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  • 2,4,6-Tri-t-butylphenyl-substituted amino-imino boranes  (1)
  • Polymer and Materials Science  (1)
  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The x-ray structure of the hydrated ammonium salt of the deoxytetranucleotide d-pApTpApT was determined by Patterson and direct methods at a resolution of 1 Å. The crystal structure contains right-handed double-helical segments formed by complementary Watson-Crick-type hydrogen bonding between the adenine and thymine bases of neighboring molecules. The minihelix contains two base pairs. The chains are antiparallel. The A-T and T-A sequences have different phosphodiester conformations. The deoxyribose-pucker and the sugar-base orientation alternate along the chain depending on the nature of the base (3′-endo for purine and 2′-endo for pyrimidine). The extended structure is stabilized by base-base, base-sugar, and hydrogen-bond interactions. The minihelix of two base pairs provides starting coordinates for model-building studies of the dA-dT polymer. A B-DNA-type polymer structure is described, which has sequence-dependent alternations of both the deoxyribose pucker and the phosphate diester bridge conformation. Such sequence-dependent DNA structures, if present locally in regions such as operator sequences, could facilitate sequence-specific interactions. The crystal study also suggests possible geometrical parameters for the replication fork.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 608 (1992), S. 147-152 
    ISSN: 0044-2313
    Keywords: 2,4,6-Tri-t-butylphenyl-substituted amino-imino boranes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Supermesityl stabilized IminoboranesAmino-iminoboranes R′(SiMe3)N-B≡N-R: IIc (R′ = CHMe2), IId (R′= CMe3) and IIe (R′ = SiMe3) carrying the supermesityl group (R) on the imino nitrogen atoms have been prepared from the corresponding fluorobis(amino)boranes Ic-e by HF-elimination using t-BuLi (IIc, d) or n-lithio-bis(trimethylsilyl)amid (IIe). The Amino-iminoboranes are thermally stable at room temperature. Upon treatment of the fluorobis(amino)boranes Ia, Ib, Ie with t-BuLi, LiF and HN(SiMe3)R′ are eliminated and the B-t-butyl substituted iminoborane III is formed. The compounds are characterized by elementar analyses and spectroscopic data (MS, IR, NMR). An X-ray diffraction study has been performed for II d.
    Notes: Amino-imino-borane R′(SiMe3)N-B≡N-R:IIc (R′ = CHMe2), IId (R′= CMe3) und IIe (R′ = SiMe3) mit R = 2,4,6-Tri-t-butylphenyl- wurden aus den entsprechenden Fluorbis(amino)boranen Ic-e durch HF-Eliminierung mit t-Butyllithium (IIc, IId) bzw. Lithiumbis(trimethylislyl)amid (IIe) erhalten. IIc-e sind thermisch stabil und bei Raumtemperatur unbegrenzt haltbar. Die Umsetzungen der Fluorbis(amino)borane Ia (R′ = Me), Ib(R′ = CH2Me) und Ie (R′ = SiMe3) mit t- Butyllithium führen zur Abspaltung von LiF und HN(SiMe3)R′, wobei sich in allen Fällen des B-t-butyl-substituierte Iminoboran III bildet. Die Verbindungen sind elementaranalytisch und spektroskopisch (MS, IR, NMR) charakterisiert. Eine Röntgenstrukturanalyse wurde von IId durchgeführt.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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