bluuebunny/crossref_metadata_2025 huggingface dataset:
1H and 13C NMR study of 2‐aminothiazole urinary tract carcinogens
Authors: Davidson R. M. , Rice J. R. , Lakshmi V. M. , Zenser T. V. , Davis B. B.
Published: May 2005

Using 1H and 13C NMR, 13C‐labelled modifications of 2‐amino‐4‐(5‐nitro‐2‐furyl)thiazole (ANFT) and its N‐formyl analogue N‐[4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl]formamide (FANFT), as well as the 5‐(S)‐substituted glutathione and N‐acetylcysteine conjugates of prostaglandin H synthase‐catalyzed peroxidative metabolism of ANFT were studied. 1H and 13C NMR chemical shifts, heteronuclear coupling constants, spin–lattice relaxation times (T1) and nuclear Overhauser enhancements (NOE) were obtained. Three‐bond coupling constants of the 13C‐labelled nucleus with the C‐5 protons of ANFT and FANFT were in close agreement but were absent in the conjugates owing to the 5‐substitution. Two‐bond coupling of the 13C‐labelled nucleus was observed with the amide proton of FANFT, but not with ANFT because of rapid exchange of the amine protons. Values of T1 were smaller in the conjugates than in FANFT or ANFT owing to their larger molecular weights. 1H spectra and NOEs provide further support for the prevalence of the 2‐aminothiazole tautomer over the 2‐iminothiazoline tautomer. Evidence is presented for a proton transfer of the C‐5 proton of ANFT, which proceeds over a time of the order of weeks in dimethyl sulphoxide and is autocatalytic. FANFT showed a different proton‐transfer reaction involving the amide proton, which occurs on a time scale of the order of days in dimethyl sulphoxide. The FANFT molecule revealed no evidence for transfer of its C‐5 proton, in contradistinction to ANFT. From a calculation of the percentage of the 13C relaxation due to the dipole–dipole mechanism, it can be concluded that for this class of sp2‐hybridized carbon (the C‐2 position of the 2‐aminothiazole system) a considerable portion of the relaxation is due to mechanisms other than dipolar.
Carbon‐13 chemical shift assignment of E‐stilbenyloxyalkanocarboxylic acids and their derivatives
Authors: Wyrzykiewicz Elżbieta , Grzesiak Jolanta , Prukała Wiesław
Published: May 2005

The 13C NMR spectra of 35 E‐stilbenols, E‐stilbenyloxyalkanocarboxylic acids and their esters and hydrazides have been calculated and fully assigned. The Ai empirical parameters of the p‐chlorostyryl, p‐bromostyryl, p‐alkoxycarbonylalkoxy, p‐carboxyalkoxy and p‐hydrazinecarbonylalkoxy groups have been calculated for use in the prediction of the chemical shifts of substituted benzenes and stilbenes.
Structure elucidation of an unexpected acylation product of dithranol: An application of improved heteronuclear two‐dimensional NOE spectroscopy
Authors: Bigler P. , Rychener M. , Séquin U.
Published: May 2005

Heteronuclear NOEs have proved to be a valuable tool for the structure elucidation of an unexpected acylation product of dithranol. The application of a modified 2D HOESY pulse sequence with improved sensitivity is demonstrated.
Diastereoisomers with three neighbouring phenyl groups. XI—Hindered phenyl and formylmethylamino group rotations in 3‐(formylmethylamino)‐1,2,3‐triphenylpropyl chlorides
Authors: Dimitrov V. S. , Kurteva V. B. , Lyapova M. J. , Mikhova B. P. , Pojarlieff I. G.
Published: May 2005

Unusually high free energies of activation for the rotation of phenyl groups, 12.1 and 11.1 kcal mol−1, are observed in the (1R*, 2S*, 3S*) and (1R*, 2R*, 3S*) isomers of 3‐(formylmethylamino)‐1,2,3‐triphenylpropyl chloride, and for the rotation of the formylmethylamino group (11.7 kcal mol−1) in the Z rotamer of the former isomer. These high barriers can be related to the interdependence of the rotation of such large planar groups in the strongly biased preferred conformations. The barriers for rotation of the formyl group are in the usual range (22.5 and 20.6 kcal mol−1) for (1R*, 2S*, 3S*) and (1R*, 2R*, 3S*) isomers, respectively.
Phosphorus—nitrogen compounds. Part 57—variable‐temperature phosphorus‐31 nuclear magnetic resonance spectroscopy of some phenyl‐substituted cyclotriphosphosphazatrienes
Authors: Deutsch W. Francis , Parkes Harold G. , Shaw Robert A.
Published: May 2005

The temperature dependence of the 31P NMR spectra of N3P3Cl6, phenyl‐substituted cyclotriphosphazatrienes, N3P3PhnCl6‐n (n = 2, 4, 6), and a series of derivaties, N3P3Ph2[X(CH2)n Y]Cl2 (where X = Y = O, NH, n = 2, 3, 4; X = Y = NMe, n = 2, 3; X = NH, Y = NMe, n = 3), of gem‐N3P3Ph2Cl4 was studied. Differential changes in chemical shift as a function of temperature were observed between different 31P nuclei. In a number of cases second‐order effects could be greatly reduced through a change in temperature. The temperature dependence of the 31P shift was found to differ with solvent, for example when CDCl3 replaced CD2Cl2.
ENDOR and triple resonance studies of 1,4‐dihydro‐1,2,4‐benzotriazinyl radicals and 1,4‐dihydro‐1,2,4‐benzotriazine radical cations
Authors: Neugebauer Franz A. , Rimmler Gösta
Published: May 2005

