bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two‐dimensional 1H NMR spectroscopy of aqueous solutions with elimination of the water resonance by transverse relaxation: Application to assignment of the 1H NMR spectrum of reduced arginine vasopressin
Authors: Larive Cynthia K. , Rabenstein Dallas L. 
Published: May 2005

AbstractThe measurement of two‐dimensional COSY and TOCSY 1H NMR spectra of aqueous solutions with elimination of the water resonance by the water attenuation by transverse relaxation (WATR) method is described. With the WATR method the water resonance can be completely and selectively eliminated, allowing observation of resonances that would normally be obscured by the water resonance or eliminated if the water resonance is suppressed by selective presaturation. COSY spectra are measured by a modified COSY pulse sequence, with a delay between the second 90° pulse of the standard COSY pulse sequence and data acquisition to eliminate the water resonance by transverse relaxation. TOCSY spectra are measured using a modified TOCSY pulse sequence which includes a delay for transverse relaxation immediately following the 90° pulse. The effectiveness of the WATR method for elimination of the water resonance from COSY and TOCSY spectra is illustrated with spectra measured for the reduced, dithiol form of arginine vasopressin in H2OD2O (90:10) solution. These spectra, together with one‐dimensional spectra and two‐dimensional ROESY spectra, also measured with elimination of the water resonance by the WATR method, are used to make the first complete assignment of the 1H NMR spectrum of reduced arginine vasopressin. Elimination of the water resonance is sufficiently complete and selective that the resonance for the α‐proton of the cys6 residue, which has a chemical shift of 4.758 ppm, is observed without interference from the water resonance. Chemical shift and J(NH, H‐α) data are also presented for native arginine vasopressin under the same solution conditions.
19F solvent shifts as molecular environmental probes
Authors: Suntioinen Sirpa , Laatikainen Reino 
Published: May 2005

AbstractThe 19F solvent shifts of trichlorofluoromethane, fluorobenzene and methyl trifluoroacetate were measured with respect to an external reference in 48 solvents and solvent mixtures. The data were modelled using various linear and thermodynamic approaches. The models based only on the chemical composition of the solvent explain the results with a correlation coefficient of 0.95–0.96, corresponding to an r.m.s. value of 0.14–0.21 ppm. Including the refractivities improves the fit slightly in some cases.
1H and 13C NMR spectra of fifteen substituted isoquinolines
Authors: Nelson Janis T. , Davis Roman 
Published: May 2005

AbstractDetailed analyses of the 1H and 13C NMR spectra of fifteen mono‐ and di‐substituted isoquinoline derivatives were carried out by two‐dimensional 1H–1H and 1H–13C shift correlation and nuclear Overhauser effect difference techniques.
17O NMR study of isomeric monochloro‐ and monohydroxy‐benzaldehydes and chlorinated salicylaldehydes
Authors: Kolehmainen E. , Knuu‐Tinen J. 
Published: May 2005

AbstractThe 17O NMR chemical shifts of isomeric monochloro‐ and monohydroxy‐benzaldehydes and chlorinated salicylaldehydes were measured at 40°C for 0.25 M CDCI3 solutions. The 17O NMR chemical shift of the carbonyl oxygen of the compounds studied varies from 506 to 573 ppm measured from external D2O. The observed variation is probably mainly due to the intramolecular hydrogen bonding between the adjacent carbonyl and hydroxyl groups. The 17O NMR chemical shift range of the hydroxyl oxygen is from 80 to 98 ppm.
Multi‐dimensional NMR experiments using selective pulses
Authors: Kessler Horst , Mronga Siggi , Gemmecker Gerd 
Published: May 2005

AbstractThis review describes the use of shaped pulses for frequency‐selective excitation, refocusing and/or mixing. The selectivity of different pulse shapes is described. Selective excitation can be used to transform 2D experiments into 1D analogues or to restrict the size in higher dimensional spectra. Soft excitation also can be used to apply techniques in homonuclear spectroscopy which are otherwise only possible in heteronuclear spectroscopy.
Transmission of electronic effects through cyclopropane. II.—Comparative modulation of 1H chemical shifts by aryloxy and aryl substituents in 2‐(donor)‐1‐(acceptor)cyclopropanes
Authors: Alonso Miguel E. , Pekerar Sarah V. 
Published: May 2005

