bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compounds with bridgehead nitrogen. 44—the conformational analysis of perhydropyrido[1,2‐c] [1,3]thiazine
Authors: Crabb Trevor A. , Jupp Philip A. , Takeuchi Yoshito 
Published: May 2005

AbstractThe 270 MHz NMR data on trans‐ and cis‐(H‐4a, H‐7)‐7‐ethylperhydropyrido[1,2‐c][1,3]thiazine show heavy conformational bias to the trans‐ and S‐inside cis‐fused conformations, respectively. Comparison of the 13C NMR spectra of these anancomeric systems with the 13C NMR spectrum of perhydropyrido[1,2‐c][1,3]thiazine indicates a trans‐⇌S‐inside cis‐conformational equilibrium for the latter compound in CDCl3 at 25°C, containing ca 75% trans‐fused conformer. The 13C NMR spectrum of perhydropyrido[1,2‐c][1,3]‐thiazine at −75°C showed 64% trans‐fused conformer and 36% S‐inside cis‐conformer.
The conformation of t‐butyl 2‐methoxy‐5, 6‐dihydro‐2 H‐pyran‐6‐carboxylates and 6,6′‐ disubstituted 2‐methoxy‐5,6‐dihydro‐2H‐pyran derivatives on the basis of 1H and 13 C NMR spectra
Authors: Chmielewski Marek , Jurczak Janusz , Zamojski Aleksander , Adamowicz Halina 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of trans‐ and cis‐tert‐butyl 2‐methoxy‐5,6‐dihydro‐2H‐pyran‐6‐carboxylates (1 and 2) and 6,6′‐disubstituted 2‐methoxy‐5,6‐dihydro‐2H‐pyrans (3‐7) have been recorded. HH and CH coupling constants are discussed in terms of the 1H6⇄6H1 conformational equilibrium. It has been found that 1 occurs exclusively in the 1H6 conformation, whereas its cis isomer, 2, exists in an equilibrium of both half‐chair forms. 6,6′‐Disubstituted 2‐methoxy‐5,6‐dihydro‐2H‐pyrans 3‐6 display spectral and conformational behaviour similar to that of 1, whereas 7 resembles 2 in this respect.
Rh NMR studies of organometallic rhodium(I) derivatives
Authors: Bonnaire R. , Davoust D. , Platzer N. 
Published: May 2005

AbstractOrganometallic rhodium(I) derivatives have been studied by 103Rh NMR. The chemical shift range extends from 609 ppm ([Rh.cp.cod]) to 2714.7 ppm ([Rh.fod.cod]). These results are supported by 13C and 31P NMR results, and give information about the bonding in these derivatives. Most of the complexes contain the cycloocta‐1,5‐diene ligand. For these complexes a linear correlation is observed between δRh and δC (olefinic carbons) (27 points, R = 0.960). For the phosphine derivatives a linear correlation is found between δRh and 1J(RhP) and, also, between δRh and parameters characterizing the basicity of the phosphine ligand. The correlation of δRh with ligand properties has been extended to a wider range of complexes by using the ‘influence parameters’ defined previously (10 points, R = 0.947). The sensitivity of δRh to steric factors is also proved.
1H and 13C chemical shift data of four peracetylated triglucoses. Application of two‐dimensional techniques
Authors: Bigler P. , Ammann W. , Richarz R. 
Published: May 2005

Abstract1H and 13C chemical shifts are reported for four peracetylated triglucoses. Assignments are based on the recently proposed two‐dimensional Relayed Coherence Transfer Technique. The chemical shift data were obtained from conventional one‐dimensional NMR spectra.
Pairwise effects of chlorine substituents on the 13C NMR chemical shifts of dichlorobicyclo[2.2.1]heptanes (norbornanes)
Authors: Laihia Katri , Paasivirta Jaakko , Pikkarainen Heikki , Aho‐Pulliainen Sirkku 
Published: May 2005

