bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbon‐13 and nitrogen‐15 NMR spectra of some methanesulphonanilides
Authors: Wazeer Mohammed I. M. , Ali Sk. Asrof
Published: May 2005

The 13C and 15N NMR spectra of some ortho‐, meta‐ and para‐substituted methanesulphonanilides were recorded. Correlations of the 13C chemical shifts with the appropriate substituent chemical shifts (SCS) for monosubstituted benzenes were excellent and showed enhancement of the substituent effects at C‐1 (para to the substituent). The C‐1 chemical shifts were also examined by means of the dual substituent parameter (DSP) and DSP‐nonlinear resonance equations. The results indicate that the —NHSO2 Me moiety is a weak electron donor. The 15N chemical shifts of the para‐substituted compounds were analysed by means of DSP equations and the results compared with those of related compounds. Ortho‐substituted compounds indicate the high sensitivity of 15N chemical shifts towards steric compression. T1 and nuclear Overhauser enhancement data for the protonated carbons of methyl‐substituted compounds are given.
Assignment of proton and carbon‐13 spectra of a sucrose ester from tobacco by inverse detected two‐dimensional heteronuclear correlated NMR spectroscopy
Authors: Himmelsbach David S. , van Halbeek Herman , Arrendale Richard F. , Severson Ray F.
Published: May 2005

The complete assignment of the proton and carbon chemical shifts of 6‐O‐acetyl‐2,3,4‐tri‐O‐(3S‐methylpentanoyl)‐α‐D‐glucopyranosyl‐β‐D‐fructofuranoside, a naturally occurring flavor precursor of tobacco, is presented. These assignments were made by comparison of the spectra obtained from 1H‐detected heteronuclear multiple quantum coherence and 1H‐detected heteronuclear multiple‐bond connectivity two‐dimensional NMR experiments.
Conformational analysis of methyl phenyl sulphoxides containing fluorine substituents in the phenyl ring based on 1H, 13C and 17O NMR chemical shifts and long‐range nJ(HF) and nJ(CF) coupling constants
Authors: Benassi Rois , Folli Ugo , Iarossi Dario , Mucci Adele , Schenetti Luisa , Taddei Ferdinando
Published: May 2005

The preferred conformations of the methylsulphinyl group in a number of phenyl methyl sulphoxides substituted in the phenyl ring with one, two or three fluorine atoms have been studied by employing a multinuclear NMR approach. From the 1H, 13C and 17O chemical shifts of the methylsulphinyl group, and the torsional angles obtained either from MO calculations or experimental determinations for a number of the compounds, empirical correlations have been derived which enabled us to extract the preferred orientation of the SO bond or of the methyl group relative to the phenyl ring in all the molecules examined. For a limited number of the compounds, the structure of the preferred conformer is satisfactorily close to the solid‐state structure found in an independent study carried out with x‐ray diffraction. The twist of the SO bond relative to the phenyl ring changes as a function of the number of ortho substituents, being highest when two substituents are present. The lowest twist, torsional angle nearly zero, was found in ortho‐monosubstituted compounds and the SO bond is oriented towards the opposite side with respect to the substituent. Analyses were also carried out of the conformational dependence of long‐range nJ(HF) and nJ(CF) coupling constants, where the first nucleus in the parentheses refers to the methylsulphinyl group. The behaviour of these coupling constants as a function of internal rotation around the exocyclic CS bond was derived from semi‐empirical INDO MO FPT calculations, and scaled interpolating equations were derived in order to reproduce the experimental results. It thus emerges that 5J(HF), 4J(CF), 5J(CF) and 6J(CF) are conformationally dependent and show, experimentally, significant changes. These parameters can be usefully employed for the conformational analysis of methyl phenyl sulphoxides.
1H and 13C NMR study of the structure of pyrazoles, imidazoles and their benzo derivatives in sulphuric acid (azolium cations)
Authors: Elguero José , Jimeno María Luisa , Yranzo Gloria I.
Published: May 2005

The NMR spectra of two imidazoles, benzimidazole, four pyrazoles and three indazoles were recorded in 98% sulphuric acid, and the 1H, 13C, 1H–1H and 1H–13C spectral parameters of the corresponding azolium ions were obtained. The 1H N‐H chemical shifts and the 1H and 13C couplings with the NH proton are discussed. All 3J(1H1H) and 4J(1H1H) coupling constants have values between 1.5 and 3.0 Hz. All 2J(1H13C) and 3J(1H13C) values are about 6 Hz, with the exception of couplings involving C‐4 in imidazolium ions [2J(C‐4,H‐5) ≈ 12 Hz, 3J(C‐4,H‐1) ≈ 3 Hz].
Configurational assignment in N‐acetylneuraminic acid and analogues via the geminal C,H coupling constants
Authors: Prytulla S. , Lambert J. , Lauterwein J. , Klessinger M. , Thiem J.
Published: May 2005

High field 1H and 13C NMR spectra were recorded of N‐acetylneuraminic acid, its methyl ester and its per‐O‐acetylated methyl ester. The sign and the magnitudes of the geminal coupling constants between the H‐3 protons and the C‐2 quaternary anomeric carbon were determined by heteronuclear 2D‐experiments. The C‐2,H‐3ax coupling in the α anomers (−8 Hz) was significantly more negative than that in the β anomers (−3 to −4 Hz). Therefore, the determination of 2J(C‐2,H‐3ax) offers a unique criterion for anomeric assignment in sialic acid ketosides. The geminal coupling constants are discussed in terms of the number and orientation of the oxygen substituents. Due to their 3‐deoxy function adjacent to the quaternary anomeric centre, sialic acids give novel contributions to the correlation of carbon‐proton coupling constants with molecular geometries in carbohydrates.
Synthesis, 1H, 13C and 31P NMR spectral studies of novel 2‐aryloxy/cyclicamino‐ 3‐(4‐methylphenyl)‐ 1H‐ naphth[ 1,2‐e] [1,3,2] oxazaphosphorine 2‐oxides/sulphides and 13C NMR data for some 4‐substituted‐dinaphtho dioxaphosphepin 4‐oxides/sulphides
Authors: Raju C. Naga , Naidu M. S. R. , John E. O. , Reddy M. C.
Published: May 2005