AbstractThe electronic interaction between donor and withdrawing substituents on vicinal carbons of cyclopropane, leading to the possible participation of the cyclopropane ring in the mesomeric transmission, was examined in the terms of the variable electron density release of the donor group consequential to the variable electron density demand by the withdrawer. Based on the large anisotropic effect caused by the donor on the 1e" and 4e′ orbitals of cyclopropane that surround the corresponding geminal cyclopropyl proton, the 1H NMR spectra of 26 2‐(donor)‐1‐(acceptor) three‐membered carbocyclic derivatives were analysed for differential effects of C‐1 substituents, with variable electron‐withdrawing capacity, on their cis protons located on C‐2 and C‐3. It was found that 2‐aryloxy groups exert a strong modulation effect on δH‐2, making this proton notably less sensitive than H‐3 to changes in anisotropy modifications caused by the C‐1 group. 2‐Aryl groups, in contrast, affect proton resonances only to a limited extent. This was interpreted as an increased electron release on the 1e" and 4e′ LUMOs of cyclopropane by the C‐2 donor as electron demand increases in the C‐1 environment, and not as a consequence of conjugation through the ring.
Applications of two‐dimensional NMR in spectral assignments of the cytotoxic triterpene saponaceolide B
Authors: Geraci Corrada , Piattelli Mario , Tringali Corrado 
Published: May 2005

AbstractCOSY, one‐bond and long‐range HETCOR NMR spectra were used in combination for the complete 1H and 13C assignments of the cytotoxic triterpene saponaceolide B. Stereochemical assignments were based on a NOESY spectrum.
Amended heteronuclear correlations by multiple quantum evolution. Theoretical aspects of an ABX spin system
Authors: Kövér K. E. , Mádi Z. , Batta Gy. 
Published: May 2005

AbstractThe results of a theoretical investigation, using a modified SMART program, on the behaviour of an ABX spin system during the basic INEPT and multiple quantum evolution pulse sequences are presented. We found, in agreement with the experimental results, that the constant time version of the multiple quantum experiment provides an almost complete suppression of spurious signals, even in the case of the most strongly coupled spin system.
Determination of the relative stereochemistry of 5α‐ and 5β‐diastereomers of [2α,3β,3aα]‐ethyl hexahydro‐2‐ (1,2,3,4‐ tetraacetoxybutyl)‐ 5,6,6‐ trimethylpyrrolo[1,2‐b] isoxazole‐3‐ carboxylate
Authors: Vasu J. , Nadkarni Pradeep J. , Trivedi Girish K. , Steigel Alois 
Published: May 2005

Abstract(±)‐4,5,5‐Trimethyl‐1‐pyrroline‐1‐oxide reacted readily with ethyl 4,5,6,7‐tetra‐O‐acetyl‐trans‐2,3‐dehydro‐2,3‐dideoxy‐L(−)‐arabinoheptenoate in anhydrous benzene to give a mixture of two diastereomeric isoxazolidines, [2α,3β,3aα,5α]‐ and [2α,3β,3aα,5β]‐ethyl hexahydro‐2‐(1,2,3,4‐ tetraacetoxybutyl)‐5,6,6‐trimethylpyrrolo[1,2‐ b] isoxazole‐3‐carboxylate. The structures and configurations of both diastereomers were determined through the use of the (1H–1H) COSY, (13C–1H) HETCOR and NOEDS techniques.
Carbon‐13 NMR spectral investigations on allenic esters: Rationalization of carbon‐13 NMR chemical shifts and relaxation times (T1)
Authors: Gandhi R. P. , Ishar M. P. S. 
Published: May 2005