ESR, ENDOR and triple resonance studies of 1,4‐dihydro‐1,3‐diphenyl‐ (1a) and 3‐tert‐butyl‐1,4‐dihydro‐1‐phenyl‐1,2,4‐benzotriazinyl (2a) and of the corresponding radical cation 3a (2a protonated at N‐4) yielded the magnitude and the sign of almost all of the 1H and 14N hyperfine coupling (HFC) constants. Their assignment was performed using various 2H labelled and/or methyl substituted derivatives. Both radical groups show major hyperfine coupling to the three 14N nuclei. In the uncharged species 1a and 2a, the spin density at N‐4 apparently directs the 1H HFC pattern in the 1,2,4‐benzotriazinyl component, a(H‐5) and a(H‐7) being larger than a(H‐6) and a(H‐8). In the radical cation, on the other hand, N‐1, with an unusually large splitting of 9.9 G, is the position of highest spin density which determines the 1H HFC pattern, a(H‐6) and a(H‐8) being larger than a(H‐7).
Configurational assignment of β‐fluoro‐β‐phenylamines using 1H and 19F NMR
Authors: Hamman Sylvain , Benaïssa Tahar , Béguin Claude G.
Published: May 2005

The 1H and 19F NMR parameters [δH‐α, δH‐β, δF, 3J(HH) and 3J(FH)] of β‐fluoro‐β‐phenylamines of the two series PhCHFCH2NR1R2 and PhCHFCH(R)‐NR1R2 in CDCl3 (amine form) and in CD3OD (protonated amine form) and those of the corresponding β‐hydroxy‐β‐phenylamines were measured. It is shown that for the protonated amines the predominant conformation is that in which the ammonium group is antiperiplanar to the phenyl group, especially for tertiary amines. Assignment of the diastereoisomers of the PhCHFCHRNR1R2 series can be made with the NMR parameters of the protonated amines: high (low) 3J(HH) values, low (high) 3J(FH) values, 19F chemical shifts to high (low) frequency are those for the threo (erythro) isomers.
Complete structural assignment in a series of thieno[3,4‐b]quinoxalines by means of 2D NMR
Authors: Legendre Lucien , Mahuteau Jacqueline , Miocque Marcel , Vierfond Jean‐Michel
Published: May 2005

The structure of pyrrolo ([4,5‐b]‐1′,2′,3′,4′‐tetrahydroquinoxaline) [1,2,3‐Im]‐ 1 ‐ methyl ‐ 3 ‐ propyl ‐ 1, 3, 3a, 4, 9, 9a ‐ hexahydrothieno[3,4‐b]quinoxaline 2,2‐dioxide, isolated in the course of a study on a series of thieno[3,4,‐b]quinoxalines, was assigned on the basis of a spectral 1H‐13C correlated inverse chemical shift experiment.
ESR spectroscopy of the 4,5‐bis(methoxycarbonyl)‐1,3,2‐dithiazol‐2‐yl radical labelled with sulphur‐33 and nitrogen‐15
Authors: Preston Keith F. , Sandall John P. B. , Sutcliffe Leslie H.
Published: May 2005

A derivative of the 1,3,2‐dithiazol‐2‐yl radical was labelled with 33S in order to evaluate the p spin densities on the sulphur atoms. This information is required to provide a full description of the SOMO which, in turn, aids the understanding of the structure of the radical dimers. An unexpected result is that the two sulphur atoms are non‐equivalent in the solid state. Calculations suggest that this is due to out‐of‐plane twisting of the substituent groups. Comparison of the ESR parameters of the bis(methoxycarbonyl) derivative with other members of the 1,3,2‐dithiazol‐2‐yl group of radicals (including the parent radical) shows that it is a good model for the whole group.
Application of cyclodextrins to chiral analysis by 1H NMR spectroscopy
Authors: Casy A. F. , Mercer A. D.
Published: May 2005

The influence of inclusion complex formation between cyclodextrins (chiefly the β‐polymer) and a variety of chiral antihistaminic and analgesic agents on the 1H NMR features of both guest and host partners is reported. In many cases equivalent protons of antipodes give resonances which differ in chemical shift after inclusion, and the potential value of the data to chiral analysis and to elucidation of the structures of the inclusion complexes is demonstrated.
Two‐dimensional NMR spectroscopy of connected transitions by linear combination of flip angle dependent cosy: An alternative scheme for E.COSY
Authors: Chandrasekhar K. , Kumar Anil
Published: May 2005

An alternative pulse scheme which simplifies and improves the recently proposed P.E.COSY experiment is suggested for the retention of connected or unconnected transitions in a coupled spin system. An important feature of the proposed pulse scheme is the improved phase characteristics of the diagonal peaks. A comparison of various experiments designed for this purpose, namely COSY‐45, E.COSY, P.E.COSY and the present scheme (A.E.COSY), is also presented. The suppression of unconnected transitions and the measurement of scalar coupling constants and their relative signs are illustrated from A.E.COSY spectra of 2,3‐dibromopropionic acid and 2‐(2‐thienyl)pyridine.
Application of 1H/13C inversely correlated NMR spectroscopy to the determination of the stereochemistry of a polysubstituted [2.2]paracyclophane
Authors: Fischer Rüdiger E. , Dabrowski Janusz , Ejchart Andrzej , Staab Heinz A.
Published: May 2005

The relative orientation of substituents in the opposite rings of one of the isomeric 4,7‐Dichloro‐5,8,12,15‐tetramethoxy‐13,6‐bis[4‐(2‐methoxycarbonylphenyl) butyl][2.2]paracyclophanes was determined by establishing by NOE their orientation relative to the bridge protons, which thus served as ‘space‐spy nuclei’. The mutual orientation of these bridge protons was ascertained by the analysis of their coupling constants, obtained from a phasesensitive COSY spectrum. The 1H and 13C resonances were assigned with the aid of 1H COSY and 1H/13C inversely correlated spectra.
Improvement of 2D NMR spectra by matching symmetry‐related spectral features
Authors: Neidig K.‐P. , Kalbitzer H. R.
Published: May 2005

A novel algorithm based on a two‐dimensional feature match is presented which compares the local features of the region containing a data point with the characteristics of the symmetry‐related area. The proposed method results in a very effective suppression of artifacts and t1 noise ridges, equal to the quality obtained by conventional spectral symmetrization. It is superior to conventional techniques because peak shapes are less distorted, it does not create spurious peaks (at the crossing of ridges), does not remove real cross‐peaks when the symmetry‐related cross‐peak is very weak and retains some of the global spectral asymmetry as important information for computerized evaluation procedures.
Computer‐aided evaluation of two‐dimensional multiple‐quantum, carbon shift correlation
Authors: Egli Huldrych
Published: May 2005

