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We applied the knowledge-based approaches from the CSD-Materials to three novel heterocycle-1-carbohydrazonamides, for which molecular geometry was obtained by means of ab initio calculations, to predict the topological properties of their supramolecular motifs in the crystalline phase. Our survey suggested competition between nitrogen atoms of the heterocycle and carbohydrazonamide moieties to act as acceptors of H-bonding with the donor -NH2 group that can result in polymorphism based on various H-bonded motifs. The possibility of H-bonded polymorphism was proven for imidazole- and triazole-1-carbohydrazones with the ToposPro knowledge databases, which contain information on relations between local connectivity of molecules and topology of the whole H-bonded system. Experimental structures obtained with single crystal X-ray diffraction belong to the most abundant H-bonded motifs with proposed probabilities in the range 6–44%, thus giving evidence that the CSD-Materials and ToposPro knowledge databases can be combined to successfully predict H-bonded networks even for molecular families with a small number of representatives.

Aza- and deazaanalogues of adenosine, including their 1-protonated forms (except for that of 1-deazaadenosine), were studied by computer computation to find a relationship between their molecular structures and substrate properties for the mammalian adenosine deaminase. The atomic charge distribution and maps of the electrostatic potential around their van der Waals molecular surface were calculated for these compounds using the ab initio STO-3G method. The conformational studies were carried out by the MM+ method of molecular mechanics. The mechanism that determines the substrate selectivity of mammalian adenosine deaminase is discussed. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2002, vol. 28, no. 4; see also http://www.maik.ru.

4-(1H-Azol-1-ylmethyl)benzohydrazides were prepared from methyl 4-(bromomethyl)benzoate, azoles, and hydrazine hydrate. Reactions of 4-(1H-imidazol-1-ylmethyl)benzohydrazide with carbonyl compounds gave hydrazones whose tautomerism was studied. From the hydrazides, 1,3,4-oxadiazoles, 1,2,4-triazole-5-thione, and N-benzoyl-N`-alkyl(aryl)sulfonylhydrazines were synthesized.

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The conformational models of the active site of adenosine deaminase (ADA) and its complexes in the basic state with adenosine and 13 isosteric analogues of the aza, deaza, and azadeaza series were constructed. The optimization of the conformational energy of the active site and the nucleoside bound with it in the complex was achieved in the force field of the whole enzyme (the 1ADD structure was used) within the molecular mechanics model using the AMBER 99 potentials. The stable conformational states of each of the complexes, as well as the optimal conformation of the ADA in the absence of ligand, were determined. It was proved that the conformational state that is close to the structure of the ADA complex with 1-deazaadenosine (1ADD) known from the X-ray study corresponds to one of the local minima of the potential surface. Another, a significantly deeper minimum was determined; it differs from the first minimum by the mutual orientation of side chains of amino acid residues. A similar conformational state is optimal for the ADA active site in the absence of the bound ligand. A qualitative correlation exists between the values of potential energies of the complexes in this conformation and the enzymatic activity of ADA toward the corresponding nucleosides. The dynamics of conformational conversions of the active site after the binding of substrate or its analogues, as well as the possibility of the estimation of the inhibitory properties of nucleosides on the basis of calculations, are discussed.