bluuebunny/crossref_metadata_2025 huggingface dataset:
A molecular dynamics approach concerning the structures of 2‐hydroxy‐ and 2‐methoxy‐benzyl methyl ethers based on thenJ(CH2,H) long‐range spin–spin couplings
Authors: Laatikainen Reino , Tuppurainen Kari
Published: May 2005

A procedure for combining experimental NMR information and, for example, molecular mechanics is described. An iterative computer program and a strategy based on the approach are applied for the determination of the torsional behaviour of the CH2group in 2‐hydroxy‐ and 2‐methoxy‐benzyl methyl ethers. The analysis gives fairly well defined potentials of the torsion and angular density functions. The least‐squares model obtained for the5J(CH2,H) coupling is in accordance with previous observations. STO‐3G levelab initiocalculations for 2‐hydroxybenzyl methyl ether are reported and are in reasonable agreement with the dynamic model.
Stereochemical assignment of the two diastereomeric 4‐tert‐butyl‐7,11‐bisarylspiro[5.5]undecane‐1,9‐diones using two‐dimensional nuclear magnetic resonance spectroscopy
Authors: Rele Dinesh H. , Mathur Hari H. , Trivedi Girish K. , Chary K. V. R.
Published: May 2005

Phase‐transfer catalysed condensation between 4‐tert‐butylcyclohexanone and bis(benzal)acetone yielded two 4‐tert‐butyl‐7,11‐bisarylspiro[5.5]undecane‐1,9‐dione diastereomers. The stereochemical assignment of these molecules was carried out using two‐dimensional (2D) NMR spectroscopy. Combined use of COSY and NOESY spectra of these diastereomers helped in unambiguous and complete proton spin system assignment. In addition, from the application of 2D J‐resolved spectra together with the Karplus equation, the exact conformation of the molecules could be established.
Spin delocalization from paramagnetic metal complexes [Cr(acac)3 and Fe(acac)3] to saturated hydrocarbons in CHCl3 and CCl4 solutions
Authors: Kitaigorodskii Alexander N. , Stepanov Alexander G. , Nekipelov Vyatcheslav M.
Published: May 2005

Paramagnetic 13C NMR shifts induced by tris(acetylacetonato)chromium(III) [Cr(acac)3] and tris(acetylacetonato)iron(III) [Fe(acac)3] in various saturated hydrocarbons were determined for the first time using a special technique.

The observed shifts, Δδspec, are the result of partial delocalization of unpaired electrons from the paramagnetic complexes on the alkanes. The value of Δδspec depends strongly on the position of a carbon atom in the hydrocarbon molecule, and tends to decrease on passing from primary to quaternary carbon atoms. The observed spin transfer seems to reflect the ‘contact charge transfer.’ The Δδspec shifts in the unsaturated hex‐1‐ene only slightly exceed those in alkanes.
13C NMR and lanthanide‐induced shifts in epoxides of Terpenes and related compounds
Authors: Schneider Hans‐Jörg , Agrawal Pawan K.
Published: May 2005

Based on literature data, and new measurements with both simple and complicated skeletons, it is shown that epoxidation‐induced shifts (EIS) usually vary by only <4ppm if compared with the corresponding olefins, but by <9 ppm if compared with the saturated analogues. Shift differences between stereoisomers (E/Z or trans/cis) are consistent and, again, similar in epoxides and olefins. Larger variations are observed only for cyclic systems in which flexibility and conformational coupling can lead to significant conformational differences between the epoxide and olefin. Yb(fod)3‐induced LIS values are regular if normalized by setting the LIS for the α‐carbon atoms to 100%; these and the EIS values can be used to confirm or correct13C signal assignments.
Proton NMR data of some 1,3‐benzodithioles
Authors: Park K. L. , Stephenson D. S. , Gryff‐Keller A. M. , Szczeciński P.
Published: May 2005

The 1H NMR spectra of 1,3‐benzodithiole and eight derivatives have been analysed. Signals of the protons in positions 4 and 7 are shifted downfield compared with those for the protons in positions 5 and 6. The inter‐ring proton–proton couplings have been determined.
Conformation‐dependent 13C chemical shifts: A new means of conformational characterization as obtained by high‐resolution solid‐state 13C NMR
Authors: Saitô Hazime
Published: May 2005

A survey of recent high‐resolution solid‐state 13C NMR studies is given to illustrate how and to what extent 13C chemical shifts of a variety of molecular systems are displaced upon conformational changes. Examples are taken from studies of alkanes, polysaccharides, polypeptides, and naturally occurring and synthetic ionophores, in which more than single conformations are available owing to either crystalline polymorphs or a variety of metal‐ligand interactions. The magnitude of the conformation‐dependent 13C chemical shifts are in many instances as large as 8 ppm and are well related to a set of torsion angles of nearby single bonds. The application of this concept to conformational characterization is also discussed.
Silicon‐29 nuclear magnetic resonance studies of aqueous silicate solutions. 8 spin–lattice relaxation times and mechanisms
Authors: Knight Christopher T. G. , Harris Robin K.
Published: May 2005

The 29Si spin–lattice relaxation times, T1(29Si), of the various silicate anions present in high‐purity alkaline silicate solutions are reported. Regular silicate cages display the longest T1(29Si) values and, in the case of the cubic octameric cage, an unexpectedly large nuclear Overhauser enhancement, indicating that, unlike the smaller silicate oligomers, the cubic octamer relaxes primarily via the (29Si, 1H) dipole‐dipole interaction. This phenomenon provides, inter alia, a simple diagnostic test for such cages.
Two‐dimensional NMR of sesquiterpenic compounds. I—application to complete assignment of 1H and 13C spectra of α‐longipinene
Authors: Faure R. , Vincent E. J. , Gaydou E. M. , Rakotonirainy O.
Published: May 2005

Total assignment of the 13C nuclear magnetic resonance spectrum of α‐longipinene was achieved from DEPT and double quantum coherence measurements, while concerted application of 1H1H homonuclear and 1H13C heteronuclear two‐dimensional chemical shift correlations provided all proton chemical shifts.
Conformational study of pyridiniumacetanilide salts by 1H NMR spectroscopy
Authors: Kovács Zsuzsanna H. , Sohår Pál
Published: May 2005

