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  • 1
    Digitale Medien
    Digitale Medien
    Excavations in drug chirality: 1. Cyclothiazide (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 2-13 
    Details
    ISSN: 0899-0042
    Schlagwort(e): drug stereochemistry ; cyclothiazide ; stereoisomerism ; chiral HPLC ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: There is a great deal of current interest in the role and importance of chirality in the development of new drugs, but little attention is being paid to the stereochemistry of older drugs. Indeed, many older chiral drugs were introduced without adequate information on their stereochemical identity or composition. We have examined one such drug, the antihypertensive diuretic agent cyclothiazide. Standard sources of drug information and the research literature do not provide data on the stereochemical composition of clinically used cyclothiazide, although scattered reports indicate that the drug may consist of “several stereoisomers.” Inspection of the chemical structure of the drug, 6-chloro-3,4-dihydro-3-(5-norbornen-2-yl)-2H-l,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide, shows that it can exist as eight stereoisomers that may form four racemates. Using synthesis, fast-atom-bombardment mass spectrometry, gas-liquid chromatography, chiral and nonchiral high-performance liquid chromatography, and nuclear magnetic resonance spectroscopy, we determined that pharmaceutical cyclothiazide is in fact a mixture of the eight stereoisomers in the form of the four racemates. The two racemates with endo configuration at the norbornene moiety predominate over the exo racemates, and small but significant differences in isomer distribution between different batches of the drug were observed. We urge that in studies of older drugs the stereochemical details be considered.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530030103
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  • 2
    Digitale Medien
    Digitale Medien
    The so-called “interconversion” of stereoisomeric drugs: An attempt at clarification (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 105-111 
    Details
    ISSN: 0899-0042
    Schlagwort(e): enantiomers ; racemization ; epimers ; epimerization ; configurational stability ; nonenzymatic reactions ; oxazepam ; amfepramone ; thalidomide ; atropine ; chlorthalidone ; pilocarpine ; 16α-substituted 3-methoxyestrones ; chlorpromazine ; telenzepine ; tofisopam ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A variety of reactions can be categorized under the global concept of the “interconversion of stereoisomers.” Thus, racemization or epimerization can result from inversion of labile chiral centers. From the examples available, some predictive rules are suggested for a chiral center of the type R″R′RC—H undergoing base-catalyzed inversion and a provisional table of affecting groups is presented. Unimolecular inversion of nonsymmetrical, nonplanar ring systems can also result in racemization or epimerization, but no generalization can yet be offered. Beside these cases of nonenzymatic reactions, a limited variety of enzymatic reactions can operate to interconvert stereoisomers, the outcome rarely being a racemic mixture. An important aspect of stereoisomer interconversion is the time scale in which the phenomenon is observed. Thus, several reactions to nonezymatic racemization or epimerization are fast compared to the duration of action of the drug and therefore have pharmacological significance, while other are slower and are of pharmaceutical relevance only. © 1993 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530050302
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  • 3
    Digitale Medien
    Digitale Medien
    Reversed-Phase LC resolutions of chiral antiarrhythmic agents via derivatization with homochiral isothiocyanates (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 2 (1990), S. 43-51 
    Details
    ISSN: 0899-0042
    Schlagwort(e): mexiletine ; flecainide ; tocainide ; propafenone ; chirality ; enantiomers ; HPLC ; homochiral derivatization ; isothiocyanates ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The search for new antiarrhythmic agents has been intense, because the established drugs for the treatment of cardiac arrhythmias are neither uniformly effective nor well-tolerated. Among the recently introduced new anti-arrhythmic agents are tocainide (TOC), mexiletine (MEX), flecainide (FLE), and propafenone (PRO). Each of these drugs is a chiral amine used clinically as the racemic mixture. We have examined the high-performance liquid chromatographic chiral resolution of the above four drugs via derivatization with homochiral derivatizing agents (HDAs). The amino functionality of the drugs was reacted with four homochiral isothiocyanates, 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate (TAGIT), (R)-α-methylbenzyl isothiocyanate (RAMBI), (S)-1-(1-naphthyl)ethyl isothiocyanate (SNEIT), and (R)-1-(2-naphthyl)ethyl isothiocyanate (RBEIT). Complete separation of the two peaks (resolution factor R = 1.5) was achieved with all four HDAs for TOC, with TAGIT, RBEIT, and RAMBI for MEX, with TAGIT and SNEIT for PRO, and only with TAGIT for FLE. SNEIT was used to develop analytical procedures for the determination of the enantiomeric composition of TOC in human urine and blood serum. The four HDAs offer several advantages over many other HDAs and should be useful in studies of enantioselective drug action and disposition.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530020107
