bluuebunny/crossref_metadata_2025 huggingface dataset:
Compounds with bridgehead nitrogen. 63—NMR spectra and stereochemistry of perhydropyrido[3,2,1‐j,k][3,1]benzoxazepines
Authors: Crabb Trevor A. , Fallah Asadollah
Published: May 2005

The configurations and conformations of diastereoisomeric 1‐(decahydroquinolin‐8‐yl)butan‐2‐ols and of perhydropyrido[3,2,1‐j,k][3,1]benzoxazepines resulting from ring closure of these compounds with formaldehyde have been assigned by 1H and 13C NMR spectroscopy.
47/49Ti NMR of some titanium compounds
Authors: Berger S. , Bock W. , Marth C. F. , Raguse B. , Reetz M. T.
Published: May 2005

The results of 47/49Ti NMR measurements on 21 organotitanium compounds are reported. A signal could be detected for only about half of the compounds measured. Methyltitanium trichloride is highly deshielded compared with TiCl4.
Electron spin resonance study of spin‐trapped radicals from gamma irradiation of glucose oligomers
Authors: Thiéry Jean M. , Thiéry Corinne L. , Agnel Jean‐Pierre L. , Vincent Patrice B. , Battesti Christine M. , Raffi Jacques J. , Evans Jeffrey C.
Published: May 2005

Radicals produced in aqueous solution by gamma irradiation of the five first glucose oligomers were trapped using 2‐methyl‐2‐nitrosopropane (MNP) and separated by high‐performance liquid chromatography. The electron spin resonance (ESR) spectra were analysed on a microcomputer with a general interactive simulation program (VOYONS). The ESR coupling constants of five radical adducts, which were found in all the oligomers, are reported. A comparison with the coupling constants previously obtained from α‐D‐glucopyranosyl,‐0‐methyl‐α‐D‐glucopyranose, O‐α‐D‐glucopyranosyl‐(1 →4)‐α‐D‐glucopyranose or polyols, irradiated in the liquid phase or in the powder state, provides new information on the chemical structures of the radicals radioinduced in glucose oligomers. As the powder ESR spectra and the main radiolytic products from the gamma‐irradiated oligomers have been found to be comparable to those from irradiated starches, this work is the first step in the elucidation of the radiolysis mechanism of starch.
Conformational study of the 4,9‐dihetero‐(Z,Z)‐cyclodeca‐1,6‐diene ring system; the mono‐ and di‐benzo analogues
Authors: Kleinpeter E. , Hartmann J. , Schroth W.
Published: May 2005

The dynamic 1H and 13C NMR spectra of a series of mono‐ and bis‐annelated 4,9‐dihetero‐(Z,Z)‐cyclodeca‐1,6‐dienes were obtained and are discussed with respect to ground‐state conformers and the barriers to ring inversion, and to the restricted rotation about exocyclic partial C,N double bonds. The ten‐membered rings are, with one exception, anancomeric chair conformers and interconvert via a combination of single bond rotations and bond angle bendings. Depending on the heteroatoms present, the series of decreasing barriers to ring inversion S > NH > O was obtained. Benzannelation decreases the free energy of activation of the same dynamic process owing to greater intramolecular transannular H,H interactions.
Comparison of one‐ and two‐dimensional techniques in the unambiguous 13C NMR spectral assignment of ellipticine and related indole derivatives
Authors: Gogoll Adolf , Plobeck Niklas A.
Published: May 2005

The 13C NMR spectra of several indole derivatives have been completely assigned by reverse detected one‐bond and long‐range CH correlation spectra (HMQC) and by selective INEPT experiments. The resolution and sensitivity of the two techniques are discussed. As a result, the literature assignments for the previously known compounds have been revised.
Through‐space 13C–19F couplings in highly‐crowded systems: Radial dependence and electronic effects
Authors: Hsee Li C. , Sardella D. J.
Published: May 2005

