bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural analysis of 3‐α‐acetyl‐20(29)‐lupene‐24‐oic acid, a novel pentacyclic triterpene isolated from the gum resin of Boswellia serrata, by NMR spectroscopy
Authors: Belsner Klaus , Büchele Berthold , Werz Udo , Simmet Thomas 
Published: July 2003

Abstract3α‐Acetyl‐20(29)‐lupene‐24‐oic acid (1) was isolated from the gum resin of Boswellia serrata. Its presence evidently suggests, that the oxidosqualene triterpene pathway of Boswellia serrata closely resembles the biosynthetic route already found in other plants. Complete 1H and 13C spectral assignments were derived from 1D and 2D NMR spectra. This is the first compound with the lupene backbone combining a 3α‐hydroxy or 3α‐acetyl group with the 24‐carboxyl group, a configuration which is typical of the classical boswellic acids. Copyright © 2003 John Wiley & Sons, Ltd.
Structural determination and complete NMR spectral assignments of a new diterpenoid obtained from triptonide by biotransformation
Authors: Ning Lili , Jiang Xiaomei , Ye Min , Guo Hongzhu , Bi Kaishun , Guo Dean 
Published: July 2003

AbstractA new diterpenoid, 12β,13α‐dihydroxytriptonide, was obtained from the transformed culture of triptonide by Catharanthus roseus cell suspension cultures. The complete 1H and 13C NMR assignments of the compound were carried out by using DEPT, COSY, HSQC, g‐HMBC and NOESY techniques. Copyright © 2003 John Wiley & Sons, Ltd.
Complete assignments of 1H and 13C NMR resonances of oleanolic acid, 18α‐oleanolic acid, ursolic acid and their 11‐oxo derivatives
Authors: Seebacher Werner , Simic Nebojsa , Weis Robert , Saf Robert , Kunert Olaf 
Published: July 2003

AbstractComplete assignments of 1H and 13C NMR chemical shifts for oleanolic acid, 18α‐oleanolic acid, ursolic acid and their 11‐oxo derivatives based on 1H, 13C, 2D DQF‐COSY, NOESY, HSQC, HMBC and HSQC‐TOCSY experiments were achieved. Copyright © 2003 John Wiley & Sons, Ltd.
Influence of the C—H· · ·N intramolecular interaction on the spatial structures and 1H and 13C NMR parameters of heteroaryl vinyl ethers and sulfides
Authors: Afonin Andrei V. , Ushakov Igor A. , Kuznetsova Svetlana Yu. , Andriyankova Lyudmila V. 
Published: July 2003

AbstractA complete analysis of the 1H and 13C spectra of the representative series of heteroaryl vinyl ethers and sulfides and heteroaryl styryl sulfides was carried out. The electronic and spatial structures of these compounds are discussed. It was shown that the C—H· · ·N intramolecular interactions in the investigated molecules influence significantly the spectral parameters and the conformational equilibrium. Copyright © 2003 John Wiley & Sons, Ltd.
NMR spectroscopy as a tool to investigate the degradation of aromatic compounds by a Pseudomonas putida strain
Authors: Bertini I. , Provenzani A. , Viezzoli M. S. , Pieper D. H. , Timmis K. N. 
Published: July 2003

AbstractPseudomonas putida strain KT2442, harbouring the pWW0 TOL plasmid, was grown with a number of different homologous aromatic acids as carbon sources. Small samples of liquid culture supernatant were collected and directly analysed by 2D NMR spectroscopy. In all cases similar compounds with olefinic signals were observed to accumulate. To elucidate the structures of these compounds, 2D NMR experiments with 500 and 600 MHz spectrometers equipped with a CryoProbe (Bruker BioSpin) were performed on samples obtained from a culture growing on 4‐methylbenzoate and, for 13C spectroscopy, on 13C‐labelled 4‐methylbenzoate. In all cases a 1,2‐dihydroxycyclohexa‐3,5‐diene‐carboxylate derivative was identified. The use of this technique helped us to identify easily some metabolites that were released into the solution by bacteria and to follow their secretion as a function of time. The high sensitivity of the present approach allowed a clear and rapid acquisition of spectra, notwithstanding the low concentration of the compounds. The benefits of introducing the use of NMR cryoprobes to perform metabolic pathway studies is demonstrated. Copyright © 2003 John Wiley & Sons, Ltd.
Assignment of chemical shifts in benzohydroxamic acid and structure of its silylated derivatives by 15N enrichment
Authors: Schraml Jan , Blechta Vratislav , Soukupová Ludmila , Karban Jindřich , Mindl Jaromír 
Published: July 2003

