Arzu Karayel

Synthesis and antimicrobial evaluation of some new substituted purine derivatives.

A series of 8,9-disubstituted adenines (4, 5, 8), 6-substituted aminopurines (10-13) and 9-(p-fluorobenzyl/cyclopentyl)-6-substituted aminopurines (16, 17, 19-30) have been prepared and the antimicrobial activities of these compounds against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA, standard and clinical isolate), Bacillus subtilis, Escherichia coli and Candida albicans were evaluated. 6-[(N-phenylaminoethyl)amino]-9H-purine (12) which has no substitution at N-9 position and 9-cyclopentyl-6-[(4-fluorobenzyl)amino]-9H-purine (24) exhibited excellent activity against C. albicans with MIC 3.12 microg/mL. These compounds displayed better antifungal activity than that of standard oxiconazole. Furthermore, compound 22 carrying 4-chlorobenzylamino group at the 6-position of the purine moiety exhibited comparable antibacterial activity with that of the standard ciprofloxacin against both of the drug-resistant bacteria (MRSA, standard and clinical isolate).

Crystal structures and intermolecular interactions of two novel antioxidant triazolyl-benzimidazole compounds

The crystal structures of 5-(2-(p-chlorophenylbenzimidazol-1-yl-methyl)-4-(3-fluorophenyl)-2,4-dihydro-[1,2,4]-triazole-3-thione (G6C) and 5-(2-(p-chlorophenylbenzimidazol-1-yl-methyl)-4-(2-methylphenyl)-2,4-dihydro-[1,2,4]-triazole-3-thione (G4C) have been determined by single-crystal X-ray diffraction. Benzimidazole ring systems in both molecules are planar. The triazole part is almost perpendicular to the phenyl and the benzimidazole parts of the molecules in order to avoid steric interactions between the rings. The crystal structures are stabilized by intermolecular hydrogen bonds between the amino group of the triazole and the nitrogen atom of benzimidazole of a neighboring molecule.

The intramolecular hydrogen bond analysis in biologically active 5-fluoro-1H-indole-2,3-dione-3-thiosemicarbazones derivatives by experimental and theoretical methods

There are several reports on the anticancer, antiviral and antibacterial activities of isatin-3-thiosemicarbazone derivatives (1-5). Investigations regarding the structure-activity relationships of 2-indolinones revealed that 5-halojenation and 3-thiosemicarbazone formations were efficient in increasing activity against a range of human cancer cells and various bacteria and viruses (3-8). In the light of these findings, 5-fluoro-1H-indole-2,3-dione 3-thiosemicarbazone derivatives were synthesized by reaction of N-substituted thiosemicarbazids with 5-fluoro-1H-indole-2,3-dione and evaluated for in vitro antituberculosis activity against Mycobacterium tuberculosis H37Rv.Their structures were confirmed by the spectral data elemental analysis and three of them were analysed by X-ray diffraction method. Due to playing a central role in the molecular structure and interactions of biologically molecules, the intramolecular hydrogen bonds (IHBs) were also calculated at the DFT level. Natural bond orbitals (NBO) calculations were used to examine the electronic characteristics of the intra-molecular hydrogen bonds . Experimental X-ray and NMR data were correlated with theoretical results. NBO energies show that the main contributions to energy stabilization correspond to LP → σ* interactions for IHBs, O1⋅⋅⋅N3–H3 and N2⋅⋅⋅N4–H4; the delocalization LP → π* for N3–N2=C2 and N3–C9=S1.

NMR, X-ray and DFT studies on antioxidant triazolylbenzimidazole derivatives

NMR, X-RAY and DFT studies on antioxidant triazolylbenzimidazole derivatives Arzu Karayel,a Süheyla Özbey,b Gülgün Ayhan-Kılcıgil,c Canan Kuş,c aDepartment of Physics, Faculty of Art and Sciences, Hitit University, 19030 Çorum, (Turkey). bPhysics Engineering Department, Hacettepe University, 06800 Ankara, (Turkey). cDepartment of Pharmaceutical Chemistry, Faculty of Pharmacy, Ankara University, 06100 Ankara, (Turkey). E-mail: karayelarzu@gmail.com