The syntheses, 1H, 13C and 31P NMR chemical shifts and 13C‐31P coupling constants of 2‐aryloxy/cyclicamino‐2,3‐dihydro ‐3‐ (4‐methylphenyl) ‐1H ‐ naphth [1,2‐e] [1,3,2]oxazaphosphorine 2‐oxides/sulphides and the 13C NMR data for 4‐substituted ‐ dinaphtho [2,1 ‐d:1′,2′‐f] [1,3,2] dioxaphosphepin 4‐oxides/sulphides are reported.
A two‐dimensional NMR strategy for the complete 1H chemical shift assignment of extended proton spin systems in triterpenoids
Authors: Loganathan Duraikkannu , Trivedi Girish K. , Chary K. V. R.
Published: May 2005

An assignment strategy that utilizes one‐dimensional lanthanide‐induced methyl proton shifts, reported 13C NMR data of model compounds and two‐dimensional 1H and 13C shift correlated spectroscopy, homonuclear proton chemical shift correlated spectroscopy and nuclear Overhauser enhancement spectroscopy methods was demonstrated to be effective for the complete 1H chemical shift assignments of extended proton spin‐systems in a triterpenoid viz., 3‐keto‐urs‐12‐en‐24‐oic acid methyl ester. Complete 13C chemical shift assignments have also been accomplished.
Determination of enantiomeric purity from solid‐state 31P MAS NMR of organophosphorus compounds
Authors: Andersen Knut Vendelboe , Bildsøe Henrik , Jakobsen Hans Jorgen
Published: May 2005

Phosphorus‐31 Magic‐Angle Spinning (MAS) NMR is shown to be an extremely useful and accurate method for the determination of the enantiomeric purity for chiral organophosphorus compounds. 31P and 13C chemical shielding tensors in racemic and enantiomeric crystals of organophosphorus compounds vary because of different crystal symmetries. This implies that solid‐state 31P (13C) MAS spectra of an enantiomerically impure sample reveal separate signals from the racemic and enantiomer crystallites. Simple integration (or deconvolution) of the MAS NMR signals can thus be used to determine the enantiomeric purity of the sample. For organophosphorus compounds the application of this technique to 31P MAS NMR is of particular interest due to the high sensitivity and large shielding anisotropy of the 31P nucleus.
Aluminium‐27 MAS NMR of Al2Ge2O7 and LaAlGe2O7: Two pentacoordinated aluminium environments
Authors: Massiot Dominique , Kahn‐Harari Andrée , Michel Daniel , Muller Dirk , Taulelle Francis
Published: May 2005

Characterization by 27Al MAS NMR of two pentacoordinated environments of aluminium has been carried out in different fields and at different spinning speeds for Al2Ge2O7 and LaAlGe2O7. Complete simulations of the spectra have been performed, including computation of the individual shape and intensity of each spinning side band, which lead to the determination of both the quadrupolar interaction parameters and isotropic chemical shifts, and enable the detection of impurities in the material. The parameters determined are:
equation image
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Kinetics of skeletal rearrangement of H2FeP[CH2CH2CH2P(CH3)2]3 by an inversion–transfer–recovery NMR method
Authors: Field Leslie D. , Bampos Nick , Messerle Barbara A.
Published: May 2005

The iron dihydride FeH2(PP3) [PP3 = P(CH2CH2CH2PMe2)3] is fluctional, with the terminal co‐ordinated phos‐phine groups undergoing intramolecular exchange in addition to the iron‐bound hydrides. The exchange kinetics of the metal‐bound hydrides was examined using a magnetization inversion–transfer–recovery method, and the activation energy was ca. 64 kJ mol−1 at 260 K. The effect of spin–spin coupling on the magnetization transfer was examined.
Application of 2D EXSY NMR spectroscopy to the study of the dynamic behaviour of aroylcyanoketene‐S,S‐dimethylacetals
Authors: Fischer G. , Kleinpeter E.
Published: May 2005

The applicability of 2D EXSY NMR spectroscopy for studying quantitatively the dynamic behaviour in three aroylcyanoketene‐S, S‐dimethylacetals was tested by means of 1H NMR spectroscopy. It can be concluded that the method is a reasonable qualitative supplement to complete line‐shape analysis.
77Se, 13C and 1H NMR spectra of phenylselenenylcycloalkanes, ‐cycloalkenes and some of their selenoxides and 125Te NMR of a tellurium analogue
Authors: Duddeck Helmut , Wagner Petra , Biallaß Armin
Published: May 2005

The 77Se, 13C and 1H NMR spectra of 46 mostly new compounds with phenylselenenyl groups attached to carbocycles and of three new corresponding selenoxides and the 125Te NMR of phenyltellurenylcyclohexane are reported. Substituent effects on the chemical shifts of these nuclei are compiled and discussed in terms of the configuration and conformation. Low‐temperature NMR spectra of some cyclohexane derivatives allowed the evaluation of thermodynamic data, such as A values of the PhSe, PhSe(O) and PhTe groups.
13C NMR study of derivatives of dibenzobarrelene, anthraquinone and anthracene
Authors: Sieckmann Ralf
Published: May 2005

Carbon‐13 chemical shifts of 22 derivatives of dibenzobarrelene, anthraquinone and anthracene are reported, each of which includes a symmetrical ortho‐benzene moiety. The assignment of the chemical shifts of the aromatic carbons of these derivatives was achieved by correlation with the corresponding 13C chemical shifts of ortho‐disubstituted benzenes.
Complete 1H and 13C NMR assignments of tallysomycin s10b by modern two‐dimensional NMR techniques
Authors: Freyder Catherine P. , Marzilli Luigi G.
Published: May 2005