AbstractCarbon‐13 NMR chemical shifts (CDCl3 and C6D6 solvents) and relaxation times (T1) were determined for carbons in a series of allenic esters [RR1CCCHCO2 Et; (1) R = R1 = H; (2) R = H, R1 = CH3; (3) R = H, R1 = CH3CH2; (4) R = R1 = CH3; (5) R = CH3, R1 = CH3CH2]. A comparison of the experimental δ13C values with those obtained by semi‐empirical additivity relationships revealed the inadequacy of these relationships to explain the obtained results. A rationalization of δ13C and relaxation time data is offered, inter alia, in terms of rotameric conformational preferences of the ester function.
Metallheteroborane chemistry. Part 8.—NMR study of some arsena‐ and stibaboranes and of the rhodadiarsenaboranes [3,3‐(PPh3)2‐3‐(H)‐closo‐3,1,2‐RhAs2B9H9] and [3‐(η5‐C5Me5)‐closo‐3,1,2‐RhAs2B9H9]
Authors: Fontaine Xavier L. R. , Kennedy John D. , McGrath Marguerite , Spalding Trevor R. 
Published: May 2005

AbstractThe cluster11B and1H NMR chemical shifts of the known arsenaborane species [7‐Me‐nido‐7‐AsB10H12], [7‐Me‐nido‐7‐AsB10H11]−, [nido‐7‐AsB10H12]−, [closo‐1,2‐As2B10H10] and [nido‐7,8‐As2B9H10]−, of the known stibaborane species [closo‐1,2‐Sb2B10H10] and [closo‐1,2‐CSbB10H11], and of the previously unreported metalladiarsenaboranes [3,3‐(PPh3)2‐3‐(H)‐closo‐3,1,2‐RhAs2B9H9] and [3‐(η5‐C5Me5)‐closo‐3,1,2‐RhAs2B9H9] were measured and assigned by [11B–11B]‐COSY, [1H–1H]‐COSY‐{11B}, and1H–{11B} NMR experiments. Similarities and trends in the cluster shielding patterns were examined in order to assess changes in supposed electronic structures.
Applications of 1H NMR selective and biselective relaxation times to elucidate the configurations and conformations of guinesines in solution
Authors: Sugiura Makiko , Sai Torei , Ichimaru Momoyo , Kato Atsushi , Takao Narao 
Published: May 2005

AbstractBoth selective (T1S) and biselective relaxation times (T1BS) were measured for the sulphur containing alkaloids, guinesine‐A, ‐B and ‐C (Ia, Ib and Ic). Their configurations and conformations were determined using the interproton distances (rij) derived from the cross‐relaxation times (σij), which were obtained from the observed T1S and T1BS values. Their configurations are concluded to be 3′,4′‐cis‐2,3′‐erythro (Ia), 3′,4′‐cis‐2,3′‐threo (Ib) and 3′,4′‐trans‐2,3′‐erythro (Ic), which are consistent with the results from x‐ray analyses and 1H NOE experiments. The preferred conformations in CDCl3 solution are also proposed for these alkaloids.
2‐fluoro‐2‐phenylacetic acid. 4—Configuration of its esters with substituted‐phenyl alcohols by 19F NMR
Authors: Barrelle Michel , Hamman Sylvain 
Published: May 2005

AbstractThe use of 2‐fluoro‐2‐phenylacetic acid as a chiral derivatizing agent allowed the distinction, by means of fluorine NMR spectroscopy, of enantiomers of alcohols L1CH(OH)L2 converted into the diastereoisomeric esters PhCHFCO2CHL1L2. The δF(RR) and δF(RS) fluorine chemical shifts of diastereoisomeric esters obtained from series of alcohols containing a substituted‐phenyl group (L1 or L2 = ZPh), and the ΔδF chemical shift differences, were linearly related to the Hammet σ parameter of Z. The ΔδF originates from the different electronic effects of L1 and L2 groups on the fluorine atom, through space, in a minor conformation. A classification of the ZPh effects on δF with respect to Ph is obtained. The configuration of substituted‐phenyl secondary alcohols, ZPhCH(OH)L, can be determined with the aid of the δF values of esters formed with PhCHFCO2H if the configuration of the unsubstituted alcohol PhCH(OH)L is known.
NMR spectra and stereochemistry of N‐acetyl and N‐benzoyl derivatives of solasodine
Authors: Patel Asmita V. , Blunden Gerald , Crabb Trevor A. 
Published: May 2005