Abstract15N isotopic enrichment was necessary for the unequivocal assignment of the 1H NMR lines to the protons in the NH–OH fragment of benzohydroxamic acid, BHXA, C6H5CONHOH, in dry dimethyl sulfoxide solutions. The assignment [δ(NH) = 11.21, δ(OH) = 9.01, 1J(15N,1H) = 102.2 Hz, 2J(15N,1H) <1.5 Hz], which is opposite to that used by other authors, confirms the assignment extended to BHXA by Brown and co‐workers from the spectra of acetohydroxamic acid. The enrichment allowed also assignment of the 29Si lines in the spectra of disilylated benzohydroxamic acid, (Z)‐tert‐butyldimethylsilyl N‐tert‐butyldimethylsilyloxybenzoimidate (2) and (Z)‐tert‐butyldiphenylsilyl N‐tert‐butyldiphenylsilyloxybenzoimidate (3), and confirmed structure of the monosilylated products, N‐tert‐butyldiphenylsilyloxybenzamide (4) and N‐tert‐butyldiphenylsilyloxy benzoimidic acid (5). Copyright © 2003 John Wiley & Sons, Ltd.
Multinuclear magnetic resonance, electrospray ionization time‐of‐flight mass spectral and molecular modelling characterization of lithocholic acid amide esters with various nitrogen heterocycles
Authors: Virtanen Elina , Tamminen Jari , Haapala Mervi , Mänttäri Pia , Kauppinen Reijo , Kolehmainen Erkki 
Published: July 2003

Abstract1H, 13C and 15N NMR and electrospray ionization time‐of‐flight mass spectrometric characterizations of five lithocholate esters of piperazine diamides are described. Two of them are cholaphane‐type cyclic structures esterified with 2,2′‐bipyridine‐4,4 ′ ‐ and pyridine‐2,6‐dicarboxylic acid and the other three esters are open structures comprising two or four lithocholyl residues. The conformational preferences of the dimeric congeners were examined by using molecular modelling and variable‐temperature 1H NMR techniques. Copyright © 2003 John Wiley & Sons, Ltd.
Use of natural abundance 15N DEPT NMR to investigate curing of urea–formaldehyde resin in the presence of wood fibers
Authors: Gill B. D. , Manley‐Harris M. , Thomson R. A. 
Published: July 2003

AbstractNatural abundance 15N NMR using a DEPT pulse sequence was employed to follow the curing of urea–formaldehyde resin in the presence of wood fiber, fiber extracts and acid or base. The advantages of 15N NMR, large range chemical shifts, simplification of spectra and lack of interference by additives, can be exploited. The disadvantages of low sensitivity and long relaxation delays are offset by using a cross‐polarization technique. Copyright © 2003 John Wiley & Sons, Ltd.
15N NMR spectra of some 3‐substituted 4(1H)‐quinolinones and their 1‐methyl derivatives
Authors: Zięba Andrzej , Maślankiewicz Andrzej , Milata Viktor , Sitkowski Jerzy 
Published: July 2003

Abstract15N NMR spectral data for 3‐substituted (chloro, bromo, acetyl, carboxy, carboethoxy, methylsulfanyl, methylsulfinyl, N,N‐dimethylsulfamoyl, nitro) 4(1H)‐quinolinones and their 1‐methyl derivatives are presented. Copyright © 2003 John Wiley & Sons, Ltd.
Detailed assignments of 1H and 13C NMR spectral data of 14 cyclopentane derivatives
Authors: Constantino Mauricio Gomes , Júnior Valdemar Lacerda , da Silva Gil Valdo José 
Published: July 2003

AbstractDetailed assignments of 1H and 13C NMR spectral data for 14 cyclopentane derivatives are reported. The assignments are based on 1D 1H and 13C NMR and on 2D shift‐correlated [1H, 13C‐HMQC], J‐resolved and NOEDIF experiments. Copyright © 2003 John Wiley & Sons, Ltd.
Assignment of the major and minor components of gentamicin for evaluation of batches
Authors: Deubner Ralph , Schollmayer Curd , Wienen Frank , Holzgrabe Ulrike 
Published: July 2003

AbstractThe antibiotic agent gentamicin sulfate is a mixture of several structurally very similar aminoglycosides. The major components of gentamicin are gentamicin C1, C1a, C2 and C2a. These major components were separated by means of column chromatography. The 1H and 13C NMR spectra of the free bases and the corresponding sulfates were assigned using HMQC, HMBC and selective TOCSY experiments. Additionally, the 1H and 13C NMR spectra of the sulfates and hydrochlorides, respectively, of the minor components were assigned. The full assignment of all components of gentamicin is necessary for the quantitative analysis of batches of gentamicin. By means of coupled liquid chromatography–NMR, several different batches were studied, revealing different compositions of batches from various sources. Copyright © 2003 John Wiley & Sons, Ltd.
Gradient‐enhanced one‐dimensional pulse schemes for quaternary and methylene carbon detection
Authors: Nagana Gowda G. A. 
Published: July 2003

