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Issue 5, 2010
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Fluorinated enamines of nucleobases as precursors of nucleoside analogues. Synthesis, spectroscopic and structural studies

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Abstract

The 1H and 19F NMR spectra of N-α-fluoro-β-trifluoromethylenamines and isostructural N-β-fluoro-β-trifluoromethylenamines of nucleobases dissolved in CDCl3 and DMSO-d6 have shown distinct differences associated with the conformational conversion between the Z and E stereoisomers. In the E stereoisomer the tetrafluoropropenyl group is rotated relative to the heteroring plane, whereas the Z stereoisomer assumes the most planar structure. The flat conformation of the Z stereoisomer is stabilised by internal hydrogen bonding between Cα–H and the carbonyl oxygen (pyrimidinic bases) or the endocyclic nitrogen (purinic bases). Large variations in the magnitudes of the chemical shifts of Cβ–H, Cα–F, C6–H and C8–H were observed, i.e. the chemical shift increased with increasing polarity and ability of DMSO-d6 to establish intermolecular hydrogen bonds in competition with intramolecular hydrogen bonds. The (Z)-N4-benzoyl-N1-(1,3,3,3-tetrafluoroprop-1-enyl)cytosine crystals undergo a phase transition at 230 K induced by the tetrafluoropropenyl substituent reorientations. Between 300 and 230 K the molecules are present in two conformations, and below 230 K the molecules gradually assume five conformations, remaining in a stable equilibrium with intermolecular forces, evidenced by single-crystal X-ray diffraction.

Graphical abstract: Fluorinated enamines of nucleobases as precursors of nucleoside analogues. Synthesis, spectroscopic and structural studies

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Publication details

The article was received on 30 Oct 2009, accepted on 08 Feb 2010 and first published on 08 Apr 2010


Article type: Paper
DOI: 10.1039/B9NJ00617F
Citation: New J. Chem., 2010,34, 894-902
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    Fluorinated enamines of nucleobases as precursors of nucleoside analogues. Synthesis, spectroscopic and structural studies

    H. Wójtowicz-Rajchel, M. Pasikowska, A. Olejniczak, A. Katrusiak and H. Koroniak, New J. Chem., 2010, 34, 894
    DOI: 10.1039/B9NJ00617F

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