The 1H and 13C NMR spectra of tallysomycin s10b (TLM), a third‐generation analog of bleomycin, were completely assigned through the use of two‐dimensional NMR experiments (NOESY, HOHAHA, HMQC, HMBC) in D2O at pH 2.5 and 6.8 (uncorrected values). Significant differences in the resonances for the β‐aminoalanine, β‐hydroxyhistidine and pyrimidinylpropionamide residues were observed owing to the protonation/deprotonation of these moieties. The assignments for TLM at pH 6.8 were compared with the latest 2D NMR‐based assignments of bleomycin A2 (BLM A2) at pH 6.7. In general the agreement was excellent, in view of the size and complexity of these anticancer antibiotics. Of the several differences found, most can be attributed to the different substitution patterns in the variable regions of the larger TLM and the BLM A2. Both drugs have similar structures in the region of protonation. For this invariant region of the molecules, comparison of the TLM 13C data at pH 2.5 with the 1D BLM A2 13C data at low pH revealed that protonation induced similar changes in chemical shift for the corresponding signals in the two drugs. It is particularly noteworthy that the glucose and mannose 13C signals shift in a very similar manner for both drugs. Since the protonation shifts of the signals of these two sugars are much too large to be attributed to inductive effects, it is highly likely that both drugs, despite the structural differences in the variable region, undergo the same conformationl changes of the gulose and mannose moieties. These chemical shift similarities at both low and high pH confirm the validity of the assignments made independently on these two large drug molecules. The few differences between the two most recent 13C assignments of BLM A2, which are based on modern 2D NMR methods, can be resolved using the TLM assignments.
Computer‐assisted studies of structure–property relationships using graph invariants
Authors: Miyashita Yoshikatsu , Ohsako Hiroyuki , Okuyama Tohru , Sasaki Shin‐Ichi , Randić Milan
Published: May 2005

The correlation between molecular path numbers and chemical shift sums found previously in smaller alkanes is extended to larger alkanes. Using data on alkanes with 2–31 carbon atoms a satisfactory regression equation (R = 0.999 and S = 7.5 is derived based on a single molecular descriptor. The simple combination of elementary path numbers, M = P0 + P1+P2 − P3, apparently adequately represents both the size of molecules and the molecular shape, i.e. variations in properties among isomers.
Comparison of rotational‐echo double‐resonance and double‐cross‐polarization NMR for detection of weak heteronuclear dipolar coupling in solids
Authors: Christensen Allyson M. , Schaefer Jacob , Kramer Karl J.
Published: May 2005

Insect exoskeleton, multiply labeled with 13C and 15N, was examined by rotational‐echo double‐resonance (REDOR) and double‐cross‐polarization (DCP) magic‐angle spinning 13C NMR. Low levels of incorporation of label make the analysis of these samples a practical test of the relative advantages of REDOR and DCP for the detection of weak, heteronuclear dipolar coupling between rare spins in solids. The sensitivity of REDOR for the detection of directly bonded 13C–15N pairs is an order of magnitude greater than that of DCP when neither label is involved in homonuclear dipolar coupling of strength comparable to the spinning frequency. However, if either of the 13C or 15N labels undergoes homonuclear spin flips, DCP gains in relative sensitivity and is easier to use for spin counting than REDOR.
13C nuclear magnetic resonance studies of pyrazolo[α]‐9(10H)‐acridinones
Authors: Boyer G. , Galy J. P. , Faure R. , Elguero J. , Barbe J.
Published: May 2005

13C NMR chemical shifts of six pyrazolo[a]‐9(10H)‐acridinones are reported; they were assigned on the basis of multiplicities, carbon–proton coupling constants, selective proton decoupling experiments and comparison with related substances.
The radical anion of (E)‐azobenzene revisited
Authors: Buser Urs , Ess Caspar H. , Gerson Fabian
Published: May 2005

The radical anion of (E)‐azobenzene, generated from the neutral compound by reaction with potassium mirror in an ethereal solvent, has been fully characterized by its hyperfine data with the use of ESR, ENDOR and TRIPLE‐resonance spectroscopy. Assignments of coupling constants to protons in the individual positions are based on comparison with the spectra of the radical anions of 4,4′‐dideuterio and 2,2′‐dimethyl derivatives. Effects of 14N hyperfine anisotropy on ESR spectra and of association with the counter ion K+ are briefly discussed.
Assignments of the 13C and 1H NMR spectra of azithromycin in CDCl3
Authors: Barber Jill
Published: May 2005

The 13C and 1H NMR spectra of azithromycin were unambiguously assigned using DEPT, 2D‐INADEQUATE, HC correlation spectroscopy and other 2D NMR methods.
1H and 13C chemical shift assignments of para‐substituted aryl 2‐acetamido‐2‐deoxy‐β‐D‐glucopyranosides
Authors: Roy René , Tropper François D. , Williams Antony J.
Published: May 2005

The 1H and 13C NMR spectra of twenty aryl 2‐acetamido‐2‐deoxy‐β‐D‐glucopyranosides and eighteen aryl 3,4,6‐tri‐O‐acetyl‐2‐acetamido‐2‐deoxy‐β‐D‐glucopyranosides have been obtained and assigned. The three‐bond proton coupling constants of these compounds were also obtained.
Structure and conformation of the hypermodified purine nucleoside wyosine and its isomers: A comparison of coupling constants and distance geometry solutions
Authors: Sierzputowska‐Gracz Hanna , Guenther R. H. , Agris P. F. , Folkman W. , Golankiewicz B.
Published: May 2005

The structural determination of modified mononucleosides is important for understanding the chemistry, structure and functional changes that they impart to the nucleic acids in which they occur. Empirical analyses of J(HH) couplings have been used to describe nucleoside conformational equilibria for the glycosidic angle (syn‐anti), the C‐4′C‐5′ exocyclic rotamers (gauche+, gauche− and trans) and the sugar pucker (N–S). Distance geometry calculations with distance constraints determined from nuclear Overhauser effects (NOE) should provide equally satisfactory structural information. Proton and carbon chemical shifts and coupling constants were used to describe structural parameters for the tricyclic nucleosides wyosine, 4,9‐dihydro‐4,6‐dimethyl‐9‐oxo‐3‐(β‐D‐ribofuranosyl)imidazo(1,2‐a)purine, and three of its isomers. Using distance geometry calculations with the 14‐19 observed NOEs per nucleoside as distance constraints, multiple structures could be produced with less than 1 Å relative mean standard deviation for the positioning of all atoms. The two methods of structural determination were consistent in their qualitative determination of syn‐anti conformation and sugar pucker.
Measurement of one‐bond proton‐carbon coupling constants of saccharides
Authors: Uhrínova Stanislava , Uhrían Dušan , Liptaj Tibor , Bella Juraj , Hirsch Ján
Published: May 2005