The helical molecule 1‐fluorobenzo[ c] phenanthrene shows a large (17.4 Hz) 13C–19F coupling resulting primarily from direct through‐space overlap between a fluorine lone pair and the sterically opposed CH bond. After application of corrections for estimated through‐bond contributions, comparison of the magnitude of this coupling with the analogous couplings in 4‐fluorophenanthrene, 10‐fluorobenzo[ a] pyrene, 11‐fluoro‐5‐methylchrysene and 7‐fluorobenzo[b] fluoranthene reveals an exponential decrease with increasing H …︁ F internuclear distance, consistent with theoretical predictions. No evidence was found for an angular dependence of the coupling. HETCOR experiments showed the signs of n+1J(HF) in 1‐fluorobenzo[ c] phenanthrene, 4‐fluorophenanthrene, 10‐fluorobenzo[ a] pyrene and 11‐fluoro‐5‐methylchrysene to be opposite to those of the corresponding nJ(CF), hence negative. Substituents at both positions 4 (para to fluorine) and 9 (para to the sterically opposed CH bond) exert only a minor influence on 5J(CF), the couplings in the latter series responding largely to sterically induced distortions of the molecular framework, and in the former series to both steric distortions and an electronic effect. The difference in 5J(CF) between isomers is a measure of the electronic effect of the substituent. Electron‐withdrawing substituents para to fluorine reduce the magnitude of the through‐space coupling whereas electron‐releasing substituents increase the coupling.
Selective excitation techniques in 13C NMR. II—new sequences for fast heteronuclear correlation
Authors: Berthault P. , Perly B. , Petitou M.
Published: May 2005

The potential of Gaussian soft pulses in the selective excitation of individual 13C multiplets is demonstrated for heteronuclear 13C–1H NMR spectroscopy. The efficiency of these techniques is demonstrated for the rapid and accurate recording of both proton chemical shifts and heteronuclear coupling constants in multi‐labelled oligosaccharides.
13C NMR of coumarins. V—3‐prenylated coumarins
Authors: Macias F. A. , Hernández‐Galán R. , Massanet G. M. , Rodriguezluis F. , Vasquez M. , Salvá J.
Published: May 2005

13C NMR data of nineteen coumarins, twelve of which bear a prenyl (isoprenoid) side‐chain at C‐3, are reported and compared with those of the C‐3 unsubstituted compounds. Unlike the linear isomers, no γ‐effect is observed in the corresponding angular derivatives; this is proposed as spectroscopic criterion for distinguishing between these isomers.
13C NMR of some chlorinated diphenyl ethers
Authors: Dawson Brian A. , Chu Ih , Viau Andre
Published: May 2005

13C NMR chemical shift assignments for 15 chlorinated diphenyl ethers, containing from two to seven chlorine substituents, were measured and interpreted. Chemical shift data for 12 of these compounds have not been previously reported. Data are based on a number of 1D and 2D experiments performed at 9.4 T.
Carbon‐13 NMR spectral analysis of oxazine derivatives and precursors
Authors: Moloney Gerard P. , Craik David J. , Iskander Magdy N.
Published: May 2005

13C NMR chemical shifts are reported for six pyridoxal‐derived and fourteen salicylaldehyde‐derived oxazines and their immediate precursors. Similar data for seven vitamin B6‐related compounds are also reported.
Conformational dependence of the one‐bond carbon–proton coupling constants in oligosaccharides
Authors: Hricovíni Miloš , Tvaroška Igor
Published: May 2005

