bluuebunny/crossref_metadata_2025 huggingface dataset:
Substituent effects on 1H chemical shifts. I—complete 1H chemical shift assignments of methyl‐substituted cyclic systems
Authors: Fisher Julie , Gradwell Michael J.
Published: May 2005

1H chemical shift assignments are presented for 2‐methyladamantane, 2‐methylnorbornane (endo and exo) and 2‐methylnorbornene (endo and exo). Resonance assignment was achieved using a variety of 1D and 2D homo‐ and heteronuclear (1H–13C) experiments. The methyl group‐induced substituent chemical shift (SCS) is derived and the SCS of protons vicinal to this group is discussed.
1H NMR study of the intramolecular rearrangements of the complexes of 2‐hydroxypropane‐1,3‐diaminetetraacetic acid with metal ions
Authors: Song Ruifang , Li Fei , Li Liang
Published: May 2005

The kinetics of the intramolecular processes of barium(II), zinc(II), cadmium(II) and lanthanum(III) complexes with 2‐hydroxypropane‐1,3‐diaminetetraacetic acid (HPDTA) were investigated by 1H NMR spectrometry. A novel result, the slow Δ, Λ conversion process at room temperature for Zn and LaHPDTA chelates, was observed. The best fittings of the experimental spectra were obtained by computer analysis. These indicate that the activation energy of the Δ, Λ conversion process increases with increasing electrostatic potential for these chelates.
Solid‐state 13C and 1H NMR study of anomalous acid salts of dibasic carboxylic acids
Authors: Merwin Lawrence H. , Ross Sidney D.
Published: May 2005

High‐resolution solid‐state 13C and 1H NMR techniques were used to study the structure of a number of anomalous acid salts of adipic, azelaic, dodecanedioic, maleic and fumaric acids. To assist in the understanding of these results, solid‐state NMR data were also obtained for the corresponding acids and a number of their ‘normal’ salts. The resulting information provides insights into the solid structure of these complexes, including approximations of the length of the hydrogen bonds present in these systems. Strong evidence is given for the presence of a symmetrical hydrogen bond for tetramethylammonium didodecanedioate. Carbon‐13 NMR measurements carried out over a range of temperatures have revealed differences in the behavior of several of these compounds which may provide clues regarding the nature of the hydrogen bond in these systems.
Conformational studies of benzophosphabicyclooctenes
Authors: Tóth Gábor , Kovács Attila , Keglevich György , Duddeck Helmut
Published: May 2005

The Friedel–Crafts reaction of P‐substituted 6,6‐dichloro‐3‐phosphabicyclo [3.1.0] hexane 3‐oxides with benzene derivarives yields selectively new tricyclic benzophosphabicyclooctenes. The relative configuration and conformation of these products were elucidated by various 1H and 13C NMR methods.
Sequential proton saturation for the heteronuclear 1D NOE experiment
Authors: Mueller C. , Bircher H. R. , Bigler P.
Published: May 2005

An improved 1D pulse sequence for detecting heteronuclear NOEs on a qualitative level is described and demonstrated. It makes use of shaped selective pulses and takes advantage of sequential perturbation of several proton resonances during one experiment and correspondingly more efficient data accumulation schemes. The method is particularly suitable for assigning quaternary carbons and for establishing connectivities between assigned molecular fragments bound to these quaternary centres.
13C NMR spectra of substituted o‐nitroanisoles and n‐butyl o‐nitrophenyl ethers
Authors: Zeegers Petrus J. , Thompson Malcolm J.
Published: May 2005

13C NMR analyses of substituted o‐nitroanisoles and n‐butyl o‐nitrophenyl ethers are reported.
Effect of pH on carbon‐13 NMR spectra of N‐dodecyl‐N, N‐dimethylamine oxide solution
Authors: Brycki Bogumil , Szafran Miroslaw
Published: May 2005

Carbon‐13 NMR chemical shifts of the non‐ionic‐cationic surfactant N‐dodecyl‐N, N‐dimethylamine oxide (C12DAO) were measured and identified by an INADEQUATE experiment. On micellization, downfield chemical shifts were found for all carbon atoms except NCH2. The shifts are most pronounced for the carbon atoms in the central part of the chain. Protonation of the micelles resulted in upfield shifts of all the carbon atoms; the magnitudes decreased with increasing distance from the nitrogen atom. A plot of several chemical shifts against pH gave titration curves and pKa values. The pKa values vary with the carbon atom used in the calculation (from pKa = 5.05 to 5.66). An AMI calculation of charge densities suggests that these variations in pKa are caused by the electric field of the OH group. The effect of N‐oxidation on the chemical shifts of the carbon atoms in five solvents was estimated.
Tautomerism of 2‐benzothiazolylmalonates and 2‐oxobenzodihydrothiazol‐3‐yl‐malonates
Authors: Solčániová Eva , Liptaj Tibor , Sutoris Viktor
Published: May 2005

The tautomerism of alkyl 2‐benzothiazolyl‐malonates and 2‐oxobenzodihydrothiazol‐3‐yl‐malonates was studied by 1H, 13C and 15N NMR spectroscopy. 2‐Benzothiazolylmalonates isomerize in solution to the NH tautomers with an intramolecular hydrogen bond between the NH …︁ OC groups, whereas 2‐oxobenzodihydrothiazol‐3‐yl‐malonates are in the CH forms. The complete assignments of the 13C NMR resonances are reported.
Comparison of different 2D NMR techniques for 13C, 31P correlation
Authors: Bast Peter , Berger Stefan , Günther Harald
Published: May 2005