Several NMR experiments, one proton and several carbon detected, were used for the determination of 1J(C,H) values in saccharides. Couplings of anomeric carbons were measured from the 13C satellites in 1H NMR spectra. The simultaneous application of several purging schemes resulted in a very good suppression of the proton signals from 12C molecules. 1J(C,H) values of all saccharides were determined by 2D J‐resolved spectroscopy using an INEPT‐type pulse sequence with a BIRD pulse for the suppression of nJ(C,H) and folding in F1. Rules for the calculation of the correct values of 1J(C,H) from the observed reduced splittings are proposed. 1J(C,H) values were also obtained from a set of J‐modulated one‐dimensional 13C spectra. A procedure for the determination of 1J(C,H) values from only two one‐dimensional experiments is proposed. Mannose derivatives (mono‐ and poly‐saccharides) were used to test and compare the individual methods. Differences in 1J(C,H) values for C‐2 and C‐3 were used for the chemical shift assignment of these carbons.
Intermolecular and intramolecular effects on the 1H and 13C shielding in some gaseous hydrocarbons at various temperatures—theory and discussion
Authors: Raynes William Thomas , Bennett Brian
Published: May 2005

Values of the first‐order derivatives of proton and 13C shielding with respect to gas density for several hydrocarbons over the temperature range 180–370 K are fitted to a long‐standing theory. The theory includes consideration of (a) the ‘site factor’ allowing for the position of the resonating nucleus in the molecule and (b) the presence of higher order interactions in the intermolecular potential. The resulting B coefficients are improved as a result of (b) and in the case of 13C shielding there is almost totally satisfactory agreement. Values of dσ0/dT, the temperature dependence of the 1H and 13C shielding extrapolated to zero density, are discussed in terms of the displacements of the nuclei from equilibrium geometry. The results suggest that attempts to relate the temperature dependence of chemical shifts of conformationally mobile compounds to the varying populations of a small number of conformers are naive. It is also necessary to take account of contributions from distorted conformers which proliferate increasingly at higher temperatures. The positive values of dσ0/dT observed for some carbon nuclei are also believed to be related to torsional motion.
Two‐dimensional nuclear magnetic resonance of sesquiterpenes. 4—Application to complete assignment of 1H and 13C NMR spectra of some aromadendrane derivatives
Authors: Faure Robert , Ramanoelina Armand R. P. , Rakotonirainy Olivier , Bianchini Jean‐Pierre , Gaydou Emile M.
Published: May 2005

The total assignment of the 1H and 13C NMR spectra of five aromadendrane derivatives, (+)‐aromadendrene (1), (−)‐alloaromadendrene (2), (+)‐ledene (3), (−)‐dehydroaromadendrane (4), (−)‐globulol (5) and (+)‐viridiflorol (6) has been performed. The 13C spectral assignment of globulol was achieved from DEPT and double quantum coherence measurements. The concerted application of 1H1H homonuclear and 1H13C heteronuclear two‐dimensional chemical shift correlations provided other 13C and all 1H chemical shifts. Moreover, the 1H assignment for compounds 13 was reexamined from the high‐field analysis of proton‐proton coupling constants.
Synthesis and 1H, 13C and 31P NMR studies of 2,10‐dichloro‐6‐aryloxy‐12H‐dibenzo [d,g] [1,3,2]‐dioxaphosphocin 6‐oxides
Authors: Reddy C. Devendranath , Reddy R. S. N. , Raju C. Naga , ElMasri Marwan , Berlin K. Darrell , Subramanian Shankar
Published: May 2005

The spectral analyses and syntheses of several novel 2,10‐dichloro‐6‐aryloxy/alkyl‐12H‐dibenzo [d,g] [1,3,2] dioxaphosphocin 6‐oxides have been achieved. Long‐range coupling [5J(H,P) = 2.4 Hz] was observed between phosphorus and the bridged methylene protons. Based upon NMR data, a tub‐like conformation is proposed for the central eight‐membered dioxaphosphocin ring. Long‐range 2J(P,O,C) and 3J(P,O,C,C) couplins were determined, as were the 31P chemical shifts for sixteen members of these new heterocycles. A variable‐temperature study of one member suggested the presence of a tub form as a reasonable candidate for one major conformer but the presence of other forms was also implied.
39K NMR study of potassium naphthalenide solutions
Authors: Sokói Maria , Grobelny Janusz , Kowalczuk Marek
Published: May 2005

Potassium naphthalenide solutions in tetrahydrofuran were studied by means of 39K NMR spectroscopy. The effect of temperature, concentration and potassium cation complexation on paramagnetic shift and relaxation behaviour was demonstrated and is discussed. An attempt was made to assess the contributions due to the various relaxation mechanisms operating at different temperatures in the systems studied.
Large CC spin–spin coupling constants across double bonds. Validity of the multiplicative approach
Authors: Kamieńska‐Trela Krystyna , Biedrzycka Zenobia , Da̧browski Andrzej
Published: May 2005

13C13C spin–spin coupling constants have been measured for a series of variously substituted ethenes. The largest 1J(CC) value, 172 Hz, was found in chlorotrifluoroethene and the smallest, 45.3 Hz, in tris(trimethylsilyl)ethene, which covers a range of 127 Hz for the 1J(CC) values. An analysis of the data revealed a large discrepancy between the experimental 1J values and those estimated by the commonly used additive increment scheme. Good agreement was found, however, between the experimental values and those calculated by means of a multiplicative scheme.
Characterization of partially deuteriated transition metal polyhydrido complexes by heteronuclear 2D NMR techniques
Authors: Nanz Daniel , Philipsborn Wolfgang Von , Bucher Urs E. , Venanzi Luigi M.
Published: May 2005

