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  • 1
    Electronic Resource
    Electronic Resource
    Studies on the comparative toxicity of S-(1,2-dichlorovinyl)-L-cysteine, S-(1,2-dichlorovinyl)-L-homocysteine and 1,1,2-trichloro-3,3,3-trifluoro-1-propene in the Fischer 344 rat (1994)
    Springer
    Archives of toxicology 69 (1994), S. 99-110 
    Details
    ISSN: 1432-0738
    Keywords: Key words 3-D-hydroxybutyrate ; Glucose ; L-lactate ; 1H NMR urinalysis ; S-Conjugate-mediated nephrotoxicity ; S-(1 ; 2-Dichlorovinyl)-L-cysteine ; S-(1 ; 2-Dichlorovinyl)-L-homocysteine ; 1 ; 1 ; 2-Trichloro-3 ; 3 ; 3-trifluoro-1-propene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The renal tubular toxicity of various halogenated xenobiotics has been attributed to their enzymatic bioactivation to reactive intermediates by S-conjugation. A combination of high resolution proton nuclear magnetic resonance (1H NMR) spectroscopy of urine, renal histopathology and more routinely used clinical chemistry methods has been used to explore the acute toxic and biochemical effects of S-(1,2-dichlorovinyl)-L-cysteine (DCVC), S-(1,2-dichlorovinyl)-L-homocysteine (DCVHC) and 1,1,2-trichloro-3,3,3-trifluoro-1-propene (TCTFP) up to 48 h following their administration to male Fischer 344 (F344) rats. In the absence of gross renal pathology, 1H NMR urinalysis revealed increased excretion of the tricarboxylic acid cycle intermediates citrate and succinate following DCVC administration. In contrast, both DCVHC and TCTFP produced functional defects in the S2 and S3 segments of the proximal tubule that were confirmed histologically. In these cases, 1H NMR urinalysis revealed increased excretion of glucose, L-lactate, acetate and 3-D-hydroxybutyrate (HB) as well as selective amino aciduria (alanine, valine, glutamate and glutamine). The significance of the proximal nephropathies induced by DCVHC and TCTFP is discussed in relation to biochemical observations on other xenobiotics that are toxic by similar mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050144
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative structure chromatography relationships in reversed-phase high performance liquid chromatography: Prediction of retention behaviour using theoretically derived molecular properties (1993)
    Springer
    Chromatographia 37 (1993), S. 241-249 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pattern recognition ; Principal components ; Multiple linear regressions ; M.O. properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of theoretically calculated molecular properties as predictors for retention in reversed-phase HPLC has been explored. HPLC retention times have been measured for a series of 47 substituted aromatic molecules in three solvent mixtures and steric and electronic properties of these compounds have been derived using semi-empirical molecular orbital and empirical theoretical methods. A subset of the experimental data (a training set) was used to derive property-retention time relationships and the remaining data were then used to test the predictive capability of the methods. Good retention time prediction was possible using derived regression equations for individual solvents and after including solvent parameters it was possible to predict retention for all solvents using a single equation. This method showed that the most useful properties were calculated log P and the calculated dipole moment of the solutes, and the calculated solvent polarisability. In addition, 90% of the data were used to train an artificial neural network and the remaining 10% of the data used to test the network; excellent prediction was obtained, the neural network approach being as successful as the regression analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278628
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  • 3
    Electronic Resource
    Electronic Resource
    High performance liquid chromatography coupled to nuclear magnetic resonance spectroscopy and mass spectrometry applied to plant products: Identification of ecdysteroids fromSilene otites (1999)
    Springer
    Chromatographia 49 (1999), S. 374-378 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; NMR spectroscopy and mass spectrometry ; Plant products ; Silene otites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC coupled in parallel to nuclear magnetic resonance (NMR) and mass spectrometry (MS) has been used to obtain1H NMR and mass spectra of a number of ecdysteroids present in an extract of the plantSilene otites. Reversed phase gradient chromatography was performed using a D20-acetonitrile-based solvent system. NMR and mass spectra were obtained for integristerone A, 20-hydroxyecdysone, 2-deoxy-20-hydroxyecdysone and 2-deoxyecdysone to provide structural confirmation using continuous and stopped flow HPLC-NMR. The combined HPLC-NMR-MS system described here provided a more comprehensive analysis of the ecdysteroids present in the extract than HPLC-NMR alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467609
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  • 4
    Electronic Resource
    Electronic Resource
    13C NMR studies of tautomerism in imidazo[4,5-c]pyridines (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 992-994 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; Tautomerism ; Inotropism ; Imidazopyridine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A detailed analysis of the 13C NMR spectra of the 1-N- and 3-N-methyl derivatives of 1H-2-(2,4-dimethoxyphenyl)imidazo[4,5-c]pyridine, utilizing long-range couplings and 2D 1H—13C correlation experiments, has led to an unambiguous assignment of all carbons. Comparison of these definitive assignments of C-3a and C-7a, in particular, with those of the tautomers of 1H-2-(2,4-dimethoxyphenyl)imidazo[4,5-c]pyridine has permitted confirmation of the predominance of the 1H-tautomer for the latter. In addition, previous conflicting assignments for 1H-imidazo[4,5-c]pyridine and its 3-N-methyl derivative are now resolved. Revision of these assignments leads to the conclusion that the 1H-tautomer of 1H-imidazo[4,5-c]pyridine is predominant.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260271016
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  • 5
    Electronic Resource
    Electronic Resource
    Tautomerism in 2-hydroxy-1-naphthaldehyde schiff bases in solution and the solid state investigated using 13C NMR spectroscopy (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 991-994 