AbstractGradient‐enhanced pulse schemes are presented for the detection of quaternary and methylene carbons. The new pulse schemes permit the detection of quaternary and methylene (—CH2) carbons or CH2 carbons alone from a single experiment. Efficient suppression of CH and CH3 carbons in all the pulse schemes is achieved by creating their antiphase magnetization and then dephasing using gradients. In the pulse schemes for detection of only CH2 carbons, the quaternary carbons are also suppressed either by dephasing using gradients or by rendering them unobservable by retaining in longitudinal order. The experimental results of the gradient pulse schemes are demonstrated on cholesteryl acetate and cyclosporin A. These one‐dimensional techniques, because of their simplicity and the ease of performing the experiments, can be important for routine chemical applications. Copyright © 2003 John Wiley & Sons, Ltd.
NMR and EPR studies of the reaction of nucleophilic addition of (bi)sulfite to the nitrone spin trap DMPO
Authors: Potapenko Dmitrii I. , Bagryanskaya Elena G. , Reznikov Vladimir V. , Clanton Thomas L. , Khramtsov Valery V. 
Published: July 2003

AbstractThe reaction of the nitrone spin trap 5,5‐dimethylpyrroline‐N‐oxide (DMPO) with sodium (bi)sulfite in aqueous solutions was investigated using NMR and EPR techniques. Reversible nucleophilic addition of (bi)sulfite anions to the double bond of DMPO was observed, resulting in the formation of the hydroxylamine derivative 1‐hydroxy‐5,5‐dimethylpyrrolidine‐2‐sulfonic acid, with characteristic 1H and 13C NMR spectra. The reaction mechanism was suggested and corresponding equilibrium constants determined. The mild oxidation of the hydroxylamine results in the formation of an EPR‐detected spectrum identical with that for the DMPO adduct with sulfur trioxide anion radical. The latter demonstrates that a non‐radical addition reaction of (bi)sulfite with DMPO may contribute to the EPR detection of SO3−• radical. This possibility must be taken into account in spin trapping analysis of sulfite radical. Copyright © 2003 John Wiley & Sons, Ltd.
Quindolinocryptotackieine: the elucidation of a novel indoloquinoline alkaloid structure through the use of computer‐assisted structure elucidation and 2D NMR
Authors: Blinov Kirill , Elyashberg Mikhail , Martirosian Eduard R. , Molodtsov Sergey G. , Williams Antony J. , Tackie Albert N. , Sharaf Maged M. H. , Schiff Paul L. , Crouch Ronald C. , Martin Gary E. , Hadden Chad E. , Guido Jane E. , Mills Kent A. 
Published: July 2003

AbstractNumerous indoloquinoline alkaloid structures have been identified from extracts of the West African plant Cryptolepis sanguinolenta. Recently, through the use of 2D NMR methods and cryogenic NMR probe technology in conjunction with computer‐assisted structure elucidation (CASE) methods, the structures of some chemical degradation products of this family of alkaloids have also been reported. We now report the characterization of a novel indoloquinoline dimeric alkaloid, quindolinocryptotackieine, through the extensive utilization of CASE methods. The NMR data presented here were collected over a decade earlier before the elucidation of the structure was possible, since manual analysis did not present a conclusive structure, whereas CASE produced a series of structures from which the structure could be verified. The original mass spectrometric (MS) data collected for the sample were problematic. Contemporary MS data were instead recollected from remaining small quantities of this alkaloid using modern instrumentation. The re‐collected data gave a usable molecular ion and several key fragment ions that were diagnostically useful. Copyright © 2003 John Wiley & Sons, Ltd.
Isolation and characterization of a Tie2 kinase inhibitory sulfated triterpenoid from a green alga of the Tuemoya genus: complete assignment of the 1H and 13C spectra of a sulfated triterpenoid Tie2 kinase inhibitor
Authors: Clement Jason A. , Zhou Bing‐Nan , Johnson Randall K. , Kingston David G. I. 
Published: July 2003