The temperature dependence of the 1H NMR spectra of some new pyridiniumacetanilide salts was investigated. In these compounds, hindered rotation around the amide NCO bond gives rise to two rotamers with unequal populations. The values of the free energy of activation (ΔG≠) were determined by the coalescence method. Correlation was observed between the values of ΔG≠, the equilibrium rotamer populations and the character of the substituent attached to the amide nitrogen. In some derivatives another conformational motion was detected, and interpreted in terms of slow rotation around the NCaryl bond.
Deuterium isotope effects on oxygen‐17 chemical shifts
Authors: Aime Silvio , Santucci Enrica , Fruttero Roberta
Published: May 2005

Large deuterium isotope effects on 17O resonances were observed for six common NMR solvents. Only in the case of acetone did the substitution of deuterium for hydrogen result in a downfield shift. The H/D isotope effect was also detected in a study of the reversible hydration of CH3CHO.
High‐field1H and13C NMR spectroscopy of some corticosteroids and related compounds
Authors: Duddeck Helmut , Rosenbaum Doris , Hani M. , Elgamal A. , Fayez Mohamed B. E.
Published: May 2005

The 400.13 MHz1H and 100.6 MHz13C NMR spectra of 12 corticosteroids and related compounds were investigated and the signals assigned by two‐dimensional techniques. The effects of substituents, carbonyl groups and epoxide formation on the chemical shifts of both nuclei are discussed in terms of intramolecular interaction and stereochemical dependence.
Application of partially relaxed 2D‐COSY spectra in spectral assignments of carbohydrates
Authors: Saunders John K. , Stevens John D.
Published: May 2005

A simple procedure to simplify the 2D‐COSY spectra of molecules in which significant T1 variations occur is described. The procedure was applied to distinguish between the methine and methylene protons of the reducing sugar L‐idose.
Lanthanide porphyrin complexes: Investigation by means of NMR spectroscopy and mathematical simulation
Authors: Babushkina T. A. , Koreneva L. G. , Zolin V. F.
Published: May 2005

The structure of a lanthanide porphyrin complex was reinvestigated using a new treatment for the paramagnetic NMR shifts. It was found to differ from that obtained previously in that the ion was closer to the macrocyclic ligand. The new treatment is based on ab initio estimation of the coefficients describing the anisotropy of magnetic susceptibility, proportional to the pseudo‐contact shifts. These coefficients were estimated using an electrostatic model of the complex; the ‘extra’ ligand (β‐diketonate) was taken into account and shown to be essential. The NMR spectrum of a non‐axial complex under conditions of restricted rotation of the ‘extra’ ligand is described.
The observed and calculated oxygen‐17 quadrupolar coupling constant in nitrous oxide
Authors: Wasylishen Roderick E. , de P. Nicholas A. Martin
Published: May 2005

Nitrogen‐14 and oxygen‐17 NMR spin‐lattice relaxation measurements on nitrous oxide yield a 17O nuclear quadrupolar coupling constant of 12.4 ± 1.2 MHz. This result compares well with the value of 12.7 MHz obtained by scaling the value calculated using ab initio molecular orbital theory at the 6–31G* level.
Synthesis and EPR and ENDOR investigations of Coppinger's radical with perdeuteriated tert‐butyl groups
Authors: von Gersdorff J. , Kirste B. , Kurreck H.
Published: May 2005

The synthesis of Coppinger's radical (galvinoxyl) with perdeuteriated tert‐butyl groups is described. Its EPR spectrum exhibits markedly decreased line widths (0.015 mT) compared with the unlabelled radical (0.039 mT). The correspondingly higher resolution allows a complete analysis of the 13C hyperfine coupling constants. A comparison of the EPR and ENDOR spectra of unlabelled and of two selectively deuteriated Coppinger's radicals is given.
13C NMR spectra of polyalkoxymethanes, and their sulphur‐ and nitrogen‐containing analogues, of an aliphatic series. Inclusion of non‐bonded interactions by the use of CO bond increments
Authors: Dostovalova V. I. , Zlotsky S. S. , Rakhmankulov D. L. , Terent'ev A. B.
Published: May 2005

13C NMR spectra of 40 substituted acetals, carbonates, ortho ethers, 1,3‐dioxocycloalkanes, 1,3‐oxothiolanes and 1,3‐oxazolidines were studied. The chemical shift of the C‐α carbon atom was found to depend both on the number (K) and type of the hetero substituents at C‐α. The effect of oxygen, nitrogen and sulphur atoms on the C‐α chemical shift was shown to be a non‐additive property relative to the unsubstituted isostructural hydrocarbons. The C‐α chemical shift in the linear and cyclic polyalkoxymethanes can be described by an equation incorporating CO bond increments and contributions from the RO substituents:

The CO increment depends quadratically on the number (K–1) of geminal neighbours of the oxygen atom under study. Good agreement between the experimental and calculated shifts can only be achieved by inclusion of nonbonded interactions between the geminal heteroatoms.
Investigation of molecular motions in a derivative of bisphenol‐A diglycidyl ether by variable‐temperature high‐resolution solid‐state carbon‐13 NMR
Authors: Everatt Brian , Harris Robin K. , Kenwright Alan M. , Packer Kenneth J. , Stark B. Peter
Published: May 2005

Variable‐temperature solid‐state 13C NMR measurements show effects due to molecular motion in spectra of 2,2‐bis[p‐(2,3‐dihydroxypropoxy)phenyl]propane (BADGETOL), which is a derivative of bisphenol‐A diglycidyl ether. Features in the spectra indicate that the motions present may not be characterized by a simple exponentially decaying autocorrelation function (single correlation‐time process), and a study of the coalescence of doublets due to reorientation between non‐equivalent sites strongly suggests that the motions are more properly characterized by a spatially inhomogeneous distribution of single correlation‐time processes.
Assignments of the1H and13C NMR spectra of 1,4‐diazaphenanthrene (benzo[f]quinoxaline) derivatives
Authors: Defay N. , Nasielski‐Hinkens R. , Nasielski J.
Published: May 2005