Three different experimental techniques are compared to find the most efficient protocol for 2D 13C, 31P correlation spectroscopy. It is shown that the best signal‐to‐noise ratio is given by the polarization transfer experiment for 31P detection and by the HMQC experiment for 13C detection. Applications of these techniques for 13C,31P correlation of β‐nicotinamide adenine dinucleotide (NAD+) and a mixture of three different mononucleotides are described.
A variable‐temperature 13C cross‐polarization magic angle spinning NMR study of some unusual dynamic and phase properties of (±)‐3,4‐di‐O‐acetyl‐1,2,5,6‐tetra‐O‐benzyl‐myo‐inositol, ‘jumping crystals’
Authors: Fattah Jamila , Twyman J. Mark , Dobson Christopher M.
Published: May 2005

Variable‐temperature 13C CP/MAS NMR experiments were carried out on crystalline (±)‐3,4‐di‐O‐acetyl‐1,2,5,6‐tetra‐O‐benzyl‐myo‐inositol. Three distinct phases can be distinguished from their NMR characteristics, each stable over a well defined temperature range, in accord with previous calorimetric studies. The differences between the spectra of the distinct phases suggest that structural variations between them are small. At least two of the aromatic ring moieties of the molecule were shown to be experiencing motional averaging in each of the three phases. Transitions between the phases, monitored by following changes in the NMR spectra, exhibited significant hysteresis but showed no evidence for pre‐organizational behaviour in the form of intermediate species. These results are discussed in the context of the unusual ‘jumping’ motion of the crystals associated with passage through the phase II–III and III–II transitions.
35Cl nuclear quadrupole resonance in 2,4‐ and 2,6‐dichlorobenzyl alcohols
Authors: Roy S. K. , Amitha B. , Uchil J.
Published: May 2005

35Cl nuclear quadrupole resonance (NQR) was studied in 2,4‐dichlorobenzyl alcohol (2,4‐DCBA) and 2,6‐dichlorobenzyl alcohol (2,6‐DCBA). The NQR spectrum of 2,4‐DCBA show four lines and that of 2,6‐DCBA two lines. The temperature dependence of the NQR frequencies from 77 K up to the respective melting points was studied. An order–disorder transition was observed in 2,6‐DCBA around 215 K. Torsional frequencies and their temperature coefficients were calculated using the temperature dependence of the NQR frequencies, and were compared with the laser Raman spectra obtained at room temperature.
1H and 13C NMR analysis of brassinosteroids
Authors: Porzel Andrea , Marquardt Volker , Adam Günter , Massiot Georges , Zeigan Dieter
Published: May 2005

The 1H and 13C NMR spectra of the two phytohormones, brassinolide and 24‐epi‐brassinolide, and the two synthetic analogues 22,23,24‐trisepi‐brassinolide and (22S,23S)‐28‐homo‐brassinolide, were assigned using 1D and 2D NMR techniques. Independent assignment strategies are presented for the 1H and 13C chemical shifts of the steroidal side‐chain.
ESR spectroscopic investigation of some 4‐substituted 1,3,2‐dithiazolyl and 2,3,1‐dithiazolyl radicals
Authors: Chung Yuen‐Li , Fairhurst Shirley A. , Gillies Duncan G. , Preston Keith F. , Sutcliffe Leslie H.
Published: May 2005

Further information has been obtained on the electronic structure of 1,3,2‐dithiazol‐2‐yl radicals. The structure has been well characterized previously except for positions 4 and 5 in the
equation image
ring. We have obtained solution and powder ESR spectra of radicals substituted with 13C in both positions and of radicals substituted with nitrogen or phosphorus in the 4‐position. It is probably the first time that a compound has been prepared containing the
equation image
ring. Two especially interesting facts emerged from the ESR spectra of these 1,3,2‐dithiazolyl radicals: the 13C‐substituted radical has a considerable amount of p spin density in the plane of the ring and the phosphorussubstituted radical has a very low unpaired spin density at the phosphorus atom. It is known that 1,3,2,4‐dithiadiazolyl radicals isomerize readily by photolysis to the symmetrical 2,3,1,4‐dithiadiazolyl radicals; we attempted the same reaction with But
equation image
and a new radical was produced that we have been unable to identify.
High‐field NMR study of the tautomers resulting from the condensation of 2‐methylindole and phenalenone in the presence of p‐toluenesulphonic acid
Authors: Tort F. , Waegell B. , Zahra J. P. , Bernasconi C. , Germanaud L. , Bessibes C. , Bounoure J.
Published: May 2005

As phenalene is an alternant hydrocarbon it is oxidized very easily to phenalenone, which condenses with various nitrogen nucleophiles in the presence of p‐toluenesulphonic acid. 2‐Methylindolylphenalene is obtained with 2‐ methylindole, together with other products. This product is a mixture of five tautomers in equilibrium, and these were analysed by homo‐ and heteronuclear two‐dimensional high‐field NMR (500 MHz) spectroscopy.
195Pt and 1H NMR study of the products of hydrolysis of Pt(L)X2, where L is an ethylenediamine derivative, and the crystal structure of [Pt(N,N‐dimethylethylenediamine) (μ‐OH)]2 (NO3)2
Authors: Rochon Fernande D. , Melanson Robert , Morneau André
Published: May 2005