AbstractThe 13C NMR spectra of nine dichlorinated bicyclo[2.2.1]heptanes (norbornanes) have been measured and assigned. The pairwise effects of chlorine substituents which cause deviations from the additivity of single‐substituent effects were investigated and are discussed. The largest effect found is the high‐field shift of carbons bearing vicinal cis substituents. In the case of geminal substitution deviations from additivity were found to be to low field and large in the γ, smaller in the β and negligible in the α chemical shifts. The observed deviations for 1,3‐disubstituted cases vary from −3.2 to +1.1 ppm at different carbons, allowing no simple explanation. Replacement of α‐hydrogen in a diaxial 1,3‐arrangement by CH3, OH or CI causes the single substituent effect, namely the γa effect, to change considerably.
Characterization of trisubstituted double bonds using 3J(CH)‐modulated spectra on simple NMR spectrometers
Authors: Highet R. J. 
Published: May 2005

AbstractA simple sequence in which 13C precessions are allowed to develop with proton coupling for a period of 1/2 3J(CH) s before initiating decoupling and acquisition allows the determination of vicinal carbon–hydrogen coupling constants to facilitate the characterization of trisubstituted double bonds. The experiment is illustrated by studies of citraconic anhydride and limonene.
The 13C NMR spectra of 1,2,3‐triazolo[1,5‐a]pyridine and some monodeuteriated derivatives
Authors: Jones Gurnos , Sliskovic D. Robert 
Published: May 2005

AbstractThe 13C signals of 1,2,3‐triazolo[1,5‐a]pyridine (1) are assigned, using the corresponding 3‐, 6‐ and 7‐deuterio‐heterocycles; coupling constants are also given for compound 1.
1H NMR spectra of the 2‐trifluoroacetyl derivatives of benzo[b]furan and benzo[b]thiophene
Authors: Benassi Rois , Folli Ugo , Iarossi Dario , Schenetti Luisa , Taddei Ferdinando 
Published: May 2005

AbstractThe 1H NMR spectra of the 2‐trifluoroacetyl derivatives of benzo[b]furan and benzo[b]thiophene were recorded at 200MHz in two solvents, chloroform and acetone. A long‐range coupling constant, 5J(HF), between the fluorine nuclei of the trifluoroacetyl group and H‐3, of a value higher than 1 Hz, was measured. From the comparison of the 1H chemical shifts of, and the solvent effects on, the trifluoroacetyl compounds and those of the corresponding 2‐acetyl derivatives, and on the basis of an empirical interpretation of the 5J(HF) coupling constant, a predominant Z conformation was tentatively assigned to these derivatives.
Carbon‐13 NMR spectra of some 4‐substituted phenacyl bromides
Authors: Fujiwara Fred Yukio , Rittner Roberto , Freire Haydeé R. 
Published: May 2005

AbstractThe 13C NMR signals for some 4‐ substituted phenacyl bromides were assigned. The experimental chemical shifts of the aromatic ring carbons are in close agreement with those calculated using substituent chemical shifts. Both the carbonyl and the α‐methylene carbons exhibit upfield shifts compared with those of the corresponding 4‐substituted acetophenones.
Effect of collision interactions on 13C nuclear magnetic shielding in monosubstituted benzenes in halogen‐containing solvents
Authors: Jackowski Karol 
Published: May 2005

AbstractThe 13C nuclear magnetic shielding in benzene and ten monosubstituted benzenes was studied when these compounds were dissolved in cyclohexane, carbon tetrachloride, tetrachloroethylene, methylene bromide and methylene iodide. The results revealed that the observed changes of 13C magnetic shielding are dependent on both the solute and solvent molecular properties, although the dependence on the solvent is much more significant. It was also shown that the solvent effects for aromatic carbons are independent of the π electron density distribution in an aromatic ring. The observed 13C deshielding was attributed mainly to overlap effects which take place during molecular collisions.
A 1H and 13C NMR study of methoxyretinoids. Spectral assignment and determination of configuration
Authors: Ernst Ludger , Hopf Henning , Natsias Konstantin 
Published: May 2005