A study is presented of the dependence on conformation of one‐bond carbon‐proton coupling constants in three 1‐4‐linked disaccharides. Calculated 1J(CH) values are based on the FPT formulation in the semi‐empirical INDO MO method. The configuration at the anomeric carbon influences the 1J(CH) value, and the 1J(C‐1′, H‐1′) values are 20–30 Hz higher than the 1J(C‐4, H‐4) values. The conformational dependence of 1J(CH) on the dihedral angle about the CO bonds is satisfactorily expressed in the analytical form 1J(CH) = A cos 2ϕ + B cos ϕ. The constants A‐E are different for the α‐ and β‐anomers. Calculated average values 〈1J(C‐1′, H‐1′)〉 = 163.7 Hz and 〈1J(C‐4, H‐4)〉 = 146 Hz for methyl β‐xylobioside using PCILO‐calculated abundances of conformers agree well with the experimental values of 162.7 and 147.5 Hz, respectively.
A proton and carbon NMR spectral study of 4‐substituted and 4,6‐disubstituted dibenzothiophenes
Authors: Katritzky Alan R. , Perumal S.
Published: May 2005

The proton and carbon NMR spectra of several 4‐substituted‐ and 4,6‐disubstituted‐dibenzothiophenes have been measured, and their chemical shifts assigned employing spin decoupling and COSY and HETCOR two‐dimensional techniques. This work rectifies several literature misassignments of 13C chemical shifts of 4‐substituted dibenzothiophenes and also examines the effects of substituents on the chemical shifts. Hence this study will be useful in the future structure determinations of mono‐ and multisubstituted dibenzothiophenes.
Studies on complex species of aluminium with aminocarboxylic acids by 27Al NMR spectroscopy
Authors: Karweer S. B. , Pillai B. P. , Iyer R. K.
Published: May 2005

The reactions of Al3+ ion with glycine, picolinic acid, 1,2‐propylenediaminetetraacetic acid and triethylenetetra‐minehexaacetic acid (HpL) were studied by potentiometric and 27Al NMR methods, and the complex species in solution at different pH values were identified. Acidic hydrolysis of the Al‐PDTA complex results in the formation of [AIL]−, [Al(H2O)LH] and [Al(H2O)2LH2]+ prior to dissociation, while base hydrolysis takes place through the monohydroxo species. Although TTHA is a decadentate ligand, the maximum number of donor sites utilized in the formation of the 1:1 Al‐TTHA complex is only five.
13C and 15N NMR study of 2,3‐diphenyltetrazolium‐5‐olate and 5‐thiolate
Authors: Kozminski W. , Jazwinski J. , Stefaniak L. , Webb G. A.
Published: May 2005

13C and 15N NMR chemical shifts are reported for 2,3‐diphenyltetrazolium‐5‐olate and ‐5‐thiolate and some of their derivatives. The data for N‐1 and C‐5 provide a very satisfactory means of distinguishing between O and S as the exocyclic substituent. The reported chemical shifts are consistent with the presence of the cyclic structures shown, rather than of the corresponding non‐cyclic structures.
Preparation and stereostructure of norbornane/ene‐condensed phenyl‐substituted O,N‐heterocycles
Authors: Sohár PÁL , Bernáth Gábor , Frimpong‐Manso Samuel , Szabó Angela E. , Stájer Geza
Published: May 2005

Norbornane/ene di‐exo‐condensed isoxazolines were reduced to amino alcohols and then cyclized to 1,3‐oxazines. The phenylimino analogues, 1,3‐oxazin‐2(3H)‐ones, the corresponding 2(3H)‐thiones and 1,4‐oxazepin‐3(4H)‐ones were also prepared. The structures, configurations and conformations of the new compounds were proved via 1H and 13C NMR studies, using DR, DNOE, DEPT and 2D‐HSC measurements in addition to the routine spectra.
One‐ and two‐dimensional 15N NMR spectroscopy of tris(trimethylsilyl)‐, tris(trimethylstannyl)‐, tris(trimethylplumbyl)‐amine and tetrakis(trimethyistannyl)hydrazine: Sign determination of various scalar coupling constants
Authors: Wrackmeyer Bernd , Zhou Hong
Published: May 2005

