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  • General Chemistry  (16)
  • Life Sciences (General)  (14)
  • Molecular Sequence Data  (12)
  • 2000-2004  (42)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Stereochemistry of Antiinflammatory Marine Sesterterpenes (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 947-953 
    Details
    ISSN: 1434-193X
    Keywords: Circular dichroism ; Configuration determination ; Sesterterpenes ; Manoalide ; Marine natural products ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absolute configuration of antiinflammatory marine sesterterpenes belonging to the manoalide and cacospongionolide structural type has been determined by comparison of the CD spectra of the natural compounds with those of analogues that have been stereoselectively synthesized. In the derived acetates the relative stereochemistry of the stereogenic centres in the pyranofuranone moiety is assigned from 1H-NMR data and the absolute configuration from CD spectra. The absolute configuration of the naturally occurring marine sesterterpenes thorectolide monoacetate, manoalide monoacetate, petrosaspongiolide M and cavernosolide has been determined.
    Additional Material: 4 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    A Facile Solid-Phase Strategy for the Synthesis of Oligonucleotide-Tetraphenylporphyrin Conjugates (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1013-1018 
    Details
    ISSN: 1434-193X
    Keywords: Oligonucleotides ; Conjugation ; Porphyrinoids ; Solid-phase synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A convenient solid-phase synthesis of oligonucleotides conjugated at the 3′-end with a tetraphenylporphyrin residue, by means of a new polymeric support bearing as a linker a lysine derivative, has been developed. A porphyrin linked 17-mer, designed for antisense experiments, has been prepared in good yields, and its hybridization properties with a complementary DNA fragment evaluated by UV thermal analysis.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chiral Ruthenium-Catalyzed Hydrogenation of β-Keto Sulfoxides (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1535-1537 
    Details
    ISSN: 1434-193X
    Keywords: Catalytic hydrogenation ; Ruthenium complexes ; Sulfoxides ; Sulfoxides ; Asymmetric induction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The diastereoselective catalytic hydrogenation of β-keto sulfoxides in the presence of ruthenium complexes was studied. Optically pure β-keto sulfoxides were hydrogenated in the presence of achiral catalysts leading to moderate yields and stereoselectivities. Using chiral ruthenium catalysts such as [(R)-MeO-BIPHEPRuBr2] and [(S)-MeO-BIPHEPRuBr2], the hydrogenation proceeded in good yields with very high diastereoselectivity. Chirality at the secondary centre of the β-hydroxy sulfoxides produced was controlled by the catalysts.
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Study of Copper(II) Polyazamacrocyclic Complexes by Electronic Absorption Spectrophotometry and EPR Spectroscopy (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 559-565 
    Details
    ISSN: 1434-1948
    Keywords: Macrocyclic ligands ; Copper ; EPR spectroscopy ; Electronic spectrophotometry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copper(II) mononuclear complexes with the polyazamacrocyclic ligands NOTA (1,4,7-triazacyclononane-N,N′,N″triacetate), DOTA (1,4,7,10-tetraazacyclo-dodecane-N,N′,N″,N″′-tetraacetate), NOTP [1,4,7-triazacyclononane-N,N′,N″-tris(methylenephosphonate)] and DOTP [1,4,7,10tetraazacyclododecane-N,N′,N″,N‴-tetrakis(methylenephosphonate)] were characterised in aqueous solution by electronic absorption spectrophotometry and electron paramagnetic resonance (EPR) spectroscopy. While two isomeric species were detected by EPR spectroscopy in frozen samples of the polycarboxylate complexes, only one complex form was found for the poly(methylenephosphonate) systems. The results obtained are in accordance with a six-coordinate pattern for the metal centre, yielding tetragonally distorted complexes in solution, in agreement with previously reported studies on CuII complexes, both in solution and in the solid state.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Complexation of Cobalt(II) at the Upper Rim of Two New Calix[4]arene/Bipyridine-Based Podands (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 683-691 
    Details
    ISSN: 1434-1948
    Keywords: Calix[4]arenes ; Bipyridines ; Podands ; Cobalt complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Introduction of one or two 2,2′-bipyridine units at the upper rim of the calix[4]arene platform was performed by means of the Wittig reaction. The resulting alkenes were hydrogenated to give two new bipyridyl-based calixarene podands, which were studied as ligands for CoII cation. The mono-bipyridyldichlorocobalt complex was notably fully characterised by 1H-NMR and X-ray crystal structure analyses, which confirmed the tetrahedral coordination mode involving the bipyridyl subunit and the two chlorine atoms around the cobalt centre.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and Characterization of Some Metal Complexes with New Nitrogen-Oxygen Donor Macrocyclic Ligands - X-ray Crystal Structures of a 26-Membered Reduced Monoprotonated Macrocycle and a 20-Membered Pendant-Arm Schiff-Base Macrocyclic Cadmium(II) Complex (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 1015-1024 