AbstractA number of modified retinals and retinoic esters carrying one or two methoxy groups or one methoxy and one methyl group on the polyene chain were investigated by 1H and 13C NMR spectroscopy. Spectral assignments were made from homo‐ and selective 13C{1H} hetero‐decoupling experiments and from chemical shift comparisons. The configurations of the polyene double bonds were derived from vicinal H,H coupling constants, from 1H and 13C chemical shifts and by measuring nuclear Overhauser enhancements. It is found that all double bonds with no additional substituents occur in the trans (E) and all methoxy‐substituted double bonds in the cis (also E) configuration. Double bonds carrying methyl groups give rise to both cis (Z) and trans (E) isomers.
1H and 13C NMR studies of some germacrones and isogermacrones
Authors: Simova S. D. , Bozhkova N. V. , Orahovats A. S. 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of the trans,trans‐, cis,cis‐ and cis‐C‐3–C‐4, trans‐C‐7–C‐8‐germacrones and of the cis‐C‐2–C‐3, trans‐C‐7–C–8, trans‐C‐2–C‐3, cis‐C‐7–C‐8‐ and cis,cis‐isogermacrones are analysed. The last two isogermacrones are new compounds. The C‐2–C‐3 double bond in the previously described isogermacrone is found to be of cis configuration, contrary to the hitherto accepted trans arrangement.
Rates and mechanisms of the intermolecular cation‐exchange reactions of sodium tetraphenylboron with sodium–nitrobenzene and with sodium–p‐nitrobenzonitrile
Authors: Atherton Neil M. , Blustin Peter H. , Humphreys Ceris A. , Shalabi Ahmed S. 
Published: May 2005

AbstractThe rates of the exchange of sodium ions between sodium tetraphenylborate and sodium–nitrobenzene or sodium–p‐nitrobenzonitrile were measured from analysis of the line broadening effect on the ESR spectra off the paramagnetic ion pairs. The rate is significantly lower for the substituted nitro compound, and it is suggested that this reflects a difference in mechanism for the two systems.
Substituent effects on 33S NMR chemical shifts in sulphones
Authors: Cassidei L. , Fiandanese V. , Marchese G. , Sciacovelli O. 
Published: May 2005

AbstractThe 33S NMR spectra of some selected sulphones demonstrate additive substituent‐induced chemical shift (SCS) effects. In dimethyl sulphone (1), replacement of a methyl group by a vinyl or a phenyl group causes an SCS effect of −7 to −8.5 ppm or −4 to −5 ppm, respectively. The 33S chemical shift in 1 is also sensitive to substitution of methyl protons. The ß‐substituent effect for methyl and phenyl groups is in the range +7 to +8 ppm and +5.5 to +6 ppm, respectively.
Conformational analysis of rigid enol‐ethers by proton nuclear magnetic resonance
Authors: Durand R. , Geneste P. 
Published: May 2005

AbstractZ,E isomers of rigid enol‐ethers were studied by proton nuclear magnetic resonance. As with oximes, it was found that the chemical shift difference (Δδ=δz−δE) for the protons α to the function in question depends on the dihedral angle between the CαH and CC bonds. This phenomenon can be explained by an electric field effect and not by a magnetic anisotropy effect. The present study has allowed the derivation of values of the volume magnetic susceptibility and the product of b×the dipole moment for the CO bond.
On the chemistry of pyrrole pigments: 57—Phytochrome model studies: Complete assignments of the 13C NMR spectra of phytochrome model compounds
Authors: Falk Heinz , Müller Norbert , Vormayr Günther 
Published: May 2005

AbstractA strategy for the assignment of aromatic 13C NMR resonances of pyrrole pigments is presented which makes use of two‐dimensional chemical shift correlation spectroscopy via one‐bond and long‐range C,H coupling constants. The complete 13C NMR assignments for a 3,4‐dihydropyrromethenone and three phytochrome model compounds (2,3‐dihydrobilatrienes‐abc) are given.
Nuclear magnetic 13C19F double resonance: Fluorine broad band decoupling
Authors: Sklenář Vladimír , Starčuk Zenon 
Published: May 2005

AbstractThe feasibility of broad band fluorine decoupling for 13C NMR spectroscopy, employing a new composite pulse sequence, is shown. The application of this sequence allows the decoupling of fluorine nuclei over almost the total range of chemical shifts in fluoroorganic compounds, at magnetic fields of up to 2.3 T, without extensive demands on the decoupler power amplifier. The range of expected chemical shifts of fluorine bonded to carbons is briefly discussed.
Carbon‐13 NMR spectra of some phosphorane‐amino compounds
Authors: Costanzi Fabio , Pianca Maurizio , Tatò Marco , Moggi Giovanni 
Published: May 2005