The signs of the coupling constants 1J(29Si15N) and 1J(119Sn15N) are positive and negative, respectively, in tris(trimethylsilyl)‐ and tris(trimethylstannyl)‐amine. This results from two‐dimensional (2D) 15N/1H heteronuclear shift correlations [at natural abundance of 15N, based on long‐range couplings 3J(1N 1H), with respect to the positive coupling constants 2J(29SiC 1H) and 2J(119SnC 1H)]. The same type of experiment proves the negative sign of 1J(119Sn15N) in tetrakis(trimethylstannyl)hydrazme and it allows the unambiguous assignment of 1J(119Sn15N) and 2J(119SnN 15N). In tris(trimethylplumbyl)‐amine, the largest value (335.7 Hz) reported so far for 1J(207Pb 15N) of plumbylamines is observed. In the case of tris(trimethylstannyl)amine, the 2D 15N/1H experiment also gave the sign of 4J(119SnNSnC1H) (positive), and this is used in the 2D 119Sn/1H experiment to prove a negative sign for 2J(119Sn 117Sn).
High‐resolution solid‐state NMR study of reversible 1,5‐proton shifts in organic solids
Authors: Vila Alejandro J. , Lagier Claudia M. , Olivieri Alejandro C.
Published: May 2005

High‐resolution CP‐MAS NMR analyses of solid organic samples where fast 1,5‐proton shifts occur between tautomeric structures are described. Attention is focused on the available techniques to establish the existence of such reactions. Dynamic interconversion is unambiguously characterized where complete line shape study involving multiple sites is possible. Reconciliation between this information and that provided by diffraction methods is stressed, the latter often suggesting the presence of unique, static structures in crystals. In cases in which reactions are in the fast limit at all accessible temperatures, the combination of CP‐MAS spectra, x‐ray or neutron diffraction data at variable temperatures and theoretical calculations of molecular properties may be helpful in establishing double minimum potential wells for the proton motion. Among these, porphyrins, arylazonaphthols and 1,3‐diketones in rigid and non‐rigid skeletons are interesting examples of current interest.
1H and 13C nuclear magnetic resonance studies of ethenyl‐substituted benzenoid aromatic compounds
Authors: Katritzky Alan R. , Hitchings Gregory J. , King Roy W. , Zhu Dong W.
Published: May 2005

1H and 13C NMR studies were carried out on 1‐ethenylnaphthalene, 2‐ethenylnaphthalene, 9‐ethenylanthracene, 9‐ethenylphenanthrene, 1‐ethenylpyrene and 1‐ethenylperylene. Assignments of proton and carbon resonances were made with the aid of 2D COSY, 2D HETCOR, 2D COLOC, 2D COLOCS, 3J(H,C) INAPT, and NOE difference spectral techniques.
Detection of long‐range couplings in oligomers and evaluation of coupling constants in polymers. Application of the 1D COSY technique
Authors: Uhrínová Stanislava , Uhrín Dušan , Liptaj Tibor , Batta Gy.
Published: May 2005

One‐dimensional COSY is shown to be a promising technique for the detection of small, unresolved proton‐proton coupling constants. Under certain circumstances the method can be more effective than two‐dimensional phase‐sensitive COSY. A detailed analysis of the experimental conditions is presented. The possible application of the method in oligosaccharide sequencing is outlined. Another potential use of one‐dimensional COSY is in the evaluation of coupling constants in macromolecules. In this case the efficiency of the polarization transfer is decreased owing to the fast transverse relaxation times of the protons. DISCO analysis was applied for the determination of coupling constants in unresolved multiplets.
Long‐range deuterium isotope effects on 13C NMR shifts of intramolecularly hydrogen‐bonded 9‐hydroxyphenalen‐1‐ones
Authors: Engdahl Carin , Gogoll Adolf , Edlund Ulf
Published: May 2005