    Details
    ISSN: 1434-1948
    Keywords: Metal complexes ; Template synthesis ; Schiff bases ; Oxaazamacrocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New series of macrocyclic Schiff-base lanthanide(III), yttrium(III), and cadmium(II) complexes, [M(1)]Xn (X = NO3-, M = Y, Ln = La-Yb except Pm and Dy; X = ClO4-, M = Cd, La, Ce, Pr, Sm, Gd, or Er) and [M(3)]Xn (X = NO3-, M = Dy; X = ClO4-, M = Er and Cd), have been prepared by cyclocondensation of O1,O7-bis(2-formylphenyl)-1,4,7-trioxaheptane with O1,O7-bis(2-aninyl)-1,4,7-trioxaheptane (1) or tris(2-aminoethyl)amine (3) in the presence of the appropriate metal salt as a template agent. The Schiff-base macrocycles 1 and 3 are also formed in the absence of a metal ion. Treatment of 1 with NaBH4 in methanol gives the diamine macrocycle 2. The reactions of LnIII, CdII, and YIII ions with 2 have also been investigated. The crystal structures of the monoprotonated ligand 2 and of the complex [Cd(3)](ClO4)2 have been determined by X-ray diffraction analysis.Supporting information for this article is available on the WWW under -//_/_http://www.wiley-vch.de/contents/jc_2005/2000/99352_s.pdf or from the author.
    Additional Material: 2 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    A Simple Polyheterotopic Molecular Receptor Derived from Bispyrazolylmethane Showing Ambivalent Allosteric Cooperation of Zinc(II) (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1913-1922 
    Details
    ISSN: 1434-193X
    Keywords: Allosterism ; Crown compounds ; Molecular receptors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of compounds 1-4 as simple systems to display allostery is described. Transport experiments (bulk liquid membrane) of ammonium cations in the presence or absence of ZnI2 in the receiving and donor phases evidenced strong negative or positive allosteric effects of the metal towards ammonium complexation, which depended on the relative arrangement of crowns with respect to the pyrazole nitrogens.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Mechanism and Extensibility of the Reaction (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 99-104 
    Details
    ISSN: 1434-193X
    Keywords: Allyl alcohols ; Organocerium reagents ; Alkenes ; Addition reactions ; Cerium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Alkylcerium reagents add to the multiple bonds of allyl and propargyl alcohols in good yields and under mild conditions. The double bond can be reduced with lithium aluminum hydride in the presence of cerium trichloride. The regiochemistry of the attack depends on electronic factors.
    Additional Material: 1 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Equilibrium Constants for Ionisation and Enolisation of 3-Nitrobutan-2-one (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1641-1646 
    Details
    ISSN: 1434-193X
    Keywords: Tautomerism ; Ketones ; Kinetics ; Ionizations ; Semiempirical calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The equilibrium constant for the keto-enol tautomerism of 3-nitrobutan-2-one KT = [enol]/[ketone] has been measured in water as 4.57 × 10-3 (pKT = 2.34) by combining the rate constants for ketonisation of the enolate form and pKa of the ketone at 25 °C. The rates of ketonisation were measured by a rapid kinetic technique and the pKa was determined spectrophotometrically and potentiometrically as 5.15. A comparison with 2-butanone and acetone shows a strong influence of the nitro group in enhancing the acidity of the substrate and in stabilizing the enol relative to the keto tautomer. By means of semiempirical AM1 calculations, good correlations were found between the atomic charge on the acidic hydrogens and the pKa (in water at 25 °C) of both tautomeric forms for a number of simple ketones whose pKas and pKTs are available in the literature. The agreement of experimental acidity constants of the enol, pKaEH, the ketone, pKaKH, and the tautomeric constant, pKT, with predicted values is satisfactory.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Studies Towards the Synthesis of Aplykurodins - Synthesis of 17,18-Dihydro-3,9-di-epi-aplykurodinone B (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 439-448 
    Details
    ISSN: 1434-193X
    Keywords: Aplykurodins ; Marine steroids ; C-C coupling ; Cyclic peroxides ; Lactonization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An approach to the synthesis of aplykurodins, ichthyotoxic marine lactones, is presented. The carbon framework was derived from vitamin D3 by conversion of the readily accessible allyl alcohol 13 to the protected Grundmann's hydroxy ketone 22 and subsequent introduction of the C2 side chain through a Pd0-promoted coupling. Highly stereoselective hetero Diels-Alder reaction with O21 produced the key intermediate peroxide 25. Functional group transformations, coupled with a series of chemo- and stereoselective reactions, finally resulted in the synthesis of the unnatural analogue 17,18-dihydro-3,9-di-epi-aplykurodinone B (6).
    Additional Material: 2 Ill.
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