(1H, 103Rh) and (1H, 103Rh){2H} inverse correlation techniques, which profit from the presence of a magnetically active central metal nucleus, were applied to the complex [RhY2(Y2){HB(3,5‐Me2pz)3}] (Y = H or D; pz = pyrazolyl) containing both ‘classical’ and ‘non‐classical’ hydrogen ligands. The sample examined was a mixture of all species ranging from the perprotio to the perdeuterio compound. It is shown that the large isotope chemical shifts of the Rh nucleus can be used to separate the 1D 1H and 1H{2H} NMR spectra of the different H/D isotopomers. The observed isotope effects are discussed.
1H NMR studies of human urine: Urinary elimination of the anticancer drug carboplatin
Authors: Ranford John D. , Sadler Peter J. , Balmanno Katherine , Newell David R.
Published: May 2005

Samples of urine from a patient obtained before and after treatment with 300 mg of the anticancer drug [Pt(II)(NH3)2(CBDCA)] (carboplatin, “Paraplatin”, where CBCDA is 1,1‐dicarboxycyclobutane) have been analysed using 500 MHz 1D and 2D 1H NMR spectroscopy. Peaks for the intact drug and the free ligand CBDCA have been assigned and are present in a mol ratio of ca. 5:1. Only about one half of the total Pt in the sample was present as intact drug. Relative to creatinine and citrate, the excretion of hippurate increased by a factor of ca. 4 after drug treatment. This work suggests that NMR spectroscopy can play a valuable rǒle in studies of carboplatin metabolism.
Natural abundance 17O NMR spectroscopic study of quinone methides
Authors: Boykin David W. , Kumar Arvind , Shevchenko Sergey M.
Published: May 2005

The 17O NMR chemical shift data for a series of substituted 10‐methyleneanthrones and related 10‐alkylanthrones in acetonitrile solution at 75°C are reported. The 17O NMR chemical shift value of 10‐methyleneanthrone is shielded by ca. 35 ppm compared with that of anthraquinone. The chemical shifts of the 10‐methyleneanthrones range from 493 ppm for 10‐bromomethyleneanthrone to 440 ppm for 10‐diethylaminomethyleneanthrone. A correlation of the 17O NMR chemical shifts of the 10‐substituted methyleneanthrones with σ+ constants is noted.
Vicinal 13C13C coupling constants in bicyclic monoterpenes
Authors: Denisov Aleksej Y U. , Tkachev Aleksej V. , Mamatyuk Viktor I.
Published: May 2005

Carbon–carbon coupling constants in monoterpene hydrocarbons (3‐carene, α‐pinene and camphene) were investigated. A selective version of the INADEQUATE experiment was used for measurements of the long‐range nJ(CC) values. The dependence of the vicinal 13C13C coupling constants on the dihedral angles and the types of molecular framework involved within the direct coupling path is discussed. The configuration of a heteroatomic derivative from α‐pinene was determined from its 3J(CC) values.
Selective long‐range 1H13C polarization transfer in nucleosides
Authors: Gmeiner William H. , Lown J. William
Published: May 2005

Selective INEPT (INAPT) experiments were used to correlate the nitrogen‐ and carbon‐bound hydrogens of nucleosides with 13C resonances via 2J(C, H) and 3J(C, H). Such experiments are useful as part of a strategy to distinguish the imino hydrogens of uridine and thymidine, which cannot be accomplished on the basis of chemical shift. The strategy involves correlation of the imino hydrogen with C‐5 using INAPT and testing whether or not the C‐5 resonance is quaternary. Polarization transfer is ineffecient for most positions in nucleosides owing to the small long‐range couplings, except the H‐6C‐5 transfer in adenosine, which results in enhancement of the 13C resonance over its equilibrium value. The efficiency of polarization transfer from H‐3 to C‐5 of thymidine depends on the base‐paired status of the nucleoside indicating a change in the 3J(C, H) on base‐pair formation. This sensitivity to electronic reorganization on base‐pair formation makes the INAPT experiment a useful probe for the base‐paired status of nucleosides and of the electronic properties of uridine and thymidine analogues.
14N and 15N NMR spectroscopic characterization and analysis of cyclic sulfur imides
Authors: Chivers Tristram , Edwards Mark , McIntyre Deane D. , Schmidtt Kenneth J. , Vogel Hans J.
Published: May 2005

The 14N and 15N NMR spectra of natural abuadance and 15N‐enriched samples of S7NH and S4(NH)4 were obtained by direct detection and by a variety of polarization transfer techniques. Sensitivity enhancements of ca 10 (compared with direct detection) for the INEPT pulse sequence and ca 100 for the HMQC (heteronuclear multiple quantum coherence) + BIRD (bilinear rotation decoupling) sequence were observed for the imides. 15N spin–lattice relaxation constants (T1) of 10.2 ± 0.1 and 12.6 ± 0.1 s were determined for S7NH and S4(NH)4, respectively. The HMQC procedure was used to obtain the 15N and 1H NMR chemical shifts and 11J(15N, 1H) values for 1,3‐,1,4‐ and 1,5‐S6(NH)2, 1,3,5‐ and 1,3,6‐S5(NH)3. The trends in NMR chemical shifts and coupling constants are discussed in the context of the known molecular structurts of cyclic sulfur imides. The use of NMR techniques for the analysis of mixtures of cyclic sulfur imides is compared with the well established methods of infrared spectroscopy and thin‐layer chromatography.
NMR spectroscopic characterization of maleic anhydride–α‐methylstyrene adducts
Authors: Komber Hartmut , Steinert Volker , Zschoche Stefan , Rätzsch Manfred , Grossmann Gisbert
Published: May 2005

Two 2:1 maleic anhydride–α‐methylstyrene adducts and two naphthalene derivatives were isolated as low molecular weight by‐products of thermal copolymerizations of maleic anhydride and α‐methylstyrene under different conditions. Their structures were deduced by means of 1H1H and 1H13C shift correlation NMR spectroscopy. The complete 1H and 13C NMR assignments are presented.
Chemical shift anisotropy and indirect coupling in SnO2 and SnO
Authors: Cossement Christophe , Darville Jacques , Gilles Jean‐Marie , Nagy Janos B. , Fernandez Christian , Amoureux Jean‐Paul
Published: May 2005

