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1996 (1)
1994 (1)
1Author    JereT. Koskinena, Mikko Koskinenb, M. Utikainenb, Berit Mannfors3, Hannu ElocRequires cookie*
 Title    Experimental and Computational Studies on Aminoguanidine Free Base, Monocation and Dication, Part I: The Crystal and Molecular Structure of Aminoguanidine Monohydrochloride and the ab In itio Structure of the Endiamine Tautomer of Aminoguanidine Free Base  
 Abstract    The crystal and molecular structure of aminoguanidine monohydrochloride, CN4H 7+.CL, in which aminonoguanidine exists in the monocation form, was determined by single-crystal X-ray diffraction. The structure of the monocation is largely similar to that of aminoguani­ dine dication as present in previously studied divalent salts. The monocation was found to exist in the form of the tautom er that allows strong resonance in the guanyl group. As compared to the dication, the terminal hydrazine nitrogen atom bears one hydrogen atom less. The monocation is planar, the only atoms deviating from the plane being the hydrogens attached to the terminal hydrazine nitrogen. Q uantum chemical calculations on the endi­ amine tautomer of aminoguanidine free base as well as on aminoguanidine monocation and dication were also perform ed by using the HF and MP2 ab initio methods and also the B3-LYP and B-LYP methods based on density functional theory. On the basis of the calculations, a predicted structure of the endiamine tautom er of aminoguanidine free base is presented. 
  Reference    Z. Naturforsch. 51b, 1771—1778 (1996); received July 5 1996 
  Published    1996 
  Keywords    Diamine Oxidase Inhibitors, Density Functional Methods, Nitric Oxide Synthase Inhibitors 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-1771.pdf 
 Identifier    ZNB-1996-51b-1771 
 Volume    51 
2Author    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