AbstractN‐Acetylation of solasodine gives only one rotameric N‐acetyl derivative compared with N‐acetyl‐3‐methylpiperidine, which exists in solution as two equally populated rotamers. The 1H and 13C NMR spectra (CDCl3) of O,N‐diacetyl‐ and O‐acetyl‐N‐benzoylsolasodine indicate significant deviations from F‐ring chair geometry. Opening of the F ring of these derivatives in CDCl3 solution at 25°C, to give the corresponding furosta‐5,20(22)‐diene derivatives, was ascertained by NMR spectroscopy.
Prediction of the carbon‐13 NMR chemical shifts of polysubstituted benzenes with homogeneous substituents
Authors: Dostovalova V. I. , Fedorov L. A. , Paasivirta J. 
Published: May 2005

AbstractA new incremental scheme for the calculation of the 13C NMR chemical shifts in polysubstituted benzenes with homogeneous substituents was derived and applied to spectral prediction for C6XnH6−n where XCH3, C2H5, i‐C3H7, CF3, F, Cl, Br, COOH. Owing to the use of only two‐particle increments the procedure is simple enough to be carried out on hand calculators, and gives complete agreement with experimental values within a few tenths of a ppm in all cases compared (76 compounds). The 13C NMR chemical shift was predicted for hexaethylbenzene with a good fit to the experiment value, and also for 20 unmeasured compounds. The present scheme can be used as an algorithm in structure‐searching programs for personal computers, and in data‐based systems.
1H, 19F and 13C NMR assignments of 5,7‐dihalogenated kynurenic acid derivatives
Authors: Huber Edward W. , Stemerick David M. , Cousino Diane M. , Harrison Boyd L. 
Published: May 2005

Abstract1H, 19F and 13C chemical shift assignments and 1H–1H, 1H–19F, 19F–19F and 19F−13C coupling constants for nine 5,7‐dihalogenated kynurenic acid derivatives are reported. Data and assignments are based on 1D and 2D NMR experiments.
1H, 13C and 17O NMR study of substituted nitropyridines
Authors: Kolehmainen Erkki , Laihia Katri , Rasala Danuta , Gawinecki Ryszard 
Published: May 2005

Abstract1H, 13C and 17O NMR spectra for 22 substituted nitropyridines were measured and their 1H NMR spectra were analysed. The most significant variations in the NMR parameters are found for isomeric hydroxy derivatives, owing to the possibility of keto–enol tautomerism. The prevalence of the keto form is observed in 2‐ and 4‐hydroxy derivatives, while the 3‐hydroxy derivative exists in its enol form. Among the three nuclei studied, 17O seems to be the best nucleus for probing the keto–enol tautomerism. No correlation is observed between the torsion angle of the nitro group and its 17O NMR chemical shift. Molecular mechanics calculations were performed to clarify the torsional energetics of the nitro group and the preferences for keto–enol tautomerism.
Conformational features of imipramine hydrochloride in aqueous solution as detected by 1H NMR relaxation analysis
Authors: Gaggelli Elena , Marchettini Nadia , Valensin Gianni 
Published: May 2005

AbstractProton NMR measurements were performed and 1H1H dipolar interaction energies were measured to delineate the conformation of imipramine in solution. Self‐association of imipramine into dimers was observed and a dimerization constant of 121 mol−1 was calculated. The motional correlation times for the monomer and the dimer were calculated at τcm = 0.18 ns and τcd = 0.36 ns, respectively. The geometry of the self‐stacked dimer was analysed by measuring intermolecular dipolar cross‐relaxation rates and interpreted in terms of the conformation of the aminoalkyl moiety.
1H and 13C NMR Spectra of (Z)‐C‐aryl N‐tert‐butyl nitrones
Authors: Murray Robert W. , Singh Megh 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of 12 (Z)‐C‐aryl N‐tert‐butyl nitrones were measured and proton and carbon assignments made. The nitrones were synthesized by the dimethyldioxirane method.
Stereochemistry of crown ethers. IV—1H/13C NMR spectroscopic study of the solution structure of some bis(benzocrown ethers)
Authors: Stoss S. , Kleinpeter E. , Holdt H.‐J. 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of some bis(benzocrown ethers) were recorded and assigned by means of 1H/13C HETCOR spectroscopy, heteronuclear selective decoupling experiments and the refocused INEPT experiment optimized for long‐range 1H, 13C coupling constants. It is shown that the efficiency of the so‐called ‘biscrown effect’ is dependent on the radii of the alkali metal ions. Long‐range 1H, 13C coupling constants, high‐field shifts within γ‐fragments in the 13C NMR spectra and NOEs from 2D‐NOESY spectra are discussed with respect to both the configuration and the preferred conformation of the studied compounds.
The pyrimidine‐iodine interaction; a study of complex formation by NMR of oriented molecules
Authors: Suryaprakash N. , Ugolini R. , Diehl P. 
Published: May 2005

