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  • Organic Chemistry  (10)
  • Wiley-Blackwell  (10)
  • American Chemical Society
  • New York : Wiley-Interscience
  • Periodicals Archive Online (PAO)
  • 1
    Electronic Resource
    Electronic Resource
    Enantioselective Allylic Substitution Catalyzed by Chiral [Bis(dihydrooxazole)]palladium Complexes: Catalyst structure and possible mechanism of enantioselection (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 265-284 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Allylpalladium complexes with chiral bis(dihydrooxazole) ligands were studied as catalysts for the enantioselective allylic substitution reaction of rac-1,3-diphenylprop-2-enyl acetate (rac-5) with the anion of dimethyl malonate (Scheme 1). Using enantiomerically pure (S,E)-1-(4-tolyl)-3-phenylprop-2-enyl acatete ((S)-25) as substrate, the reaction was shown to proceed by a clean ‘syn’ displacement of acetate by dimethyl malonate (Scheme 6). The [Pd11(η3-allyl)] complex 18 and the analogous [Pd(η3-1,3-diphenylallyl)] complex 20, both containing the same bis(dihydrooxazole) ligand, were characterized by X-ray structure analysis and by NMR spectroscopy in solution. The structural data reveal that steric interactions of the allyl system with the chiral ligand result in selective electronic activation of one of the allylic termini. The higher reactivity of one allylic terminus toward nucleophilic attack is reflected in a significantly longer Pd—C bond and a shift of the corresponding 13C-NMR resonance to higher frequency.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780202
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  • 2
    Electronic Resource
    Electronic Resource
    Investigation of enantioselective ligand-protein binding and displacement interactions using capillary electrophoresisThis work was previously presented in part at the 2nd UK International Symposium on Capillary Electrophoresis, York, UK, September 1992, and at the 4th International Symposium on Chiral Discrimination, Montreal, Canada, September 1993. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 230-238 
    Details
    ISSN: 0899-0042
    Keywords: human serum albumin ; electrokinetic chromatography ; chiral drugs ; ligand-ligand interactions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When a protein such as human serum albumin is added to the separation buffer in capillary electrophoresis, the mobility of solutes which bind to that protein may be altered. The change in mobility of the solute is a function both of the strength of the binding interaction, and the difference in mobility between the free solute and protein additive. By adding other ligands which themselves bind to the protein, the strength of the solute-protein binding may be modified, leading to a measurable change in the mobility of the solute. These effects are particularly striking for chiral compounds, where enantioselectivity may be completely lost on addition of a competitive ligand. Capillary electrophoresis with human serum ablumin as a buffer additive was used to separate the enantiomers of benzoin and three phenothiazine derivatives. A comparison of the binding of (S)-benzoin to human serum albumin as determined by capillary electrophoresis and by ultrafiltration was made. A variety of other ligands were then added to the buffer along with the protein, and the effects on mobility and enantioselectivity were studied. The displacers included (R)- and (S)-oxazepam hemisuccinate, (R)- and (S)-warfarin, nitrazepam, phenylbutazone, and octanoic acid. From the results obtained, it seems that capillary electrophoresis may be a useful, rapid method to screen for drug-drug interactions. There are some advantages of using this technique to study protein-ligand interactions: Only very small amounts of ligand are needed (useful when dealing with metabolites); for chiral compounds, if protein binding is stereoselective, then the method is also stereoselective, so single enantiomers are not needed; finally, measurements are obtained in solution, without the need for immobilization of the protein. A disadvantage is that the ligand and protein must have significantly different electrophoretic mobilities. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060404
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  • 3
    Electronic Resource
    Electronic Resource
    Extent of chiral inversion of the 2-arylpropionic acids by Cordyceps militaris (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 528-534 
    Details
    ISSN: 0899-0042
    Keywords: chiral inversion ; ibuprofen ; ketoprofen ; flurbiprofen ; indoprofen ; suprofen ; fenoprofen ; metabolism of 2-arylpropionic acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fungus Cordyceps militaris has been previously shown to be capable of inverting the chirality of 2-phenylpropionic acid from its (R)-enantiomer to its (S)-antipode. The structure of this compound is similar to the 2-arylpropionic acid non-steroidal anti-inflammatory drugs, which have also been reported to undergo a similar chiral inversion process in mammals and man. We report here an investigation into the substrate specificity of the enzyme system present in C. militaris using pure enantiomers and racemates of ibuprofen and ketoprofen and racemates of indoprofen, suprofen, flurbiprofen, and fenoprofen and the structurally related compounds 2-phenylbutyric acid and 2-phenoxypropionic acid as substrates, using optimised incubation conditions developed for the inversion of 2-phenylpropionic acid. The results demonstrated that C. militaris is