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1992 (1)
1978 (1)
1Author    H.-D Liidemann, H. Pladi, E. W. Esthof, L. B. TownsendRequires cookie*
 Title    Conformations of 3-Deazaadenosine, 3-Deaza-8-azaadenosine, and Benzimidazole-1-ß-D-riboside in Solution: H RNM R-, Proton-Relaxation-Time-, and Nuclear-Overhauser- Effect Studies  
 Abstract    The solution conformations of 3-deazaadenosine, 3-deaza-8-azaadenosine, and benzimidazole-l-/5-D-riboside have been determined by nuclear magnetic resonance methods in aqueous and ammonia solutions. The two-state S N model of Altona and Sundaralingam is used to analyse the ribose moiety. In order to characterize the orientation of the base relative to the ribose, longitudinal proton relaxation time and nuclear Overhauser enhancement measurements have been carried out. It is shown that 3-deazaadenosine and benzimidazole-l-/?-D-riboside exist preferentially in the S-syn-g+/t (70%) and the N-anti-g+/t (30%) conformation families. In the case of 3-deaza-8-aza-adenosine, some destabilization of the g+ rotamer occurs. In this case, the pulsed methods seem to indicate a preference of the base for the anti range. 
  Reference    Z. Naturforsch. 33c, 305 (1978); received February 17/March 30 1978 
  Published    1978 
  Keywords    Nucleosideanalogs, Conformations, NMR, NOE 
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 TEI-XML for    default:Reihe_C/33/ZNC-1978-33c-0305.pdf 
 Identifier    ZNC-1978-33c-0305 
 Volume    33 
2Author    W. Olfram, M. Eier-Augensteina+, BarendV. Burger1-, HendrikS C Spiesb, WinaJ G BurgerRequires cookie*
 Title    Conformational Analyses of Alkylated /^-Cyclodextrins by NMR Spectroscopy  
 Abstract    /?-Cyclodextrin was derivatized with 1-bromoalkanes o f different chain lengths. The yield as well as the purity o f the resulting cyclodextrin derivatives were improved by using solvent m ix­ tures instead o f pure solvents. The heptakis(2,6-di-0-alkyl)-and heptakis(2,3,6-tri-0-alkyl)-/?-cyclodextrins were studied by means o f N M R spectroscopy employing one-dimensional as well as two-dimensional N M R techniques. Analysis o f the N M R data showed that only in completely derivatized /^-cyclodextrins the cyclodextrin torus undergoes a conform ational change. Best separation factors were found for the cyclodextrin derivative with the highest in­ ternal mobility as determined from the corresponding NT,-values, the validity o f which was confirmed by NOE determinations. Therefore, 13C relaxation times could be used as a measure o f the efficiency and usefulness o f a given cyclodextrin derivative as an enantioselective sta­ tionary phase. 
  Reference    Z. Naturforsch. 47b, 877 (1992); received March 22 1991 /January 2 1992 
  Published    1992 
  Keywords    Peralkylated /^-Cyclodextrins, Chiral Stationary Phases, Spin-Lattice l3C Relaxation, NOE, N M R Spectra 
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 TEI-XML for    default:Reihe_B/47/ZNB-1992-47b-0877.pdf 
 Identifier    ZNB-1992-47b-0877 
 Volume    47