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  • Chemistry  (19)
  • Life Sciences (General)  (14)
  • 2000-2004  (33)
  • 1
    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
    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
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional gas chromatography ; thermal desorption modulator ; temperature programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In comprehensive two-dimensional gas chromatography, two individual separations are coupled by means of a rotating thermal desorption modulator interface. The injection pulse introduced via the interface onto the second column should be as short as possible. Parameters affecting the modulator operation are studied. In the set-up used in this study, the temperature of the second column can be programmed independently from that of the first column. Optimization of the second-dimension separation to minimize peak broadening and maximize resolution is discussed and an elegant approach to determine second-dimension retention times using a non-constant modulation frequency is demonstrated. The high separation power of the comprehensive system is demonstrated by the analysis of technical and biota samples containing chlorinated biphenyls and toxaphene.
    Additional Material: 7 Ill.
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  • 4
    ISSN: 1434-1948
    Keywords: Pyrazolate complexes ; Palladium ; Platinum ; N ligands ; Bridging ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trinuclear complexes containing pyrazolate bridging ligands of the type [NBu4]2[{(C6F5)2 M(μ-pz)(μ-X)}2M′] (M, M′= Pd or Pt; X = Cl, OH, or pz) (Hpz = pyrazole) have been prepared using [NBu4][M(C6F5)2(acac)] (acac = acetylacetonate) or [NBu4]2[M2(C6F5)4(μ-OH)2] and [M′Cl2(Hpz)2] or [M′(Hpz)4]2+ as starting materials. Asymmetric homo- and heterobimetallic complexes of the types [NBu4][R2M(μ-pz)2Pd(η3-allyl)] and [R2M(μ-pz)2M′L2] (allyl = C3H5 or C4H7; L2 = 2 PEt3 or bipy; R = C6F5 or C6Cl5; M, M′ = Pd or Pt) have been obtained starting from [NBu4][MR2(pzHpz)] and [Pd(η3-allyl)(acac)] or [M′L2Cl2], respectively. The identity of the new complexes has been established by NMR (1H, 19F and 31P) spectroscopy. The crystal structure of [{(C6F5)2Pd(μ-pz)(μ-Cl)}2Pd]2- has an inversion centre, with a bent appearance of the Pd3(μ-pz)2(μ-Cl)2 moiety. The crystal structure of [(C6F5)2Pd(μ-pz)2Pd(η3-C4H7)] has also been determined by single-crystal X-ray diffraction, where a boat conformation of the central “Pd2N4” six-membered rings is observed.
    Additional Material: 2 Ill.
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  • 5
    ISSN: 1434-1948
    Keywords: Copper ; Oxygenase ; Copper-oxygen radical species ; RPY2 ligand ; Oxygenation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe the reactivity of new copper AlkylPY2 type complexes which react with dioxygen and thus hydroxylate an aliphatic C-H bond of the ligand in the same manner as copper-containing monooxygenases.
    Additional Material: 1 Ill.
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  • 6
    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
    ISSN: 1434-193X
    Keywords: Cup-shaped PAHs ; Host-guest compounds ; Host-guest chemistry ; Cyclizations ; Semiempirical calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Cyclotrimerisation of benzo-polycyclic bromostannylalkenes 8a-d with Cu(NO3)2·3H2O in THF affords benzotri(benzonorbornadienes) 3a-d as a mixture of the syn and anti isomers. The ratio of syn to anti is close to the 1:3 statistical value in most cases (i.e. in cyclotrimers 3a,b,d), but highly in favour of the anti isomer in 3c, where steric hindrance by the methoxy groups plays an important role in the stereochemistry of the cyclotrimerisation. The substrates for the cyclotrimerisation, i.e. the bromostannyl alkenes 8a-d, were prepared from bromoalkenes 7a-d by treatment with base (LDA) and quenching with trimethyltin chloride. In turn, bromoalkenes 7a-d were prepared from alkenes 5a-d by radical bromination-elimination. The reaction conditions used were designed to minimise Wagner-Meerwein rearrangements that would lead to unwanted bromo isomers. The cup-shaped syn cyclotrimers 3a-d exhibit high electron density within the cavity as determined by AM1 semiempirical calculations of their electrostatic potential surfaces and are valuable substrates for supramolecular chemistry. As an example, it is shown that fullerene C60 is drawn into solution in acetonitrile by complexation with both the syn and anti trimer of benzonorbornadiene 3a.
    Additional Material: 1 Tab.
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  • 8
    ISSN: 1434-193X
    Keywords: Self-assembly ; Vapor-pressure osmometry ; Resorcin[4]arenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Resorcin[4]arene tetracarboxylic acids 5,6 (A) and resorcin[4]arene tetrapyridines 2,3 (P) self-assemble in chloroform solution to form stable heterotopic AP dimers. Data from NMR titration and dilution experiments, as well as from vapor-pressure osmometry (VPO), indicate that the AP dimer is formed with an association constant greater than 107 M-1. Solid-solution extraction experiments are indicative of the formation of a 2:1 trimer (A2P), while self-associated homotopic species (A2 and A3) can be detected by NMR and VPO. Analysis of the heterotopic noncovalent assembly process over a range of compositions shows that these other species are much less stable than the AP heterodimer, which is the exclusive species at an A/P concentration ratio of 1:1 (〉 99.7% of the total at 10 mM).
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 559-565 
    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.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 677-680 
    ISSN: 0935-6304
    Keywords: Capillary ; fast separations ; mass spectrometry ; vacuum ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---There is a constant drive to speed up GC separations. Shorter analysis times provide more analyses per day, which reduces cost. One approach is to reduce column length and column diameter and columns of 0.15 mm i.d. have indeed grown in popularity. However, the majority of applications are still done with 0.25 mm and 0.32 mm columns.
    Additional Material: 10 Ill.
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