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  • Organic Chemistry  (122)
  • 1995-1999  (32)
  • 1990-1994  (46)
  • 1960-1964  (39)
  • 1945-1949  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and Biological Evaluation of 14-Alkoxymorphinans. Part 9Part 8:[1].. 14-O-ethyl-5-methylnaltrexone, and opioid antagonist with unusual selectivity (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 476-480 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 14O-Ethyl-5m-ethylnaloxone (7) and 14O-ethyl-5-methylnaltrexone (8) have been prepared starting from 14O-ethyl-5-methyloxycodone (9) in several steps. Both, 7 and 8, were found to be opioid antagonists in vitro and in vivo. Compound 7 exhibited some selectivity for μ opioid receptors, whereas compound 8 did not show selectivity for any of the receptor types. In the AcOH-writhing antagonism test, 8 was not able to antagonize morphine-induced antinociception, but antagonized fentanyl- and sufentanil-induced antinociception.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760131
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  • 2
    Electronic Resource
    Electronic Resource
    New Triterpene Saponins from Herniaria glabraDedicated to Prof. K. Hiller on the occasion of his 65th birthday (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 385-390 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three new saponins 1-3 were isolated from Herniaria glabra by means of prep. HPLC and TLC. The structures were established mainly by a combination of 2D-NMR techniques (COSY, TOCSY, ROESY, HMQC, and HMBC) as O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1-→6)-O-[β-D-glucopyranosyl-(1→2)]-β-D-glucopyranosyl medicagen-28-ate (herniaria saponin 4; 1), O-β-D-glucopyranosyl-(1→3)-O-α-L-rhamnopyranosyl-(1→2)-O-[β-(3R)-D-apiofuranosyl-(1→3)]-β-D-4-O-acetylfucopyranosyl 3-O-(β-D-glucuronopyranosyl)-16α-hydroxymedicagen-28-ate (herniaria saponin 5; 2), and O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-[β-D-6-O-acetylglucopyra nosyl-(1→2)]-β-D-glucopyranosyl medicagen-28-ate (herniaria saponin 6; 3).
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790207
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  • 3
    Electronic Resource
    Electronic Resource
    Ein erstes Beispiel eines porphyrinoiden Fulvalens: Synthese, Struktur, ESR- und elektrochemische UntersuchungenProf. Dr. Fabian Gerson in Anerkennung seiner Beiträge zum Verständnis von π-Systemen gewidmet (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 2456-2476 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A First Example of a Porphyrinoid Fulvalene: Synthesis, Structure, ESR and Electrochemical InvestigationsThe macrocyclic tetraepoxy-1H-[21]annulen-1-one 4 can by synthesized by the cyclizing Wittig reaction of 5,5′-carbonylbis[furan-2-carboxaldehyde] (11) and the bisphosphonium salt 12, obtained from 2,2′-bifuran-5,5′-dicarboxaldehyde (13). According to an X-ray structure analysis, the annulenone 4 is not planar in the crystal; the 1H-NMR spectra of 4 reveal an averaged planarity with respect to the NMR timescale. The McMurry reaction of 4 yields fulvalene 3 in 43% yield as the most expanded fulvalene hithertoo known. The X-ray structure analyses of 3 surprising establishes a ‘syn’-orientation of the two rings with respect to the central C=C bond, thus forming a basket-like molecule. The 1H-NMR spectrum confirms the averaged planarity of both macrocycles in 3. CV and spectroelectrochemical measurements of 3 suggest a reversible two-electron reduction producing dianion 15 with two aromatic, anionic 5a,15a-didehydro-10H-21,22,23,24-tetraoxa-5a,15a-dihomocorrole (= tetraoxa[22]porphyrin(2.1.2.0)) ring systems containing 22π electrons each. The formation of 15 can also be achieved chemically by reaction of 3 with metallic potassium. The dication 16 of 3 may be antiaromatic, but the exact electronic structure is dubious. ESR and ENDOR investigations on the radical cation and the radical anion of 3 indicate that the free electron is delocalized in the entire molecule.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800814
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  • 4
    Electronic Resource
    Electronic Resource
