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  • Organic Chemistry  (45)
  • Aerodynamics
  • GENERAL
  • Inorganic Chemistry
  • 1995-1999  (45)
  • 1955-1959
  • 1945-1949  (24)
  • 1997  (45)
  • 1948  (24)
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Publisher
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  • 1995-1999  (45)
  • 1955-1959
  • 1945-1949  (24)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Hydrogen Bonding and Conformational Analysis of Chelate-Stabilized Alkoxopalladium(II) Complexes Derived from Amino Alcohol Ligands (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 35-44 
    Details
    ISSN: 0009-2940
    Keywords: Alkoxopalladium(II) ; Conformational analysis ; Hydrogen bonding ; Two-dimensional and cage structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of palladium acetate with two equivalents of di- and triethanolamines RN(CH2CH2OH)2 in the presence of a base affords the new chelate-stabilized alkoxo Pd(II) complexes [Pd(OCH2CH2N(R)CH2CH2OH)2] [R = Me (1), Et (2), n-Bu (3), benzyl (4) or CH2CH2OH (5)]. These N,O-ligated complexes are isolated in high yield as yellow, crystalline solids and are thermally stable despite the presence of several β-hydrogen atoms in the ligand system. Both complexes possess a square-planar palladium coordination geometry with the two oxygen atoms positioned mutually trans. The most notable difference in the molecular structures is that 1 forms a two dimensional network of intermolecular O-H≡O hydrogen bonds, whereas 5 forms intramolecular O-H⃛O hydrogen bonds, which cage the palladium center. In solution 1-4 exist as a diastereoisomeric mixture (a racemic enantiomeric pair SNSN, RNRN and a mesomeric form RNSN) in a 1:1 molar ratio, and this ratio is independent of temperature in nonalcoholic solvents, When complexes 1-4 are dissolved in protic solvents (e.g. MeOH) the diastereomeric excess is temperature-dependent due to an exchange process between the meso diastereoisomer and the (racemic) enantiomeric pair. Thermodynamic parameters for this process in a mixture of MeOH-toluene have been determined with NMR and show this process to be influenced by the steric nature of the alkyl substituent (R) on nitrogen. A conformational analysis based on 1H-NMR coupling constants within the N,O-chelate ring of complexes 1-4 provides details on the solution structure of the ring in both diastereoisomers.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300106
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  • 2
    Electronic Resource
    Electronic Resource
    Zur Kenntnis des Kohlenstoffringes. 45. Mitteilung. Über die Gültigkeitsgrenze der Bredt' schen Regel bei bicyclischen Verbindungen mit einem vielgliedrigen Ring (1948)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 31 (1948), S. 92-97 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19480310119
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  • 3
    Electronic Resource
    Electronic Resource
    High-performance liquid chromatography of imine stereoisomers on cellulose-based chiral stationary phases (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 727-731 
    Details
    ISSN: 0899-0042
    Keywords: chiral HPLC ; amylose tris(3,5-dimethylphenylcarbamate) ; cellulose tris(3,5-dimethylphenylcarbamate) ; cellulose tris(4-methylbenzoate) ; imine enantiomers ; e.e. determination ; imine isomerization reaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A high-performance liquid chromatographic method has been developed for the analysis of the intermediate imines and end products in an asymmetric isomerization route toward optically active amines. Separation of the imine enantiomers was performed on commercially available Chiralcel OD-H, Chiralcel OJ, and Chiralpak AD chiral stationary phases. All substituted imine enantiomers could be readily resolved with selectivities (α) higher than 1.10 using the Chiralpak AD column. By derivatization with ring-substituted benzaldehydes, aromatic amines were converted into Schiff base derivatives and the enantiopurity of these amines was determined. Chirality 9:727-731, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
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    Static Investigation of a Multiaxis Thrust-Vectoring Nozzle With Variable Internal Contouring Ability (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The thrust efficiency and vectoring performance of a convergent-divergent nozzle were investigated at static conditions in the model preparation area of the Langley 16-Foot Transonic Tunnel. The diamond-shaped nozzle was capable of varying the internal contour of each quadrant individually by using cam mechanisms and retractable drawers to produce pitch and yaw thrust vectoring. Pitch thrust vectoring was achieved by either retracting the lower drawers to incline the throat or varying the internal flow-path contours to incline the throat. Yaw thrust vectoring was achieved by reducing flow area left of the nozzle centerline and increasing flow area right of the nozzle centerline; a skewed throat deflected the flow in the lateral direction.
