bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two‐dimensional NMR studies of Pt(2‐methallyl)(SnCl3)(styrene). Recognition and interpretation of simultaneous exchange processes via 1H noesy
Authors: Ammann Christian , Pregosin Paul S. , Rüegger Heinz , Grassi Mariella , Musco Alfredo 
Published: May 2005

AbstractThe 1H NMR spectrum of Pt[η3‐CH2C(CH3)CH2](SnCl3)(PhCHCH2) (1), which is complicated by the existence of two isomers, has been interpreted using (195Pt, 1H)‐INVERSE, J‐resolved, COSY‐90 and NOESY two‐dimensional methods. The two isomers are shown to be involved in slow exchange processes, and one intermediate in the exchange, Pt[CH2C(CH3)CH2](SnCl3) (4), has been identified and characterized via 1H, 13C, 119Sn and 195Pt spectroscopy. NOESY measurements show that neither 1 nor 4 is involved in an η3 →η1 isomerization, so that 4 must be involved in the dynamics with 1 via loss of a tin‐containing fragment, presumably SnCl3−. Uncoordinated PhCHCH2 has been detected in solution and shown to exchange with the complexed PhCHCH2 in both isomers of 1.
Establishing long‐range connectivities in polynuclear aromatics through the use of two‐dimensional MLEV‐17‐based isotropic mixing
Authors: Johnston Milton D. , Martin Gary E. 
Published: May 2005

AbstractA method for observing long range 1H;1H coupling pathways of polynuclear aromatics using the HOHAHA (TOCSY) experiment is described. The method affords a potentially superior alternative to the more established long range optimized COSY (LRCOSY) experiment. Hexahelicene derived phenanthro[3′,4′:3,4]phenanthro[2,1‐b]thiophene is employed as a model compound to demonstrate the method.
13C NMR studies of cis–trans isomerization of N‐benzylidene‐propyl‐ and ‐substituted aryl‐amines induced by a lanthanide shift reagent
Authors: Al‐Rawi Jasim M. A. , Saleem L. M. N. 
Published: May 2005

AbstractThe 13C chemical shifts of cis‐ and trans‐benzylidenepropylamine and substituted benzylideneanilines were analysed after additons of Eu(fod)3. The cis/trans ratio increases as the amount of lanthanide shift reagent increased. The cis isomers showed large lanthanide‐induced shifts, whereas the trans isomers showed little or no effect.
13C nuclear magnetic resonance study of some phosphinolipids: Assignments and conformational studies
Authors: Kallinowski Georg , Vogt Walter 
Published: May 2005

Abstract13C chemical shifts and 31P, 13C spin‐spin coupling constants are reported for six model phosphinates and eight synthetic phosphinolipids. The complex spectra of the synthetic phosphinolipids could be assigned from increments and couplings derived from the model compounds. Based on these investigations the 3J(PC) couplings of 7–15 Hz indicate a preferential trans orientation of the respective head‐group carbon relative to the phosphorus. This behaviour is similar to that of natural phosphatidylcholine lipids.
Studies on the benzoxazine series. 2—Preparation and1H and13C NMR structural study of some substituted 1,2‐dihydro‐4H‐3,1‐benzoxazines
Authors: Neuvonen Kari , Pohtola Riitta , Pihlaja Kalevi 
Published: May 2005