The 1H and 13C NMR spectra of 9‐hydroxyphenalenone (1) and 9‐hydroxy‐2‐methylphenalenone (2) have been completely assigned. Primary and secondary deuterium isotope effects were determined in three solvents (chloroform, acetone and dimethyl sulphoxide), including the effect of temperature on the secondary isotope effects. Both negative and large long‐range secondary isotope effects were found for both 1 and 2. The average secondary isotope effects for corresponding carbons follow the same sign and magnitude pattern in both compounds.
Two‐dimensional NMR study of eledoisin
Authors: Yang Ta‐Horng , Chang Tsung‐Yi , Yu Chin
Published: May 2005

The 1H and 13C NMR spectra of eledoisin, an antidiuretic hormone, were studied by two‐dimensional NMR techniques. All the 1H and 13C NMR resonances were unambiguously determined from a combination of the 2D homo‐ and hetero‐nuclear NMR spectra.
Dynamic NMR study of the electronic state of heteroaromatics. IX—π‐Electron deficiency of various substituted thiazinethiones, thiazinium salts and analogous pyrimidines by means of barriers to rotation about exocyclic partial C,N double bonds
Authors: Kleinpeter E. , Schroth W. , Pihlaja K.
Published: May 2005

The 1H NMR spectra and the barriers to rotation about exocyclic partial C,N double bonds of various series of thiazinethiones 1, the corresponding thiazinium salts 5–9 and some pyrimidinethiones 10–13 are reported and discussed with respect to the π‐electron deficiency of these heteroaromatic compounds. Substituent influences are critically considered; in particular, the C,N barrier differences of C,NMe2 and C, pyrrolidino were used to estimate the type of dynamic process, which is different in pyrimidinethiones 10–13 and thiazinethiones/thiazinium salts 1–9. The compounds studied corroborate the pseudo‐chalcogeno analogy principle. Previously studied compounds are included to display the π‐electron deficiency influence of the heterocyclic system on the 1H chemical shifts of NR2, phenyl, the H‐5 protons and the exocyclic barriers to C,N rotation; adequate quantitative estimations are reported.
Inverse editing of protons in two‐dimensional homonuclear and heteronuclear relayed COSY spectra
Authors: Wollborn U. , Leibfritz D.
Published: May 2005

Several 1D and 2D inverse proton editing pulse sequences have recently been introduced. One of these, the REPAY sequence, allows the individual editing of XH or XH2 groups. Some new 2D combinations of one‐ and two‐dimensional REPAY experiments with a COSY or TOCSY transfer are described. These combinations provide various possibilities for structural elucidation: the determination of heteronuclear long‐range coupling constants nJ(CH) (n = 2, 3), the editing of XH or XH2 groups in two‐dimensional H,H COSY spectra and the editing of XH or XH2 groups in X,H COSY spectra followed by a relayed transfer. In contrast to earlier versions of SHIPPED‐COSY experiments, the spectra show improved sensitivity and offer the possibility of selecting XH2 groups only, and contain no 1J(XH) coupling because of heteronuclear X decoupling.
NMR spectra and conformational analysis of substituted 2,3‐dihydro‐[1,5]benzoxazepin‐4(5H)‐one derivatives
Authors: Ott Jürgen , Hiegemann Monika , Duddeck Helmut
Published: May 2005

The 1H and 13C NMR spectra of 26 2,3‐dihydro‐[1,5]benzoxazepin‐4(5H)‐one derivatives and four thiono analogues are interpreted in terms of conformational equilibria. Similar to 1,3,4,5‐tetrahydro‐2H‐1,5‐benzodiazepin‐2‐ones, these compounds favour boat conformations of the seven‐membered ring. In the lactams the conformational energy difference is very low, whereas a difference of 0.3 kcal mol−1 is recorded for the thionolactams, the conformation with the quasi‐axial methyl group also being preferred.
Carbon‐13 NMR relaxation study of the overall and internal motions in compounds containing n‐octyl chains
Authors: Bull Lucy M. , Gillies Duncan G. , Matthews Stephen J. , Sutcliffe Leslie H. , Williams Antony J.
Published: May 2005