A computer program for the automated interpretation and data evaluation of two‐dimensional multiple‐quantum, carbon shift correlations is presented. The program handles the assignment of CH, CH2 and CH3 groups and diastereotopic CHAHB groups. The correlated chemical shifts for carbons and protons are listed in the computergenerated output table, together with a value for the multiple‐quantum splittings and signal intensities. Examples are given which demonstrate that the program produces lists of correlated chemical shifts for carbons and protons, together with the group assignment for solutions of pure compounds and for more demanding cases. Emphasis is paid on possible misinterpretations, and ways to overcome the problem by user interaction are shown.
Radicals induced by illumination of a mixture of unsaturated fatty acids with ultraviolet light at 77 K
Authors: Melø Thor B. , Mahmoud Gharib S.
Published: May 2005

Electron paramagnetic resonance has been used to identify the radicals produced by photoirradiation of a mixture of polyunsaturated fatty acids in ethanol. One solvent and one solute radical were formed during irradiation under anaerobic conditions at 77 K. The radicals were formed in hydrogen transfer reactions belonging to Type I photosensitization processes, and were produced from the same photosensitizer. The yield of the solvent radical varied linearly with the mixing ratio of the fatty acids in ethanol whereas the solute radical, as expected, varied with the concentration of the solute to the second power. The solute radical decayed by secondary thermal reactions at 77 K into a third radical with no hyperfine interaction structure. When oxygen was present in the sample the superoxide radical or, possibly, a peroxy radical was also produced. At 77 K the effect of the antioxidant spermine was to increase the yield of radical formation by preventing the recombinations of solvated electrons with the ionized sensitizer. Spermine is hence acting as an electron scavenger in this system. These results indicated that photoirradiation will cause radical formation by hydrogen transfer reactions and hence contribute to initiation processes in the oxidation of polyunsaturated fatty acids, and that spermine is not operative as an antioxidant in the initiation phase of the total oxidation.
15N‐13C spin coupling as a probe of electronic structure in benzenediazonium ions: INDO—SOS—MO calculations and steric inhibition of resonance
Authors: Axenrod T. , Huang X. H. , Tufaro D. , Watnick C. , Webb G. A.
Published: May 2005

The magnitude of 1J(15N13C) in para‐substituted benzenediazonium ions has been used to assess the importance of the several resonance forms contributing to the ground state of the ion. From a comparison of values observed in 4‐nitro‐ and 4‐dimethylamino‐benzenediazonium ions and their respective 3,5‐dimethyl derivatives, it is concluded that diazo‐type structures are important only with strong electron‐releasing substituents in the aromatic ring. INDO–SOS–MO calculations indicate that the large and negative Fermi contact term dominates this interaction.
Determination of the stereochemistry of isoxazolidinium salts by nuclear Overhauser effect difference spectroscopy
Authors: Liguori A. , Ottanà R. , Romeo G. , Rotondo E. , Sindona G. , Uccella N.
Published: May 2005

The configurations of some isoxazolidinium salts have been determined by nuclear Overhauser effect difference spectroscopy (NOEDS). The stereochemical findings give a good explanation of the different reactivities experienced in the five‐membered ring‐opening process as a function of the steric requirement of the system.
Complete spectral assignments of cevadine and veratridine by 2D NMR techniques
Authors: Krishnamurthy V. V. , Casida John E.
Published: May 2005

The long‐range CH correlation NMR experiment (with decoupling of modulation of intensities due to one‐bond couplings during refocusing) and the double quantum coherence correlation spectroscopy (DQCOSY) experiment were used, together with the standard one‐bond CH correlation and COSY spectra, for complete 13C and 1H spectral peak assignments of veratrine (a 2:1 mixture of cevadine and veratridine). The long‐range CH correlation experiment determined the long‐range CH connectivity network, thus indirectly providing carbon–carbon connectivity. The DQCOSY experiment proved to be a complementary technique to the standard COSY experiment in unraveling and/or confirming proton–proton connectivities in this highly crowded proton spectrum.
Scalar 13C, 1H and 13C, 19F spin—spin couplings between carbonyl carbons and aromatic protons (or fluorine) in (η6‐arene)tricarbonylchromium complexes
Authors: Szeczeciński Przemyslaw , Gryff‐Keller Adam
Published: May 2005

Spin–spin coupling between carbonyl carbons and aromatic protons (or fluorine atoms) in several (η6‐arene)tricarbonylchromium complexes has been observed for the first time. The values of the coupling constants are of the order of 0.6 Hz for protons and 2 Hz for fluroine, and seem to depend on the electron‐donating properties of the aromatic substituent.
Computer predictions of 13C spectra. II—Alcohols and ketones
Authors: Bastard J. , Bernassau J. M. , Bertranne M. , Maia E. R.
Published: May 2005

A methodology is described which allows the rationalization of the 13C chemical shifts of a variety of compounds including alkanes, alcohols and ketones. The geometries of 250 rigid compounds were computed by the MM2 force field. Multiple linear regression analysis was used to model the 13C shifts from topological, geometric and energetic parameters. Among these parameters, the most important were those corresponding to interatomic distances, hybridization state of the quaternary carbons and energetic parameters. The final result is a rationalization of the 13C chemical shifts with an average RMS error of 1.25 ppm.
Determination of ligand lifetimes in the Ni(glycerol)+ complex by proton NMR spin—lattice relaxation time measurements
Authors: Larsson Tomas , Kowalewski Jozef
Published: May 2005

The activation enthalphy and entropy for ligand exchange in the weak complex Ni(glycerol +) were estimated by variable‐temperature proton spin–lattice relaxation time measurements at 9.4 and 6.3 T on a 0.044 molal solution of NiCl2 in glycerol. A description of the dynamic process in terms of a simple two‐site exchange model yields ΔH≠ = 18.4 ± 1 kJ mol−1 and ΔS≠ = −114 ± 3 J mol−1 K−1.
Conformational analysis. 15—Lanthanide‐induced shift investigation of 2‐exo‐norborneol using tailored models of lanthanide complexation
Authors: Abraham Raymond J. , Rowan A. E.
Published: May 2005

The complete assignment of the proton chemical shifts for 2‐exo‐norboreol was obtained from a COSY experiment at 250 MHz. Using these assignments the conformation of this molecule in solution was studied using the lanthanide‐induced shift technique, applying a new three‐site lanthanide complexation model (LIRAS4) reflecting the coordination geometry at the hydroxyl oxygen atom.