capable of inverting the chirality of all the compounds investigated, which suggests that the active sites of the enzymes are very flexible with regard to the molecular dimensions of the substrate molecule and the spatial occupation of the groups surrounding the chiral centre. Metabolism of all the substrates was observed but the rate of metabolism varied extensively depending on the substrate. Achiral HPLC analysis was used to detect any potential metabolites and the results suggested that the site of the metabolism appeared to be at the aliphatic side groups only, with the aromatic ring being left intact in all cases. These results suggest that C. militaris could be a valuable tool in the investigation of the prospective metabolic fates of new 2-arylpropionic acids during their development. Chirality 10:528-534, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    A mechanistic investigation of the microbial chiral inversion of 2-phenylpropionic acid by Verticillium lecanii (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 254-260 
    Details
    ISSN: 0899-0042
    Keywords: microbial chiral inversion ; 2-phenylpropionic acid ; kinetic isotope effect ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previous investigations have described the development of nongrowing suspension of Verticillium lecanii as a microbial model of the mammalian chiral inversion of the 2-arylpropionic acids (2-APAs). Mechanistic studies in mammals have shown that inversion involves loss of the α-methine proton but retention of the original atoms at the β-methyl position, and a mechanism has been proposed involving enzymatic epimerisation of acyl-CoA thioester derivatives of the substrate. Inversion of the 2-APAs by V. lecanii exhibits extensive intersubstrate variation in the presence, rate, extent, and direction of inversion, which are different from those observed in mammalian systems, possibly indicating differences in the mechanism of inversion between mammalian and microbial cells. This study involved the investigation of proton/deuterium exchange by 1H-nuclear magnetic resonance following incubation of deuterated derivatives of 2-phenylpropionic acid (2-PPA), a model compound, in cell suspensions of V. lecanii and incubation of undeuterated 2-PPA in cell suspensions containing D2O. The results indicated that the inversion of 2-PPA by V. lecanii also involved exchange of the α-methine proton but complete retention on the original atoms at the β-methyl position. No kinetic deuterium isotope effect was observed, indicating that loss of the α-methine proton is not the rate-limiting step of the inversion process. This suggests that the observed differences between microbial and mammalian systems probably involve the stereoselective acyl-CoA thioester formation step and not the subsequent epimerisation of the resultant diastereomers. Chirality 9:254-260, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Polarimetric detection in high-performance liquid chromatography (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 1 (1989), S. 251-264 
    Details
    ISSN: 0899-0042
    Keywords: optical activity ; optical rotation ; chiroptical detection ; enantiomeric purity ; chiral separation ; enantioselective reactions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiroptical detection for HPLC is particularly useful as a selective detection method for chiral molecules, and in enantiomeric purity determination with partial chiral separation or without chiral separation. The recent development of laser-based polarimeters with microdegree sensitivity has increased the applicability of optical rotation detection in HPLC. The detection limit of these instruments is submicrogram on-column for many chiral compounds in analytical HPLC. A variety of applications of the selective detection of optically active molecules are reviewed. The use of polarimetric detection with partial chiral separation is considered, both as an aid to method development and for enantiomeric purity determination. Finally applications to enantiomeric purity determination without chiral separation are reviewed, with the dual use of nonchirally selective and chiroptical detectors to determine the total amount and optical purity of the analyte. Determinations of chiral purity for samples of high enantiomeric excess are described, which with laser-based instrumentation may give accuracies of better than ± 1% with sample loadings of 50 μg on an achiral column. Applications to the study of enantioselective reactions are also considered, with determination of enantiomeric excess in near-racemates to better than ± 0.1%.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530010403
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  • 6
    Electronic Resource
    Electronic Resource
    Alkylation of 2,3-Dihydro-1,4-diazepinium Salts (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1387-1392 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alkylierung von 2,3-Dihydro-1,4-diazepinium-SalzenN-Unsubstituierte 2,3-Dihydro-1,4-diazepinium-Salze 4a - d werden mit Iodmethan/Kaliumcarbonat in Dimethylformamid leicht N-methyliert (→5a - d). Das 2,3-Dihydro-5,7-diphenyl-1,4-diazepinium-Salz 4d konnte zwar N-ethyliert, aber nicht N-isopropyliert werden, vermutlich aus sterischen Gründen. Sterische Wechselwirkungen zwischen benachbarten 1,4-Alkyl- und 5,7-Phenylsubstituenten am Dihydrodiazepiniumring lassen sich NMR-spektroskopisch nachweisen. 2,3-Dihydro-6-(hydroxyphenyl)-1,4-diazepinium-Salze (2a, b) werden zunächst an den Stickstoffatomen methyliert (→1a, b) und erst danach an der Hydroxygruppe (→3a, b).