    Keywords: Aerodynamics
    Type: NASA-TP-3628 , NAS 1.60:3628 , L-17570
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    CFL3D: Its History and Some Recent Applications (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The history of the Computational Fluids Laboratory -3D (CFL3D) Navier-Stokes computer code is discussed and a comprehensive reference list is given. Three recent advanced applications are presented (1) Wing with partial-spanflap, (2) F/A-18 with forebody control strake, and (3) Noise predictions for an advanced ducted propeller turbomachinery flow.
    Keywords: Aerodynamics
    Type: NASA-TM-112861 , NAS 1.15:112861 , Gudunov''s Method for Gas Dynamics: Current Applications and Future Developments; May 01, 1997 - May 02, 1997; Ann Arbor, MI; United States
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    NASA TECHNICAL REPORTS
  • 6
    Electronic Resource
    Electronic Resource
    Synthesis of Unnatural Lipohilic N-(9H-Fluoren-9-ylmethoxy)carbonyl-Substituted α-Amino Acids and Their Incorporation into Cyclic RGD-Peptides: A structure-activity studyDedicated to Peter Welzel on the occasion of his 60th birthday (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 1280-1300 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The αv/β3 integrin is implicated in human tumor metastasis and angiogenesis. It has been shown that structures of the sequence cyclo(-Arg1-Gly2-Asp3-D-Phe4-Xaa5-) (I) and cyclo(-Arg1-Gly2-Asp3-Phe4-D-Xaa5-) (II) bind with high affinity and the latter with high selectivity to this receptor. The residues Xaa and D-Xaa accept a broad variety of amino acids. Here, we report on the synthesis, activities, and conformational analysis of cyclic Arg-Gly-Asp (RGD) peptides containing liophilic amino acids Xaa or D-Xaa in position 5. For I, these were (2S)-2-aminohexadecanoic acid (Ahd) and N′-hexadecylglycine (Hd-Gly) and in II, D-Ahd and Hd-Gly, and, for control purposes, Ahd were incorporated (Fig. 1). The enantiomerically pure a-amino acids were obtained by non-enantioselective synthesis and subsequent enzymatic separation of isomers using acylase I (Scheme). Hd-Gly was prepared in a modified procedure according to Stewart from ethyl bromoacetate and hexadecylamine (Scheme). The synthesis and physicochemical properties of the corresponding (9H-fluoren-9-ylmethoxy)carbonyl (Fmoc) derivatives, compatible with solid-phase peptide synthesis, are described. Structure elucidation by NMR reveals that the lipid modification has no significant impact on the template structures when incorporated into them. For peptides I with Xaa = Ahd or Hd-Gly (1 or 2), a βII′/γ-turn-like arrangement with D-Phe in i+1 position of the β-turn is found. Peptides II with D-Xaa = D-Ahd or Hd-Gly (3 or 4) exhibit a βII′/γ-turn conformation with Gly in i+1 position of the β-turn, whereas II with Ahd instead of D-Xaa, i.e., lacking a D-amino acid in position 4 or 5 (5). adopts no defined conformation. However, in assays of receptor specificity employing human αvv/β3 integrin, the compounds exhibit IC50 values ranging from nanomolar to less than millimolar. These results indicate that although the arrangement of the pharmacophoric groups is preserved in the target compounds, the biological activity is highly dependent on spatial requirements of the lipid anchor in the receptor binding pocket. Obviously, only certain positions do not affect the binding.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800423
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  • 7
    Electronic Resource
    Electronic Resource
    Cyclo-β-peptides: Structure and tubular stacking of cyclic tetramers of 3-aminobutanoic acid as determined from powder diffraction dataDedicated to Professor Hans Paulsen on the occasion of his 75th birthday (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 173-182 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-state structures of three stereoisomer, 1-3, of the cyclic tetramer of 3-aminobutanoic acid are presented. These cyclo-β-peptides were found to be highly insoluble materials, and it proved to be impossible to grow crystals of sufficient quality for X-ray single-crystal analysis. The samples of 1-3 were, however, suitable candidates for structure determination from powder diffraction data (Fig. 1), and the application of this method is described. All three isomers have been found to adopt tubular structures (Figs. 2-4) in a fashion similar to those already observed for certain cyclo-α-peptides. The stacks of 16-membered rings are held together by four nonlinear C=O…H—N H-bonds between pairs of molecules (Fig.5).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800116
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  • 8