The substrate geometry which was found to give the best correlation between the calculated and observed shifts was not in agreement with the optimized geometry calculated using ab initio methods, the CCO angle being optimized as 108° in the former compared with 110.80° in the latter. The lanthanide complex geometry found indicated that one of the sites (trans to H‐2n) was occupied by the hydroxyl proton with the shift reagent bound to two other sites. This was supported by the increase in the vicinal J(HCOH) coupling observed on addition of the shift reagent. This LIRAS4 solution was then refined using a more complex model, HARDER, which treats each site as being independent of each other. The final two‐site solution obtained reflects the symmetry about the binding site in this molecule, and gave an excellent correlation between the observed and calculated shifts (Rx = 2.594, RR = 3.20 Å, PhiR = 105°, PsiR = 130°, RL = 3.00 Å, PhiL = 130°. PsiL = 130°).
High‐field aluminium‐27 nuclear magnetic resonance investigations of sodium aluminate solutions
Authors: Akitt J. W. , Gessner W. , Weinberger M.
Published: May 2005

The 27Al chemical shift, line widths and intensities have been measured for a series of sodium aluminate solutions with a range of sodium and aluminium concentrations. The aluminium is present entirely as the anion [Al(OH)4]− in all but the most concentrated solutions, where intensity is lost owing to the formation of species with very broad lines. The viscosities of the solutions were also measured and it was shown that these accounted to a great extent for the observed changes in line width, so that the unusually wide lines seen in the most concentrated solutions cannot be said to arise from dimeric species.
Identification of C‐glycopyranosides and C‐glycofuranosides by 13C NMR and 1H NMR. Complete assignment of their spectral data using carbon–proton chemical shift correlation spectroscopy
Authors: Wright Brian , Hughes Leslie R. , Qureshi Sheila S. , Davidson Alan H.
Published: May 2005

C‐Glycopyranosides and C‐glycofuranosides were identified using 13C and 1H chemical shift and coupling constant data. Full assignments for all α‐ and β‐anomers were made possible by recourse to carbon–proton chemical shift correlation spectroscopy. Greater steric shielding effects were observed on the carbon atoms in cis‐1,2‐substituted compounds compared with their trans counterparts. Consistent proton chemical shift differences were also noted in that the anomeric protons resonate at lower field in all cis‐1,2‐isomers.
Suppression of uninformative peaks in two‐dimensional relayed‐NOESY spectra
Authors: Cavanagh John , Titman Jeremy J. , Keeler James
Published: May 2005

Two‐dimensional relayed‐NOESY spectra are of utility in assigning connectivities in crowded spectra. A modified version of this pulse sequence is described which removes uniformative diagonal peaks and one other type of unwanted peak. The resulting spectra are less crowded and can be interpreted more easily.
The γ‐butyrolactone ring puckering
Authors: Galache M. P. , Garcés P. , Esteban A. L. , Diez E. , Guilleme J.
Published: May 2005

The 60 and 100 MHz 1H NMR spectra of γ‐butyrolactone were analysed in detail. The best set of coupling values (Hz ± 0.03) is 3J = 7.86, 3J = 6.27, 3J = 9.52, 3J = 6.86, 4J + 4J = −0.18, 2JA − 2JB = 3.89 and 2JB − 2JC = 4.86 (A, B and C refer to α, β and γ protons, with respect to the ring oxygen, and c and t mean the same and opposite side of the ring, respectively). The 3J values support the conclusion that the molecule is interconverting between two equivalent conformations of near envelope type with the β‐carbon out of the mean plane defined by the fragment COCOC.
Rotational dynamics of flexible‐chain molecules. 13C NMR relaxation study of hydrocarbon chains attached to a heavy anchor
Authors: Dais Photis
Published: May 2005

13C spin‐lattice relaxation times (T1) were measured for resolved carbons in flexible‐chain molecules consisting of a hydrocarbon chain attached to benzophenone at the para position. Effective correlation times, teff, were determined from T1 data and used to discuss the motional features of these molecules as a function of chain length, chain unsaturation and type of linkage by which the chain is attached to the benzophenone moiety. Of particular interest is the finding that the overall motion and chain mobility are greatly affected by the introduction of an unsaturated bond in the chain, depending on its configuration and location in the hydrocarbon tail.
1H NMR studies on alkyl‐substituted, 2,3‐ and 3,4‐annulated tetrahydro‐thiophenes
Authors: Kiesewetter Rene , Anklam Elke , Margaretha Paul
Published: May 2005

1H NMR chemical shifts and coupling constants allow the configurational and conformational analysis of both the (rigid) annulated and the (non‐rigid but conformationally homogeneous) alkyl‐substituted 2,3‐ and 3,4‐tetrahydrothiophenes.
Effects of misoptimization of the BIRD pulse on one‐bond modulation effects in long‐range heteronuclear chemical shift correlation spectra
Authors: Salazar Miguel , Soltero Luis R. , Zektzer Andrew S. , Martin Gary E.
Published: May 2005

BIRD pulses have been shown to provide an effective means of decoupling one‐bond modulation of long‐range response intensity. It is not possible to optimize the BIRD pulse effectively when there is a range of one‐bond coupling constants. To examine the effects of misoptimization of the fixed delays (τ) in the BIRD pulse, the simple alkaloid norharmane was employed. Long‐range heteronuclear correlation spectra were recorded using a modified pulse sequence containing a BIRD pulse midway through the Δ2 interval. The experiment was optimized for 10.3 and 11.1 Hz, which correspond to a valley and a peak in the response intensity curve when the experiment is performed without the BIRD pulse midway through Δ2. The delays in the BIRD pulse were variously optimized for values ranging from 80 to 175 Hz. The results suggest that the BIRD pulse is effective in decoupling one‐bond modulations of response intensity even when the τ delays are grossly misoptimized for the one‐bond coupling constantin question.
Identification of the b, d, and e analogs of vitamin B12 as monocarboxylic acids by 15N NMR spectroscopy
Authors: Difeo Thomas J. , Schiksnis Robert A. , Kohli Rakesh K. , Opella Stanley J. , Nath Amar
Published: May 2005