AbstractIn addition to the parent compounds, nine methyl‐substituted 1,2‐dihydro‐4H‐3,1‐benzoxazines with and withoutN‐methyl substitution were prepared. The chain tautomer could only be detected in the case of 1,2‐dihydro‐2‐(p‐nitrophenyl)‐4H‐3,1‐benzoxazine in solution. The configurational and conformational assignments were based on1H and13C NMR data. The calculations of the methyl substituent effects on the heterocyclic ring (half‐chair structure) carbons gave a good fit between the observed and calculated shifts and made in possible to estimate that 1,2‐dihydro‐4‐methyl‐4H‐3,1‐benzoxazine is a 75:25 and itsN‐methyl derivative a 69:31 mixture of the 4eq′‐ and 4ax′‐ forms. 1,2‐Dihydro‐trans‐1,2,4‐trimethyl‐4H‐3,1‐benzoxazine is also not conformationally homogeneous, but is a 43:57 mixture of the 2eq,4ax′‐ and 2ax,4eq′‐ forms. A comparison of the13C chemical shift correlations with those of 3,4‐dihydro‐2H‐1,3‐benzoxazines also improves the structural knowledge about the latter series. Whereas theN‐methyl groups in 3,4‐dihydro‐2H‐1,3‐benzoxazines are axially orientated, model calculations reveal that theN‐methyl substitutions in the title compounds can be orientationally heterogeneous.
Synthesis and conformational analysis of dibenzodithiocin derivatives
Authors: Sohár P. , Kövesdi I. , Szabó J. , Katócs Á. , Fodor L. , Szücs E. , Bernáth G. , Tamás J. 
Published: May 2005

AbstractN‐(3,4‐Dialkoxyphenylthiomethyl)aroylamides (la, b) reacted with phosphoryl chloride to give not only the expected 4H‐ and 2H‐1,3‐benzothiazine derivatives (4a, b and 5a, b), but also dibenzodithiocins of new (dibenzo[d,g][1,3]dithiocins 2a, b) and known (dibenzo[b,f][1,5]dithiocins 3a, b) types. The analogous reaction of the 4‐methylaroylamide 8a furnished the 4H‐1,3‐benzothiazine 9a, the dibenzo[b, f][1,5]dithiocin derivative 10a and benzonitrile. In contrast, 8b (the chloro analogue of 8a) furnished only benzonitrile and bis(4‐chlorophenylmercapto)methane (11). The structures of the new compounds were confirmed by IR, 1H and 13C NMR, and (in part) by mass spectrometry. Temperature‐dependent 1H NMR studies were used for the conformational analysis of 2a and its disulphone 6a; the nature and free enthalpies of activation of the two different conformational motions occurring at higher temperatures were determined.
13C NMR study of 2‐iodoso‐ and 2‐iodoxy‐benzoic acids and their sodium salts
Authors: Katritzky Alan R. , Duell Bradley L. , Gallos John K. , Durst H. Dupont 
Published: May 2005

AbstractThe 13C NMR spectra for selected 2‐iodosobenzoic acids, their sodium salts and the sodium salts of the corresponding iodoxybenzoic acids were measured and carbon assignments made using 2D and NOE experiments and relaxation times. Iodoso and iodoxy groups deshielded the ipso‐carbon in these compounds by approximately 25 and 55 ppm, respectively, relative to the corresponding iodo compounds. The 13C NMR spectra of the 2‐iodosobenzoate anions were almost identical with those of the corresponding free acids, both possessing cyclic structures. The iodoxybenzoic acids are either insoluble in, or oxidize, suitable NMR solvents (i.e. DMSO‐d6, DMF‐d7). The cyclic structure postulated for iodoxybenzoate anions is supported by their 13C chemical shifts.
Substituent chemical shifts in NMR. Part 4—1H SCS in some 2‐substituted norbornanes and bornanes
Authors: Abraham Raymond J. , Barlow Andrew P. , Rowan Alan E. 
Published: May 2005

AbstractThe 1H chemical shifts and substituent chemical shifts (SCS) were recorded for several monosubstituted norbornanes and bornanes. The observed substituent effects are generally similar for the two ring systems, but difter considerably from those observed for the cyclohexanoid systems in steroids. A consistent trend for the eclipsed C‐2—C‐3 fragment in this ring system is that all the substituents produce the largest SCS on the trans oriented proton, rather than the spatially nearer cis oriented proton. Indeed, for the OH substituent these SCS are opposite in sign, that for the cis oriented proton being negative (i.e. to high field). This trend is not observed in the cyclo‐hexane system, in which the distance dependence of the vicinal SCS is as expected. The major cross‐ring SCS are of the 2‐endo substituents with the C‐6 protons, giving a large positive SCS at the 6n proton and a small negative SCS at the 6x proton. This trend is very similar to that observed in the cyclohexane ring (axial‐axial SCS), and suggests a similar electric field mechanism.
Improvement of carbon‐detected H,H‐TOCSY experiments by employing a DEPT transfer
Authors: Kessler H. , Gemmecker G. , Köck M. , Osowski R. , Schmieder P. 
Published: May 2005