    Details
    ISSN: 0749-1581
    Keywords: Schiff bases ; Tautomerism ; 13C NMR CP/MAS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C and 1H NMR spectra of six Schiff bases formed from 2-hydroxy-1-naphthaldehyde and substituted anilines were measured and assigned in a variety of solvents. Based on the 13C chemical shifts and 3J(CH,NH), the ratio of the keto-amine and phenol-imine tautomers was derived using both 13C chemical shifts and 1H-1H coupling constants, the two methods giving comparable results. The solid-state 13C NMR spectra of two of these Schiff bases were also measured and interpreted. Based on chemical shift assignments from solution NMR, which showed a relationship between certain shifts and the proportions of the tautomers, it has been shown that these compounds exist essentially as the keto-amine form in the solid, the tautomer previously shown to be the more thermodynamically stable.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260311107
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  • 6
    Electronic Resource
    Electronic Resource
    Separation and characterization of components of peptide libraries using on-flow coupled HPLC - NMR spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 857-863 
    Details
    ISSN: 0749-1581
    Keywords: peptides ; HPLC-NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The efficiency of directly coupled HPLC - NMR spectroscopy for the separation and characterization of synthetic peptide libraries was investigated using a model system based on a mixture of all 27 tripeptide combinations of alanine (A), methionine (M) and tyrosine (Y) as the C-terminal amides. The 1H NMR spectra were obtained in real time using on-flow HPLC - NMR spectroscopy at 600 MHz and 21 of the 27 peptides were identified on the basis of chemical shifts and coupling constants, including the use of diagnostic values derived from 1H NMR spectra and 1H—13C and 1H—15N HMQC studies on authentic A—A—A—OH and Y—Y—Y—OH. The effects on 1H NMR chemical shifts of pH and of varying proportions of acetonitrile and water as occurred during the gradient elution HPLC run were evaluated. The HPLC - NMR approach could provide a facile method for investigating the relative efficiency of resin-based peptide synthesis for different amino acid combinations and should rapidly provide data suitable for deriving structure-retention time relationships for peptides.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260331103
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  • 7
    Electronic Resource
    Electronic Resource
    A multinuclear magnetic resonance study of protonation in imidazo[1,2-a]pyrazine (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 874-877 
    Details
    ISSN: 0749-1581
    Keywords: NMR ; 13C ; 15N ; Protonation ; Imidazo[1,2-a]pyrazine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 13C NMR spectra are reported and assigned for imidazo[1,2-a] pyrazine and for N-1-methyl- and N-7-methyl-imidazo[1,2-a] pyrazinium iodides. The effect of protonation on the chemical shifts of the parent molecule is demonstrated, and through the use of 13C and 15N NMR spectra the site of protonation is deduced to be at N-1, in contrast to 2-aryl substituted compounds synthesised as potential cardiotonic agents where protonation occurs at N-7.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260281008
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  • 8
    Electronic Resource
    Electronic Resource
    G. A. Webb (editor). Annual reports on NMR spectroscopy, vol. 23. Academic Press, London, 1991, pp. 425, £65.00 (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 1233-1233 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260291214
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  • 9
    Electronic Resource
    Electronic Resource
    1H and 13C NMR studies of the protonation of isomeric methoxysulmazole analogues (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 573-575 
    Details
    ISSN: 0749-1581
    Keywords: Inotropism ; Imidazopyridine ; 13C NMR ; 1H NMR Tautomerism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The major protonation sites of six cardiotonic isomeric 2-aryl-n-methoxy-1H-imidazo[4,5-b]- and -[4,5-c]-pyridines (n = 4-7) were determined by 1H and 13C NMR methods. All the 1H-imidazo[4,5-c]pyridines and the 7-methoxy derivative of sulmazole were found to protonate at the pyridyl nitrogen. Protonation occurred at the imidazo nitrogen, however, for the 5- and 6-methoxy derivatives of sulmazole.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280703
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  • 10
    Electronic Resource
    Electronic Resource
    Multinuclear magnetic resonance study of tautomerism in fluorinated β-diketones (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 645-650 
    Details
    ISSN: 0749-1581
    Keywords: 1H NMR ; 13C NMR ; 19F NMR ; β-Diketones ; Tautomerism ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Multinuclear NMR experiments on fluorinated β-diketones have furnished information on the various tautomers present in solution and their proportions. 2-Trifluoroacetyl-1-indalone in CDCI3 solution exists in the enol form, as a mixture of exocyclic and endocyclic cis-enols with the exocyclic form favoured, but in DMF-d7 solution the equilibrium shifts to 40% enol, 60% hydrate with the enol and hydrate being in slow exchange on the NMR time scale. 2-Trifluoroacetyl-1-tetralone in CDCI3 solution exists only as the enol forms, approximately equally populated, but in DMF-d7, unlike the indalone, no hydrate is formed although there is now 6% of the keto form present in slow exchange. The experimental results were compared with calculated data produced using molecular orbital simulations. These agree with the NMR results and predict that the tetralone enol tautomers are both significantly populated at room temperature but that the indalone exists primarily as the exocyclic enol. The oxygen-oxygen internuclear distance in the hydrogen bond was estimated from the OH proton chemical shift based on a calibration from solid-state data from model compounds, and agrees well with the predictions using the molecular mechanics approach.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280716
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