The1H and13C NMR spectra of 1,4‐diazaphenanthrene (benzolfquinoxaline) (1) and some of its derivatives have been fully assigned and most of the coupling constants have been measured. The compounds examined bear a piperidino or methoxy group at the 2‐ or 3‐position, or a chlorine atom at the 2‐, 3‐ or 9‐position. The spectra of theN‐1‐oxides of 1 and of 1,4,5,8‐tetraazaphenanthrene are also given. The syntheses are described.
Proton and carbon‐13 NMR studies of 2‐aminothiazoles and 2‐iminothiazolines
Authors: Tseng C. K.
Published: May 2005

Proton and 13C NMR chemical shifts and coupling constants of 2‐aminothiazoles and 2‐iminothiazolines are reported. The one‐bond CH, vicinal H‐H, geminal CH and vicinal CH coupling constants of 2‐aminothiazoles and 2‐iminothiazolines are discussed in terms of tautomerism between amino forms and imino forms. The site of charge centered either on the ring nitrogen or the exocyclic nitrogen atom in the protonated 2‐aminothiazole is also discussed.
103Rh NMR studies of cyclometallated Rh(III) Schiff's base complexes
Authors: Arz C. , Pregosin P. S. , Anklin C.
Published: May 2005

103Rh, 31P and 1H NMR data are reported for the cyclometallated Rh(III) complexes of the type RhH(Y)()L2, where Y can be either an anionic or neutral ligand, is a carbon—nitrogen bidentate ligand arising from cyclometallation at the imine carbon of the Schiff's bases derived from 2‐amino‐3‐methylpyridine and substituted benzaldehydes and L can be either PPh3, AsPh3 or SbPh3. There is only a modest dependent of δ (103Rh) on the nature of the benzaldehyde, a substantial change as a function of L and the most significant sensitivity, >800 ppm, as a function of Y. It is suggested that 103Rh NMR spectroscopy may be useful in the study of linkage isomers of SCN−.
An alternative to the 2D INADEQUATE experiment for detecting scalar coupling correlations between protonated and unprotonated carbons
Authors: Lee Kenneth S. , Morris Gareth A.
Published: May 2005

The two‐dimensional INEPT‐INADEQUATE experiment gives correlation peaks for unprotonated carbons which show only half of the total available signal, because the enhanced 13C signal generated by polarization transfer is shared equally between protonated and unprotonated coupling partners by the double quantum filtration step. If precautions are taken to attenuate unwanted signals from protonated carbons, then the double quantum filtration step may be dispensed with, leaving a hydrogen‐carbon‐carbon relay sequence. This gives unidirectional coherence transfer, ensuring that the maximum possible signal is concentrated in a single cross‐peak identifying the correlation between protonated and unprotonated carbons. By extending the basic HCC relay sequence to include an evolution period an enhanced 13C‐13C COSY 2D spectrum may be produced, with the further advantage over the 2D INADEQUATE experiment that the range of 13C‐13C coupling constants detectable is limited only by the available resolution.
Carbon‐13 NMR chemical shifts of representative nitriles and nitro compounds
Authors: Bailey William F. , Cioffi Eugene A.
Published: May 2005

The 13C NMR chemical shifts of nitriles and nitro compounds derived from nineteen aliphatic and seven aromatic systems have been recorded and assigned. The shifts are compared with those of the hydrocarbons to give the substituent effects of the CN and NO2 groups.
NMR structure of partially oriented tellurophene: Correction of molecular deformations and determination of bond interaction parameters
Authors: Diehl P. , Kellerhals M. , Lounila J. , Wasser R. , Hiltunen Y. , Jokisaari J. , Väänänen T.
Published: May 2005

Solvent effects on the NMR geometry of tellurophene due to correlation between vibration and rotation have been determined and corrected in various liquid crystals, resulting in a unique solvent‐independent structure. Simultaneously, the bond interaction parameters, which describe the torques acting on the bonds of the molecule in the anisotropic liquid crystal potential (giving rise to deformations and to the molecular orientation), have been measured. A linear relationship has been detected between the CH bond interaction parameters for tellurophene and for methane in the same solvents.
Non‐ionic X‐ray contrast agents: Detection of ambient temperature isomers of congested hexasubstituted benzenes with multipositional hindered rotations
Authors: Bradamante Silvia , Vittadini Giorgio
Published: May 2005

Serinol amides of triiodoisophthalic acid bearing an acylamino group are non‐ionic x‐ray contrast agents; in addition to the expected isomerism due to hindered rotations around the amide NCO bonds, the atropoisomerism associated with the hindered rotations around the aryl–CO and aryl–N bonds was investigated by 1H and 13C NMR.

The assignment of signal multiplicity to the different rotamers in solution for a series of N, N′‐bis[2‐hydroxy‐1‐(hydroxymethyl)ethyl]‐2,4,6‐triiodoisophthaldiamides, 5‐substituted with (hydroxyacetyl)amino (5), S‐(–)‐ (2‐hydroxy‐1‐oxopropyl)amino (6), (hydroxyacetyl)methylamino (7), and S‐(‐)‐(2‐hydroxy‐1‐oxopropyl)‐methylamino (8) groups was approached by interpreting simpler systems such as S‐(–)‐3‐N‐[2‐hydroxy‐1‐ (hydroxymethyl)ethyl]‐5‐[(2‐hydroxy‐1‐oxopropyl)amino]‐2,4,6‐triiodoissophthalmic acid (2) and its corresponding amide 3, or more symmetric molecules such as N,N′‐bis[2‐hydroxy‐1‐(hydroxymethyl)ethyl]‐5‐amino‐2,4,6‐triiodoisopht haldiamide (4).