15N NMR spectra of b−, d−, and e‐cyanocobalamin (vitamin B12) and the products of their amidation with 15N‐labeled ammonia show that these analogs are monocarboxylic acids of vitamin B12 which result from hydrolysis at the respective propionamide groups.
13C NMR studies of 2‐ and 3‐methyl‐ and 2‐ and 3‐formyl‐indoles. Nitro and phenyl derivatives
Authors: Erra‐Balsells R. , Frasca A. R.
Published: May 2005

13C chemical shifts are reported for a series of nitro and phenyl derivatives of 2‐ and 3‐methylindoles and 2‐ and 3‐formylindoles, measured in DMSO‐d6. The 13C substituent chemical shift (SCS) data are discussed and compared with 1H SCS data.
1H and 13 NMR study of the structure of 3‐N‐(4‐ and 5‐benzimidazolyl or benztriazolyl)amino derivatives of prop‐2‐enoic acid in the liquid and solid states
Authors: Goljer Igor , Milata Viktor , Ilavský Dušan
Published: May 2005

Benzimidazole‐ and benzotriazole‐amino derivatives of prop‐2‐enoic acid were studied by 1H NMR spectroscopy in the liquid state and by 13C NMR spectroscopy in the liquid and solid states. The spectra shows tautomerism of the benzimidazole and benzotriazole rings, E‐Z isomerism of the double bond of the propenoic acid substituent and the conformation around the amino NHCH bond. The formation of an intramolecular hydrogen bond between the amino proton and the COOR group of propenoic acid is discussed. The structures of the derivatives are presented on the basis of the 13C CP‐MAS NMR spectra in the solid state.
Configuration and solvent‐dependent conformation of thiaprotoberberines
Authors: Sohár P. , Fodor L. , Szabó J. , Bernáth G.
Published: May 2005

The C‐13 configurations of several 13‐carboxy‐ and 13‐carbalkoxy‐thiaprotoberbanes were determined and evidence of the solvent dependence of their conformations was provided by 1H and 13C NMR and DNOE measurements.
The pyrethrins and related compounds 36—1H and 13C NMR spectra of cis‐ and trans‐aryl‐substituted cyclo‐pentanoid alcohols and of their pyrethroidal esters
Authors: Janes Norman F. , Khambay Bhupinder P. S.
Published: May 2005

The 1H and 13C NMR spectra of a range of 1‐, 2‐ and 3‐pheny1, ‐benzyl and ‐phenethyl substituted cyclopentanols and cyclopentylmethyl alcohols and related unsaturated compounds are reported, and assigned using heteronuclear shift correlations. Shift profiles for simple cis‐ and trans‐1,3‐disubstituted cyclopentanes are shown to apply also to those with bulkier substituents, and thence stereochemistries can be assigned to isomeric components in mixtures.
Electron paramagnetic resonance study of the complex formed between copper and 1‐[2(S)‐3‐mercapto‐2‐methylpropionyl]‐L‐proline (Captopril) in solid and aqueous solution
Authors: Evans Jeffrey C. , Morris Caroline R. , Rees Sian B. , Rowlands Christopher C. , Williams David R.
Published: May 2005

EPR spectroscopy was used to elucidate the nature of the interaction between copper and the antihypertensive agent 1‐[2(S)‐3‐mercapto‐2‐methylpropionyl]‐L‐proline (Captopril) in both solid and aqueous solutions. The EPR spectra indicate that binding to copper(II) occurs via the ligand oxygens rather than the thiol moieties, and that the EPR‐detectable copper is greatly reduced on complexation. The EPR parameters for the solid copper(II) complexes are in the range g∥ = 2.374−2.386, g⟂ = 2.076−2.086 and A = 13.5 mT, and the parameters for the aqueous solutions are giso = 2.107−2.129 and A = 7.1−8.6 mT.
13C NMR studies on the structure of aminosulfonic acids in dimethyl sulfoxide and water
Authors: Benoit Robert L. , Boulet Danielle , Fréchette Monique
Published: May 2005

The 13C NMR spectra of three aminosulfonic acids (HA) [p‐aminobenzenesulfonic acid (sulfanilic acid), amino‐methanesulfonic acid and 2‐aminoethanesulfonic acid (taurine)] and their anions (A−) and cations (H2A+) were obtained using aqueous H2SO4, fuming H2SO4 and Me2SO solutions of trifluoromethanesulfonic acid. The chemical shifts of HA, A− and H2A+ and the protonation and deprotonation shifts of HA are compared with corresponding data for related amines and sulfonic acids in Me2SO and water. Our results indicate that the three aminosulfonic acids are essentially zwitterionic in Me2SO.
2‐phenylisatogen: A study of molecular dynamics using 13C NMR spin‐lattice relaxation times
Authors: Stoddart Barry , Hooper Malcolm
Published: May 2005

13C NMR spin‐lattice relaxation times (T1) were measured for 2‐phenylisatogen in CDCl3 solution. The nonequivalence of the T1 values for the various protonated carbons in this molecule indicates that molecular motion is anisotropic. Analysis of the T1 data using the Woessner formalism for axially symmetric ellipsoids yields a set of diffusion coefficients for overall and internal motion. The phenyl ring undergoes internal motion relative to the larger isatogen ring system. A variable‐temperature study of T1 behaviour in the range 301−363 K indicates that the major motions of the molecule have identical activation energies, viz. 10.5 ± 0.5 kJ mol−1, and that the ratios of derived diffusion coefficients remain constant with temperature. These results suggest that solvent interactions play a major role in controlling the motions of the molecule.
Principal component analysis of the 13C NMR shifts of norbornyl derivatives
Authors: Tostes J. G. Ribeiro , Seidl P. R. , Bruns R. E.
Published: May 2005