AbstractA new version of the 2D combination of TOCSY and H,C‐COSY is proposed which uses the DEPT technique for the heteronuclear transfer. Hence the resulting 2D spectrum can be easily corrected to pure absorption mode for optimum resolution in both dimensions. In contrast to an earlier published version with a partially refocused INEPT sequence and delayed heteronuclear decoupling in F2, the new variant does not generate any base‐line distortions interfering with interesting signals. In addition, experimental spectra obtained from cyclosporin A and a cyclic hexapeptide also show improved sensitivity compared with the INEPT version. In all these experiments, the information about direct HC connectivities is lost owing to the TOCSY transfer preceding the heteronuclear transfer. This information can, however, be provided by a version with only partial heteronuclear decoupling in F1, which can be easily obtained by shifting the refocusing 180° 13C pulse out of the centre of t1. Thus all couplings can be reduced to a fraction of their original value, as long as the large 1J coupling still causes a visible doublet splitting in the 2D spectrum. The reduced heteronuclear couplings lead to a spectrum which is easy to interpret, since the resulting small splittings of the direct cross‐peaks are unlikely to interfere with other signals. In addition, all long‐range couplings in F1 are also scaled down, thus causing less line broadening and therefore higher sensitivity.
13C CP‐MAS study of the polymorphs of naphthazarin and of some methyl derivatives
Authors: Olivieri Alejandro , Paul Iain C. , Curtin David Y. 
Published: May 2005

AbstractThe high‐resolution 13C solid‐state NMR spectra of naphthazarin polymorphs and some of its derivatives having methyl substituents are discussed. Differences observed between the spectra of the A and B forms and that of the C modification of naphthazarin are explained by invoking hydrogen‐bonding effects. The 2‐methyl and 2,3‐dimethyl derivatives show spectra consistent with their x‐ray‐determined structure as being mainly composed of the tautomer bearing the substituents on the quinonoid ring. The 2,7‐dimethyl‐substituted compound undergoes a fast intramolecular proton migration at room temperature between tautomers present in nearly equal amounts.
Selection and chromatographic removal of paramagnetic relaxation reagents
Authors: Herzog H. , Gosciniak B. , Buddrus J. 
Published: May 2005

AbstractBoth Cr(acac)3 and Fe(acac)3 can be used as relaxation reagents in INADEQUATE 13C NMR measurements. Removal of the reagents is accomplished by silica gel chromatography, the choice of the eluent being dependent on the polarity of both the reagent and the organic compound.
Complete assignments of the 1H and 13C NMR spectra of testosterone and 17α‐methyltestosterone and the 1H parameters obtained from 600 MHz spectra
Authors: Hayamizu Kikuko , Kamo Osamu 
Published: May 2005

AbstractComplete sets of 1H chemical shifts and spin coupling constants of testosterone and 17α‐methyltestosterone were determined by analysis of the 600 MHz 1H NMR spectra. The spin coupling constants of the two compounds have similar values, but the substitution of a methyl group at the 17α‐position changes the 1H chemical shifts of some protons on the C and D rings: low‐field shifts for H‐12α, H‐14α and H‐16α and high‐field shifts for H‐12β and H‐16β. The two‐dimensional 1H‐1H COSY and NOESY methods were used for unambiguous assignments, including those for the signals of H‐16α and H‐16β which are interchanged in the present paper from the assignment reported previously. Two‐dimensional 1H‐13C shift correlated spectroscopy was also used to complement the 1H and 13C assignments. The effect on the 13C chemical shifts of methyl substitution at the 17α‐position is briefly discussed.
Two‐dimensional NMR spectral study of the tautomeric equilibria of D‐fructose and related compounds
Authors: Jaseja Mahesh , Perlin Arthur S. , Dais Photis 
Published: May 2005