The magic angle solid‐state NMR spectra of SnO2 and SnO were recorded and analysed. The chemical shift tensor anisotropy is much smaller for SnO2 (136 ppm) than for SnO (975 ppm). Simple calculations suggest that the latter is mainly due to the asymmetry in the valence electron cloud of the tin atom in SnO. An SnSn indirect coupling of 8300 Hz was found in SnO, indicating the possibility of Sn 5s orbitals at the top of the valence band of SnO.
Hydrogen‐1 and aluminum‐27 NMR study of Al(ClO4)3 in aqueous mixtures of dimethylformamide and urea
Authors: Fratiello Anthony , Kubo‐Anderson Vicki , Azimi Soheil , Fowler Cynthia , Marinez Eric , Perrigan Richard , Shayegan Shadi , Yao Betty
Published: May 2005

A competitive solvation study of Al(III) in water–dimethylformamide (DMF) and water–urea mixtures was carried out by 1H and 27Al NMR spectroscopy. At temperatures low enough to slow proton and ligand exchange, separate 1H resonance signals were observed for bulk and coordinated ligand molecules, and for 27Al in different solvation complexes. The 1H NMR data confirmed hexacoordination of Al(III) at all concentrations, monodentate binding at the oxygen atom of both DMF and urea, preferential solvation by both organic ligands, the presence of steric hindrance to complexation, particularly by DMF, and the identification of the complexes responsible for the 27Al spectra. It also showed a non‐equivalence of the amido groups in urea, in both the complex and free states, presumably owing to hindered rotation about the carbon—oxygen bond. In contrast to previous reports, the 27Al spectra for the water–DMF and water–urea solutions showed well resolved signals for the species [Al(H2O)n–6Ln]3+ (n = 0–6; L = DMF or urea), including two isomers for one of the water–urea complexes. The 27Al NMR data reflected the stronger preferential solvation by urea.
1H, 13C and 17O NMR spectral study of 4,1‐disubstituted naphthalenes
Authors: Perumal Subbu , Vasuki Gnanasambandam , Wilson David A. , Boykin David W.
Published: May 2005

The 1H, 13C and 17O NMR spectra of several 4,1‐disubstituted naphthalenes, viz. 4‐substituted 1‐ acetylnaphthalenes (series 1), 4‐substituted 1‐nitronaphthalenes (series 2), 4‐substituted 1‐methoxynaphthalenes (series 3) and 4‐substituted 1‐naphthyl methyl sulphides (series 4), were measured. The 17O and 13C chemical shifts of these 4,1‐disubstituted naphthalenes were compared with those of the corresponding 4,1‐disubstituted benzenes and analysed using the dual substituted parameter (DSP) equation. It is concluded that in series 1, 2 and 4 the substituent effects from the 4‐substituent to the C‐1 carbon and the side‐chain atoms are transmitted more effectively than those in the corresponding 4,1‐disubstituted benzenes, whereas the transmission in series 3 is almost equal to that in the analogous benzene series, viz. 4‐substituted anisoles. The reverse substituent effects displayed by the H‐8 chemical shifts of series 1 and 2 and the existence of linear relationships between the chemical shifts of H‐8 and the 17O chemical shifts of the oxygen of both the acetyl and nitro groups in series 1 and 2, respectively, are ascribed mainly to changes in the electron densities on the oxygen of the carbonyl and nitro groups affecting the diamagnetic screening of the proton.
Full assignments of the 13C and 1H NMR spectra of azithromycin in buffered D2O and DMSO‐d6
Authors: Brennan Richard J. , Barber Jill
Published: May 2005

The 13C and 1H NMR spectra of azithromycin in D2O and DMSO‐d6 have been unambiguously assigned using a range of 1 and 2D NMR methods. Similarities to the spectra of azithromycin in CDCl3 and of erythromycin A ketone in the same solvents are discussed.
On‐line monitoring of the Krebs cycle in isolated heart mitochondria by 13C NMR spectroscopy
Authors: Offermann Werner , Fiedler Evi , Helmle‐Kolb Corinna , Hofer Werner , Kugel Harald , Reese Torsten , Werk Willi , Leibfritz Dieter
Published: May 2005

When isolated rat heart mitochondria were incubated with [3‐13C]pyruvate in the presence of oxygen and aspartate or malate, the spin label 13C was incorporated into the components of the Krebs cycle, which we monitored in situ by 13C NMR spectroscopy. In the spectra 21 isotopomers of citrate, 2‐ketoglutarate, glutamate, succinate, fumarate, malate and aspartate were conclusively found and the presence of ten more isotopomers could be inferred from metabolic reasons. Chemical shifts, δ, carbon–carbon coupling constants, J, and spin–lattice relaxation rates, T1, of these compounds were measured in suspensions of isolated mitochondria during respiration. It is demonstrated that the 13C signal of Tris buffer can be used to follow the respirational change in pH. It is shown by comparison of the spectra of a complete suspension and its fluid and solid components, that the observed signals are entirely due to the supernatant solution, and not to the mitochondrial matrix. By supplying different cosubstrates it was possible to emphasize various parts of the Krebs cycle. Mitochondria incubated with aspartate released only labelled glutamate and aspartate, whereas the cosubstrate malate allowed the observation of all the metabolites mentioned above. The appearance of multiplet signals indicated recycling of metabolites and can be understood in terms of known metabolic pathways and trans‐membrane transport. The spectroscopic and biochemical information which is necessary in order to evaluate series of carbon spectra recorded during stimulus experiments performed with suspensions of isolated mitochondria is presented.
Correlation of oxygen‐17 substituent‐induced chemical shifts: Meta‐ and para‐substituted methyl benzoates
Authors: Exner Otto , Dahn Hans , Péchy Péter
Published: May 2005