The hydrolysis reactions of complexes of the type Pt(L)X2 where L is ethylenediamine (en), N,N‐ dimethylenediamine (N,N‐Me2en), N,N‐dimethylenediamine (N,N′‐Me2en) and N,N,N′, N′‐tetramethylethylenediamine (Me4en) were studied. The halo ligands were removed by precipitation with AgNO3 and the pH of the resulting filtrate, which was about 2, was adjusted to 5.8 (pD = 6.2). The study of the products formed was carried out by multinuclear NMR spectroscopy. The 195Pt NMR spectra showed the presence of several hydrolysed products, especially with en. The hydroxo‐bridged dimer can be synthesized in a pure state with all the ligands except en. The results on the latter ligand contradict the published results on the synthesis of the en hydroxo‐bridged dimer whose biological properties were studied. When Pt(L)I2 is used as starting material a small quantity of chloro species was always observed, indicating that the reactant contained a small quantity of Pt(L)ICI. The crystal structure of the [Pt(N,N‐Me2en)(μ‐OH)]2(NO3)2 dimer was determined. The compound belongs to the P21/c space group, with a = 8.262(5), b = 10.960(8), c = 11.405(8), β = 121.07(5)°, Z = 2 and ρcalc = 2.720 mg m−3. The results showed that this is the trans isomer with an inversion centre between the two Pt atoms. There is a considerable strain inside the four‐membered ring, as shown by the reduced internal angles OPtO′ = 79.1(6)0 and PtOPt′ = 101.0(6)°.
Dynamics of lysine hydrochloride dihydrate measured by carbon‐13 NMR spectroscopy
Authors: Swanson Scott D. , Bryant Robert G.
Published: May 2005

The 13C NMR spectra for L‐lysine hydrochloride dihydrate are reported for static samples and samples spinning at the magic angle, which provide resolution of each carbon resonance. The spectra and the T1s, T1p and T1 relaxation times for the carbon atoms demonstrate that there is little motion of the side‐chain in this crystal environment. The carbon spin–lattice relaxation is approximately accounted for by rotational motions of the ammonium ions in the range 50–100 ns and motions of the water molecules in the region of 50 ps or 70 ns. The backbone motions are relatively unimportant for relaxation of the carbon spins.
Application of HMQC to the measurement of J(H, H) homonuclear coupling constants
Authors: Yang Daiwen , Xu Xiaolong , Ye Chaohui
Published: May 2005

Homonuclear scalar coupling constants can be measured in HMQC experiments by increasing the resolution in the F2 dimension; in addition, the CH chemical shift correlation can be obtained. This approach is illustrated using the experimental spectra of chenodeoxycholic acid (CDCA). The 1H NMR spectrum for CDCA was completely assigned; the J(H, H) and 1J(C,H) values and the CH correlation were obtained from the 2D HMQC spectrum.
Carbon‐13 relaxation study of motional properties of lacto‐N‐neotetraose in solution
Authors: Bagley Stephen , Kovacs Helena , Kowalewski Jozef , Widmalm Göran
Published: May 2005

Carbon‐13 spin–lattice relaxation times and NOE factors are reported for a tetrasaccharide, lacto‐N‐neotetraose, in solution as a function of temperature and magnetic field. The data that are outside the extreme narrowing regime are analysed using the ‘model‐free’ approach of Lipari and Szabo. The global reorientation is assumed to be isotropic. The experimental data for the inner rings can be fitted very well using a simplified version of the equations, neglecting the local motion term in the spectral densities. The complete expression for the spectral densities is required for the outer rings, and three different fitting procedures are compared.
13C NMR study of the substituent effects in ortho‐substituted nitrobenzenes
Authors: Rasala Danuta , Gawinecki Ryszard
Published: May 2005

13C NMR chemical shifts of 22 ortho‐substituted nitrobenzenes are reported. Except for those on C‐3 and C‐5, the effects of the interacting nitro group and the substituent are non‐additive. The chemical shifts of the ipso, ortho and para carbons in the spectra and those of monosubstituted benzenes are linearly dependent. Multiparameter correlation analysis shows a predominant field/inductive effect on the ipso compared with both the ortho and para carbon chemical shifts. It shows that the Reynolds non‐electronic factors evaluate the substituent chemical shifts of the ipso and ortho positions much better than the Charton steric parameters. Moreover, both in ortho‐ and para‐substituted nitrobenzenes the substituent exerts almost the same shift on the ipso carbon atom. This suggests that the studied compounds, except those carrying very bulky groups, show a high tendency to be planar.
Characterization of symmetrical and unsymmetrical thiol–disulfide interchange reactions by one‐and two‐dimensional magnetization transfer NMR spectroscopy
Authors: Keire David A. , Guo Wei , Rabenstein Dallas L.
Published: May 2005

One‐ and two‐dimensional magnetization transfer NMR methods were used to characterize symmetrical and unsymmetrical thiol–disulfide interchange reactions in the glutathione‐cysteamine system. The chemical system consists of four symmetrical and two unsymmetrical thiol–disulfide interchange reactions. In terms of the magnetization transfer experiment, these reactions can be treated as two three‐site exchange networks, one for exchange of the cysteamine moiety among cysteamine, cystamine and the cysteamine part of the glutathione–cysteamine mixed disulfide and another for exchange of the glutathione moiety among glutathione, glutathione disulfide and the glutathione part of the mixed disulfide. Two‐dimensional 13C{1H} EXSY NMR spectroscopy was used to identify specific exchange reactions which take place on the time scale of the magnetization transfer experiment at a given pD. The kinetics of the interchange reactions were quantitatively characterized using an overdetermined version of the one‐dimensional 13C{1H} EXSY experiment and a 13C{1H} selective inversion‐transfer experiment with a linear‐least‐squares analysis of the time course data. Second‐order rate constants were calculated for all six of the thiol–disulfide interchange reactions from the pseudo‐first‐order rate constants obtained from the selective inversion‐transfer experiments.
1H, 13C and 17O NMR spectroscopic study of four bicyclo [3.1.1]heptenes (derivatives of α‐pinene) and four bicyclo[3.1.1]heptanes (derivatives of β‐pinene)
Authors: Laihia Katri , Kolehmainen Erkki , Malkavaara Petteri , Korvola Jorma , Mänttäri Pia , Kauppinen Reijo
Published: May 2005

