polarization transfer and acquisition under band‐selective proton decoupling conditions. The multiple‐site proton decoupling eliminates splittings due to homonuclear spin couplings, thereby in practice simplifying the measurement of coupling constants from the anti‐phase splittings. In addition, the sensitivity is improved by approximately 50%.
79,81Br effects in the high‐resolution 13C NMR spectra of solid bromoaromatic compounds: Dipolar and indirect (79,81Br, 13C) interactions studied by ‘Inverse’ first‐order perturbation theory
Authors: Alarcón Sergio H. , Olivieri Alejandro C. , Carss Steven A. , Harris Robin K. 
Published: May 2005

AbstractSplittings in the 13C cross‐polarization magic angle spinning spectra of 1, 4‐dibromobenzene and 4‐bromo‐3, 5‐dimethylpyrazole are reported. They arise from (79,81Br, 13C) interactions influenced by the quadrupolar nature of the bromine nuclei. They are analysed using both ‘inverse’ perturbation and exact theories to yield data on both isotropic and anisotropic coupling, including the signs. The spectra also enable the sign of the bromine quadrupole coupling constant to be confirmed as positive.
Isomeric equilibria of 1‐Methylamino‐2‐nitroethene
Authors: Kozerski L. , Krajewski P. , Bednarek E. 
Published: May 2005

AbstractThe solvent and concentration dependence of the isomeric equilibria of 1‐methylamino‐2‐niroethene were studied by 1H and 13C NMR spectroscopy. The results are used for clarification of the controversy regarding the content of the E form in CDCI3 solution, correcting an earlier suggestion concerning the stereochemical assignments around the C‐1N bond in the E form and verification of the values of the olefinic one bond proton—carbon spin—spin coupling constants, 1J(C,H), reported recently. An unambiguous means of assigning the stereochemistry around the C‐1N bond in the E isomer is suggested, based on using the complementary information from 3J(C‐2,NH) and 3J(H‐1,NH), in addition to the 3J(Me,H‐1) vicinal coupling constant.
1H and 13C NMR study of stereoisomers of 3‐(arylpropenylidene)isobenzofuran‐1(3H)‐ones
Authors: Sveshnikov Nikolay N. , Nikulin Victor I. 
Published: May 2005

AbstractA study of the 1H and 13C NMR spectra of a series of E,E‐ and Z,E‐isomers of 3‐(arylpropenylidene)isobenzofuran‐1 (3H)‐ones [1a–d and 2a–d, respectively] was carried out. The E,E‐ and Z,E‐isomers 1a–d and 2a–d were recognized by the local anisotropy effect of the double and triple bonds of the substituents experienced by H‐4 in E,E‐isomers; in Z,E‐isomers; in contrast to their E,E‐analogues, upfield shifts of C‐4 and C‐8 due to the HH γ‐cis effect were observed.