ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Organic Chemistry  (52)
Collection
Keywords
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    On the Stability of the Schiff Bases of Pyridoxal 5′-Phosphate with Polypeptides Containing L-Lysine (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1749-1756 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We determined the apparent equilibrium constant of formation, KpH, of the Schiff bases of pyridoxal 5′-phosphate (PLP) and poly- and copolymers containing L-lysine, as a function of pH at 25° and a constant ionic strength of 0.1 M. The KpH values obtained at acidic and neutral pH were larger that those reported for Schiff bases of PLP and hexylamine. We determined calorimetrically ΔH of formation of Schiff bases of PLP and poly(L-lysine) (-4.5′kcal/mol), and PLP and hexylamine (-3.4 kcal/mol) at pH 7.00. Semi-empirical theoretical calculations (INDO and AMI methods) of a model compound of Schiff base of PLP and polypeptide containing L-lysine show the capability of specific interactions between groups of PLP and the peptide skeleton.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740817
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Stereoselective inhibition of rat brain cyclooxygenase by dexketoprofen (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 281-285 
    Details
    ISSN: 0899-0042
    Keywords: dexketoprofen ; enantiomer ; stereoselectivity ; brain ; cyclooxygenase ; rat ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although it has been assumed that the effects of nonsteroidal antiinflammatory drugs (NSAIDs) are mainly the result of their action on local synthesis of prostaglandins, there is growing evidence to suggest that they may also exert a central analgesic action. Some authors have suggested that inhibition of prostaglandin synthesis in the brain could contribute to the analgesic action. The effect of dexketoprofen trometamol (tromethamine salt of the enantiomer (+)-S-ketoprofen) on prostaglandin synthesis was investigated in rat brain fragments and in cyclooxygenase preparations from rat brain microsomes. Effects of the (-)-R-enantiomer and the racemic mixture were also evaluated. Significant levels of prostaglandin F2α (PGF2α) were synthesized in rat brain fragments after 10 min of incubation at 37°C. Dexketoprofen was found to be a potent inhibitor of this PGF2α production in rat brain (IC50 = 6.2 nM), and it completely suppressed PGF2α production at 1 μM concentration. In addition, inhibition of PGF2α synthesis by dexketoprofen was highly stereoselective since the enantiomer (-)-R-ketoprofen was significantly less potent (IC50 = 294 nM); with this enantiomer, even at high concentrations such as 1 μM, less than 60% inhibition was achieved. These results correlated with those obtained in the study of racemic ketoprofen and its enantiomers on cyclooxygenase activity of rat brain microsomes, where dexketoprofen also inhibited enzymatic activity stereoselectively. IC50 values obtained for dexketoprofen, (-)-R-ketoprofen, and rac-ketoprofen were 3.5 μM, 45.3 μM, and 5.8 μM, respectively. The above results could be related to the potent analgesic effect of dexketoprofen observed in vivo, which was also stereoselective. Taken together, these findings suggest that prostaglandin synthesis inhibition in rat brain by dexketoprofen could be associated, at least in part, with the analgesic effect of this NSAID. Chirality 9:281-285, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of phenoxarsin-10-yl 2-R2N-cyclopent-1-ene-1-carbodithioate (R = H, C2H5, cyclo-C6H11CH2) and the crystal and molecular structure of the 2-amino (R = H) derivativeSupplementary X-ray crystallographic data are lodged with the Cambridge Crystallographic Data Centre, UK. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 9 (1995), S. 133-140 
    Details
    ISSN: 0268-2605