Four derivatives of 2, 6, 6‐trimethylbicyclo[3.1.1]hept‐2‐ene (α‐pinene) and four derivatives of 2‐methylene‐6, 6‐dimethylbicyclo[3.1.1]heptane (β‐pinene) were synthesized and their 1H, 13C and 17O NMR spectra were measured, analysed and assigned. The 1H NMR spectral parameters were obtained by computer‐aided analyses of the very complex multi‐spin, second‐order spectra. Some of the 13C NMR chemical shift assignments of these compounds reported in the literature should be changed, based on these accurate 1H NMR spectral analyses and carbon‐proton chemical shift correlated spectra (COSY). The new assignments are supported by the 1J(C, H) values, which show a strong dependence on the bond angle and the steric strain of the ring system concerned.
13C NMR studies of α,ω‐bis(p‐anisyl)alkanes and α,ω‐bis(3‐iodo‐4‐methoxyphenyl)alkanes
Authors: Asleson Gary L. , Catlin Kelly K. , Heldrich Frederick J.
Published: May 2005

13C NMR studies were performed for a series of homologous iodinated and uniodinated α,ω‐bis(aryl)alkanes. Spectral assignments were made by utilization of DQCOSY, HETCOR‐LR and 1D coupled and decoupled 13C experiments.
Sesquiterpenes. 13C and 1H NMR chemical shifts of new thujopsane and nootkatane derivatives
Authors: Wolff Peter
Published: May 2005

The 13C and 1H NMR spectra of thujopsanone oxime, 7‐halo‐7‐nitrosothujopsanes, nootkat‐1‐one oxime and 1‐chloro‐1‐nitrosonootkatane are reported.
Structural studies in the bicyclo [3.1.1]heptane series by 1H and 13C NMR
Authors: Badjah‐Hadj‐Ahmed A. Y. , Meklati B. Y. , Waton H. , Pham Q. T.
Published: May 2005

The 1H and 13C NMR spectra of 22 pinane derivatives have been recorded and completely assigned. The spectral data for this set of compounds provide information about the conformation of these molecules and allow the deduction of the various structural effects observed in the bicyclo[3.1.1]heptane series.
Oxygen‐17 NMR study of electronic and steric effects in furan‐2,3‐dione derivatives
Authors: Hnach M. , Zineddine H. , Faure R. , Aycard J. P.
Published: May 2005

17O NMR was used to probe the steric and electronic substituent effects in furan‐2,3‐dione derivatives. The carbonyl 17O chemical shifts correlate with Hammett constants and IR carbonyl stretching band frequencies for 5‐(para‐substituted‐phenyl)furan‐2,3‐diones.
13C NMR spectra of linear trimers of buta‐1,3‐diene obtained from the Ziegler–Natta process
Authors: Lubnin A. V. , Podkorytov I. S. , Bresler L. S.
Published: May 2005

Titanium‐based Ziegler–Natta catalysts for the polymerization of buta‐1,3‐diene give linear trimers of butadiene among other by‐products. A combination of 1H and 13C NMR, DEPT and 2D‐INADEQUATE gives exhaustive assignments of their 13C NMR spectra and affords their structures. All these trimers are dodeca‐2,4,6,10‐tetraenes which have an isolated cis double bond. The internal double bond of the conjugated triad has a trans configuration in each isomer, and the trimers differ only in the outer double bonds. The 13C NMR spectra of the timers reveal that the signal position of the carbon involved in the conjugated double bond series is mainly controlled by the configuration of the adjacent double bond and, to a lesser extent, by the geometry of its own double bond. The oligomers studied serve as models for polyacetylene. Some reassignments in the spectra of oligomers of terminal acetylenes are proposed.
Carbon‐13 shielding tensors for metal acetates
Authors: Ali Ahmed A. M. , Harris Robin K.
Published: May 2005

Carbon‐13 shielding tensor data for eight metal acetates, obtained by analysis of spinning sideband manifolds of slowspinning CP/MAS spectra, are presented and discussed.
1H and 13C NMR spectroscopy of substituted bis‐1,3,4‐oxadiazoles
Authors: Tashtoush Hasan , Al‐Talib Mahmoud , Odeh Nedal
Published: May 2005

Dehydration of N,N′‐diacylalkanedioic acid dihydrazides with phosphoryl chloride gave 5,5′‐disubstituted‐2,2′‐(1,n‐alkanediyl)bis‐1,3,4‐oxadiazoles. The structures of these compounds were elucidated by 1H, 13C NMR, UV and IR spectroscopy.
ESR spin probe study of water within covalently crosslinked, dextran‐based microbead hydrogels (Sephadex® G)
Authors: Windle John J. , Scherrer Rene
Published: May 2005

Aqueous suspensions of dextran‐based Sephadex® G microbeads of progressively increasing degrees of covalent crosslinking and concomitantly decreasing water content formed a two‐phase system consisting of the waterswollen microbeads of diameter 100‐300 μm, the hydrogel phase, and of the surrounding water, the aqueous phase. These suspensions were analyzed by ESR spectroscopy using a series of small amphipathic nitroxide spin probes which partitioned between the two phases. Probe partition coefficients increased with decreasing gel water content for the more hydrophobic probes and decreased for the more hydrophilic probes. The ESR spectra of the suspensions consisted of the superposition of the spectra for the probes in the two phases. From the partition coefficients and the spectral parameters of the probes in the suspension and in the aqueous phase, relative rotational correlation times, τc, and isotropic nitrogen nuclear hyperfine splitting constants, aN, for the probes in the aqueous hydrogel interior were determined. For each probe, τc increased and aN decreased with increasing crosslinking and decreasing gel water content, indicating increasing microviscosity and decreasing dielectric constant and hydrophilicity for the gel water. The alterations in the gel water properties resulted from increasing gel matrix–water interactions and were further enhanced for water within the restricted volumes (compartments) in the most highly crosslinked hydrogels (Sephadex G‐15 and G‐10). In addition, the aN values indicated that two hydrogen bonds were formed to the nitroxide group of the probes in water and that, in the hydrogels, the hydrogen bonding contribution to aN progressively increased as the water content decreased.
The solute conformation of opioid ligands of the 4‐arylpiperidine class: α‐Promedol and related compounds
Authors: Casy Alan F. , Ogungbamila Francis O.
Published: May 2005