Oxygen‐17 NMR spectra of 45 substituted methyl benzoates in acetonitrile were measured at natural abundance. The substituent‐induced chemical shifts (SCS) of the carbonyl oxygen correlate well with the σm and σ substituent constants in two separate correlations for meta and para derivatives; principal component analysis (PCA) is only slightly better [particularly for the N(CH3)2 substituent]. The 17O SCS generally depend on the same factors as the 13C SCS of the β‐carbon of alkenes, provided comparison is made between compounds of similar polarity. SCS of the methoxyl oxygen depend less precisely on σm or σp, with some unexplained deviations.
Trimethylstannylboranes—inverse detection of broad 119Sn NMR signals in solution and solid‐state 119Sn cross‐polarization magic angle spinning NMR
Authors: Wrackmeyer Bernd , Kupče Ēriks , Kümmerlen Jörg
Published: May 2005

Extremely broad 119Sn resonances, as the result of 1J(119Sn,11B) scalar coupling, were readily detected, even for diluted samples (5 mg in 0.5 ml of C6D6), via inverse two‐dimensional 1H{119Sn} NMR experiments. Two bis(amino)trimethylstannylboranes and four dialkylaminobis(trimethylstannyl)boranes were studied. The reaction between diisopropylaminobis(trimethylstannyl)borane and trimethoxyborane was monitored by the same technique, leading to the detection of diisopropylaminomethoxytrimethylstannylborane and dimethoxytrimethylstannylborane as reaction products. Crystalline dicyclohexylaminobis(trimethylstannyl)borane was studied by 119Sn CP/MAS NMR. In spite of the proximity of 119Sn to the quadrupolar 11B nucleus, meaningful spectra could be obtained in a short time (≤ 2 h).
Differential rates of NH proton exchange reactions of two isomeric enamines
Authors: Yavari Issa , Hosain‐Nia Azar
Published: May 2005

Proton NMR spectra of (E)‐ and (Z)‐[1,2‐bis(methoxycarbonyl)vinyl]aminotoluene were obtained in neutral and basic solutions at 25°C. Base‐catalysed NH proton exchange of the E isomer was found to be about 50 times faster than for the Z isomer. The results are rationalized by consideration of electronic and hydrogen bonding effects.
Regular and relayed heteronuclear correlations by a single two‐dimensional experiment involving an RF gradient
Authors: Canet D. , Brondeau J. , Montigny F. , Humbert F.
Published: May 2005

In order to achieve a better suppression of signals arising from protons non‐bonded to the considered heteronucleus, two (π/4) proton pulses are used in the HMQC sequence: one, at the very beginning, replaces the classical (π/2) pulse and the other is at the end of the sequence. In addition, a spin‐lock purging period improves the elimination process. This novel sequence is shown to provide the conventional heteronuclear correlations and, in addition, relayed homonuclear (proton–proton) correlations. A simple methodology capable of sorting out both types of correlations is proposed. However, this procedure entails a sensitivity loss by a factor of two.
Stereochemical study of imines and their N‐borane adducts by 1H, 11B, 13C and 15N NMR
Authors: Ariza‐Castolo Armando , Paz‐Sandoval M. Angeles , Contreras Rosalinda
Published: May 2005

The synthesis and NMR spectra of the N‐borane adducts of two diimines, N‐borane‐bis(α‐phenylethylidene)ethylenediamine and N‐borane‐bis(α‐phenylbenzylidene)ethylenediamine, and four imines, N‐borane‐α‐methylethylidene‐2‐phenylethylamine, two N‐borane‐α‐phenylethylidene‐n‐butylamines and N‐borane‐α‐phenylbenzylidene‐n‐butylamine, are reported. The NMR spectra of the N‐borane adducts of these imines can be used to determine their configuration.
Substituent‐dependent conformational changes in 6β‐substituted codeine derivatives
Authors: Szilágyi László , Makleit Sándor , Hosztafi Sándor , Simon Csaba
Published: May 2005

Complete 1H and 13C NMR data are reported for eleven isocodeine and seven dihydroisocodeine derivatives bearing various substituents at position 6. In isocodeines having bulky succinimido or phthalimodo groups at C‐6 ring C adopts a half‐boat conformation, characterized by the quasi‐equatorial orientation of the C‐6N bond. The distortion from the usual boat form is due to steric interactions between C‐14 and β‐substituents at C‐6, and it is greater in 14‐hydroxy derivatives than in isocodeines unsubstituted at this position. In dihydroisocodeines the conformation of ring C is close to a chair, irrespective of the steric demand of the substituent at C‐6.
13C nuclear magnetic resonance studies on pyrano‐ and dihydropyrano‐1,3‐ diphenylprop‐2‐enones
Authors: Parmar V. S. , Sharma S. K. , Vardhan A. , Sharma R. K. , Gupta S. , Malhotra S. , Boll P. M.
Published: May 2005

The 13C NMR spectra of 19 differently substituted pyrano‐ and dihydropyrano‐1,3‐diphenylprop‐2‐enones were recorded and the results are discussed. The data will be useful in the identification of new and natural chalcones.
Region‐selective inverse‐detected long‐range heteronuclear chemical shift correlation using shaped pulses
Authors: Crouch Ronald C. , Spitzer Timothy D. , Martin Gary E.
Published: May 2005

F1 region‐selected variants of the HMBC experiment were compared and evaluated. In particular, a significant advantage was demonstrated for an E‐BURP‐2 pulse over a Gaussian 270° pulse for region‐selected applications. The Gaussian 270° pulse would still, however, be the preferred pulse for use in single‐resonance, on‐resonance selective excitation. Data are presented from NMR spectrometers both equipped and not equipped with programmable pulse modulators (waveform generators). Pulse evaluations were performed using the simple heteroaromatic alkaloid quindoline; application of the technique to the important immunosuppressive cyclic peptide cyclosporin‐A is also presented and discussed.
Concerted use of homo‐ and heteronuclear 2D NMR in the elucidation of the structure of a novel pentaester of 19‐hydroxyingol from Euphorbia marginata seeds
Authors: Branch Sarah K. , Rowan Michael G.
Published: May 2005