    The Deoxygenation and Isomerization of Artemisinin and Artemether and Their Relevance to Antimalarial ActionDedicated to the memory of our late colleague Professor Wolfgang von Oppolzer (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1475-1487 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The treatment of artemisinin (1) and β-artemether (6) with Zn dissolving in AcOH for a few hours results in mono-deoxygenation giving deoxyartemisinin (5) and deoxy-β-artemether (7), respectively, as the sole product. In contrast, submission of 1 to FeCl2 · 4 H2O in MeCN at room temperature for 15 min causes only isomerization, (3aS,4R,6aS,7R,10S,10aR)-octahydro-4,7-dimethyl-8-oxo-2H-10H-furo[3,2-i] benzopyran-10-yl acetate (8) and (3R)-3-hydroxydeoxyartemisinin (9) being produced in 78 and 17% yield, respectively. The action of FeCl2 · 4 H2O in MeCN on 6 is similar. Under the same conditions, 6 gives products analogous to 8 and 9 accompanied by an epimeric mixture of 2-[4-methyl-2-oxo-3-(3-oxobutyl)cyclohexyl]propanaldehyde in yields of 32, 23, and 16%, respectively. No epoxide is formed on repeating the last two experiments in the presence of cyclohexene. The deoxygenation of 1 and 6 by Zn is rationalized in terms of its oxophilic nature. The catalyzed isomerization of 1 and 6 by Fe2+ is attributed to the redox properties of the Fe2+/Fe3+ system.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790520
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  • 5
    Electronic Resource
    Electronic Resource
    Extrem aufgeweitete Tetrathiafulvalene mit Polyen-Spacern. Carotinoide Tetrathiafulvalene. Polymethin-tetracyanotetrathiafulvalen-Radikalkationen, eine neue Klasse von ViolenenProf. Dr. Siegfried Hünig zum 75. Geburtstag gewidmet (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1497-1517 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extremely Expanded Tetrathiafulvalenes with Polyene Spacers. Carotinoid Tetrathiafulvalenes. Polymethin-Tetracyanotetrathiafulvalene Radical Cations, a New Class of ViolenesThe synthesis of extended tetrathiafulvalenes 11 with di-, tetra-, hexa-, octa-, deca- and dodecamethine spacers is described by a PPh3-induced Wittig-reaction-like condensation of the corresponding polyenedials 10 with 2-thio-1,3-dithiole-4,5-dicarbonitrile (9). By the same procedure, the dimethyloctamethine- and the tetramethyl-hexadecamethine-tetrathiafulvalenes 14 and 15, respectively, were obtained. The extended tetrathiafulvalenes represent multistep vinylogous redox systems of the ‘violene type’. They can be oxidized to give the cyanine-like radical cations, e.g. 11sem, 14sem, and 15sem, and the dications, e.g. 11ox, 14ox, and 15ox; their UV/VIS/NIR spectra are reported. The crystal and molecular structure of (all-E)-2,2′-(octa-2,4,6-trien-1,8-diylidene)bis[1,3-dithiole-4,5-dicarbonitrile] (11e) was determined: it is a rod-like, planar molecule; in the crystal, it forms staples along the longest molecule axis. The CV measurements confirm that the redox potentials of 11, 14, and 15 decrease asymptotically with the increasing length of the spacer. Because of the close relationship of the extended tetrathiafulvalenes (ETTF's) to the carotinoids, they are named ‘caroviologenes’; they formally belong to the class of molecular wires.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790522
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  • 6
    Electronic Resource
    Electronic Resource
    Solution Structure of [Me-L-Leu7]Didemnin B Determined by NMR Spectroscopy and Refined by MD Calculation (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 25-47 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several homo- and heteronuclear two-dimensional NMR techniques were used to assign all H- and C-resonances of the two conformers A and B of [7-(N-methyl-L-leucine)]didemnin B. Didemnine is a biologically highly active cytostaticum and immunosuppressivum. The assignment of the aliphatic C-atoms were done by the inverse H,C-COSY with TOCSY transfer which connects complete proton spin systems and represents them on C-atoms. The structure of both conformers (A and B) in (D6)DMSO solution was derived from homo- and heteronuclear couplings (J), temperature dependencies of NH protons, and NOE effects. Distances determined from the latter were used for refinements by restrained MD calculations using the GROMOS program. The solution structure of [Me-L-Leu7]didemnin B (A and B) was compared to that of didemnin B. The backbone structure of the macrocyclic ring and of the linear side-chain moiety are very similar in conformer A and didemnin B, though the Ist1-Hip2 region of the ring is slightly ex tended in conformer A. This may be caused by the influence of the Me-L-Leu7 residue in A and may be responsible for its reduced biological activity in comparison to didemnin B. The more weakly populated conformer B exhibits a βVI turn in the linear side-chain moiety.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730104