The NMR spectra (chiefly 1H) of isomeric 2,5‐ and 2,3‐dimethyl‐4‐phenyl‐4‐piperidinols, related esters and trans‐ 2,6‐dimethyl‐4‐propionyloxy‐4‐phenylpiperidine HCl (all N‐methylated) have been assigned and analysed in terms of solute conformation. Preferred forms include 4‐ax‐phenyl and 4‐eq‐phenyl chairs and, in the case of the γ‐2,3‐dimethyl‐4‐piperidinol base, a boat conformation. In several cases the existence of pairs of N‐protonated epimers has been demonstrated. The findings are important both to the conformational analysis of saturated six‐membered heterocycles and to stereoactivity analyses of opioid ligands of the 4‐arylpiperidine class.
Two‐dimensional NMR spectra of asbestinin diterpenes isolated from Briareum asbestinum (Pallas). Total stereochemical assignment by two‐dimensional NMR techniques
Authors: Rodriguez Abimael D.
Published: May 2005

The concerted application of two‐dimensional phase‐sensitive COSY, RELAY, ROESY and 13C‐1H shift correlation spectroscopy in the structural elucidation and stereochemical assignment of a new asbestinin diterpene, (Z‐11‐acetoxy‐4‐deoxyasbestinin‐(D), is reported. The results reveal that these two‐dimensional techniques are invaluable for the stereochemical assignment of proton resonances in the 4‐deoxyasbestinin series which overlap in 1H NMR and homonuclear correlation spectra.
Electron paramagnetic resonance, ENDOR and TRIPLE resonance study of some 9,10‐anthraquinone radicals in solution
Authors: Vuolle Mikko , Mäkelä Reijo
Published: May 2005

EPR, ENDOR and TRIPLE resonance spectra were recorded for 1,8‐dihydroxy‐3‐methyl‐9,10‐anthraquinone and 9,10‐anthraquinone‐2‐carboxylic acid anion radicals and the 9,10‐anthraquinol‐2‐carboxylic acid cation radical. EPR spectra were recorded for the 5,8‐dideuterio‐1,4‐dideuterioxy‐9,10‐anthraquinone anion radical, the 6,7‐dideuterio‐1,4‐dideuterioxy‐9,10‐anthraquinone anion radical and the 1,4‐dihydroxy‐9,10‐anthraquinol cation radical. The coupling contants of the 1,4‐dihydroxy‐9,10‐anthraquinone anion radical were assigned by deuteriation.
Structure of Manasse's dimer from endo‐2‐hydroxyepicamphor by NOE difference spectroscopy
Authors: Banks Malcolm R. , Gosney Ian , Grant Keith J. , Reed David , Hodgson Philip K. G.
Published: May 2005

Reduction of (1R)‐(+)‐camphorquinone by zinc in acetic acid yields a mixture of endo‐2‐hydroxyepicamphor and 3‐hydroxycamphor. The former undergoes reaction in anhydrous methanol with HCl gas to furnish a stable crystalline solid, first reported in 1902. High‐resolution electron impact mass spectrometry showed the solid to be a dimer of formula C22H36O4. The 13C{1H} spectrum showed 11 discrete environments, in keeping with a symmetrical dimer. High‐field 1H NOE difference experiments were used to determine not only the connectivity but also the stereochemistry of the system. All of the NOE experiments are consistent with only one structure, that of the symmetrical dimer. In addition, 2D carbon‐proton correlation experiments (HETCOR) were used to assign unambiguously its 13C{1H} spectrum.
NMR relaxation and ESR spin probe studies of some surfactant micelles
Authors: Bratt Peter J. , Gillies Duncan G. , Krebber Angelika M. L. , Sutcliffe Leslie H.
Published: May 2005

Multi‐frequency relaxation studies combined with the ‘two‐step’ and ‘three‐step’ models for molecular motion have been applied to a range of anionic surfactant molecules. From the internal dynamic parameters (τf and S) conclusions have been drawn about the dependence of surfactant molecular dynamics inside micelles on molecular structure, and two unusual conformations have been identified. Slow correlation time (τs) data have also been obtained for these compounds. Three deuteriated surfactant molecules were subjected to the ‘three‐step’ model and data are presented showing how the dimensions of the non‐spherical micelles vary with temperature. An ESR spin probe study has been carried out on the compounds giving probe rotational correlation times at various temperatures. Information on alkyl chain packing at or near the water/micelle interface can be obtained from the derived thermodynamic parameters.
Peptide group chemical shift computation
Authors: Herranz José , González Carlos , Rico Manuel , Nieto José L. , Santoro Jorge , Jiménez Maria A. , Bruix Marta , Neira José L. , Blanco Francisco J.
Published: May 2005