    Notes: N-Unsubstituted 2,3-dihydro-1,4-diazepinium salts 4a - d are N-methylated readily (→5a - d) by using iodomethane and potassium carbonate in dimethylformamide. The 2,3-dihydro-5,7-diphenyl-1,4-diazepinium salt 4d could be N-ethylated but not N-isopropylated, presumably for steric reasons. Vicinal crowding between, 1,4-alkyl and 5,7-phenyl substituents at the dihydrodiazepinium ring is evident from NMR spectra. 2,3-Dihydro-6-(hydroxyphenyl)-1,4-diazepinium salts (2a, b) are methylated first at the nitrogen atoms (→1a, b) and only then at the hydroxy group (→3a, b).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860809
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  • 7
    Electronic Resource
    Electronic Resource
    Bromination of 2,3-Dihydro-6-(hydroxyphenyl)-1,4-diazepinium Salts (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1380-1386 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Bromierung von 2,3-Dihydro-6-(hydroxyphenyl)-1,4-diazepinium-Salzen2,3-Dihydro-6-(4-hydroxyphenyl)-1,4-diazepinium-Salze 3a, b werden in der meta-Position des Phenylsubstituenten leicht mono- (→4a, b) und dibromsubstituiert (→5a, b). 2,3-Dihydro-6-(3-hydroxyphenyl)-1,4-diazepinium-Salze 6a, b werden in der para-Position des Phenylsubstituenten leicht monobromsubstituiert (→7a, b). Eine zweite Bromsubstitution (→8a, b) findet in ortho-Position statt - überraschenderweise, da die ortho-Position von 6-Arylsubstitutenten in 1,4-Diazepiniumsalzen einem elektrophilen Angriff gewöhnlich nicht zugänglich ist. Überlegungen zum Mechanismus dieser Bromsubstitutionen werden angestellt. - 1,2-Dihydro-5-(hydroxyphenyl)-2-oxopyrimidinium-Salze 11a, b werden unter gleichen Reaktionsbedingungen nicht bromsubstituiert.
    Notes: 2,3-Dihydro-6-(4-hydroxyphenyl)-1,4-diazepinium salts 3a, b are readily mono- (→4a, b) and di-brominated (→5a, b) at the meta-position of the phenyl substituent. 2,3-Dihydro-6-(3-hydroxyphenyl)-1,4-diazepinium salts 6a, b are readily mono-brominated (→ 7a, b) at the para-position of the phenyl substituent. A second bromination (→8a, b) takes place at an ortho-position, surprisingly, since ortho-positions of 6-aryl substituents in 1,4-diazepinium salts are usually not susceptible to electrophilic attack. Mechanistic features of these brominations are considered. - 1,2-Dihydro-5-(hydroxyphenyl)-2-oxopyrimidinium salts 11a, b were not brominated under similar conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860808
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  • 8
    Electronic Resource
    Electronic Resource
    Diazepines, 27. Effects of Substituents on the Bromination of 2,3-Dihydro-1,4-diazepinium Salts (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 133-135 
    Details
    ISSN: 0170-2041
    Keywords: Bromination ; Diazepinium salts, dihydro ; Steric effects, long-range ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Diazepine, 27. - Substituenten-Einfluß auf die Bromierung von 2,3-Dihydro-1,4-diazepinium-SalzenDie Bromierung der Ringposition 6 von 2,3-Dihydro-1,4-diazepinium-Salzen 1 sowie der p-Stellung von 6-Phenylresten wird sterisch nicht nur durch Substituenten in vicinalen Ringpositionen sondern auch durch solche in den Stellungen 1, 2 und 4 behindert.