It is shown that it is possible to discriminate between the contributions of the different types of hindered rotations in order to obtain the appropriate, although approximate, free energies of activation. Secondary aryl carboxamides 5‐8 constitute a rare case of aryl–CO hindered rotation detectable at room temperature. Analysis of the NMR data clearly indicates that in 5‐8 the population ratio of the syn and anti families is 1: 1 and also that of the E and Z conformers. In addition, the secondary anilides 5 and 6 show fast rotation around the aryl–N bond and exhibit a conformational preference for the endo isomer only. The tertiary anilides 7 and 8, instead, present the coexistence of the endo and exo forms whose ratio is dependent on the solvent.
Oxygen‐17 NMR spectral studies of selected aromatic sulfones
Authors: Kelly Jeffery W. , Evans Slayton A.
Published: May 2005

Oxygen‐17 NMR spectra of several organosulfur compounds containing the arylsulfonyl group (ArSO2–) are reported. Shielding effects are interpreted in terms of γ‐ortho CH interactions with the sulfonyl oxygens rather than conjugative interactions involving the aryl substituent and the attached SO2 group. The lanthanide shift reagent Eu(fod)3 is useful for discriminating ‘internal and external’ accidental chemical shift coincidence.
13C NMR spectroscopy of phorbol esters
Authors: Pieters Luc A. C. , Vlietinck Arnold J.
Published: May 2005

The 13C NMR spectral data of fourteen phorbol derivatives, which are commercially available or which were extracted from the seed oil of Croton tiglium L. (Euphorbiaceae), and of six common acyl substituents of naturally occurring phorbol esters were recorded and the signals assigned. The spectral data for this series of model compounds appeared to be important tools for the identification and the structure elucidation of naturally occurring and semi‐synthetic diterpene esters related to phorbol.
Dimethoxy aromatic compounds. IV.—determination of stereochemistry of 2,3,6,7‐tetraalkoxy‐9,10‐dihalomethyl‐9,10‐dihydroanthracenes by 13C NMR chemical shifts
Authors: Lamartina Liliana , Ceraulo Leopoldo , Natoli Maria C.
Published: May 2005

The analysis of the 13C NMR spectra of several 2,3,6,7‐tetraalkoxy‐9,10‐dihalomethyl‐9,10‐dihydroanthracenes showed a strong dependence of the chemical shift values on the orientation of the halomethyl groups. On this basis it was possible to determine both the configuration (cis or trans) and conformation of the isomers, even if only one isomer was available.
Stereochemical studies of 3‐aryl‐3‐methylpiperidines of potential opioid ligand activities by high‐resolution 1H and 13C NMR spectroscopy
Authors: Casy A. F. , Iorio M. A. , Madani A. E.
Published: May 2005

The 1H (270, 400 MHz) and 13C (22.5, 67.5 MHz) NMR spectra of a series of 2,3‐3,5‐ and 3,6‐dimethyl‐3‐(m‐hydroxy‐m‐methoxy‐phenyl)piperidines of proven or potential opioid ligand activity are reported. The data were analysed in terms of configuration and preferred conformation, and some key deductions were confirmed by NOED and 2D COSY experiments. In the 3,5‐dimethyl derivatives, isomers with preferred axial or equatorial 3‐aryl substituents were identified.
Carbon‐13 chemical shift assignment of alkoxycarbonylalkylthiouracils and 3‐oxothiazolo[3,2‐a(or ‐c)]pyrimidin‐5‐ones
Authors: Wyrzykiewicz ElżBieta , Wybieralska Jadwiga
Published: May 2005

The 13C NMR spectra of sixteen isomeric 2‐and 4‐alkoxycarbonylalkylthiouracils, eightnew 2,4‐dialkoxycarbonylalkylthiouracils and eight isomeric 3‐oxothiazolo[3,2‐a]‐and 3‐oxothiazolo[3,2‐c]‐pyrimidin‐5‐ones have been calculated and fullyassigned. The AiK empirical parameters of the 2‐thio, 4‐thio, 6‐methy1, 2‐alkoxycarbonylalkylthio, 4‐alkoxycarbonylalkylthio, P‐alkoxycar‐bonylalkyl, 4‐alkoxycarbonylalkyl, N‐3‐carbonylalkylthio‐2‐, N‐3‐carbonylalkylthio‐4, N‐3‐carbonylalkyl‐2‐thio and N‐3‐carbonylalkyl‐4‐thio groups were calculated for the predictions of the chemical shifts of substituted uracils.
NMR study of the lithium salts of aniline derivatives
Authors: Ide Shoichi , Iwasawa Kazuhisa , Yoshino Akihiro , Yoshida Tadayoshi , Takahashi Kensuke
Published: May 2005

1H, 7Li, 13C, and 15N NMR spectra were observed for lithium salts of aniline derivatives in THF solutions. The delocalization of excees charge into the phenyl ring of the salts was confirmed from the 1H and 13C chemical shift data in comparison with those of the neutral molecules. Their 15N atoms were approximately 40 ppm less shielded comparison with those of the neutral molecules, and these are discussed in terms of hybridization change and electron densities at the nitrogen atoms. The one‐bond 15N‐1H coupling constants of the salts are approximately 55 Hz and are smaller than those of the neutral molecules.
Restricted rotations about exocyclic partial double bonds. The electronic state of heteroaromatic six‐membered rings
Authors: Kleinpeter E. , Spitzner R. , Schroth W.
Published: May 2005

Temperature‐dependent13C and1H NMR spectra of three series of six‐membered heteroaromatic systems with NR2substituents attached to pyrylium/thiopyrylium salts and pyrones/thiopyrones have been recorded. The rotational barriers thus determined about the exocyclic partial double bonds are discussed in terms of dominating mesomeric structures, in order to describe the electronic state and the spatial conditions in the molecular framework. Cyanine and merocyanine substructures have been identified by NMR and express the electronic state predominantly present in the compounds.
Compounds with bridgehead nitrogen 52—NMR spectra and stereochemistry of the 2‐alkylperhydroimidazolo[3,4‐a]pyridines
Authors: Banting Lee , Crabb Trevor A.
Published: May 2005