AbstractThe 13C NMR spectra of a series of compounds of the type R1P(NR22)nPh3−n X− are reported. A net trend toward larger 1J(PC) values with an increasing number of dialkylamino substituents is observed.
Carbon‐13 nuclear magnetic resonance spectra of some heterocyclic D‐homoandrostanes
Authors: Marcano Deanna , De Méndez Jeannette , Ortiz Ana C. , Salinas Mirna 
Published: May 2005

AbstractThe 13C chemical shift data of several D‐homoandrostanes with heteroatoms (N,O) in the 17a‐position are reported. Heteroatom effects on the shieldings of the carbons of rings C and D are discussed.
Carbon‐13 NMR spectra of some phenanthrene derivatives from Aristolochia indica and their analogues
Authors: Achari Basudeb , Bandyopadhyay Soumitra , Chakravarty Ajit K. , Pakrashi Satyesh C. 
Published: May 2005

Abstract13C NMR spectra of compounds related to aristolochic acid and aristololactam, the constituents of Aristolochia indica, have been studied to determine the chemical shifts and coupling constants of polysubstituted phenanthrenes. Selective 1H decoupling and long‐range couplings were utilized for the assignments. Substituent‐induced chemical shifts and also the effects on coupling constants could be deduced in some cases. Anion formation was found to be particularly helpful in the interpretation of the spectra of carboxylic compounds. Shift assignments of some structurally related compounds could also be made.
Correlation of apparent myelin measures obtained in multiple sclerosis patients and controls from magnetization transfer and multicompartmental T2 analysis
Authors: Tozer D.J. , Davies G.R. , Altmann D.R. , Miller D.H. , Tofts P.S. 
Published: May 2005

AbstractTwo relatively new techniques purport to give measures of the myelin content of brain tissue. These measures are the myelin water fraction from multicompartmental T2 analysis, and the semisolid proton fraction from analysis of magnetization transfer (MT). The myelin water fraction is the fraction of signal with a T2 of less than 50 ms measured from a 32‐echo sequence. It is believed to originate from water trapped between the myelin bilayers. The semisolid proton fraction is thought to include protons within phospholipid bilayers and macromolecular protons, and may also be a measure of myelin content. Multicompartmental T2 and MT imaging were carried out on controls and patients with multiple sclerosis (MS), and estimates of the semisolid proton and myelin water fractions were obtained from white matter (WM), gray matter (GM), and MS lesions. These were then correlated for each tissue and subject group. Positive correlations were seen for MS lesions (r ≈ 0.2) and in WM in patients (r = 0.6). A negative correlation (r ≈ −0.3) was seen for GM. These results indicate that the two techniques measure, to some extent, the same thing (most likely myelin content), but that other factors, such as inflammation, mean they may provide complementary information. Magn Reson Med 53:1415–1422, 2005. © 2005 Wiley‐Liss, Inc.
Self‐navigated multishot echo‐planar pulse sequence for high‐resolution diffusion‐weighted imaging
Authors: Nunes Rita G. , Jezzard Peter , Behrens Timothy E. J. , Clare Stuart 
Published: May 2005

AbstractSingle‐shot techniques have preferentially been adopted for diffusion‐weighted imaging due to their reduced sensitivity to bulk motion. However, the limited spatial resolution achievable results in orientational signal averaging within voxels containing a distribution of fibers. This leads to impaired performance of tracking algorithms. To combat partial volume effects, high‐resolution multishot techniques can be used but, being more sensitive to motion, require phase correction to obtain artifact‐free images. While separately acquiring 2D navigator echoes is an effective approach, it is not very efficient as the navigators do not contribute signal to the final image. Here a self‐navigated interleaved echo planar imaging (EPI) sequence based on EPI with keyhole (EPIK) is proposed. The refocusing reconstruction method is successfully adapted to EPIK and compared to the standard linear approach. The resultant improvement in resolution is shown to lead to a significant increase in anisotropy in fiber‐branching areas and can potentially offer a superior ability to detect fine tract splits. Magn Reson Med 53:1474–1478, 2005. © 2005 Wiley‐Liss, Inc.
Botulinum toxin therapy in hemifacial spasm: Clinical and electrophysiologic studies
Authors: Geller Bruce D. , Hallett Mark , Ravits John 
Published: May 2005