    Notes: Bromination at the 6-position of 2,3-dihydro-1,4-diazepinium salts 1 or at the p-position of a 6-phenyl substituent is subject to steric hindrance, not only by substituents at vicinal sites in the ring(s), but also by substituents at the 1-, 2-, and 4-positions.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890127
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  • 9
    Electronic Resource
    Electronic Resource
    Experiments towards the Preparation of 6-Hydroxy-,6-Methoxy-, and 6-(hydroxyphenyl)-2,3-dihydro-1,4-diazepinium Salts and 1,2-Dihydro-5-(Hydroxyphenyl)-2-oxopyrimidinium Salts (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1368-1379 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Versuche zur Herstellung von 6-Hydroxy-, 6-Methoxy- und 6-(Hydroxyphenyl)-2,3-dihydro-1,4-diazepinium-Salzen sowie von 1,2-Dihydro-5-(hydroxyphenyl)-2-oxopyrimidinium-SalzenDie Herstellung einiger 2,3-Dihydro-6-(hydroxyphenyl)-1,4-diazepinium-Salze (11c - f) und 1,2-Dihydro-5-(hydroxyphenyl)-2-oxopyrimidinium-Salze (17a, b) ausgehend von 3-(Hydroxyphenyl)vinamidinium-Salzen (10b, c) wird beschrieben. Versuche zur Herstellung eines 3-(2-Hydroxyphenyl)vinamidinium-Salzes führten stattdessen zu einer Mischung formylsubstituierter Benzofuranone (15 and 16). Versuche zur Darstellung von 2,3-Dihydro-6-hydroxy-1,4-diazepiniumsalzen (1a - c) ergaben anstatt der gewünschten 1,4-Diazepiniumsalze andere Produkte; 2,3-Dihydro-6-methoxy-1,4-diazepinium-Salze (7a, b) konnten jedoch erhalten werden.
    Notes: The preparation of a number of 2,3-dihydro-6-(hydroxyphenyl)-1,4-diazepinium salts (11c - f) and of 1,2-dihydro-5-(hydroxyphenyl)-2-oxopyrimidinium salts (17a, b) from 3-(hydroxyphenyl)vinamidinium salts (10b, c) is described. Attempted preparation of a 3-(2-hydroxyphenyl)vinamidinium salt gave instead a mixture of formyl-substituted benzofuranones (15 and 16). Attempted preparation of 2,3-dihydro-6-hydroxy-1,4-diazepinium salts (1a - c) provided products other than diazepinium salts, but 2,3-dihydro-6-methoxy-1,4-diazepinium salts (7a, b) were prepared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619860807
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  • 10
    Electronic Resource
    Electronic Resource
    5-Dimethylselenanyliden-2.2-dimethyl-4.6-dioxo-1.3-dioxan, ein neues stabiles Selenoniumylid (1971)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 753 (1971), S. 196-198 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 5-Dimethylselenanylidene-2,2-dimethyl-1,3-dioxane-4,6-dione, a New Stable Selenonium YlideThe preparation of the title compound, the dimethylselenonium ylide 2 of Meldrum's acid, together with some of its spectral data, is described. This ylide is unreactive in the Wittig reaction.
    Notes: Es wird die Darstellung des im Titel genannten Dimethylselenoniumylids 2 der Meldrumsäure unter Angabe einiger seiner Spektraldaten beschrieben. Das neue Ylid konnte nicht zur Wittig-Reaktion gebracht werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.19717530117
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