Principal component analysis was applied to the 13C NMR chemical shifts of the seven carbon atoms of the norbornyl framework for 75 molecules. Two two‐dimensional principal component projections are shown to be sufficient to distinguish the main electronic and steric substituent effects contributing to these shifts. These effects allow a comparison of the (three‐, four‐ and five‐membered) ring and non‐ring substituents and their influence on the shifts of carbon atoms of the norbornyl framework. Four classes of molecules, each with characteristic chemical behaviour, are identified. Exo‐endo class discrimination and exo‐endo patterns of isomer pairs are emphasized, especially with regard to cyclic substituents on norbornyl systems.
13C chemical shift non‐equivalence in methylene carbons of monosubstituted cyclohexanes
Authors: Ito Hiroshi , Renaldo Alfred F. , Johnson Robert D. , Ueda Mitsuru
Published: May 2005

Monosubstituted cyclohexanes were synthesized by addition of a cyclohexyl radical to olefins bearing different substituents at the α‐position. Six distinct methylene 13C resonances were observed, indicating that the methylene carbons located at the 2 and 6 positions and at the 3 and 5 positions are not magnetically equivalent. This magnetic non‐equivalence (anisochronism) observed in the monosubstituted cyclohexanes is due to the introduction of an asymmetric center β to the prochiral C‐1 ring carbon.
Studies on systems of salts and mixed solvents 35—27 Al NMR investigations of AlCl3‐water‐N,N‐dimethylformamide solutions using the solid‐state MAS technique
Authors: Hallas E. , Emons H.‐H. , Siedler M. , Thomas B.
Published: May 2005

Conventional liquid‐state 27Al NMR spectra of concentrated solutions of the AlCl3‐water‐N,N‐dimethyl‐N‐Dimethylformamide formamide system contain comparatively broad non‐structured lines. Application of MAS leads to a reduction in the line width and a structuring of the spectra. This allowed the experimental determination of the chemical shifts of [Al(H2O)6−x(DMF)x]3+ (x = 0−6) mixed‐ligand complexes. The investigations demonstrate an example of the applicability to liquids of the NMR MAS technique, which was originally developed for solids. They underline the existence, in a reduced form, of ‘solid‐type’ interactions within the investigated solutions.
13C NMR studies of some tricyclo[3.2.1.02,4]octanes
Authors: Wilt James W. , Peeran Mehboob , Ramakrishnan Subramanian , Crumrine David S.
Published: May 2005

The 13C NMR chemical shifts for a series of exo‐ and endo‐3,3‐diphenyltricyclo[3.2.1.02,4]octanes are reported. Comparisons with the parent exo‐ and endo‐tricyclo[3.2.1.02,4]octanes and with bicyclo[2.2.1]heptanes show that most of the chemical shifts are additive. Substituent effect constants are presented for the tricyclo[3.2.1.02,4]octyl system. Pronounced deshielding effects are seen in the endo series for C‐6 and −7 of the alkene endo‐3,3‐diphenyltricyclo[3.2.1.02,4]oct‐6‐ene, the epoxide endo‐3,3‐diphenyltricyclo[3.2.1.02,4]octan‐6,7‐exo‐oxide, and the tetracyclic exo‐3,3‐diphenyltetracyclo[3.3.1.02,406,8]nonane. The chemical shifts of C‐3 and −8 are diagnostic for endo vs. exo substitution.
2D heteronuclear NOE spectroscopy with full ω1 decoupling. A method for elimination of 13C1H coupling dependence
Authors: Kövér Katalin E. , Batta Gy.
Published: May 2005

‘Constant‐time’ experiments are proposed for heteronuclear 2D NOE spectroscopy which provide full decoupling in the ω1 dimension. The heteronuclear coupling modulation of signal intensities is removed by a slight modification of the basic constant‐time experiments. This new sequence seems to be appropriate for routine applications.
Involvement of exciplexes in the photolysis of aliphatic ketones in deuteriochloroform: CIDNP evidence
Authors: Zhang Mao‐Xi , Liu Zhong‐Li , Wu Lung‐Min , Liu You‐Cheng
Published: May 2005

Photolysis of 4‐acetyl‐4‐ethoxyformylcyclohexanone and 4‐acetyl‐4‐phenylcyclohexanone in deuteriochloroform showed an unusual polarization which suggests that a singlet exciplex of the ketone with deuteriochloroform may be involved in the Norrish type I reaction.
Solid‐state NMR study of a series of aminophosphonic acids
Authors: Harris Robin K. , Merwin Lawrence H. , Hägele Gerhard
Published: May 2005

High‐resolution 31P, 15N and 13C NMR spectra have been obtained for nine solid aminophosphonic acids under conditions of high‐power decoupling, cross‐polarization and magic‐angle spinning. The NMR evidence shows that the asymmetric unit is a single molecule in all cases, which is consistent with the available diffraction studies. Phosphorus‐31 shielding tensor components determined from static and slow‐spinning MAS spectra are given for a number of the compounds.
Complete 1H and 13C NMR assignment of two α‐isosparteine salts by the use of two‐dimensional NMR spectroscopy
Authors: Simeonov Mario F. , Spassov Stefan L. , Duddeck Helmut , Majchrzak‐Kuczyńska Urszula , Skolik Jerzy
Published: May 2005

Two‐dimensional phase‐sensitive homo‐ and hetero‐nuclear shift correlation methods, in addition to homo‐ and hetero‐nuclear relayed coherence transfer, COLOC and NOESY experiments, were used to obtain a complete proton and 13C assignment of α‐isosparteine methiodide and α‐isosparteine methylene diiodide.
Lanthanide‐induced shifts in the 1H NMR spectra of N,N‐dimethylformamide and N, N‐dimethylacetamide: Limitations of the point methyl model
Authors: Ladd J. A.
Published: May 2005

The shifts induced in the 1H NMR spectra of N,N‐dimethylformamide and N,N‐dimethylacetamide by Pr(fod)3, have been measured by the reciprocal method and the results analysed using various models of the substrate molecules. Only those models which take full account of the stereochemistry of the methyl groups give a reasonable description of the induced shifts. It is also demonstrated that there is only one time‐averaged position of the lanthanide ion in the framework of the substrate molecule which adequately fits the experimental results.
Tellurium‐125 NMR investigations on coordination compounds of tellurium(II) with unsaturated dithio, thioseleno and diseleno ligands
Authors: Dietzsch Wolfgang , Olk Ruthmaria , Hoyer Eberhard , Meiler Wolfgang , Robien Wolfgang
Published: May 2005