It has been found that protein NH protons on top of a peptide group plane experience large upfield conformation shifts. The joint analysis of this effect and other known effects of the peptide group on proton chemical shifts has led to a two‐term empirical expression for peptide group proton chemical shift computation as a function of protein backbone conformation. Both terms are expressed by McConnell's point‐dipole shielding expressions, one referred to an axis perpendicular to the peptide plane and origin in the coordinate centre of the OCN atoms and the other referred to an axis along the carbonyl bond and origin close to the oxygen atom. Values for the two constants have been determined by least‐squares fitting of the C‐α, H and amide NH chemical shifts of the protein ubiquitin. As a cross‐check on the validity of the expression, the C‐α, H and NH shifts of ribonuclease and BPTI (basic pancreatic trypsin inhibitor) have been computed. The general agreement between the observed and computed shifts and the correlation coefficients found (0.72 on average) indicate that the expression accounts for the main physical effects of the protein peptide group on the proton chemical shifts. It is shown that, together with ring current shifts, the expression explains the main characteristics of the C‐α, H and amide NH chemical shifts in proteins.
Proton NMR study on rhamnolipids produced by Pseudomonas aeruginosa
Authors: Choe Bo‐Young , Krishna N. Rama , Pritchard David G.
Published: May 2005

The extracellular rhamnolipids α‐L‐rhamnopyranosyl ‐ 3‐ hydroxydecanoyl ‐3‐ hydroxydecanoate and α‐L‐ rhamnopyranosyl‐(1 → 2)‐αL‐ rhamnopyranosyl ‐ 3 ‐ hydroxydecanoyl ‐ 3 ‐ hydroxydecanoate were isolated from the culture broth of Pseudomonas aeruginosa grown under growth‐limiting conditions. Proton NMR spectra of these rhamnolipids were characterized.
Substituent‐induced chemical shift 13C NMR study of substituted 2‐phenylthiazolidines
Authors: Umarani R.
Published: May 2005

The analysis of the 13C NMR chemical shifts of 16 substituted 2‐phenylthiazolidines shows that the 1,3‐thiazolid‐2‐yl group exerts a deshielding effect at the ipso carbon (C‐1′) and shielding effects at the ortho and para positions of the benzene ring (C‐2′ and C‐4′), and that the transmission of the resonance effect from the substituents in the phenyl ring to the benzylic carbon (C‐2) in the thiazolidine heterocycle is diminished by the polarizable nitrogen and sulphur atoms.
Signs of 19F1H and 19F13C spin–spin coupling constants mainly transmitted through space
Authors: Rae I. D. , Weigold J. A. , Contreras R. H. , Yamamoto G.
Published: May 2005

The details of two‐dimensional 13C1H correlated spectra have provided information about the relative signs of J(C, F) and J(F, H) for several molecules in which C, F and H are mutually coupled. Unlike signs are found for J(C, F) and J(F, H) when the coupling pathways lie approximately in the plane, but serious deviations from planarity can bring about changes in sign of J(F, H) and J(C, F).
Autoaggregation phenomena in quinine solutions
Authors: Uccello‐Barretta Gloria , Bari Lorenzo Di , Salvadori Piero
Published: May 2005

The coexistence of monomer and dimers of quinine was established in quinine solutions by investigating the temperature and concentration dependence of the NMR spectral parameters. Their conformations were determined by a combination of accurate 2D NOESY and proton‐selective relaxation rate measurements.
Proton NMR investigation of some substituted 1,3‐thiazolidin‐4‐ones
Authors: Woolston Christopher Richard Joseph , Lee John Barry , Swinbourne Frederick John , Thomas William Anthony
Published: May 2005

The 1H NMR spectra of a series of 2,3‐diaryl‐1,3‐thiazolidin‐4‐ones were measured and the ABX systems due to the heterocyclic ring protons were formally analysed. The chemical shifts and coupling constants were examined in relation to the structures concerned. The effects of S‐oxidation of these compounds on the spectral parameters were investigated. The 1H chemical shifts of 3‐benzyl‐2‐phenyl‐1,3‐thiazolidin‐4‐one and 3‐butyl‐2‐phenyl‐1,3‐thiazolidin‐4‐one suggested the presence of a preferred conformation about the NCH2 bond.
Use of 3J(13C,1H) in the stereochemical assignment of lactonic norbornene derivatives
Authors: Parella Teodor , Casas Ramon , Ortuño Rosa M.
Published: May 2005

The determination of 3J(13C,1H) for two sets of diastereoisomeric norbornene‐derived lactones was achieved by using fully coupled 13C spectra or the SINEPT‐2D method. The stereochemical elucidation of these compounds was performed by using long‐range carbo‐proton couplings, combined in some cases with NOE techniques and heteronuclear 2D correlations. Torsional angle dependence and the influence of γ‐substitution in the 13C‐α—C‐β—C‐gM‐1H fragment on 3J(13C,1H) values were verified in these cases.
Ab initio13C nuclear shielding calculations for some hydrocarbons using the GIAO procedure
Authors: Kurosu Hiromichi , Webb Graham A. , Ando Isao
Published: May 2005

The results of some ab initio GIAOCHF 13C shielding calculations for some hydrocarbons, performed with several basis sets, are reported and compared with experimental data. Optimized and experimental molecular geometries have been used in these calculations. The effect of the choice of basis set and geometric parameters on the calculated shieldings are discussed.
Thermo‐ and photochromic dyes: Spiro(indolinebenzopyrans). 2—detailed assignment of the 1H NMR spectra and structural aspects of the closed form of 1,3,3‐trimethylspiro(indoline‐2,2′‐benzopyrans)
Authors: Keum Sam‐Rok , Lee Ki‐Bong , Kazmaier Peter M. , Manderville Richard A. , Buncel Erwin
Published: May 2005

The proton NMR assignments for a series of 12 thermo‐ and photochromic 1,3,3‐trimethylspiro(indoline‐2,2′‐benzopyrans) dyes is reported. All of the protons in the dye molecule were assigned through a combination of homonuclear decoupling experiments and correlation spectroscopy. The relative stereochemistry of the indolino gem‐dimethyl groups was assigned so that, for the S‐epimer, the pro‐R methyl was found to resonate at 1.24 ppm while the pro‐S methyl appeared at 1.37 ppm for compound 1.
Carbon‐13 nuclear magnetic resonance relaxation study of chymotrypsin inhibitor 2 (CI‐2)
Authors: Leatherbarrow Robin J. , Matthews Stephen J.
Published: May 2005