AbstractThe use of two‐dimensional NMR techniques and spin simulation afforded a detailed set of chemical shift and spin–spin coupling data for the main tautomeric forms of D‐fructose in dimethyl sulfoxide and aqueous solutions. Differences in vicinal coupling parameters for β‐D‐fructofuranose in the two solvents are taken as evidence that this tautomer incorporates intramolecular hydrogen bonding in dimethyl sulfoxide, which helps to account for its exceptional prominence in this solvent. The enhanced proportion of α‐D‐fructofuranose in dimethyl sulfoxide over that in water also receives comment. Also described are corresponding data from NMR measurements on the tautomeric equilibria of disaccharides that contain a D‐fructose reducing‐end residue, and of the homomorphic ketose, L‐galacto‐2‐heptulose, i.e. structurally related compounds that may entail different kinds of hydrogen‐bonding possibilities. Evidence indicating the presence of extensive inter‐residue hydrogen bonding within the individual tautomers of the disaccharide turanose is provided by the pattern of hydroxyl proton chemical shifts in dimethyl sulfoxide.
2D NMR studies on mortonin A, C and D. Unambiguous assignment of 13C chemical shifts
Authors: Rodríguez‐Hahn L. , Jiménez M. , Díaz E. , Jankowski K. , Davoust D. , Fagerness P. 
Published: May 2005

AbstractHigh‐field 2D NMR studies of mortonins were performed at 500 MHz (1H) and 125 MHz (13C). Unambiguous assignment both of the 13C data to the carbon skeleton and that of the proton chemical shifts in these molecules was achieved, together with the establishment of the configuration of the asymmetric centres. Some previously reported signals have been reassigned.
13C NMR study of quipazines
Authors: Joseph‐Nathan P. , García‐Martínez C. 
Published: May 2005

AbstractThe complete assignment of the 13C NMR spectra of a series of biologically active quipazines substituted at position C‐5, C‐6 or C‐7 of the quinoline moiety provides evidence for a strong conjugation between the π‐electron cloud of the pyridine ring and the nitrogen lone pair of the piperazinyl residue. The SCS values of these quipazines are compared with those of the analogous quinolines, and their deviations are discussed in terms of conjugation effects.
13C,1H spin–spin coupling. X—Norbornane: A reinvestigation of the karplus curve for3J(13C,1H)
Authors: Aydin Rafet , Günther Harald 
Published: May 2005

Abstract13C,2H spin–spin coupling constants over one, two and three bonds were measured from the 100‐MHz13C NMR spectra of deuteriated isotopomers of norbornane‐d1, (1) and fenchane‐2‐d1(2) and also of a number of mono‐deuteriated alkyl‐substituted adamantanes. The magnitudes of the correspondingJ(13C,1H) values derived from these data by application of the well known relationshipJ(X,1H) = 6.5144J(X,2H) are discussed with respect to the structural data for the hydrocarbons, which were taken from force field calculations with the Allinger MM2 method. In particular, the dihedral angle dependence and the Karplus curve for3J(13C,1H) are investigated. Coupling constants calculated by the FP‐INDO method are compared with the experimental data, and the effect of substitution by additional CC bonds in α‐, β‐ and γ‐positions of the13C‐αC‐βC‐γH bond fragment is elucidated. If substituent effects that arise through branching and methyl substitution in 1 and 2 are taken into account for dihedral angles ϕ > 90°, one derives3J(13C,1H) = 4.50 − 0.87 cos ϕ + 4.03 cos 2ϕ withJ(0°) = 7.7,J(60°;) = 2.0 andJ(180°) = 9.4 Hz.
1D and 2D NMR study of some allenic carotenoids of the fucoxanthin series
Authors: Englert Gerhard , Bjørnland Terje , Liaaen‐Jensen Synnøve 
Published: May 2005