In contrast to perhydro‐oxazolo[3,4‐a]pyridine and perhydrothiazolo[3,4‐a]pyridine, which adopt equilibria in CDCl3 solution at room temperature containing ca 70% trans‐fused conformers in equilibria with O‐ or S‐inside cis‐fused conformers, 2‐alkylperhydroimidazolo[3,4‐a]pyridines are found to adopt equilibria containing >98% trans‐fused conformers. Comparison of NMR parameters of 2‐methylperhydroimidazolo[3,4‐a]pyridine with those of the two isomers of 1,2‐dimethylperhydroimidazolo[3,4‐a]pyridine indicates an equilibrium for the former compound between the two trans‐fused conformers, with ca 83% of that conformation containing a trans arrangement of nitrogen lone pairs of electrons. These observations are explained in terms of the generalized anomeric effect.
Medium effects on nitrogen nuclear shielding in methyl nitrate and methyl isothiocyanate assessed by the solvaton model
Authors: Witanowski M. , Sitkowski J. , Biernat S. , Sudha L. V. , Webb G. A.
Published: May 2005

14N nuclear shielding data are reported for methyl nitrate and methyl isothiocyanate in a variety of solvents covering a wide range of polarizabilities and hydrogen bonding properties. The non‐specific solute‐solvent effects on the nitrogen shielding are accounted for by means of INDO/S‐SOS shielding calculations incorporating the solvaton model. Specific hydrogen bonding effects on the nitrogen shielding are estimated from a four‐parameter equation which reflects both solvent properties and the corresponding solute responses.
Carbon‐13 NMR spectral studies on chalcones and acetophenones
Authors: Patra Amarendra , Ghosh Gargi , Sengupta Pradip K. , Nath Swadhin
Published: May 2005

Carbon‐13 signal assignments of eighteen polyoxygenated chalcones and thirteen polysubstituted acetophenones are reported.
Analyses of the 500 MHz 1H spectra of the 3‐Methyl ethers of estrone, estradiol and their 14α‐methyl analogues
Authors: Bischofberger Karl , Bull James R. , Chalmers Anthony A.
Published: May 2005

The 500 MHz 1H spectra of the 3‐methyl ethers of estrone, estradiol and their 14α‐methyl analogues were assigned by proton decoupling and analysed by second‐order calculations for chemical shifts and coupling constants. Introduction of a 14α‐Me group effects consistent deshielding of 1,3 diaxially disposed protons. Coupling constant values show characteristic changes for ring D protons, and suggest that some minor perturbation in the H‐9α, ‐11α, ‐11β region is caused by the additional methyl group.
Quantitative proton magnetic resonance of plasma from uraemic patients during dialysis
Authors: Grasdalen Hans , Belton Peter S. , Pryor Jack S. , Rich Gillian T.
Published: May 2005

Proton nuclear magnetic resonance (1H NMR) has been used to measure rapidly concentrations of metabolites in plasma from patients with chronic renal failure (CRF) and normal subjects. Detailed quantitative analyses of spectra are presented for four CRF patients during haemodialysis, two patients in early stages of renal failure and two normal subjects. For patients on acetate dialysis, the method clearly shows how well exogenous acetate is metabolized during and after dialysis. Our results indicate a discrepancy between creatinine concentrations measured by 1H NMR and by the kinetic Jaffé reaction method, and also point to high betaine concentrations in plasma from some patients on maintenance haemodialysis and taking folate supplement.
Substituent and ring size dependence of the coupling constant
Authors: Collins M. J. , Hatton P. M. , Sternhell S. , Tansey C. W.
Published: May 2005

The magnitude of the 4J proton‐proton coupling constant across the fragment CH3CCH (a probe of the bond order between the central sp2‐sp2 hybridized carbon atoms) has been found to be essentially independent of substitution on a toluene fragment and on the size of the ring containing the ortho‐allylic fragment. The coupling constant is sensitive to direct substitution on the ortho‐allylic fragment, especially where the substituent is placed α to the methyl group.
13C NMR spectra of some 2′‐nitromethane‐and N‐(methylsulphonyl)‐2′‐nitromethane‐sulphonanilides
Authors: Hasan Misbah Uul , Badar Yasmeen , Qureshi Ikram
Published: May 2005

The 13C chemical shifts in several 2′‐nitromethanesulphonanilides and N‐(methylsulphonyl) ‐ 2′ ‐ nitromethanesulphonanilides are reported. Analysis of the 13C shifts provides an insight into the electronic and steric interactions in these compounds. A comparison of the 2′‐nitromethanesulphonanilides with the corresponding anilines reveals that substitution of a methylsulphonyl group causes an upfield shift of 10–13 pprn for C‐1 while the ortho carbons, C‐2 and C‐6, are deshielded by 4‐6 and 1‐3 ppm, respectively. The unequal shielding of the two ortho carbons is noteworthy. Substitution of a second methylsulphonyl group on nitrogen causes similar changes in the chemical shifts but their magnitude is different. In several compounds the effect of para substituents is not equal at the two ortho or meta carbons.
Conformational correlation of purine nucleosides by high‐field carbon‐13 NMR data
Authors: Nair Vasu , Young David A.
Published: May 2005

Correlation of the nucleic acid base conformation in 43 purine nucleosides with high‐field 13C NMR data is described. A key to the correlation is the chemical shift difference between C‐2′ and C‐3′.
The complete, unambiguous assignment of the 13C NMR spectrum of erythromycin A*
Authors: Ager David J. , Sood Cynthia K.
Published: May 2005

The 13C NMR spectrum of erythromycin A (1) has been unambiguously assigned by use of the 2D INADEQUATE technique in conjunction with DEPT. Previously reported assignments were found to be in error. The effect of solvent, which semms to be negligible on the conformation, was also investigated.
1H, 13C, 15N, 17O and 77Se NMR of selenenamides
Authors: Paulmier Claude , Lerouge Patrice , Outurquin Francis , Chapelle Stella , Granger Pierre
Published: May 2005

Numerous areneselenenamides derived from ammonia, primary and secondary amines and two N,N‐bis(arylseleno)alkylamines have been studied. The selenenamides bearing an electron‐withdrawing substituent on the aromatic moiety are stable. The 1H, 13C and 77Se chemical shifts and some coupling constants are reported.