    Keywords: phenoxarsine ; ACDA ; carbodithioates ; arsenic ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenoxarsin-10-yl derivatives of 2-amino-cyclopent-1-ene-1-carbodithioic acid, (ACDA), and its N-alkyl derivativesO(C6H4)2 AsS2C - C5H6 -  NHR-2 (R = H, CH2CH3, CH2C6H11,), have been prepared by reacting O(C6H4)2AsCI with the corresponding ACDA 1,1-dithioic acid. The compounds were obtained by stirring stoichiometric amounts of the reagents in ethanol, over 24 h, at room temperature. The scale of the preparations were in the order of 2 mmol and the yields of the compounds ca 75%. The reactions were carried out in absolute ethanol. The compounds were characterized by IR, mass and NMR (1H, 13C) spectroscopy. The molecular structure of O(C6H4)2AsS2C - C5H6 - NH2-2 was determined using X-ray diffractometry, achieving an R-value of 6.3%; this compound is monomeric and contains an asymmetric monometallic biconnective 1,1-dithiolato ligand [As - S(1) 2.272(2) å, As … S(2) 3.125(2) å]. An intramolecular hydrogen bond is established between one hydrogen atom of the NH2 group and the sulfur [S(2)] atom involved in the secondary interaction to arsenic. The dihedral angle (150.3(3)°) of the phenoxarsine moiety is practically unaffected by substitution of chlorine on arsenic by the carbodithioato ligand.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590090207
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Kinetic and thermodynamic parameters for Schiff-rase formation between 5′-deoxypyridoxal and hexylamineSupported by the CICYT and the universidad de Alcalá de Henares (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 1991-1998 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermodynamic parameters involved in the formation of Schiff bases between 5′-deoxypyridoxal and hexylamine were determined at different pH values and a constant ionic strength (0.1 M). The overall and individual rale constants of formation and hydrolysis at 10, 15, 20, 25, and 30° were also determined. The enthalpy of the overall formation process was found to be negative at all the pH values assayed except the neutral, while its entropy was always positive. The results obtained show the great relevance of the phosphate group at C(5′) to the stabilization of the Schiff bases of pyridoxal 5′-phosphate.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730723
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    New Sesquiterpene Lactones and Other Constituents from Centaurea paui (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 527-532 
    Details
    ISSN: 0947-3440
    Keywords: Centaurea paui ; Sesquiterpenes ; Heliangolides ; Elemanolides ; Terpenoids ; Natural products ; Phytochemistry ; Lactones ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aerial parts of Centaurea paui afforded, in addition to several known sesquiterpene lactones, the two new elemanolides 2-4, the new elemane derivative 5 as well as the five new heliangolides 14-18. Their structures were elucidated by spectroscopic methods, especially high-field NMR spectroscopy. The structure of the heliangolide 12 previously isolated from this plant, has been confirmed by X-ray diffraction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970313
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Key intermediates in cyclotriveratrylene chemistry: A new route to the enantiomers of C3-cyclotriphenolene and cryptophane-C (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 446-453 
    Details
    ISSN: 0899-0042
    Keywords: cyclotriveratrylene ; cyclotriphenolene ; cryptophane ; thiovanillin ; resolution ; enantiomers ; diastereoisomers ; circular dichroism ; exciton chirality ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new route to (+)-(M) and (-)-(P)-cyclotriphenolene (1) is described, starting from 4-mercapto-3-methoxybenzaldehyde (thiovanillin (7)), which was converted into rac-3-methoxy-4-[(1-carboxyethyl)thio]benzyl alcohol (9). The latter was resolved by crystallization of its cinchonidine salts to give (-)-9, to which (S) absolute configuration was assigned. On reaction with formic acid, (-)-(S)-9 afforded the C3-cyclotiveratrylene diastereomers (-)-(P)-11a and (-)-(M)-11b which were separated and submitted to Raney Ni desulfuration to give the (+) and (-)-cyclotrianisylene enantiomers (4), which in turn were converted to (+) and (-)-1 on demethylation. Finally, (-)-1 was transformed into (+)-cryptophane-C according to a previously described method. Chirality 9:446-453, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    Stereoselective metabolic pathways of ketoprofen in the rat: Incorporation into triacylglycerols and enantiomeric inversion (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 163-172 
    Details
    ISSN: 0899-0042