AbstractThe allenic carotenoid all‐trans‐(3S,5R,6S,3′S,5′R,6′R)‐19′‐butanoyloxyfucoxanthin, isolated from the marine chrysophyte Pelagococcus subviridis, and its 9′‐cis isomer, obtained in 45% yield on iodine‐catalysed stereomutation, were submitted to a detailed 1H and 13C NMR analysis. For comparison, all‐trans‐fucoxanthin [(3S,5R,6S3′S,5′R,6′R)‐5,6‐epoxy‐3,3′,5′‐trihydroxy‐6′,7′‐didehydro‐5,6,7,8,5′,6′‐hexahydro‐β,β‐caroten‐8 ‐one‐3′‐acetate] was included in the study. The complete assignments of the 400 MHz 1H NMR spectra and of the 100.6 MHz 13C NMR spectra, including the stereochemistry, were possible by application of two‐dimensional 1H,1H chemical shift correlated spectroscopy (2D COSY), 1D and 2D total correlation spectroscopy (TOCSY, HOHAHA), rotating‐frame nuclear Overhauser spectroscopy (ROESY, CAMELSPIN) and 1H‐detected one‐bond (with and without 13C decoupling) and multiple‐bond 1H, 13C‐correlated 2D spectroscopy. The 9′‐trans to 9′‐cis stereomutation was unequivocally proved for 19′‐butanoyloxyfucoxanthin, mainly by 1D and 2D ROESY experiments; this is in contrast to a previously claimed 6′R → 6′S stereomutation in related allenic carotenoids.
13C NMR studies of the solution molecular dynamics of tricyclic antidepressants
Authors: Casarotto Marco G. , Craik David J. , Munro Sharon L. A. 
Published: May 2005

Abstract13C NMR spin–lattice relaxation times (T1s) and nuclear Overhauser enhancements (NOE's) were measured for a series of clinically used tricyclic antidepressants (TCAs), imipramine (1), amitriptyline (2), doxepin (3) and dothiepin (4), at two magnetic field strengths (corresponding to 13C frequencies of 75 and 100 MHz). The measurements were carried out at a range of solution concentrations in CDCI3 and D2O in order to determine the factors that influence overall and internal molecular dynamics in these systems. Both the hydrochloride salts and free bases were examined. For solutions in CDCI3 over a range of concentrations, or for low‐concentration (0.03 M) solutions in D2O, T1 and NOE measurements were independent of magnetic field strength, indicating that motion of the TCAs was in the ‘extreme narrowing limit.’ In contrast, for 0.3 M solutions of the hydrochloride salts in D2O, T1 and NOE measurements were field dependent, indicating the presence of significantly slower molecular mobility. It is proposed that micelles are present at this concentration and are responsible for reduced overall tumbling of the TCAs. Several degrees of internal motion were detected by the relaxation and T1 measurements, viz. rapid flexing motion of the benzylic bridging carbons in the central seven‐membered ring and segmental motion of the side‐chain. From an examination of the effect of solvent, concentration and protonation state of the side‐chain on the latter motion, it was possible to derive information on side‐chain conformations and interactions.
Study of the frozen water–poly(vinyl alcohol) system by 2H and 13C NMR spectroscopy
Authors: Gusev D. G. , Lozinsky V. I. , Vainerman E. S. , Bakhmutov V. I. 
Published: May 2005

Abstract2H and 13C NMR techniques were used to investigate the thermodynamic state of water molecules and of poly(vinyl alcohol) (PVA) chain segments in frozen 10% PVA solutions in 99.8% and 8.5% 2H2O in the ‐66 to 3°C temperature range. The minimum amount of water not entering into the structure of ice is shown to correspond to a ratio of three water molecules to four PVA hydroxyl groups. The quantity of unfrozen water in the investigated systems was observed to change in the 5‐6°C range next to the melting point of pure water. The measurements show that, within the same temperature interval, the temperature decrease is accompanied by a sharp decrease in the 2H spin‐lattice relaxation time T1, whereas 13C T1 and the width of the 13C NMR signals increase up until the resolved PVA signals disappear. The correlation time of the motion of water deuterons and the PVA chain segments was calculated from the 2H and 13C T1 data. The interrelation between the data obtained and the cryostructurization processes leading to the formation of gels in frozen aqueous PVA solutions is discussed.
Two‐dimensional homonuclear and heteronuclear correlation NMR studies of diprenorphine: A prototypic 6α, 14α‐endo‐ethanotetrahydrothebaine
Authors: Mazza Samuel M. , Erickson Ronald H. , Blake Paul R. , Lever John R. 
Published: May 2005