For N.N‐dialkyl‐o‐nitrobenzeneselenenamides, the 77Se NMR and the 17O NMR give evidence of an Se‐O interaction. In N‐alkyl derivatives, a hydrogen bond between the amine group and the ortho‐substituent is proposed to explain the deshielding of the selenium nucleus.
13C NMR spectral data of some N‐vanillyl‐, N‐piperonyl‐ and N‐veratryl‐alkylaminoalkylamides
Authors: Baldessari Alicia , Gros Eduardo G.
Published: May 2005

13C NMR spectra for 66 N‐vanillyl‐and‐piperonyl‐ and N‐veratryl‐chloralkyl‐and‐alkylaminoalkyl‐amides are reported. Relative substituent effects are discussed.
Experimental methodology for high‐resolution solid‐state NMR of heavy‐metal spin‐1½ nuclei
Authors: Harris Robin K. , Sebald Angelika
Published: May 2005

The choice of standard compounds for setting up CP MAS NMR experiments on the nuclei 77Se, 119Sn, 195Pt, 199Hg and 207Pb in organometallic compounds is discussed. Spectra of suitable compounds are presented, together with the relevant optimum acquisition parameters (contact times, recycle delays).
Conformational dependence of 17O chemical shifts in 1,3‐dioxa‐2‐silacyclooctanes: Anomeric effect
Authors: Kupče Ē. , Liepiņš E. , Zicmane I. , Lukevics E.
Published: May 2005

17O NMR spectra of 1,3‐dioxa‐2‐silacyclooctanes have been studied. The 17O NMR signal of derivatives existing in the crown conformation is shifted downfield by 7–10 ppm relative to derivatives existing predominantly in conformations belonging to the boat–chair family. This shift is assumed to be due to the anomeric effect in 1,3‐dioxa‐2‐silacyclooctanes.
17O NMR studies on substituted N‐arylacetamides and aryl acetates: Torsion angle and electronic effects
Authors: Boykin David W. , Deadwyler Gina H. , Baumstark A. L.
Published: May 2005

17O NMR spectroscopic data at natural abundance in acetonitrile at 75°C were obtained for sixteen N‐arylacetamides, three N‐methyl‐N‐arylacetamides and seven aryl acetates. The 17O chemical shifts of the N‐arylacetamides are significantly influenced by both electronic and steric factors. A Hammett plot of the data for 4‐substituted N‐arylacetamides gives a slope of 22 ppm. Ortho substituents result in significant shielding effects, in contrast to previously reported results for conjugated ketnoes. A quantitative relationship between 17O chemical shift data and torsion angle was found for the sterically hindered arylacetamides. Electronic effects on the aryl acetate 17O chemical shifts are, in comparison, greatly reduced. Steric factors for aryl acetates show even smaller effects on the 17O chemical shifts.
Elimination of direct responses and one‐bond modulations in long‐range heteronuclear chemical shift correlation spectra through the use of low‐pass J filters and BIRD pulses
Authors: Salazar Miguel , Zektzer Andrew S. , Martin Gary E.
Published: May 2005

Modified long‐range heteronuclear chemical shift correlation pulse sequences which incorporate both BIRD pulses midway through the Δ2 magnetization transfer delay and low‐pass J filters are described. The BIRD pulse provides the means of decoupling one‐bond modulations of response intensity when magnetization is transferred to protonated carbons. The one‐ and three‐step low‐pass J filters utilized eliminate responses due to directly attached protons over a range of one‐bond coupling constants.

Results obtained by long‐range optimization of the conventional heteronuclear chemical shift correlation pulse sequence, the previously reported pulse sequence containing only the BIRD pulse midway through Δ2 and the two new pulse sequences described in this work are compared using 2,3‐dihydrofuran as a model compound.

The low‐pass J filters have no adverse effects on the ability of the BIRD pulse to decouple one‐bond modulations. Modulation decoupling in the modified pulse sequences was confirmed using the 3J(C‐3, H‐1) coupling pathway of the simple alkaloid norharmane. The response intensities, however, were up to 10% lower with a one‐step low‐pass J filter when compared with the simpler pulse sequence containing only the BIRD pulse midway through Δ2.
Two‐dimensional NMR analysis of himachalol and its correlation with other sesquiterpenoids of the himachalane series
Authors: Prakash Om , Roy Raja , Kulshreshtha D. K.
Published: May 2005

High‐field 1H NMR studies of himachalol (1) have been carried out by two‐dimensional NMR methods. The stereochemical aspects of this molecule were studied through the application of stereospecific coupling constants, the nuclear Overhauser effect and lanthanide‐induced chemical shifts. Complete and unambiguous 13C chemical shift assignments of 1 have been made for the first time by using two‐dimensional heteronuclear (1H13C) correlation NMR spectroscopy, DEPT, broad‐band proton decoupling and selective heteronuclear spin decoupling 13C NMR methods. Complete 13C chemical shift assignments of isocentdarol, centdarol and centdarone have also been made using some of the above techniques and their stereostructures have been corrected.
Utility of 13C NMR spectroscopy in monitoring the course of a complex reaction sequence: Reaction of pyrrole with formaldehyde
Authors: Katritzky Alan R. , Law Kam Wah
Published: May 2005

The complex course of the reaction of pyrrole with formaldehyde has been completely elucidated by quantitative 13C NMR spectroscopy using the inverse‐gated decoupling technique. The final product is 2,5‐bis(hydroxymethyl)pyrrole (with a free 1‐position), but three main intermediates containing 1‐hydroxymethyl groups were identified, and the rise and subsequent fall of their populations followed. The intermediacy of additional compounds (formals) also renders the reaction more complex. The molar fractions of four hydroxy‐methylpyrroles present in the reaction mixtures were calculated from the 13C NMR data and plotted against time. At 45 and 65°C pyrrole reacted completely with formaldehyde in 1 h and in less than 30 min, respectively. This work illustrates the utility of the 13C NMR investigation of an industrially important reaction.
13C and 1H NMR studies of structure and tautomerism in some perimidines
Authors: Woodgate P. D. , Herbert J. M. , Denny W. A.
Published: May 2005