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands. Part XLIIIPart XLII [1]. Tetraazamacrocyclic nickel(II) and copper(II) complexes with aliphatic methylthio- and methoxy-substituted pendant chains (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 241-252 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 14-membered tetraazamacrocyclic Ni2+ and Cu2+ complexes of 4 (1, 4, 8-trimethyl-11-[(2-methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), 5. (1, 4-dimethyl-8, 11-bis[2-(methylthio)ethyl]-l, 4, 8, 11-tetraazacyclotetradecane), and 7 (1, 4, 8, ll-tetrakis[2-(methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), with pne, two, and four methylthio-substituted pendant chains, respectively, and the Ni2+ complex of 6 (1, 4-dimethyl-8, 11-bis (2-methoxyethyl)-1, 4, 8, 11-tetraazacyclotetradecane), with two methoxy-substituted pendant chains, were synthesized and their chemistry studied with regard to modelling F430. Solution spectra in H2O, MeCN, and DMF indicate participation of the side chain in metal coordination when the donor group is a thioether, whereas no coordination with the metal ion is observed with the ether group. Similarly the X-ray structures of the thioether-containing compounds [Ni(5)](ClO4)2, [Cu(5)](ClO4)2, and [Cu(7)](ClO4)2 show a coordination number of 5, whereas that of [Ni(6)](ClO4)2 with ether pendant chains, shows a coordination number of 4. Cyclic voltammetry of these complexes in MeCN reveals that Ni2+ is reversibly reduced to Ni+ between -0.64 and -0.77 V vs. SCE, the potential being influenced by the nature and number of the pendant chains. At more negative potentials, the thioether is cleaved, whereby a thiol is formed; the thiol is then oxidized at ca. + 0.8 V vs. SCE, when a glassy carbon electrode is used, or at ca. 0 V vs. SCE at a dropping Hg electrode. No cleavage of the ether bond in [Ni(6)](ClO4)2 is observed under similar conditions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800122
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  • 9
    Electronic Resource
    Electronic Resource
    ‘Mixed’ β-Peptides: A unique helical secondary structure in solution. Preliminary communication (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 2033-2038 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Hexapeptides 1-5 and a β-dodecapeptide 6 with sequences containing two different types of β-amino acids (aliphatic proteinageous side chains in the 2- or in the 3-position) have been prepared. CD (Fig. 1) and NMR measurements indicate that, with one exception, the secondary structures formed by these new β-peptides differ from those of isomers studied previously. Detailed NMR analysis of the β-hexapeptide 5 (with alternating β2,β3-building blocks) and molecular-dynamics simulations have produced a minimum energy conformation (Fig. 2,b)which might be described as a novel irregular helix containing ten- and twelve-membered H-bonded rings. This demonstrates the great structural variability of β-peptides, since three different helical secondary structures have been discovered to date.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800703
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  • 10
    Electronic Resource
    Electronic Resource
    Nucleotides. Part LIIPart LI: [1]. Synthesis and biological activity of new base-modified (2′-5′)oligoadenylate trimers (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 1053-1060 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some new (2′-5′)oligoadenylate trimers, i.e., 22-28, containing the antiviral nucleoside ribavirin (= 1-(β-D-ribofuranosyl)-1H-1,2,4-triazole-3-carboxamide; 7) and the synthetic cytokine 6-(benzylamino)purine riboside (= N6-benzyladenosine; 1) in different positions of the trimer, have been synthesized by the phosphotriester method. The selectively blocked nucleosides 2-6 and 8-11 and the 2′-phosphodiesters 13 and 14, used for the oligonucleotide syntheses, were synthesized from the corresponding unprotected ribonucleosides 1 and 7, and isolated by silica-gel column chromatography. The fully deblocked trimers 22-28 were purified by ion-exchange chromatography on DEAE-Senacell 23-SS. The newly synthesized compounds were characterized by physical means. The ability of synthesized trimers to inhibit HIV-1 replication and to improve RNase L activation were investigated. Some of the synthesized trimers showed also biological inhibition of HIV-1 reverse transcriptase and HIV-1-induced syncytia formation. It was shown that AdoBn-containing trimers inhibited HIV-1-induced syncytia formation 〉 1500-fold, independently of the position of the AdoBn residue in the oligomer chain.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800404
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