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  • 4
    Digitale Medien
    Digitale Medien
    Mechanismus der Bischler-Napieralski-Reaktion (1972)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 84 (1972), S. 947-949 
    Details
    ISSN: 0044-8249
    Schlagwort(e): Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ange.19720841909
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  • 5
    Digitale Medien
    Digitale Medien
    Effects of bifunctional interactions in the chemical ionization mass spectrometry of carboxylic acids and methyl esters (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1976), S. 188-196 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The methane chemical ionization mass spectra of dodecan-1, 10-dioic acid and the methyl ester show enhanced water and methanol elimination relative to monofunctional analogs. Elimination of acetic acid from 1,10-diacetoxydecane, however, was reduced relative to 1-acetoxydecane. This appears to be the result of bifunctional interactions. The steric requirement of this interaction is shown in an homologous series of dicarboxyl compounds. The change in interfunctional separation is shown to affect the proton and ammonium ion affinities in the ammonia chemical ionization spectra of the dicarboxyl compounds in a manner explained in terms of proton and ammonium ion complex formation. The observation is extended to various other functional groups.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210110215
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  • 6
    Digitale Medien
    Digitale Medien
    Hydrolysis, methanolysis and ammonolysis of dicarboxylic acids and methyl esters under conditions of chemical ionization mass spectrometry (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1976), S. 197-206 
    Details
    ISSN: 0030-493X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chemical ionization mass spectra of dicarboxylic acids and methyl esters show fragmentation and unimolecular reactions with reagent gases water, methanol, ammonia and methyl ether, which differ from those observed with hydrocarbon reagents methane and isobutane. These reactions involve exchange of the reagent gas for water or methanol of the dicarboxyl compounds as well as secondary exchange of both functions. An effort has been made to determine the mechanism of these reactions and to determine the structural requirements necessary for their occurrence.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/oms.1210110216
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  • 7
    Digitale Medien
    Digitale Medien
    Mass spectra of N-[(S)-α-methoxy-α-(trifluoromethyl)phenylacetyl] derivatives of chiral amines. Stereochemistry of amphetamine metabolism in the ratAbbreviations: MTPA = (S)-α-methoxy-α-(trifluoromethyl)-phenylacetyl. (1978)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1978), S. 32-37 
    Details
    ISSN: 0306-042X
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The electron impact mass spectra of the N-[(S)-α-methoxy-α-trifluoromethylphenylacetyl] derivatives of amphetamine and several related compounds have been studied with the purpose of developing an assay for the enantiomers of the amines based on selected ion monitoring gas chromatography mass spectrometry. Stable isotope labeled analogs were used to elucidate the fragmentation pattern. The molecular ions are present in the spectra but are weak. The 1-phenyl-1-methoxy-2,2,2-trifluoroethyl cation is of significant intensity in all of the spectra. Other major fragmentations include a McLafferty rearrangement to give styrene radical ions, α-cleavage to nitrogen, and formation of benzyl cations derived from the amine or aminoester portion. An analytical procedure was developed for the simultaneous determination of the concentration of the enantiomers of amphetamine in rat urine. The method is based on selected ion monitoring gas chromatographic mass spectrometric analysis of the N-[(S)-α-methoxy-α-(trifluoromethyl)phenylacetyl] derivatives and uses amphetamine labeled with deuterium in the methyl group as internal standard. Using this procedure it was found that rats administered racemic amphetamine intraperitoneally excrete slightly more of the S enantiomer than of the R.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bms.1200050107
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