AbstractThe interaction of pyrimidine with iodine when both are dissolved in a liquid crystal solvent has been studied. The considerable changes observed in the degrees of order of pyrimidine can be quantitatively attributed to complex formation between the nitrogen atoms and iodine along axes forming angles of 30° with the nitrogen–nitrogen axis and in the molecular plane. The complex formation does not affect measurably the proton and carbon positions of pyrimidine.
The (Z)/(E)‐configurational analysis of isolated double bonds in pheromones and unsaturated fatty acids. The use of 1D and 2D J‐resolved 1H CW off‐resonance techniques in 13C NMR spectroscopy
Authors: Radeglia Reiner , Poleschner Helmut , Heydenreich Matthias 
Published: May 2005

AbstractThe 1H CW off‐resonance decoupled 13C NMR spectra of pheromones and unsaturated fatty acids were measured for the determination of the configuration of double bonds of the type CH2CH  CHCH2. The decoupling frequency corresponded to the resonance frequency of the CH2 protons. The 2nd order splittings in the observed multiplets of the olefinic carbon atoms allow an approximate determination of the vicinal coupling constant between the olefinic protons, and the configurational assignment of the double bond.
Homonuclear scalar 6Li6Li spin–spin coupling: First direct observation and detection via the 6Li,6Li INADEQUATE experiment,
Authors: Eppers Oswald , Günther Harald , Klein Klaus‐Dieter , Maercker Adalbert 
Published: May 2005

AbstractA homonuclear 6Li,6Li spin–spin coupling has been directly measured in the case of the dimer of (E)‐2‐lithio‐1‐phenyl‐1‐o‐lithiophenylpent‐1‐ene. This constitutes the first direct observation of such a parameter. The well known INADEQUATE experiment in its one‐ and two‐dimensional versions is applied for the first time to a spin system of spin‐1 nuclei. It is demonstrated that the experiment is very sensitive for the detection of 6Li,6Li spin–spin interactions, and thus provides a promising alternative to the COSY experiment and an additional tool for structural studies on organolithium compounds in solution.
1H, 13C and 17O NMR study of aromatic ring‐substituted monochloro‐ and monobromo‐(E)‐3‐phenylpropenals
Authors: Kolehmainen Erkki , Laihia Katri , Mänttäri Pia 
Published: May 2005

AbstractTrans‐Cinnamaldehydes (CAs) or o‐, m‐ and p‐X‐(E)‐3‐phenylpropenals; (X = Cl or Br) were synthesized and their 1H, 13C and 17O NMR spectra were measured, assigned and analysed. The long‐range benzylic couplings are discussed in terms of the conformational characteristics of the related styrene systems. The 1H, 13C and 17O NMR substituent chemical shifts of the CA derivatives were compared with those of styrene and explained by the π‐electron delocalization in the conjugated CCCO bond system of CA.
13C NMR spectra of 1‐pyrroline 1‐oxides, 2H‐pyrrole 1‐oxides and related compounds
Authors: Black David St C. , Strauch Richard J. 
Published: May 2005