AbstractAnalysis of the 1H–1H COSY, 13C–1H HETCOR and NOESY spectra of diprenorphine, a prototypic 6α, 14α‐endo‐ethanotetrahydrothebaine, yielded 1H NMR and 13C NMR assignments which should aid in spectral studies of structural congeners from this class of opioid ligands. 13C NMR assignments were in accord with those previously reported, with the exception of the C‐17 and C‐18 carbon resonances, which were shown to be reversed. Specific assignments for the non‐equivalent C‐20 and C‐21 methyl groups were possible through NOESY due to intramolecular hydrogen bonding between the 19‐hydroxy and the 6‐methoxy groups. The piperidyl ring presented a chair conformation, similar to that of morphine, with an equatorial N‐cyclopropylmethyl moiety.
Tumour inhibitory triazenes. 5—15N NMR study of 1‐aryl‐3,3‐dialkyltriazenes
Authors: Wilman Derry E. V. 
Published: May 2005

AbstractThe variation of the 15N chemical shifts with substitution for a series of 1‐aryl‐3,3‐dialkyltriazenes is decribed. Good correlations were found between the relative chemical shifts at all three nitrogen sites and the electronic properties, as measured by the substituent coefficient, coefficient, σ, for the meta and para substituents in the aryl group. No such correlations were evident for variations in the 3‐alkyl substituents.
Amended heteronuclear correlations by multiple‐quantum evolution. Stereosequence assignments of polymers with improved sensitivity
Authors: Kövér K. E. , Borbély J. , Batta Gy. 
Published: May 2005

AbstractIt is demonstrated that the Müller and Bolton type of multiple‐quantum heteronuclear shift correlation is a promising tool for stereosequence assignments of polymers. Slight modification of the basic MQ pulse sequence results in a 2–3‐fold gain in sensitivity compared with the conventional single‐quantum spectra while retaining the one‐quantum frequency scale in the F1 dimension.
Structures of zearalenone and zearalanone in solution: A high‐field NMR and molecular modelling study
Authors: Cordier Christine , Gruselle Michel , Jaouen Gérard , Hughes Donald W. , McGlinchey Michael J. 
Published: May 2005

AbstractThe complete 1H and 13C NMR spectra of the mycotoxin zearalenone are described. An analysis of all the vicinal proton–proton coupling constants, together with molecular modelling results, leads to a three‐dimensional structure very similar to those observed x‐ray crystallographically for related systems. Analogous data on zearalanone reveal that whereas the overall molecular geometry is similar to that of zearalenone, the alkyl terminus of the 12‐membered bridging moiety is now oriented almost orthogonally to the aromatic ring plane.
DNMR of small ring paracyclophanes
Authors: Sternhell S. , Tansey C. W. , Tobe Y. , Kakiuchi K. , Kobiro K. 
Published: May 2005

AbstractThe fluxional behaviour of 4‐methyl[2] paracyclo[ 2] (2,5)furanophane, [6] paracyclophane, 8‐methyl[6]‐paracyclophane and 8‐hydroxymethyl[ 6] paracyclophane was studied by dynamic NMR spectroscopy to yield kinetic parameters which were compared with available data for related compounds.
Miscibility of polymer blends investigated by 1H spin diffusion and 13C NMR detection
Authors: Schmidt‐Rohr Klaus , Clauss Joachim , Blümich Bernhard , Spiess Hans Wolfgang 
Published: May 2005

AbstractThe miscibility of two high‐performance polymers, an aromatic poly(ether‐imide) and a poly(aryl‐ether‐ketone), was investigated by a novel combination of solid‐state NMR techniques. This involves a new type of selection of 1H magnetization based on chemical shift differences, 1H spin diffusion during the mixing time and high‐resolution 13C detection. Mixing of components on a molecular scale is proved directly.