Substituted adenine quartets: interplay between substituent effect, hydrogen bonding, and aromaticity.

Adenine, one of the components of DNA/RNA helices, has the ability to form self-organizing structures with cyclic hydrogen bonds (A), similar to guanine quartets. Here, we report a computational investigation of the effect of substituents (X = NO, Cl, F, H, Me, and NH) on the electronic structure of 9-adenine and its quartets (A-N1, A-N3, and A-N7). DFT calculations were used to show the relationships between the electronic nature of the substituents, strength of H-bonds in the quartets, and aromaticity of five- and six-membered rings of adenine.

Substituent effects on the stability of the four most stable tautomers of adenine and purine.

Substituent effects at the C2-, C8- and N-positions of adenine and purine in their four the most stable tautomers are studied by means of B97D3/aug-cc-pvdz computation applying substituents of varying electronic properties: NO, CN, CHO, Cl, F, H, Me, OMe, OH and NH. The substituent effect is characterized by the substituent effect stabilization energy (SESE) and substituent Hammett constant . For adenine, SESE is obtained with purine as the reference system.

Copper-catalyzed direct C-H arylselenation of 4-nitro-pyrazoles and other heterocycles with selenium powder and aryl iodides. Access to unsymmetrical heteroaryl selenides.

A one-pot, Cu-catalyzed direct C-H arylselenation protocol using elemental Se and aryl iodides was developed for nitro-substituted, -alkylated pyrazoles, imidazoles and other heterocycles including 4-chromen-4-one. This general and concise method allows one to obtain a large number of unsymmetrical heteroaryl selenides bearing a variety of substituents. The presence of the nitro group was confirmed to be essential for the C-H activation and can also be used for further functionalisation and manipulation.

Structural Characterization and Pharmaceutical Properties of Three Novel Cocrystals of Ethenzamide With Aliphatic Dicarboxylic Acids.

Ethenzamide (ET) was screened in cocrystallization experiments with pharmaceutically acceptable coformer molecules to discover materials of improved physicochemical properties, that is, higher solubility and better stability. Three novel cocrystals of ET with glutaric, malonic, and maleic acids were obtained by neat grinding and slow evaporation from solution. The purpose of the study was to notice the changes in the geometry and interactions of ET molecule in crystalline phase introduced by different acid and relate them to physicochemical properties of pure ET.

The study of interactions with a halogen atom: influence of NH group insertion on the crystal structures of meta-bromonitrobenzene derivatives.

Halogen atoms in molecular crystals may be involved in various interactions, often playing a very important role in structure stabilization. By introducing electron-donating groups, such as NH, the electron density of the molecule is changed and thus interactions with the bromine substituent may alter. Herein, the crystal structures of meta-bromonitrobenzene and its NH-substituted derivatives are analyzed.

Synthon preference in the cocrystal of 3,4,5-trifluorophenylboronic acid with urea.

The comprehensive description of the crystal structure of a novel 1:1 cocrystal of 3,4,5-trifluorophenylboronic acid with urea, CHBFO·CHNO, is presented. Both components are good candidates for crystal engineering as they can create a variety of supramolecular synthons. The preference for the formation of different hetrosynthons is verified based on theoretical calculations.