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'Tautomerism' in keywords Facet   Publication Year 1994  [X]
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1Author    M. Ikko Koskinen3, IlpoM. Utikainenb, Hannu EloaRequires cookie*
 Title    Crystal and Molecular Structure of Aminoguanidine Sulphate, an Important Enzyme Inhibitor and Starting Material of Drug Syntheses  
 Abstract    Aminoguanidine is not only an agent with a variety of pharmacological effects but also an im portant starting material of am idinohydrazone-type drugs and enzyme inhibitors. There­ fore, we have now synthesized am inoguanidine sulphate CN4H 82+.S 0 42~ and determined its structure by single-crystal X-ray diffraction. The doubly protonated (dication) form o f am ino­ guanidine that is present in the sulphate could, in principle, exist in the form of several differ­ ent tautom ers. The crystal studied consisted exclusively of one tautomer: one of the nitrogens of the hydrazine moiety bears three hydrogen atoms while the other one (the one bound to the carbon) bears one hydrogen. The other two nitrogens are bound to two hydrogens each. The predominance of this tautom er can be explained by the very strong resonance in it. The dica­ tion of aminoguanidine is remarkably planar. The hydrogens of the hydrazine moeity are, however, clearly out of the plane of the other atoms. There is a strong hydrogen bond between the proton of the m onoprotonated nitrogen and one sulphate oxygen. This bond obviously causes the deviation of the hydrogen from the plane. The bonds between the carbon atom and the adjecnt nitrogens are essentially equally long, indicating that each bond has approxim ately the same am ount of double bond character. One of the positive charges of the dication is thus delocalized, being shared by all of the atoms of the C N 3 moiety. In this respect, the structure is similar to that of all bis(amidinohydrazones) whose structures have been determined. The other positive charge of aminoguanidine dication is localized at the nitrogen bearing three hydrogens. 
  Reference    Z. Naturforsch. 49b, 556—560 (1994); received December 6 1993 
  Published    1994 
  Keywords    Bis(guanylhydrazones), Diamine Oxidase Inhibitors, Nitric Oxide Synthase Inhibitors, Resonance, Tautomerism 
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 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-0556.pdf 
 Identifier    ZNB-1994-49b-0556 
 Volume    49