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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis, Characterization and Dynamic Behavior of Mono- and Dinuclear Palladium(II) Carbene Complexes Derived From 1,1′-Methylenebis(4-alkyl-1,2,4-triazolium) Diiodides (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1965-1971 
    Details
    ISSN: 1434-1948
    Keywords: Palladium ; Carbenes ; Metallacycles ; 1,2,4-Triazole ; Coordination modes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mononuclear palladium carbene complexes 2a-c and 3 derived from 1,1′-methylenebis(4-alkyl-4,5-dihydro-1H-1,2,4-triazole-5-ylidene) have been obtained by the reaction of 1,1′-methylenebis(4-alkyl-1,2,4-triazolium) diiodides 1a-d with palladium acetate under mild conditions. The mononuclear complexes 2a-c have been transformed into their corresponding trans-binuclear complexes 4a-c. All compounds were characterized by spectroscopic techniques and the dynamic behavior of 2a-cand 4a-c has been studied. The X-ray structures of 2a and 4c are reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Enantioselective synthesis of highly functionalized 4-piperidones by the asymmetric imino-diels-alder reaction of chiral 2-amino-1,3-butadienesAbbreviations used in this article: NaHMDS: sodium bis(trimethylsilyl)-amide; TMS: trimethylsilyl; MOM: methoxymethyl; TBDMS: tert-butyldimethylsilyl; 3-Fu: 3-furyl; p-MeOPh: 4-methoxyphenyl; o-BrPh: 2-bromophenyl; p-BrC6H4CO: 4-bromobenzoyl; (R)-MPTA: (R)-α-methoxy-α-Phenyl-α-trifluoromethylacetyl. (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 805-811 
    Details
    ISSN: 0947-6539
    Keywords: asymmetric Diels-Alder reactions ; butadienes ; Diels-Alder reactions ; piperidones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral 2-amino-1,3-butadienes 1 derived from commercially available (S)-2-methoxymethylpyrrolidine react with aromatic N-trimethylsilylaldimines and N-phenylaldimines in the presence of ZnCl2 to give, after the reaction workup, 4-piperidones 4 and 6, respectively, with moderate to very high enantiomeric excesses. In addition, the absolute configurations of derivatives of 4 a and 4 g were determined by circular dichroism and NMR spectroscopy on the Mosher ester, respectively.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.1460020710
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  • 3
    Electronic Resource
    Electronic Resource
    Conformation and self-association of a hybrid peptide of cecropin a and melittin with improved antibiotic activity (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 838-846 
    Details
    ISSN: 0947-6539
    Keywords: aggregation ; antibiotics ; circular dichroism ; helices ; peptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 15-residue hybrid peptide containing residues 1-7 from cecropin A and residues 2-9 from melittin, CA-(1-7)M(2-9), is a potent antibiotic with broader activity than cecropin A, but without the cytotoxic character of melittin. The conformational behaviour of CA(1-7)M(2-9) including the formation of multimeric species in solution has been investigated by circular dichroism, ultracentrifugation, electrospray mass spectrometry, NMR and energy calculations. Addition of hexafluoroisopropanol or liposomes causes the appearance of a CD spectrum characteristic of a helical structure that changes with pH, buffer and peptide concentration. The concentration dependence is atypical, as the ellipticity at 222 nm decreases with peptide concentration and is not correlated with a correponding decrease in helix content as measured from the NMR spectra. The presence of aggregated structures is demonstrated by ultracentrifugation and ES-MS experiments, which also provide an indication of the stoichiometry. Longrange NOEs suggest a model of aggregation with neighbouring molecules packed antiparallel. Aggregation causes very slow proton-deuterium exchange in some amide protons in the C-terminal region and provides a method for estimating a very large association constant (ca. 106M-1) as well as the stoichiometry of the aggregates. The tendency to aggregate seems to be an inherited feature from melittin and may enhance the antibiotic activity either by faciliting the incorporation of the peptide into the membrane in large quantities or by promoting the disruption of the membrane.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.1460020715
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  • 4
    Electronic Resource
    Electronic Resource
    Formal [4 + 3], [4 + 2], [4 + 1] cycloadditions and acid-base reaction of 2-methyl-1,3-dimorpholino-1,3-butadiene with Fischer carbene complexes (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1629-1637 
    Details
    ISSN: 0947-6539