Carbon‐13 T1 and NOE measurements were used to study the internal motions of the single phenylalanine residue in CI‐2 and in a mutant in which an arginine residue adjacent to the Phe had been replaced with an alanine residue. Each protein was specifically enriched with [13C6‐ring]phenylalanine. The arginine to alanine modification resulted in a reduction of the order parameter, S2, from 0.39 to 0.32 for the internal motions of the aromatic ring. This is consistent with the aromatic side‐chain of Phe 69 being less restricted, as a consequence of the removal of the neighbouring bulky side chain. Wild‐type CI‐2 was also successfully enriched with [2‐13C]glycine. An average order parameter of 0.60 was obtained for the α‐carbon positions of the three glycine residues. When bound to the serine protease chymotrypsin, S2 remains unchanged within experimental error. However, the overall tumbling, derived from NMR, slows by a factor of 5, consistent with the increase in molecular weight.
Simple estimation of the conformational homogeneity of 2,5‐disubstituted‐1,3‐dithianes by means of their 1H NMR spectra
Authors: Graczyk Piotr P. , Mikolajczyk Marian
Published: May 2005

A simple method for the correction of free energy differences, ΔG°exp, obtained via the equilibriation of 2‐substituted 5‐tert‐butyl‐1,3‐dithianes, is proposed on the basis of the 1H NMR data for diastereoisomers. It suggests, in contrast to the opinion of other workers, that these derivatives can be used in order to establish the preference of a substituent connected to the anomeric carbon atom. A simple procedure for the comparison of the amount of twist‐boat forms is also demonstrated.
NMR spectra of abieslactone and its 3‐ keto derivative
Authors: Tkachev Alexey V.
Published: May 2005

The carbon resonances of two naturally occurring triterpene compounds of the 9βH‐lanostane series (abieslactone and the corresponding 3‐keto derivative) have been unambiguously assigned. 2D heteronuclear chemical shift‐correlation NMR studies suggest that at least two conformations of the 3‐keto derivative are likely to be present in solution.
β‐NAD+ and its stack interaction
Authors: Zieger G. , Konrat R. , Sterk H.
Published: May 2005

Cross‐relaxation interactions between the nicotinamide moiety and the adenine moiety of NAD in D2O solution were unambiguously revealed by steady‐state NOE experiments, transient NOE experiments and synchronous nutation experiments. The experimental results, which allow a concise description in terms of auto‐relaxation and cross‐relaxation, are interpreted as the result of a stacking interaction. Studies of 13C relaxation and investigations on ternary mixtures with 6‐methylpurine give evidence for an inter‐ rather than intra‐molecular stack interaction, at least in the NMR concentration range.
Two‐dimensional NMR spectroscopy of glycosides
Authors: Krebs Hans C. , Habermehl Gerhard G.
Published: May 2005

Two‐dimensional NMR spectroscopy was used for the structure elucidation of glycosides. In particular, the connectivity between different sugar residues and between sugar and acid moieties is discussed.
Conformational analysis. Part 19—conformational analysis of 6‐deoxy‐6‐fluoro‐D‐glucose (6DFG) in solution
Authors: Abraham Raymond J. , Chambers Eric J. , Thomas W. Anthony
Published: May 2005

The conformation of D‐glucopyranose and 6‐deoxy‐6‐fluoro‐D‐glucose (6DFG) in solution, as determined by 1H and 19F NMR, is reviewed. The 1H NMR spectra of α‐ and β‐methyl D‐glucopyranosides and 6DFG in methanol, acetone, DMSO, and aqueous solution were acquired and fully analysed. A 19F NMR spectrum of the methanol 6DFG solution, together with a 1H COSY spectrum of α‐6DFG in methanol, were recorded. Accurate analyses of the ABC and ABCX spectra produced by the CHCH2OH and CHCH2F moieities, respectively, were performed, and from the vicinal J(H‐5,H‐6) coupling constants the populations of the three possible staggered rotamers about the C‐5C‐6 bond were calculated. The rotamer in which F is antiperiplanar to the ring O is particularly disfavoured, whereas the rotamer with F antiperiplanar to H‐5 is most favoured. This general trend was seen for both pyranose anomers in all four solvents.
A 13C T1 study of conformational and molecular mobility of mono‐ and difucosyllactoses
Authors: Ejchart Andrzej , Dabrowski Janusz
Published: May 2005

Overall and internal motions of lactose Galβ(1 → 4)Glcα and its three fucosylated derivatives Fucα(1 → 2)Galβ(1 → 4)Glcα, Galβ(1 → 4) [Fucα(1 → 3)] Glcα and Fucα(1 → 2)Galβ(1 → 4) [Fucα(1 → 3)] Glcα were investigated in Me2SO‐d6 using the spin–lattice relaxation times of 13C nuclei, T1(13C), measured at 8.5 and 11.7T. The relaxation data of the ring carbons in lactose and the lactosyl core of its derivatives were well described by the axially symmetric motion of the molecule. However, the interpretation of the T1(13C) of ring carbons in fucose residues required the assumption of a conformational mobility about the appropriate glycosidic bonds. For this purpose, a bistable, jump model of internal motion with a varying angle between the rotation axis and the symmetry axis of the overall tumbling was developed. The internal rotation of hydroxymethyl groups in Glc and Gal residues was also analysed quantitatively; the rotation in Glc was found to be slower than that in Gal. The internal rotation of methyl groups in fucoses undergoing a complex motion was interpreted semi‐quantitatively.
Structural analysis of oligosaccharide chains of glycolipids by two‐dimensional NMR
Authors: Inagaki Fuyuhiko
Published: May 2005