The 13C NMR spectra of some 1‐ and 2‐substituted perimidines and perimidinium salts are discussed and assigned. Although the spectra of most of the 2‐substituted perimidines are comparatively simple, several examples display 13C and 1H spectral characteristics indicative of inhibition of prototropic tautomerism.
1H bridging and terminal hydride T1 values. Comments on classical vs non‐classical hydride identification using T1 criteria
Authors: Ammann C. , Isaia F. , Pregosin P. S.
Published: May 2005

Hydride 1H T1 values are reported for a selected series of ruthenium, iridium and platinum complexes. These T1 values range from 6.9 to 0.05 s with the shortest value, 0.05 s, assigned to a complex containing both hydride and coordinated molecular hydrogen, i.e. “M(H2)”. There are nuclear Overhauser enhancements arising both from protons on coordinated ligands and other hydride ligands. It is suggested that the molecular weight of the complex and the measurement conditions can be important factors for T1.
High‐power 13C and 1H nuclear magnetic resonance in dry gluten
Authors: Belton P. S. , Duce S. L. , Colquhoun I. J. , Tatham A. S.
Published: May 2005

High‐resolution, solid‐state 13C NMR spectra of wheat gluten obtained under a variety of acquisition conditions are reported. These spectra are compared with the results from a 1H relaxation study of dry gluten in which the transverse relaxation times, the spin–lattice relaxation times in the rotating frame and the spin–lattice relaxation times in the laboratory frame at three different Larmor frequencies are characterized. It is concluded that 13C experiments, the proton transverse relaxation measurements and the rotating frame results distinguish between protein and lipid motional environments, whilst the laboratory frame proton spin–lattice relaxation results detect two separate protein environments. The relationship between the laboratory frame spin–lattice relaxation time constants and Larmor frequency is consistent with a model of macromolecular motion in which the polymer chains are held between cross‐link points. Observed changes in the various proton relaxation times on removal of lipid or disruption of disulphide cross‐links are interpreted in terms of the frequency and anisotropy of molecular motions in the gluten system.
13—Lanthanide‐induced shift (LIS) investigation of the conformation of aryl sulphones using a novel lanthanide–sulphone complexation model
Authors: Abraham Raymond J. , Haworth Ian S.
Published: May 2005

The conformation of diphenyl sulphone and 3,4′‐dichlorodiphenyl sulphone has been studied by the lanthanide‐induced shift (LIS) technique. The lanthanide–sulphone complexation model was established using the conformationally rigid dibenzothiophene sulphone molecule. Several models were tried, including both monodentate and bidentate coordination of oxygen to lanthanide. Poor results were obtained for the bidentate models, but three different monodentate models (one‐, two‐ and three‐site) all gave reasonable solutions. The binding position in the three‐site model was established using the program LIRAS4, an adaptation of LIRAS3, with an LnO geometry having R and ϕ values of 2.8 Å and 150° being suggested. Site populations were 16%, 42% and 42% in sites 1, 2 and 3, respectively.

Diphenyl sulphone has insufficient data (ΔM values) for a complete analysis, but the more extensive data set for 3,4′‐dichlorodiphenyl sulphone allowed a full analysis which indicated a preferred twist angle of the phenyl rings (θ) of 90°, using all the monodentate models. However, the three‐site model produced significantly lower errors in the predicted shifts and also suggested an identical lanthanide position to that found for dibenzothiophene sulphone. Site populations were 0%, 50% and 50% in sites 1, 2 and 3, respectively, the zero occupancy of site 1 being rationalized in terms of steric interactions with the H‐1 protons. Preferential binding of the shift reagent to the SO bond trans to the meta‐chlorine atom (65%) was observed.
Long‐range protoncarbon‐13 coupling constants of monosaccharides by selective heteronuclear 2D‐J NMR spectroscopy
Authors: Morat Claude , Taravel François R. , Vignon Michel R.
Published: May 2005

Long‐range J(CH) values were measured for six glycoside derivatives by a selective 2D‐J heteronuclear sequence. The values obtained are discussed in terms of conformational effects and constitute a valuable contribution to 2J and 3J comprehension.
Assignment of the NMR spectra of benzo[b]triphenyleno[1,2‐d]thiophene through the application of zero quantum proton—proton correlation combined with proton‐detected long‐range multiple quantum heteronuclear chemical shift correlation
Authors: Zektzer Andrew S. , Sims L. D. , Castle Raymond N. , Martin Gary E.
Published: May 2005

Assignment of the congested proton and carbon NMR spectra of heterocyclic benzo[b]triphenyleno[1,2‐d]thiophene was accomplished through the concerted application of several two‐dimensional NMR experiments. The inherent insensitivity of homonuclear zero quantum coherence to magnetic field inhomogeneity was used to advantage in disentangling the heavily overlapped proton NMR spectrum. Direct heteronuclear pairings were established using heteronuclear correlation with broad band homonuclear vicinal proton decoupling. Limited sample availability and solubility precluded complete establishment of long‐range heteronuclear correlations by conventional means. Proton‐detected long‐range heteronuclear multiple quantum coherence did, however, provide sufficient long‐range heteronuclear correlations to complete the assignment.

A comparison of the data obtained from COSY and zero quantum experiments is presented; the ability of each to establish proton connectivities is discussed. Sensitivity limitations inherent in the conventional long‐range optimized heteronuclear chemical shift correlation experiment are contrasted with the advantages of the proton‐detected long‐range heteronuclear multiple quantum correlation experiment. Practical limitations of the latter are considered.
Long‐range CH correlation 2D NMR spectroscopy 2—effect of TANGO and BIRD pulses
Authors: Krishnamurthy V. V. , Casida John E.
Published: May 2005

The basic CH correlation sequence, with the delays lengthened to facilitate long‐range correlations, was modified by using TANGO and BIRD pulses (both basic and composite) to facilitate both the suppression of one‐bond cross‐peaks and the decoupling of long‐range cross‐peak intensity modulations due to one‐bond coupling. The relative effectiveness of these modifications is illustrated with nicotinamide as a model compound. The use of a combination of the basic TANGO pulse and the basic BIRD pulse achieves both of these aims. The composite TANGO pulse can replace the basic TANGO pulse when more effective suppression of one‐bond cross‐peaks is needed. The use of the composite BIRD pulse during refocusing increases F1 noise and artifacts and is therefore not recommended.
Stereochemistry of crown ethers. I. Conformational and dynamic behaviour of N‐tosyl‐substituted diaza crown ethers
Authors: Kleinpeter E. , Gäbler M. , Schroth W.
Published: May 2005