    Keywords: C-H activation ; carbene complexes ; cycloadditions ; 1,3-diamino-1,3-butadiene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Methyl-1,3-dimorpholino-1,3-butadiene 1 reacted with α,β-unsaturated Fischer carbene complexes to give a wide range of different products depending on the substitution pattern. Thus, sevenmembered rings (4, 5 and 6) could be obtained from chromium complexes 2 with aromatic or vinylic groups at the β position. Similar results were observed when α-methyl-substituted carbene complex 7 a was used. Six-membered carbocycles (derivatives of cycloadducts 12 and 13) were isolated after reaction with both chromium and tungsten complexes bearing one or two alkyl groups at the β position (10 and 11). Moreover, cyclopentenones 20 were the main products when the starting carbene complexes were alkyl-substituted at both α and β positions (19a, b) or when aromatic (19c, d) instead of vinylic complexes were used. A bicyclo[4.1.0]heptene system 18 has also been obtained in the special case of reaction with β,β-dimethylvinylchromium complex 13b; its formation could be explained as a formal carbene insertion into a C-H bond. The behaviour of diene 1 towards alkoxymethylcarbene complexes 22 was unusual. The different reaction products (cyclopentadienes 23, bicyclo[3.1.0]hexenes 24, aromatic amine 25 and metallatrienes 26) imply a mechanism in which the deprotonation of the carbene complex by the diene is followed by Michael addition to the iminium salt formed.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031012
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  • 5
    Electronic Resource
    Electronic Resource
    Isolation of Transmetalation Intermediates in the Stille Cross-Coupling Reaction of Stannanes: Synthesis of Palladacycles, Ligand Substitution, and Insertion Reactions (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 1596-1606 
    Details
    ISSN: 0947-6539
    Keywords: organostannanes ; palladium complexes ; palladacycles ; Stille reaction ; transmetalation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A strategy based on a Stille cross-coupling reaction of organostannanes interrupted at the reductive elimination step has been applied to the synthesis of oxa- and azapalladacycles with the general formula cis-[PdArR(L)2]. The synthesis of oxapalladacycles was achieved under mild conditions by reaction of 2-iodo- or 2-bromophenyloxymethylstannanes with [Pd(PPh3)4]. The synthesis of an aza analogue was similarly carried out from the corresponding 2-iodoaniline derivative. One of the substituted oxapalladacycles rearranged to release steric strain between the palladium and a chloride substituent on the aryl ring, an isomerization promoted by traces of water. In one case, the arylpalladium(II) intermediate of oxidative addition was isolated by using a palladium(0) complex with a bidentate diphosphane. A variety of new palladacycles, including complexes with weakly coordinating ligands, were prepared by ligand substitution. Reaction of the palladacycles with dimethyl acetylene-dicarboxylate led to the formation of chromenes or dihydroquinolines by insertion followed by reductive elimination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960021219
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  • 6
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    Molecular cloning and disease association of hepatitis G virus: a transfusion-transmissible agent (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-01-26
    Description: An RNA virus, designated hepatitis G virus (HGV), was identified from the plasma of a patient with chronic hepatitis. Extension from an immunoreactive complementary DNA clone yielded the entire genome (9392 nucleotides) encoding a polyprotein of 2873 amino acids. The virus is closely related to GB virus C (GBV-C) and distantly related to hepatitis C virus, GBV-A, and GBV-B. HGV was associated with acute and chronic hepatitis. Persistent viremia was detected for up to 9 years in patients with hepatitis. The virus is transfusion-transmissible. It has a global distribution and is present within the volunteer blood donor population in the United States.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Linnen, J -- Wages, J Jr -- Zhang-Keck, Z Y -- Fry, K E -- Krawczynski, K Z -- Alter, H -- Koonin, E -- Gallagher, M -- Alter, M -- Hadziyannis, S -- Karayiannis, P -- Fung, K -- Nakatsuji, Y -- Shih, J W -- Young, L -- Piatak, M Jr -- Hoover, C -- Fernandez, J -- Chen, S -- Zou, J C -- Morris, T -- Hyams, K C -- Ismay, S -- Lifson, J D -- Hess, G -- Foung, S K -- Thomas, H -- Bradley, D -- Margolis, H -- Kim, J P -- New York, N.Y. -- Science. 1996 Jan 26;271(5248):505-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Genelabs Technologies, Redwood City, CA 94063, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8560265" target="_blank"〉PubMed〈/a〉
    Keywords: Acute Disease ; Amino Acid Sequence ; Base Sequence ; Blood Donors ; Blood Transfusion/*adverse effects ; Blood-Borne Pathogens ; Chronic Disease ; Cloning, Molecular ; Consensus Sequence ; Disease Transmission, Infectious ; Flaviviridae/genetics ; Genome, Viral ; Hepatitis Viruses/chemistry/*genetics/isolation & purification ; Hepatitis, Viral, Human/epidemiology/transmission/*virology ; Humans ; Molecular Sequence Data ; Polymerase Chain Reaction ; RNA Viruses/chemistry/*genetics/isolation & purification ; RNA, Viral/blood/genetics ; Sequence Alignment ; United States/epidemiology ; Viral Proteins/chemistry/genetics ; Viremia/epidemiology/virology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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