125Te NMR spectra of tellurium(II) complexes containing dithiolene or other unsaturated 1,1‐dithio, 1,1‐thioseleno or 1,1‐diseleno ligands are reported. According to their chemical shift values, the complexes can be divided into three groups, well separated by several hundred ppm.
Quantitative analysis and determination of the enantiomeric purity of glycerides by 13C NMR spectroscopy. Application to the lipase‐catalysed transesterification of triacylglycerides
Authors: Rabiller Claude , Maze Françoise
Published: May 2005

13C NMR spectroscopy can be used for the quantitative analysis of mixtures of glycerides and the enantiomeric purity can be determined by using Eu(hfbe)3‐d reagent. This technique was applied to the study of the reaction mixture obtained from the transesterification of tributyrin catalysed by My‐lipase (Candida cylindracea). A ‘preference’ of this lipase for the pro‐R ester function of tributyrin is demonstrated.
Effect of methylation on the association ability of purine and pyrimidine in aqueous solutions. A 1H NMR chemical shift study
Authors: Aradi Ferenc , Földesi András
Published: May 2005

The self‐association of 6‐methylpurine and 4‐methylpyrimidine and their hetero‐association with caffeine and theophylline in deuterium oxide at 35°C were studied by measuring the concentration‐dependent changes in proton chemical shift. The association parameters were calculated using simple and competitive dimer models. The self‐association constants for 6‐methylpurine and 4‐methylpyrimidine were found to be 2.24 ± 0.07 and 0.200 ± 0.007 1 mol−1, respectively, and the hetero‐association constants could be ordered in the decreasing series caffeine‐6‐methylpurine (4.85 ± 0.12 1 mol−1) > theophylline‐6‐methylpurine (4.11 ± 0.15 1 mol−1) > caffeine‐4‐methylpyrimidine (1.45 ± 0.13 1 mol−1) > theophylline‐4‐methylpyrimidine (0.98 ± 0.10 1 mol−1). The equilibrium constants imply that methylation enhances the association ability and the upfield dimer shifts can be interpreted in terms of a stacking‐like interaction.
Linear and angular effects on the 1H and 13C NMR spectra of tricyclic aromatic ketones formally derived from tetralone
Authors: Buchanan G. W. , Tong P. T. , Wightman R. H. , Dawson B. A.
Published: May 2005

Complete unambiguous assignments of 1H and 13C chemical shifts for α‐tetralone, a related dihydroanthracenone and two related dihydrophenanthrones are presented. Data are based on results of 400 MHz 1H−1H and 1H−13C COSY experiments, and permit an evaluation of linear vs. angular endo and exo ketone orientation on the NMR parameters.
6Li J‐modulated 13C spin‐echo spectra. Selective observation of alkyllithium aggregates
Authors: Thomas Ruthanne D. , Ellington Donald H.
Published: May 2005

A 13C spin‐echo technique with gated 6Li decoupling has been developed for the selective observation of different alkyllithium aggregates, (RLi)n. The spectral editing technique is based on the fact that both the multiplicity of the 13C resonance and the magnitude of the observed 13C6Li coupling are a function of the number of coupled 6Li nuclei. The method was shown to differentiate between three types of tert‐butyllithium‐6Li: dimers, fluxional tetramers and non‐fluxional tetramers.
Assignment of phosphate groups and determination of P,H coupling constants in the DNA fragment d(CGTACG) by 31P 2D NMR experiments
Authors: Ragg Enzio , Mondell Rosanna , Garbesi Anna , Colonna Francesco P. , Battistini Carlo , Vioglio Sergio
Published: May 2005

2D 31P/1H correlation spectroscopy has been used to assign individual phosphates in the self‐complementary DNA fragment d(CGTACG), which is present in solution as a B‐DNA type double helix. 31P chemical shift variation with temperature and with the base sequence has been studied, and evidence is given of a steric clash between purines in the minor groove, affecting the chemical shift of the innermost TpA phosphate. For this hexanucleotide there is a good correlation of 31P shifts with both the helical twist (∑1) and roll angle (∑2) Calladine‐Dickerson sum functions. Different types of linear correlations, also including data from other nuclotides, have been performed. The results show that it is more appropriate to consider the change in chemical shifts as it occurs during melting rather than the actual 31P shifts. An interesting correlation was also found between 31P chemical shifts and P,H‐3′ coupling constants.
Partial editing in heteronuclear J‐resolved solid‐state NMR spectroscopy
Authors: Tekely P. , Brondeau J. , Retournard A. , Canet D.
Published: May 2005

A solid‐state analogue of the double echo sequence and gated decoupling used previously for the determination of carbon multiplicities in liquids is described; it was applied to the simplification and assignment of 13C CP‐MAS spectra in solids. This procedure permits partially edited 13C CP‐MAS subspectra to be obtained directly by means of distinct experiments performed under an identical length of the evolution period.
13C NMR of coumarins I: 3‐(1,1‐Dimethylallyl) derivatives
Authors: Macís F. A. , Massanet G. M. , Rodriguez‐Luis F. , Salvá J.
Published: May 2005

The 13C NMR data of nine 3‐(1,1‐dimethylallyl)coumarins are reported and compared with those of the corresponding C‐3 unsubstituted compounds. A spectro‐scopic criterion for distinguishing C‐3 alkylated dihydrofurano‐ from dihydro‐pyrano‐coumarins is proposed.
Reaction of dibenzalcyclohexanone with hydroxylamine hydrochloride. 2D NMR elucidation of the structure of the products
Authors: Dlaz Eduardo , Barrios Héctor , Ortiz Benjamin , Sánchez‐Obregón Rubén , Yuste Francisco , Reynolds W. F. , Aguilera Jose Luis , Caballero Efrén
Published: May 2005

