No abstract

Carboxylates of amidines (I, II), substituted guanidine (III) and iso(thio)ureas (IV, V) were prepared. Nonempirical quantum chemical treatment of the electronic structure of simple com· pounds I-V, based on total molecular geometry optimization, their preparation and physico· chemical data are reported. Interaction between the two amidinium nitrogens and carboxylate oxygens is mediated by hydrogen bonds and alternation of charge distribution.

Various p-substituted benzamidinium formates (I), acetates (II), trifluoroacetates (III) and pyruvates (IV) were prepared and the nature of the amidinium-carboxylate interactions were examined by 1H and 13C NMR spectra. The spectroscopic data are consistent with the presumption that the carboxylic part is only slightly influenced by the diverse substitution of the aromatic benzamidinium ring.

The "abbreviated" model of NAD, 1-[3-(adenin-9-yl)-2-hydroxypropyl]-3-carbamoylpyridinium chloride (VIIIa), and its 2,6-diaminopurine (VIIIb), 3-deazaadenine (VIIIc), guanine (VIIId) and cytosine (VIIIe) analogues were prepared by the Zincke reaction. The (R)-isomer of the adenine model VIIIa (compound IX) was prepared for chiroptical studies. As shown by NMR, UV and CD spectra, neither in dimethyl sulfoxide nor in water any intramolecular π-π interactions exist between the heteroaromatic systems.