Homo‐ and heteronuclear 2D NMR techniques were used to elucidate the structure of a novel pentaester of 19‐hydroxyingol from Euphorbia marginata seeds. The diterpene skeleton was identified by 1H 1D and 2D COSY spectra. Heteronuclear 2D 13C1H shift correlation spectroscopy was used to assign the 13C signals. The position of the esterified hydroxymethyl group at C‐10 was identified by NOE difference spectroscopy. The nature of the five ester groups and their corresponding positions on the diterpene skeleton were identified by a combination of long‐range 2D 13C1H correlation experiments and 13C spectra with 1H selective decoupling.
High‐resolution solid‐state 195Pt nuclear magnetic resonance in hexachloroplatinates(IV)
Authors: Hayashi Shigenobu , Hayamizu Kikuko
Published: May 2005

High‐resolution solid‐state 195Pt NMR spectra of ammonium, potassium and sodium hexachloroplatinate(IV) and its hydrate were investigated using magic angle spinning of the sample. The isotropic part of the spectra has fine structure originating from dipole–dipole interaction and indirect spin coupling between platinum and chlorine nuclei. The fine structure was analysed theoretically, yielding the indirect spin coupling constants and their anisotropies.
Study of the dynamics of ferrocene enclathrated in β‐ and γ‐cyclodextrins by one‐dimensional switching‐angle sample spinning NMR spectroscopy
Authors: Imashiro Fumio , Kuwahara Daisuke , Kitazaki Nobuyuki , Terao Takehiko
Published: May 2005

13C chemical shift powder patterns of ferrocene enclathrated in β‐ and γ‐cyclodextrins were measured by one‐dimensional switching‐angle sample spinning NMR spectroscopy. The ferrocene molecules were found to precess with a precession angle of 69° in γ‐cyclodextrin. In β‐cyclodextrin the ferrocene molecules I–III, in different motional states, were enclathrated with populations of 0.42, 0.32 and 0.26, respectively; ferrocene I is tightly enclathrated and rotates around its fivefold axis, whereas ferrocenes II and III precess with precession angles of 30° and 42°, respectively.
Ab initio study of the 13C NMR chemical shifts for some polyene compounds as models for the chromophore of rhodopsin
Authors: Wada M. , Sakurai M. , Inoue Y. , Chûjô R.
Published: May 2005

Ab initio NMR shieldings, based on the Hansen and Bouman theory, were calculated for some polyene compounds in order to apply the method to retinal proteins. It is shown that the ab initio results reproduce well the magnetic properties peculiar to the polyene 13C chemical shifts. In addition, the 13C and 15N shieldings were calculated for several amines as model compounds of the retinal moiety located in bacteriorhodopsin, and the effect on the chemical shifts of the syn–anti orientation about the CN double bond and the protonation of the Schiff base was investigated.
6Li15N heteronuclear multiple quantum correlation (HMQC) spectroscopy: Application to the structure determination of lithium 2,2,6,6‐tetramethylpiperidide mixed aggregates
Authors: Gilchrist James H. , Harrison Aidan T. , Fuller David J. , Collum David B.
Published: May 2005

A heteronuclear multiple quantum correlation (HMQC) experiment was used to correlate the 6Li and 15N chemical shifts of mixed aggregates of [6Li, 15N]lithium 2,2,6,6‐tetramethylpiperidide with [6Li]LiBr, [6Li]LiCl, and [6Li]lithium cyclohexenolate. Optimization of the experiment to spin systems containing more than one weak spin is discussed. The two‐dimensional correlations represent a substantial improvement in sensitivity and resolution relative to one‐dimensional methods.
1H‐detected studies of geminal 29Si13C couplings: Dependence of coupling sign and magnitude on molecular structure
Authors: Kupč Ēriks , Wrackmeyer Bernd
Published: May 2005

The magnitude and signs of geminal 29SiZ13C coupling constants were determined for nine derivatives of representative organosilicon compounds [Z = C(sp2, sp3), N, O, (two‐ and three‐coordinate), Si, S] from 1H‐detected two‐dimensional (2D) Ψ‐BIRD‐HSQC and Ψ‐BIRD‐HMQC pseudo‐triple resonance 1H29Si(13C) and 1H13C(29Si) experiments. The high sensitivity of the method allowed the measurements to be carried out in less than 1 h using 2–10 mg of the respective compound. Couplings as small as 0.45 Hz have been resolved. The couplings ranged from −21.4 to +2.2 Hz, showing regular dependence on the nature, hybridization and coordination of the intervening Z atom.
Flip angle calibration of NMR pulses
Authors: Goez Martin
Published: May 2005

Different one‐dimensional methods for the measurement of the effective flip angles of NMR observation pulses are discussed, and their stability against the noise of the experimental input data is compared. A new multipulse scheme is presented which is much better suited for the determination of small flip angles. Effects of dipolar interactions in a solid on the accuracy of the results are estimated. Experimental tests are given, showing the feasibility of the proposed calibration method.
Natural abundance 17O NMR spectra of some sulphinylimines and isocyanates
Authors: Vedova C. O. Della , Duddeck H. , Praas H.‐W.
Published: May 2005

The 17O chemical shifts of nine sulphinylimines and isocyanates are reported and discussed in terms of electronic and mesomeric effects. Unusually large values were found for the sulphinylimines. The differences in acyl fluorides compared with acyl chlorides are rationalized on the basis of a mesomeric form, implying an increase of the carbonyl bond order.
Assignment of proton NMR resonances and conformational analysis of the K13CK cystatin‐like peptide
Authors: Samsoen Catherine , Lebrun Evelyne , Van Rapenbusch Roland , Davoust Daniel , Lalmanach Gilles
Published: May 2005

The assignments of the proton NMR signals and the conformational analysis of the cystatin‐mimicking peptide K13CK (Lys‐Val‐Gly‐Gly‐Gln‐Val‐Val‐Cys‐Gly‐Ala‐Pro‐Trp‐Lys) in aqueous solution at pH 3.2 have been achieved using two‐dimensional DQF‐COSY, HOHAHA and ROESY nuclear magnetic resonance techniques. The chemical shifts, the magnitudes of the coupling constants, the temperature dependences of the amide protons and the intramolecular NOEs were used to obtain information on the conformation. The NMR spectra of cysteine proteinase inhibitor K13CK demonstrate a cis‐trans isomerism at the Ala10Pro11 peptide bond.