The reaction of dibenzalcyclohexanone with hydroxylamine hydrochloride affords three compounds: the oxime of 2‐benzylidenecyclohexanone (2), 3‐phenyl‐7‐benzylidene‐3,3a,4,5,6,7‐hexahydro‐2,1‐benzisoxazole (3) and 3‐phenyl‐3,3a,4,5,6,7‐hexahydro‐2,1‐benzisoxazole‐7‐spiro‐2′‐(3′‐phenylaziridine) (4). Their structures were deduced by 2D NMR analysis. Single‐crystal x‐ray diffraction was used to confirm the structure and stereochemistry of 4. A possible mechanism for this reaction is proposed.
Full assignments of the 1H and 13C NMR spectra of the antibiotic kirromycin (mocimycin)
Authors: Barber Jill , Derome Andrew E. , Howard Tina D. , Lian Luyun , Tebb Graham
Published: May 2005

The 1H nuclear magnetic resonance spectra of kirromycin in acetone‐d6 and in buffered D2O have been assigned using a range of one‐ and two‐dimensional NMR techniques. The 13C NMR spectrum of kirromycin in acetone‐d6 has also been assigned, and compared with the 13C NMR spectrum of its N‐methyl analogue, aurodox.
13C and 1H NMR study of structure and structural dynamics of tautomeric 2‐ethoxycarbonylthiolane‐3‐thiones
Authors: Duus Fritz
Published: May 2005

2‐Ethoxycarbonylthiolane‐3‐thione (1) and its 5‐methyl, 5‐phenyl, 5,5‐dimethyl and 4,5‐dimethyl derivatives (2–5) were studied in solution by 13C and 1H NMR spectroscopy, using solvents of various polarity. Compounds 1–4 exist entirely in the tautomeric (Z)‐enethiol form, i.e. they are in fact 2‐ethoxycarbonyl‐3‐mercapto‐4,5‐dihydrothiophenes (1C‐4C), apparently irrespective of their molecular surroundings. Compound 5 exists predominantly as the pair of enantiomeric (and hence NMR‐indistinguishable) 2‐ethoxycarbonyl‐3‐mercapto‐4,5‐dimethyl‐4,5‐dihydrothiophenes having a trans location of their ring‐methyl groups, i.e. 5C(4R, 5R) and 5C(4S, 5S). The diastereomeric counterparts 5C(4R, 5S)/5C(4S, 5R) are observable as minor constituents, co‐existing with the former in a double two‐step equilibrium system, involving tautomeric 2‐ethoxycarbonyl‐3‐mercapto‐4,5‐dimethyl‐2,5‐dihydrothiophenes as intermediates.

The 13C chemical shifts of C‐4 and C‐5 of the unsubstituted and mono‐ and di‐methyl‐substituted 4,5‐dihydrothiophenes (1C, 2C, 4C, 5C) are describable in terms of additive methyl‐substituent shielding.

The observed solvent‐induced displacement of the mercapto proton chemical shift is interpreted in terms of the solvent's ability to effect pertubation of the intramolecular S—H ⃛O hydrogen bonding.

Vicinal couplings between ring protons at C‐4 and C‐5 are influenced by substitution at C‐4 and C‐5, and also by the nature (polarity) of the solvent used. The measured coupling constants have been rationalized in terms of the conformational mobility of the 4,5‐dihydrothiophene framework. A methyl group at C‐5 has little significance for conformational preference. A phenyl group at C‐5 preferentially occupies the near‐equatorial position. The conformational equilibrium of the trans‐4,5‐dimethyl‐4,5‐dihydrothiophenes 5C(4R, 5R)/5C(4S, 5S) apparently depends on the solvent's polarity, a more polar solvent favouring the conformer having near‐diaxial methyl groups.
Proton‐detected C,H correlation NMR techniques for the complete assignment of all proton and carbon resonances of a cyclic peptide
Authors: Hofmann Mechtild , Gehrke Matthias , Bermel Wolfgang , Kessler Horst
Published: May 2005

The assignment of the proton and carbon spectra of the cyclic peptide cyclo(‐Phe1‐Pro2‐Thr3‐Lys(Z)4‐Trp5‐Phe6‐) was accomplished by the application of multiple quantum proton‐detected heteronuclear correlation spectroscopy. Since the proton spectrum shows severe overlap, the carbon chemical shifts were used to disentangle the proton resonances. The methodology described is useful even in cases where only limited quantities of materials are available.

The combination of (i) a proton decoupled C,H correlation spectrum and (ii) a (not decoupled) H‐relayed C,H correlation gave the assignments of all CHn groups. The non‐protonated carbons, i.e. the carbonyl carbons of the peptide bond, were assigned with a C,H correlation optimized for long‐range couplings, an experiment that also gave helpful information about the conformational features of the hexapeptide.

The cyclic peptide contains a Phe‐Pro cis‐peptide bond forming a βVI‐like bend and a β‐turn about the amino acids Thr‐Lys‐Trp‐Phe. Although the conventional discussion of NMR parameters indicates a strong preference for one conformation, the quantitative evaluation of NOE‐derived distances in restrained MD calculations proves that the type of β‐turn in the last‐mentioned region is not unique. Whereas the MD calculations converge to a βII' turn, the vicinal proton coupling constants are in better agreement with type βI. Thus a dynamic equilibrium of the backbone is proposed.
EPR and ENDOR study of chiral nitroxides
Authors: Stegmann Hartmut B. , Schaber Frank‐Martin , Schuler Paul , Scheffler Klaus
Published: May 2005

Racemic and achiral alkyl aryl nitroxides were examined at various temperatures. The restricted rotation of the aminoxyl substituents was indicated both by the β‐proton coupling constants and by the inequivalence of the aromatic ortho protons. These results are interpreted by the presence of two different rotamers which may lead to two splitting constants for the β‐proton. The capability for inter‐ and intra‐molecular hydrogen bond formation in the nitroxides investigated was demonstrated. However, complexes consisting of chiral radicals and chiral auxiliaries do not show hyperfine structures which unambiguously indicate diastereomeric species. Therefore, hydrogen bonding between chiral molecules is not sufficient for chiral recognition if an alteration of the hyperconjugation angle does not occur. Simple steric interactions can result in the doubling of the β‐proton coupling constant, independently of diastereomeric complex formation.