AbstractThree patients with idiopathic hemifacial spasm were studied clinically and electrophysiologically before and after injections of botulinum toxin into the involved periocular and facial muscles. The spasms were improved for approximately 3 months, and the effect was repeatable on reinjection. The spasms diminished only as long as the muscles were clinically weak, and spasms were observed electromyographically even though therapy eliminated the clinical spasms. Uninjected muscles continued to have spasms. Transmission of excitation from the zygomatic branch to the marginal mandibular branch of the facial nerve and vice versa in all patients was unaltered after therapy, but the amplitude of the response was decreased. The efficacy of botulinum toxin in hemifacial spasm appears to be related to the production of muscle weakness; there is no demonstrable effect on phenomena believed to be ectopic excitation or ephaptic transmission in the facial nerve.
Effect of chain length on nuclear quadrupole interaction of nitrogen‐14 in aminated n‐alkanes
Authors: Murgich Juan , Santana R. Magaly 
Published: May 2005

AbstractThe 14N nuclear quadrupole resonance (NQR) spectra of several aminated n‐alkanes of the type CH3(CH2)xNH2(CH2)xNH2 at 77 K are reported and analysed in the framework of a semi‐empirical theory. The NQR data presented oscillations for x<6 and reached limiting values for x≥6. The results obtained are discussed in terms of inductive and conjugative effects, as well as the possible contributions of the hydrogen bond network presented in the solid state.
1H NMR spectra of diastereomeric 1,4‐disubstituted 2,3‐diphenylbutanes; examples of ABXX′ A′B′ and A2XX′A2′ spin systems
Authors: Spassov S. L. , Berova N. D. , Hawkes G. E. , Randall E. W. 
Published: May 2005

AbstractThe 1H NMR spectra of the meso‐ and (±)‐forms of some 1,4‐disubstituted 2,3‐diphenylbutanes were measured at 400 MHz. The spectral parameters were determined by iterative computer analysis, treating the protons as ABXX′A′B′ or (in some cases) A2XX′A2′ systems.
The antarctic lichens: 1—The stereochemistry of 7β‐acetoxy‐22‐hydroxyhopane from Pseudocyphellaria freycinettii, indigenous to S. Georgia
Authors: Howarth O. W. , Rickard T. M. A. , Sainsbury M. 
Published: May 2005

AbstractFrom differential spin decoupling and nuclear Overhauser enhancement experiments, the 400 MHz 1H NMR spectrum of the triterpene 7β‐acetoxy‐22‐hydroxyhopane is interpreted to establish the α‐configuration of the side‐chain at C‐21.
13C NMR chemical shifts of thiols, sulfinic acids, sulfinyl chlorides, sulfonic acids and sulfonic anhydrides
Authors: Freeman Fillmore , Angeletakis Christos N. 
Published: May 2005

Abstract13C NMR spectra of thiols, sulfinic acids, sulfinyl chlorides, sulfonic acids and sulfonic anhydrides have been obtained. The data are discussed in terms of the additivity of the deshielding effects exerted by the sulfur functionality at the α‐ or β‐position, and the shielding effects produced by the sulfur function at the γ‐position.
Conformational analysis: XXI—1H NMR study of 4,5‐dimethyl‐, 2,4,5‐trimethyl‐ and 2,2,4,5‐tetramethyl‐1,3‐dithiolanes
Authors: Pihlaja Kalevi , Keskinen Raimo , Eskonmaa Mauri , Nurmi Timo 
Published: May 2005

AbstractThe 60 MHz 1H NMR spectra of seven differently substituted 4,5‐dimethyl‐1,3‐dithiolanes have been recorded and analysed. Configurational assignments are made and conformational aspects are discussed in the light of the spectral parameters.
13C Nuclear magnetic resonance spectroscopy of biliverdin IX dimethyl esters and related compounds
Authors: Petrier Christian , Dupuy Claude 
Published: May 2005