The variable‐temperature 1H and 13C NMR spectra of some N‐tosyl diaza crown ethers have been obtained. They are discussed with respect to the preferred conformers of the crowns and the free energies of activation of the interconversional process of the large ring. Both the preferred conformers and the ring interconversional barriers have been found to be strongly dependent on the structure and the ring size of the studied compounds.
13C Nuclear magnetic resonance spectroscopy of 4‐methylcoumarins (4‐methyl‐2H‐1‐benzopyran‐2‐ones)
Authors: Parmar V. S. , Singh S. , Boll P. M.
Published: May 2005

The 13C NMR spectra of 36 differently substituted 4‐methylcoumarins (4‐methyl‐2H‐1‐benzopyran‐2‐ones) have been recorded. The effects of an alkyl side‐chain at C‐3 on the chemical shift values and that of a methoxy or an acetoxy group in place of a hydroxy group have been observed and rationalized. This study may be helpful in the structure elucidation of new and natural 4‐methylcoumarins.
13C NMR spectra of some trichothecene mycotoxins and derivatives
Authors: Avent Anthony G. , Grove John Frederick , Hanson James R.
Published: May 2005

A general strategy, using well established techniques, is outlined for the assignment of signals in the 13C NMR spectra of the trichothecene mycotoxins and some related rearrangement products. Heteronuclear NOE difference spectra were employed to assign resonances from quaternary carbons. An example of the use of spin–echo J modulation is given.
Pseudohalogen chemistry. VIII—Substituent constants (Z) for the thiocyanato group in the estimation of the chemical shifts of vinyl protons in α,β‐unsaturated thiocyanates
Authors: Guy Robert G.
Published: May 2005

Substituent constants for the thiocyanato group (Z = 0.94, Z = 0.45 and Z= 0.41) have been derived by an additivity procedure, and shown to reproduce the chemical shifts of vinyl protons in a wide variety of α,β‐unsaturated thiocyanates with an accuracy of ±0.30 ppm in 94% of the cases studied. Deviations due to tBu and COR groups are discussed in terms of steric and field effects.
Assignment of proton and carbon NMR signals of didemnin A in solution
Authors: Kessler H. , Will M. , Sheldrick G. M. , Antel J.
Published: May 2005

Several one‐ and two‐dimensional techniques have been used to assign the 1H and 13C NMR spectra of the cyclic heptadepsipeptide didemnin A in DMSO. The composition and sequence of the amino acid residues was known beforehand and could be confirmed by heteronuclear proton–carbon long‐range couplings using the COLOC experiment and a recently proposed new inverse technique using Gaussian‐shaped pulses. The aliphatic methyl resonances of the isostatin, hydroxyisovalerylpropionyl, N‐methylleucine and leucine residues were assigned by means of the TOCSY and NOESY techniques. Aliphatic carbon assignment was performed by inverse correlation via heteronuclear double quantum coherence.
15N CP‐MAS NMR study of azo–hydrazone tautomerism of some Azo dyes
Authors: Lyčka Antonín , Jirman Josef , Schneider Bohdan , Straka Jaroslav
Published: May 2005

The 20.28 MHz 15N CP‐MAS NMR spectra of 15N doubly labelled 3‐methyl‐1‐phenylpyrazole‐4,5‐dione 4‐phenylhydrazone (1), 4‐hydroxyazobenzene (2), 2‐hydroxy‐5‐tert‐butylazobenzene (3) and 1‐phenylazo‐2‐naphthol (4) were measured and the temperature dependence of δ(15N) was followed. For 4, representing a mixture of the azo and hydrazone forms, the hydrazone content was calculated from the 15N chemical shifts of both nitrogen atoms at various temperatures. The two calculations gave identical results. In comparison with measurements in solution, the hydrazone content in 4 is slightly higher in the solid state. Thermodynamic data were calculated using the temperature dependence of In K (K = [hydrazone form]/[azo form]). Some hydrazone content was found in 2 in the solid state, in contrast to the measurements in solution.
Selective heteronuclear NOE enhancements in benzoheterocycles. Effect of ring size on indirect three‐spin effects
Authors: Redondo Jordi , Sánchez‐Ferrando Francisco , Valls Montserrat , Virgili Albert
Published: May 2005

The 80 MHz 1H NMR and 20 MHz 13C NMR spectra of five 4‐methylcoumarins, six 4‐methyl‐2(1H)‐quinolones and nine 3‐methylbenzo[b]furans, including six new compounds, were fully assigned. Homonuclear 1H{1H} NOEs and selective heteronuclear 13C{1H} NOEs were measured after low‐power pre‐saturation of the methyl protons. Indirect, negative heteronuclear NOE enhancements were found in suitable three‐spin systems of the 13C1H{1H} type, and their magnitude was found to be dependent on ring size. The first examples of indirect, heteronuclear NOE enhancements on non‐protonated carbons are described.
Two‐dimensional NMR spectra of sesquiterpenes. II—Noesy study of some sesquiterpene lactones with pseudoguaianolide, 3,4‐seco‐pseudoguaianolide and guaianolide skeletons
Authors: Aljančić‐Šolaja Ivana , Milosavljević Slobodan , Djermanović Miodrag , Stefanović Milutin , Macura Slobodan
Published: May 2005

The application of phase‐sensitive 2D 1H NOE NMR spectroscopy (PS NOESY) in the stereochemical assignment of sesquiterpene lactones such as 4‐oxo‐3,4‐seco‐ambrosan‐6,12‐olide‐3‐oic acid methyl ester, 4‐oxo‐6‐hydroxypseudoguai‐11(13)‐en‐8,12‐olide and 8‐angeloyloxy‐10‐acetoxyguai‐3‐en‐6‐,12‐olide is reported.