The 13C nuclear relaxation behaviour of n‐alkyl chains in a variety of compounds can be described in terms of two relaxation times, one for tumbling (τc) and one for each carbon nucleus for the internal motions (τc). Relaxation data for the quaternary carbon nuclei of n‐octylbenzene and n‐octyl cyanide have been used to determine τc) and their activation energies [Ea(τc)]. These values have enabled τe and their associated activation energies [Ea(τe)] to be calculated for each carbon in the alkyl chains of the two compounds. In these compounds the values for C‐6 appear to be invariant with τe(298) = 15 ± 2 ps and Ea(τc) = 15 ± 1 kJ mol−1. Assuming that these are universal values for all n‐octyl chains, we have used them to calculate τe and Ea(τe) for other simple n‐octyl compounds, thus allowing τc and E.a(τc) to be determined. It was found that Ea(τc) values correlate well with those for Ea(n/T) obtained from viscosity measurements. Di‐n‐octyl ether shows motional properties similar to those of the straightchain compounds.

Simultaneous fitting of relaxation rate and NOE enhancement data measured over a range of radiofrequencies and temperatures permits a wealth of motional properties to be discerned when there is a suitable frequency dispersion. Both tri‐n‐octylamine and polydecene tumble sufficiently slowly to allow both relaxation rate and NOE data to be used to evaluate τc and τe and their activation energies without making any assumptions about C‐6. The values of τc(298) and Ea(τc) obtained from C‐6 for tri‐n‐octylamine are 314 ± 12 ps and 18.5 ± 0.4 kJ mol−1, respectively, and the corresponding values for polydecene are 576 ± 41 ps and 16.1 ± 1.3 kJ mol−1, respectively.
13C, 13C coupling constants of isotopically perturbed molecular systems: Cyclohexane, benzene
Authors: Roznyatovsky Vitaliy A. , Sergeyev Nickolay M. , Chertkov Vyacheslav A.
Published: May 2005

13C, 13C coupling constants in benzene and cyclohexane were measured using monodeuteriated derivatives where 13C, 13C two‐spin subsystems become slightly non‐equivalent (benzene, 1J = 55.88, 2J = 2.46, 3J = 10.04; cyclohexane, 1J = 33.10, 2J = 2.12, = 3J 2.05; all couplings in hertz within the error limits of 0.01 Hz). 12C/13C isotope effects for the 13C chemical shifts were found to be non‐additive.
Boron‐11 quadrupole coupling constants deduced from nuclear relaxation of closo‐borane and carborane solutions
Authors: Pascal Y. L. , Convert O.
Published: May 2005

An analysis of the 11B relaxation rates was carried out for different solutions of closo‐borane dianions B12H and B10H and for a solution of o‐carborane, C2B10H12. The temperature dependence of these relaxation rates shows the similar interactions of these molecules with the medium. For o‐carborane, 13C relaxation rate measurements provide an evaluation of the correlation time τc and of the microviscosity of the medium. By using these values it is possible to estimate the quadrupole coupling constants for the borane dianions. The results are supported by theoretical data on the electric field gradient using the STO‐3G method.
The double‐DANTE sequence applied to NMR of complex carbohydrates
Authors: Poppe Leszek , van Halbeek Herman
Published: May 2005

The double‐DANTE sequence was implemented in 1D TOCSY and NOESY experiments to overcome some typical problems in the NMR of carbohydrates. In the 1D TOCSY experiment the double‐DANTE sequence serves to invert simultaneously two resonances belonging to the same scalar‐coupled spin system, thereby substantially increasing the sensitivity of the technique for subspectral editing and providing a valuable alternative to relayed TOCSY in overcoming small‐J bottlenecks in monosaccharides such as galactose and sialic acid. Spin‐diffusion artifacts in 1D NOESY experiments that are mediated by more than one spin can be effectively eliminated by applying a double‐DANTE pulse train for saturation of the mediators during the mixing time. In certain cases, the double‐DANTE sequence is also capable of eliminating the three‐spin effect in 1D 13C{1H} NOE difference spectroscopy.
Through‐bond transmission of polar substituent effects in the bicyclo [2.2.2]octane ring system as monitored by 119Sn NMR chemical shifts: A 119Sn NMR study of 10‐substituted 9‐trimethylstannyltriptycenes
Authors: Adcock William , Iyer V. Sankar
Published: May 2005