Abstract13C NMR data for forty 1‐pyrroline 1‐oxides, six 2H‐pyrrole 1‐oxides, three 2H‐pyrroles, eight 1‐pyrrolines and four related oxaziridines are reported. Comparisons are made with respect to the five‐membered ring carbons, subdividing them as the central carbons, the nitrone carbon and the gem‐dimethyl‐substituted carbon adjacent to nitrogen. The effects of substituents on the ring are also discussed.
Characterization of methyl derivatives of cyclopentadiene monomer and dimer by 13C NMR spectroscopy
Authors: Laurens T. , Nicole D. , Rubini P. , Lauer J. C. , Matlengiewicz M. , Henzel N. 
Published: May 2005

AbstractThe assignment of the carbons of different isomers of methylcyclopentadiene monomers (Me‐CPD) and dimers (diMe‐DCPD) has been performed directly in a mixture, without previous separation of these products, by analysing data from quantitative 13C NMR spectra of the mixtures and applying a J‐modulated spin–echo sequence. Semi‐empirical rules for the influence of methyl groups on the chemical shifts of carbons in pentenic and norbornyl ring systems have been formulated and utilized to assign the absorptions. The same method can then be applied to the carbon assignments in cyclopentadiene–methylcyclopentadiene codimers (Me‐CPD), and it is possible to develop additivity rules and predict chemical shifts for diMe‐DCPD based on the chemical shifts for the carbons of these codimers.
Structural characterization of (±)‐3‐aryl‐1‐azabicyclo[2.2.2]octan‐3‐ols by two‐dimensional NMR spectroscopy and X‐Ray crystallography. I
Authors: Arias‐Pérez M. S. , Cosme A. , Gálvez E. , Florencio F. , Fonseca I. , Sanz J. 
Published: May 2005

AbstractA series of (±)‐3‐aryl‐1‐azabicyclo[2.2.2]octan‐3‐ols were synthesized and studied by 1H, 13C and 2D NMR spectroscopy, and the crystal structure of (±)‐3‐(4‐methylphenyl)‐1‐azabicyclo[2.2.2]octan‐3‐ol was determined by X‐ray diffraction. The combined use of COSY, NOESY and 1H–13C correlation spectra of these compounds helped in the unambiguous and complete assignments of the bicyclic carbon and proton spin system. This study allows the establishment of the proton magnetic parameters for the quinuclidine moiety. Standard values of 1H1H coupling constants are proposed in order to analyse more complex quinuclidine derivatives.
13C and 195Pt NMR of para‐substituted N,N‐dialkyl‐N′‐benzoylthioureas and their cis‐[ML2] complexes, M = Pd(II) and Pt(II)
Authors: Koch Klaus R. , Matoetoe Mangaka C. 
Published: May 2005

AbstractA series of neutral cis‐[ML2] complexes, where M = Pd(II) and Pt(II) and L = para‐substituted N,N‐dialkyl‐N′‐benzoyl‐thio‐urea anion, were examined by means of 13C and 195Pt NMR. Unambiguous assignment of the thiocarbonyl carbon atom in these complexes was achieved with 13C isotopic enrichment and the resolved nJ(195Pt, 13C) coupling satellites.
Gas to solution shifts of 129Xe and 13C of methane are linearly related
Authors: Diehl P. , Ugolini R. , Suryaprakash N. , Jokisaari J. 
Published: May 2005

Abstract129Xe gas to solution shifts, which generally do not correlate well with solvent parameters, are shown to be linearly related to the 13C gas to solution shifts of methane in the same solvents. Since the shifts are attributed exclusively to van der Waals effects, and 129Xe is 27.1 times more sensitive to these effects than 13C, 129Xe is suggested as a reference for van der Waals shifts induced in different nuclei.
Structure elucidation of the oligosaccharide calonyctin A by the concerted use of 1D and 2D NMR techniques
Authors: Serratrice Guy , Pastor Raphaël , Hu You‐Chuan 
Published: May 2005

AbstractThe chemical structure of a plant growth substance, calonyctin A, was determined by NMR spectroscopy. The 13C and 1H spectral assignments were obtained using a combination of DEPT, heteronuclear chemical shift correlation, 1H–1H COSY, 1H–1H NOESY and inverse long‐range 1H–13C correlation. Calonyctin A was found to be a mixture of two homologous glycosides, each containing four rhamnoses and two aglycones. The configuration of the rhamnoses and the structural linkage between the six molecular fragments are reported.