    Keywords: arylpropionic acid ; ketoprofen ; enantiomer ; stereoselectivity ; Coenzyme A thioester ; hybrid triacylglycerols ; inversion ; adipose tissue ; hepatocytes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomeric bioinversion of ketoprofen (KP) enantiomers and their incorporation into triacylglycerols were investigated in the rat (1) in vitro, using liver homogenates, subcellular fractions, and hepatocytes, and (2) in vivo, in different tissue samples after oral administration of the radiolabelled compounds. In liver homogenates or subcellular fractions, the enantiomer (S)-ketoprofen (S-KP) was recovered unchanged, whereas (R)-ketoprofen (R-KP) was partially converted into its Coenzyme A (CoA) thioester and inverted to S-KP. Both processes occurred mainly in the mitochondrial fraction. This supports the mechanism of inversion via stereoselective formation of CoA thioesters of R-KP, already described for other non-steroidal anti-inflammatory drugs. Incorporation into triacylglycerols was detected after incubation with intact hepatocytes in the presence of added glycerol. The process was stereoselective for R-KP vs. S-KP (covalently bound radioactivity 26,742 ± 4,665 dpm/106 cells vs. 6,644 ± 3,179 dpm/106 cells, respectively). However, no incorporation was found in liver samples after oral administration of either R-KP or S-KP. On the contrary, in adipose tissue samples a significant and stereoselective formation of hybrid triacylglycerols was observed: 11,076 ± 2,790 dpm.g-1 for R-KP vs. 660 ± 268 dpm.g-1 for S-KP. The incorporated R/S ratio, higher in adipose tissue (R/S = 17) than in hepatocytes (R/S = 4), indicates that fat may be the main tissue store for the xenobiotic R-KP in rats. © 1996 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 8
    Electronic Resource
    Electronic Resource
    Kinetic Study on Stability of Schiff Base of Pyridoxal 5′-Phosphate and Leucine in Water Media with Cationic Surfactants (1992)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 75 (1992), S. 1029-1038 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the stability of the Schiff bases formed between pyridoxal 5′-phosphate (PLP) and leucine in the presence of (hexadecyl)trimethylammonium bromide (CTAB) over a wide pH range by determining the kinetic constants of formation and hydrolysis of these compounds. The results show that the stability of the Schiff bases is increased by the presence of CTAB as a result of increased rates of formation and decreased hydrolysis rate constants. The ionic head groups of CTAB favour the formation of the bases, while its hydrophobic rests protect the imine double bond from hydrolysis. This model system permits one to obtain partially hydrophobic media with no need for any non-aqueous solvents.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19920750406
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Degradation of Cephaloridine on Alkaline Hydrolysis (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 1619-1625 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic study on the alkaline hydrolysis of cephaloridine (1) at pH 10.5 and 37° was carried out using ion-pair reversed-phase HPLC. The main resulting degradation products, the 7-epimer 2 of 1, the Δ2-isomer 3 of 1, and the 3-methylidene compound 4 were identified. The presence of a pyridinio group at C(31) results in a slightly increased formation constant for the 3-methylidene compound 4 and the 7-epimer 2, and introduces a new reaction: the isomerization of the double bond at C(3) in the dihydrothiazine ring to C(2).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760418
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Theoretical Calculations of β-Lactam Antibiotics. Part VI. AM1 calculations of alkaline hydrolysis of clavulanic acid (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1557-1569 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase basic hydrolysis of clavulanic acid (a) was studied by using the AM1 semi-empirical method. The results obtained show that the hydroxyethylidene side chain at C(2) is pivotal to the stability of the different reaction products involved. The products with an open oxazolidine ring are more stable than those with a closed ring fused to the β-lactam ring. This behaviour differs from that of penicillins and cephalosporins where the most stable degradation products are those with an intact thiazolidine or dihydrothiazine ring, respectively, fused to the β-lactam ring. The different chemical reactivity of clavulanic acid relative to penicillins and cephalosporins could explain the disparate behaviour of the latter two types of compound towards β-lactamases. Once the acyl-enzyme intermediate of clavulanic acid has been formed, it can evolve with cleavage of the oxazolidine ring to form a difficult to deacylate compound.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770611
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...