A series of 10‐substituted(X)‐9‐trimethylstannyltriptycenes (2a) were synthesized and characterized and the 119Sn chemical shifts measured. Comparisons were made of the 119Sn substituent chemical shifts (SCS) of 2a and the corresponding values of 4‐substituted(X)bicyclo[2.2.2]oct‐1‐yltrimethylstannanes (1a), which confirm the previous conclusion that ‘through‐three‐bond’ effects or double‐hyperconjugation strongly regulate the 119Sn shifts of the latter system. A more restricted series of 10‐substituted(X)‐9‐methyltripycenes (2c) were acquired and their 13CH3SCS compared with those of the corresponding bicyclo[2.2.2]octanes (1c). Significant ‘through‐bond’ contributions are also indicated for the latter system.
ESR parameters of 5,5‐dimethylpyrrolidine 1‐oxide (DMPO) spin adducts in the photochemical decomposition of azo compounds
Authors: Cholvad Vladimir , Szaboova Katarina , Staško Andrej , Nuyken Oskar , Voit Brigitte
Published: May 2005

Splitting constants and g values are reported for 5,5‐dimethylpyrrolidine 1‐oxide spin adducts with radicals such as substituted‐Ph˙, NaSO3˙, PhS2˙, and others observed in the photochemical decomposition of azo compounds in various solvents.
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

The 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

The 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

Detailed 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

The 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

This 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

The 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

COSY, 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

The 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

(±)‐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

Carbon‐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

The 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

Both 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

The 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

N‐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

A 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

1H, 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

1H, 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

Proton 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

The 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

The 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

The 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

The 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

A 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

Trans‐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

13C 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

The 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

A 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

A 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

129Xe 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

The 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.
Multi‐frequency, variable‐temperature and high‐pressure study of carbon‐13 spin—lattice relaxation in tetraoctyltin
Authors: Gillies Duncan G. , Matthews Stephen J. , Sutcliffe Leslie H.
Published: May 2005

Carbon‐13 NMR spin–lattice relaxation times, T1, and nuclear Overhauser effect data were obtained for neat tetra‐n‐octyltin at 22.5 and 100.6 MHz over a wide temperature range. T1 values were also measured at 25.16 MHz at pressures up to 211 MPa. The ambient‐pressure data were fitted to the ‘model‐free’ two‐correlation time spectral density with a temperature‐dependent order parameter, S2. The pressure data were interpreted by assuming that internal motions of the octyl chain are independent of pressure while the overall (tumbling) motion and S2 are pressure dependent. The values of the motional parameters for tetra‐n‐octyltin lie in the ranges expected for compounds containing long n‐alkyl chains. The results show that this approach is applicable to complex liquids such as synthetic lubricants of the polydecene type.
13C NMR chemical shifts of ω‐haloalkyl‐trimethylsilyl and ‐tert‐butyldimethylsilyl ethers
Authors: Poleschner Helmut , Heydenreich Matthias
Published: May 2005

The 13C NMR chemical shifts of Me3SiO(CH2)n(1, X = I, n = 2–6, 8, 10; 2, X = Br, n = 2, 4, 6, 8, 10; 3, X = Cl, n = 2, 4, 6; 4, X = F, n = 6) and t‐BuMe2SiO(CH2)n(5, X = I, n = 2–4; 6, X = Cl, n = 4) are presented and assigned.