AbstractBioassay‐guided fractionation of an extract of a Tuemoya sp., using an assay for inhibitors of the enzyme Tie2 kinase, afforded a mixture of the sulfated cycloartanol triterpenoids 1 and 2. We report the full 1H and 13C NMR spectral assignments for 1 and the 13C NMR spectral assignments for 2. Copyright © 2003 John Wiley & Sons, Ltd.
Conformational study of fosinopril sodium in solution using NMR and molecular modeling
Authors: Liu Songbai , Shi Yanhong , Zhang Qingwen , Song Guoqiang 
Published: July 2003

AbstractTwo conformers of fosinopril sodium in methanol were unambiguously established using 2D NMR methods and variable‐temperature NMR experiments. Differences in their conformational structure were shown to be related to the rotational energy barrier about the amide bond and hydrophobic interaction. The relationship between the 3D structure and activity is discussed. It is suggested that the trans‐conformer may be more biologically active owing to its stacking structure and strong hydrophobic interaction and the cis‐conformer could be more easily hydrolyzed because of its extended structure. Copyright © 2003 John Wiley & Sons, Ltd.
Back analysis of model parameters in geotechnical engineering by means of soft computing
Authors: Pichler B. , Lackner R. , Mang H. A. 
Published: July 2003

AbstractIn this paper, a parameter identification (PI) method for determination of unknown model parameters in geotechnical engineering is proposed. It is based on measurement data provided by the construction site. Model parameters for finite element (FE) analyses are identified such that the results of these calculations agree with the available measurement data as well as possible. For determination of the unknown model parameters, use of an artificial neural network (ANN) is proposed. The network is trained to approximate the results of FE simulations. A genetic algorithm (GA) uses the trained ANN to provide an estimate of optimal model parameters which, finally, has to be assessed by an additional FE analysis. The presented mode of PI renders back analysis of model parameters feasible even for large‐scale models as used in geotechnical engineering. The advantages of theoretical developments concerning both the structure and the training of the ANN are illustrated by the identification of material properties from experimental data. Finally, the performance of the proposed PI method is demonstrated by two problems taken from geotechnical engineering. The impact of back analysis on the actual construction process is outlined. Copyright © 2003 John Wiley & Sons, Ltd.
Development of the DYNA3D simulation code with automated fracture procedure for brick elements
Authors: Tabiei Ala , Wu Jin 
Published: July 2003

AbstractNumerical simulation of cracked structures is an important aspect in structural safety assessment. In recent years, there has been an increasing rate of development of numerical codes for modelling fracture procedure. The subject of this investigation is implementing automated fracture models in the DYNA3D non‐linear explicit finite element code to simulate pseudo 3D crack growth procedure. The implemented models have the capabilities of simulating automatic crack propagation without user intervention. The implementation is carried on solid elements. The methodology of implementing fracture models is described. An element deletion‐and‐replacement remeshing procedure is proposed for updating the explicit geometric description of evolving cracks. Fracture parameters such as stress intensity factors, energy release rates and crack tip opening angle are evaluated. The maximum circumferential stress criterion is used to predict the direction of crack advancement. Seven crack problems are presented to verify the effectiveness of the methodology. Mesh sensitivity and loading rate effects are studied in the validation of the presented procedure. Copyright © 2003 John Wiley & Sons, Ltd.
Fast direct solution of the Helmholtz equation with a perfectly matched layer or an absorbing boundary condition
Authors: Heikkola Erkki , Rossi Tuomo , Toivanen Jari 
Published: July 2003

AbstractWe consider the efficient numerical solution of the Helmholtz equation in a rectangular domain with a perfectly matched layer (PML) or an absorbing boundary condition (ABC). Standard bilinear (trilinear) finite‐element discretization on an orthogonal mesh leads to a separable system of linear equations for which we describe a cyclic reduction‐type fast direct solver. We present numerical studies to estimate the reflection of waves caused by an absorbing boundary and a PML, and we optimize certain parameters of the layer to minimize the reflection. Copyright © 2003 John Wiley & Sons, Ltd.
A variant of the subspace iteration algorithm for generalized eigenproblems
Authors: Rajendran S. , Liew K. M. 
Published: July 2003

AbstractA variant of the subspace iteration algorithm for the generalized eigenproblem, Kp= λMp, is proposed. The algorithm does not require the computation of the projected stiffness matrix, and hence, the projected eigenproblem turns out to be a standard eigenproblem as against the generalized eigenproblem of the classical algorithm. This results in appreciable saving in the number of operations of the Rayleigh–Ritz step and hence the solution time, particularly when a large number of eigenvalues are to be computed. The numerical experiments suggest that the proposed algorithm can yield a saving in solution time of up to 28% for certain eigenproblems. Copyright © 2003 John Wiley & Sons, Ltd.
Discrete equivalent time integration methods for transient analysis
Authors: Muǧan Ata 
Published: July 2003

