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'CD Spectra' in keywords Facet   section ZfN Section B  [X]
Facet   Publication Year 1997  [X]
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1Author    Zofia Plesnar3, Stanisław Malanowski3, Zenon Lotowskib, JacekW. Morzyckib, Jadwiga Frelek, Jacek WójcikdRequires cookie*
 Title    Stereospecific Association of C-20 Epimers of 3/?-Hydroxy-16-oxo-24-nor-17-azachol-5-eno-23-nitryle  
 Abstract    The cryoscopic measurements show that title compounds are strongly associated in CHC13 solutions. The association of the 20 R epimer is distinctly less pronounced than that of the 205 epipmer. Self-association of the 205 epimer leads to the formation of very large com­ plexes. The 20 R epimer forms associates via water molecules. The dissimilarity may be ex­ plained in terms of different accessibility of the lactam carbonyl groups in the two epimers for the association. It is proposed that the association process is controlled by the configura­ tion at the carbon atom C(20) and conformation around the C(20)-C(22) bond. Populations of side chain conformations of both epimers were determined by means of proton nuclear magnetic resonance. It was found for the 20 R epimer that the t and the -g rotamers are almost equally populated, and the rotamer +g is excluded. For the 205 epimer the +g rotamer predominates over the t one, and the -g rotamer is excluded. The N M R data are fully consistent with the results of the molecular modelling studies. 
  Reference    Z. Naturforsch. 52b, 749—756 (1997); received 
  Published    1997 
  Keywords    Self-Association, Cryoscopic Measurements, Conformational Analysis, CD Spectra, Azasteroids 
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 TEI-XML for    default:Reihe_B/52/ZNB-1997-52b-0749.pdf 
 Identifier    ZNB-1997-52b-0749 
 Volume    52