Coherence transfer methods, such as multiple‐relayed COSY and homonuclear Hartman–Hahn spectroscopy, were applied to extract subspectra of constituent monosaccharides, which allowed complete assignments of the proton resonances of oligosaccharide chains of glycolipids. The chemical structure of oligosaccharide chains of glycolipids could be determined by the combination of coherence transfer methods and NOESY experiments.
Characterization of dinitrobenzimidazoles using NOE difference and heterocorrelated NMR
Authors: Freyer Alan J. , Nissan Robin A. , Wilson William S.
Published: May 2005

Several 1‐(2′,4′,6′‐trinitrophenyl)dinitrobenzimidazoles (1‐picryldinitrobenzimidazoles) were synthesized as part of an ongoing study of heterocyclic nitro compounds as energetic materials and their structure–property relationships. The 1‐picryl‐4,6‐dinitrobenzimidazoles and their 1‐methyl analogs were examined by several NMR techniques in order to confirm their structures, and assignment strategies are discussed. Nuclear Overhauser enhancement (NOE) difference spectroscopy and 1H/13C correlation experiments were used to make definitive assignments of the 1H and 13C NMR spectra. It was found that both solvent and temperature had significant effects on the chemical shifts of the benzimidazole protons. This was especially true for the 1‐picryl derivatives.
NMR study of conformation and configuration in C‐20‐substituted 5β,14β‐pregnanes, 5β‐pregn‐14‐enes and 21‐nor‐5β,14β‐pregnanes
Authors: Marat Kirk , Templeton J. F. , Ling Yangzhi
Published: May 2005

Coupling constants and nuclear Overhauser effect measurements were used to establish the C‐20 configuration and the conformation about the C‐17C‐20 bond in a series of sixteen C‐20‐substituted 5β,14β‐pregn‐14‐enes. In the 14β‐pregnane series the conformation of the C‐17 side‐chain is variable, whereas in the pregnenes the side‐chain adopts a conformation in which H‐17 is anti to H‐20. The C‐17 side‐chain conformation of two 21‐nor‐5β,14β‐pregnanes was also determined. In the 21‐nor compounds a C‐20 hydroxyl adopts a conformation anti to H‐17, while a C‐20 nitro group is anti to C‐13.
Low‐temperature NMR of ε‐caprolactam
Authors: Borgen Gerd , Rise Frode
Published: May 2005

The conformation of ε‐caprolactam (1‐azacycloheptan‐2‐one) was studied by low‐temperature 2 D 1H and 13C NMR. Only one conformer was found in solution from the 13C NMR spectra recorded down to −155°C. This conformer was shown, by infrared spectroscopy, to be the same as that found in the crystals of ε‐caprolactam. A conformational process with a free energy of activation of 43 kJ mol−1, coalescence temperature −65°C, was interpreted as geminal 1H exchange. The assignments of the 13C and 1H shifts were made by 2 D NMR. Splitting of all averaged signals for geminal protons into axial and equatorial signals was demonstrated at −100°C.
1H NMR lanthanide‐induced shift investigation of highly flexible molecules—a new approach
Authors: Lehmann J. , Kleinpeter E.
Published: May 2005

A new method for lanthanide‐induced shift (LIS) calculations of highly flexible structures was developed using molecular geometries obtained from the random variation of dihedral angles (up to ten) which are rotating freely and independently of each other. The result of the new method (program JLLISMUL) is a data set containing the specified random dihedral angles and the corresponding agreement factor R (as a criterion for the fitting of the calculated and experimental LIS values). For comparison, the same random procedure was also used for parallel force field calculations using the molecular mechanics program PIMM. The results obtained by the new method are in very good agreement with known or reported preferred conformations of five highly flexible molecules which were used as examples for examining the new strategies of obtaining the preferred conformers. The minima of both the ‘LIS R factor hyper surface’ and the ‘energy hyper surface’ are rapidly accessible.
Three‐bond 13C1H coupling constants for chrysanthemic acid and phenothrin metabolites: Detection by two‐dimensional long‐range 13C1H J‐resolution spectroscopy
Authors: Ando Tetsu , Koseki Nozomu , Toia Robert F. , Casida John E.
Published: May 2005

Two‐dimensional long‐range 13C1H J‐resolution spectroscopy (LRCJR) was used to measure three‐bond 13C1H coupling constants [3J(C,H)] for trans‐ and cis‐chrysanthemic acid, methyl trans‐pyrethrate and some microsomal metabolites of the trans‐chrysanthemate biophenothrin. The carbon of the methyl cis‐disposed to an attached proton shows a larger 3J(C,H) value than does the trans‐carbon for the dimethyl‐substituted cyclopropane and epoxide rings. The reverse situation applies for the analogous dimethyl vinyl grouping. The 3J(C,H) values are not altered on conversion of one of the olefinic geminal methyl groups to a hydroxymethyl or methoxycarbonyl functionality, but increase on transformation to an aldehyde. These 3J(C,H) values are in agreement previous results from long‐range CH COSY experiments, and provide a useful method for determining the stereochemistry of chrysanthemic acid derivatives.
Magnetic field dependence of internal interactions in nuclear spin systems
Authors: Ding Shangwu , Ye Chaohui
Published: May 2005

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

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

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

Solasodine and diosgenin have been widely used as starting materials for the partial synthesis of cortisone, progresterone and C21 steroidal derivatives (oral contraceptives). This study involved the total 1H and 13C spectral assignments of these two important compounds by using two‐dimensional NMR techniques (COSY, CSCM and HMBC), and resulted in unambiguous spectral assignments, especially in the convoluted regions of the spectra (1H, 0.7–2.0 ppm; 13C, 28–35 ppm).