AbstractIt was recently shown in a series of papers that the frequency response of temporally discretized finite element equations and, consequently, the achievable accuracy cannot be manipulated independently in different frequency ranges. In addition, there exist limitations on the achievable accuracy of a time integration method no matter what the order of accuracy of the method is. Motivated by this fact, a family of time integration methods is derived in the time domain based on the principle that the exact solution of the semidiscrete equation of a system and the solution of the time integration method match at discrete time steps. It is necessary to pursue an exact match at discrete time steps, i.e. discrete equivalence, since the solutions of semidiscrete equations are obtained only at the time steps. Two time integration methods, that are exact at the time steps, are obtained based on the impulse and ramp response invariance principles. Numerical examples are presented to show the advantage of the proposed methods and to compare the performance of them with the performance of some popular methods. Copyright © 2003 John Wiley & Sons, Ltd.
Curved quadratic triangular degenerated‐ and solid‐shell elements for geometric non‐linear analysis
Authors: Kim C. H. , Sze K. Y. , Kim Y. H. 
Published: July 2003

AbstractCompared to the large number of curved quadrilateral degenerated‐ and solid‐shell elements, there are only a very few curved triangular degenerated‐ and solid‐shell elements. Based on the assumed natural strain sampling scheme previously developed for a quadratic degenerated‐shell element for linear analysis, this paper devises geometric non‐linear six‐node degenerated‐shell and twelve‐node solid‐shell elements. Both elements can be curved and are only equipped with the standard nodal d.o.f.s. Careful consideration has been exercised to circumvent various locking phenomena that plague degenerated‐ and solid‐shell elements. Numerical examples are presented to illustrate their efficacy. Copyright © 2003 John Wiley & Sons, Ltd.
Extension of a paediatric diabetes home care service
Authors: Kirk J , Thomas E , McEvilly A , Shaw N 
Published: July 2003

AbstractAt the end of 1994 a paediatric diabetes specialist nurse (PDSN) was appointed to extend the paediatric diabetes home care service between the Birmingham Children's Hospital and a district general hospital (City Hospital) in Birmingham. As a result 24‐hour home care can now be offered to newly diagnosed and existing paediatric patients with diabetes at City Hospital. The initial mean HbA1c for the clinic was 9.8%, which since then has fallen to a mean of 8.95% (range 7.9–9.4%); a mean reduction of 0.85%. As a result of home care there has been a sustained reduction in bed‐days for newly diagnosed patients (median five patients per year) and for re‐admissions of existing patients. In addition to any long‐term benefits arising from improvement in diabetic control, the cost savings of reduction in bed‐days alone at £235 per day (Total £15110 per year) outweigh the cost of the PDSN post (£14800 per year). Copyright © 2003 John Wiley & Sons, Ltd.
A countywide primary care annual audit fails to demonstrate an improvement in diabetes care between 1996 and 2001
Authors: Masding MG , Adams A , Dawson A , Gatling W 
Published: July 2003

AbstractMultipractice audit is widely used and can affect diabetes care. We reviewed the Dorset diabetes audit between 1996 and 2001 to investigate the prevalence of diabetes and to examine if the processes of diabetes care change over time.Data on prevalence of diabetes and the numbers of patients who underwent annual diabetes review, foot and eye screening, and measurement of blood pressure (BP), creatinine and HbA1c was obtained from 102 out of 109 Dorset general practices (involving a total population of 663466 people) on an annual basis between 1996 and 2001.The prevalence of diabetes rose from 2.34% (95% CI 2.30, 2.37) in 1996/97 to 2.59% (2.55, 2.63) in 2000/01. The proportion of patients undergoing the process of diabetes care fell slightly over the five years: annual review 92.7% (92.1, 93.3) to 85.0% (84.4, 85.6), p<0.001; foot review 80.5% (79.9, 81.1) to 71.7% (71.0, 72.4), p<0.001; eye review 76.7% (75.9, 77.5) to 65.5% (64.8, 66.2), p<0.001; BP measurement 89.8% (89.2, 90.5) to 86.7% (86.1, 87.2), p<0.001; creatinine measurement 84.0% (83.3, 84.7) to 80.1% (79.5, 80.7), p<0.001; HbA1c measurement 88.4% (87.8, 88.0) to 86.3% (85.8, 86.8), p<0.001.The prevalence of diabetes in Dorset rose significantly between 1996 and 2001, adversely affecting diabetes complication screening rates. Screening rates for diabetes complications deteriorated over the five years of our study, after an initial rise when the audit was newly established. Alternative strategies to improve diabetes care may be necessary to change clinical practice. Copyright © 2003 John Wiley & Sons, Ltd.