AbstractThe 13C NMR spectra of differently substituted or conformationally restrained biliverdins have been recorded. Certain characteristics are found for these tetrapyrrolic systems, i.e. the chemical shifts of the methine bridge carbons, the vinyl groups and the bis‐lactam form. This study, in conjunction with other spectroscopic data, may be used to assign the structures of biliverdins IX αβγλ, phorcabilin, isophorcabilin and neobiliverdin IXλ.
Substituent and solvent effects on the 19F chemical shifts of 3‐ and 4‐XCH2‐substituted fluorobenzenes
Authors: Happer D. A. R. , Steenson B. E. , Newman R. H. 
Published: May 2005

AbstractSubstituent effects on the 19F chemical shifts of a series of 3‐ and 4‐XCH2‐substituted fluorobenzenes have been studied in five different solvents (dimethyl sulphoxide, acetone, chloroform, carbon tetrachloride and benzene). The results show that in both series substituent effects (other than inductive effects) contribute in at least some cases to the overall shifts, but that these showed little solvent dependence. The meta series showed a proportionately greater solvent dependence than the para series, and this is attributed to the greater importance of ‘through solvent’ direct field effects in the former.
Carbon‐13 NMR spectra of taxane‐type diterpenes: Oxiranes and oxetanes
Authors: Rojas Anibal C. , De Marcano Deanna , Méndez Bernardo , de Méndez Jeannette 
Published: May 2005

AbstractThe 13C NMR spectra of a series of nine taxane derivatives are reported. A detailed analysis of the assignments is presented. Observed long‐range substituent effects are explained on the basis of the proximity of rings A and C in this type of molecules.
Selective detection of multiplets via double quantum coherence: A 19F NMR study of perfluorodecalin
Authors: Fung B. M. 
Published: May 2005

AbstractCommercially obtained perfluorodecalin (octadecafluorodecahydronaphthalene) contains a mixture of cis‐ and trans‐isomers, the 19F NMR signals of which overlap. The spectrum can be simplified and assignments can be made by using techniques based on double quantum coherence. The INADEQUATE method eliminates peaks due to the cis‐isomer, and the DOUBTFUL method selectively detects two quartets of the trans‐isomer.
Use of concentration‐dependent relaxation rates for carbon‐13 chemical shift assignment of symmetric tetraalkylammonium salts in acetonitrile
Authors: Dando Neal R. , Gold Harvey S. , Dyboski Cecil 
Published: May 2005

AbstractThe assignment of 13C chemical shifts of several symmetric tetraalkylammonium salts in acetonitrile is based on alkyl chain carbon spin–lattice relaxation rates (T1−1), and on concentration‐dependent changes in these rates.
17O NMR study of isomeric 2‐R‐2‐oxo‐1,3,2‐dioxaphosphorinanes
Authors: Bock Paul L. , Mosbo John A. , Redmon John L. 
Published: May 2005

AbstractOxygen‐17 NMR spectra were obtained from the four pairs of isomeric 2‐R‐2‐oxo‐1,3,2‐dioxaphosphorinanes, where R=OMe (2), NMe2 (3), H (4) or Me (5). The isomerism has been previously shown to be configurational at phosphorus, with one isomer of each pair having an equatorial phosphoryl oxygen (a isomer), and the other an axial orientation for phosphoryl oxygen (b isomer). Only data for the phosphoryl oxygen are reported. Substitution of OMe or NMe2 for H or Me produced upfield shifts of 27.9‐41.8 ppm. In all cases, the chemical shifts of the a isomers were upfield of the b analogs, with differences of 7.9, 18.0, 20.3 and 8.6 ppm for 2—5, respectively. The absolute values of 1J(31P17O) were 5–9 Hz larger for the a isomers.
Nitrogen‐15 NMR studies of 1,4‐benzodiazepines: 2—The triazolobenzodiazepines
Authors: Scahill Terrence A. , Smith Stanford L. 
Published: May 2005

AbstractNitrogen‐15 NMR data for a series of 21 triazolobenzodiazepines are presented, including 15N chemical shifts and substituent effects. The line assignments made by correlation to other model compounds were confirmed by a shift reagent and protonation study. A Yb(dpm)3 study on alprazolam showed that the molar shifts of the four nitrogens ranged from 35 to 150 ppm.