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of Unique Ceramides and Cerebrosides Occurring in Human Epidermis (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 616-630 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sphingolipids 1a, b and 2a, b which play important roles in epidermal barrier function, were synthesized by N-acylation of C18-sphingosine 3 and 1-O-glucosylated C18-sphingosine 6, respectively, with ω-acyloxy-substituted fatty acids 4 and 5 (Scheme 1). These fatty acids were obtained from ω-hydroxy-substituted fatty acids 8 and 9 by esterification with linoleic acid (7). The C34-fatty acid 8 was prepared as follows: C25-Compound 18 was obtained by means of a Wittig reaction of C13-aldehyde 13 with C12-phosphonium salt 15 or of C12-aldehyde 24 with C13-phosphonium salt 21, respectively, and subseqent hydrogenation and O-deprotection (Scheme 2). Alternatively, 8 was prepared via 30 by copper-catalyzed coupling of C13-alkyl halide 19 with the Grignard reagent derived from C12-alkyl bromide 14 (Scheme 2). Oxidation of 18 to aldehyde 39 and Wittig reaction with C9-phosphonium salt 41 furnished the desired ω-hydroxy-substituted fatty acid 8, after O-deprotection (Scheme 3). Similarly, Wittig reaction of C11-phosphonium salt 22 with C12-aldehyde 24 furnished C23-aldehyde 40, after hydrogenation, O-deprotection, and oxidation; Wittig reaction with compound 41 and subsequent deprotection afforded the desired C32-fatty and 9 (Scheme 3). an alternative strategy furnished compound 8 by a coupling reaction of alkyne 53 with ω-bromo-substitued fatty acid 52, obtained from compounds 24 and 47 by Wittig reaction, hydrogenation, and introduction of bromide (Scheme 4). Hydrogenation (Lindlar's catalyst) of the resulting C34-alkyne 54 and deprotection furnished 8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760141
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  • 8
    Electronic Resource
    Electronic Resource
    The Molecular and Crystal Structure of the Glycopeptide A-40926 Aglycone (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1916-1924 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a glycopeptide antibiotic A-40926 aglycone was investigated by X-ray analysis at -120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) Å. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F 〉 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790714
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  • 9
    Electronic Resource
    Electronic Resource
    Chirality of azelastine and flezelastine: Investigation of their enantiomers (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 366-369 
    Details
    ISSN: 0899-0042
    Keywords: azelastine ; flezelastine ; fractional crystallization ; antiallergic/antiasthmatic ; chiral discrimination ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The racemic phthalazinone derivatives azelastine and flezelastine were resolved via formation of diastereomeric salts and fractional crystallization thereof. The optical purity of the enantiomers was checked by HPLC. Pharmacological investigations in vitro and in vivo related to antiallergic/antiasthmatic activity revealed some stereospecific differences. However, chiral discrimination could not be observed with regard to overall activity of azelastine and flezelastine. © 1993 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050517
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  • 10
    Electronic Resource
    Electronic Resource
    Stereoselective pharmacokinetics of methadone in beagle dogs (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 492-495 
    Details
    ISSN: 0899-0042
    Keywords: enantiomers ; methadone ; pharmacokinetics ; beagle dog ; iv administration ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pharmacokinetics of methadone were studied in beagle dogs (n = 4) following intravenous administration of the racemate (0.5 mg/kg) and of the individual (R)-(0.25 mg/kg) and (S)-enantiomers (0.25 mg/kg) using a stereospecific HPLC assay. There was no significant difference between the pharmacokinetic parameters of (R)-methadone and (S)-methadone following administration of the individual enantiomers. Stereoselective differences were evident following administration of the racemate (P values for differences in AUC and CL were 0.001 and 0.046, respectively) and the clearance of the (S)-enantiomer was increased when administered as part of the racemate (316 ± 81 vs 487 ± 128 ml/min, P = 0.04). The data suggest that stereoselective disposition including potential enantiomer-enantiomer interactions should be considered in pharmacokinetic-pharmacodynamic studies of (R,S)-methadone. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060608
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