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'Arabinofuranosyladenine Analogues' in keywords
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1980 (1)
1Author    G. Klimke, I. Cuno, H.-D Lüdem, R. Mengel, M. J. RobinsRequires cookie*
 Title    Arabinose Conformations of 9-ß -D-Arabinofuranosyladenine (ARA-A) Analogues Modified at the 2',3' or 5' Positions  
 Abstract    The solution conformations o f 9-/?-D-arabinofuranosyladenine analogues modified at the 2',3' or 5' positions are derived from the HRNMR spectra and the longitudinal relaxation rates o f the protons. The compounds studied are: 9-/?-D-arabinofuranosyladenine and its 2/-amino-2'-deoxy, 2'-chloro-2'-deoxy, 2'-azido-2'-deoxy, 3'-amino-3'-deoxy, 3'-bromo-3'-deoxy, 3'-chloro-3'-deoxy, 3'-fluoro-3'-deoxy, 3'-azido-3'-deoxy, 2',3'-diamino-2/,3'-dideoxy, 2',5'-diamino-2',5'-di-deoxy and 2',5'-diazido-2',5'-dideoxy analogues. It is derived from the data that the conforma­ tional equilibria o f the furanoside rings can be described by the two state N <*> S model of Altona and Sundaralingam. The emphasis in this work is to study systematically the influence o f the different chemical modifications upon the conformational equilibria o f the nucleosides. For the arabinosides it is found that substitution o f the hydroxyl groups at C2' or C3' by other atoms or groups always stabilizes the N conformation of the arabinose ring. The only exception is fluorine, where S is stabilized. The preference for the N state is correlated with an increasing population o f the g + rotamer of the exocyclic 5'-CH2OD group. From the relaxation study o f 2'-chloro-2'-deoxy-arabinofuranosyladenine the position of the syn <=> anti equilibrium o f the base was estimated to be predominantly anti. Thus a preference for the anti-N-g+ conformation was derived for the arabinosides excluding an intramolecular hydrogen bond between the 2' and 5' hydroxyl groups that was found in the solid state. The stabilization o f the N conformer in the modified compounds can be qualitatively explained by steric effects. 
  Reference    Z. Naturforsch. 35c, 853 (1980); received June 25 1980 
  Published    1980 
  Keywords    Arabinofuranosyladenine Analogues, Conformation, NMR 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0853.pdf 
 Identifier    ZNC-1980-35c-0853 
 Volume    35