Investigation of Oxygen Influence to the Optical Properties of Tirapazamine

New data on 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine) fluorescence has been obtained using the Perkin–Elmer UV-vis-NIR spectrophotometer Lambda 950 experimental technique in combination with the extensive DFT-theory approach. Based on the results obtained, we revealed that theoptical properties of the molecule under study remain significantly unchanged when the number of oxygen substitutions decreases from 2 to 0. Here we also present the results of the study of the influence of acetonitrile and ethyl acetate on the fluorescence of tirapazamine with the different number of oxygen atoms. Results of our investigation indicate the formation of anion in the case of 3-amino-1,2,4-benzotriazine 1,4-dioxide with two oxygen atoms and their transformation to tirapazamine with one oxygen atom.

Hydrogen-atom and oxygen-atom transfer reactivities of iron(iv)-oxo complexes of quinoline-substituted pentadentate ligands

The reactivities of Fe(iv) oxido complexes of two pentadentate ligands are related to steric and electronic properties of the ligands.

An overview on synthesis and reactions of coumarin based compounds

Oxygen-containing heterocycles are largely distributed in natural and synthetic compounds. Coumarins are among the most famous heterocycles which possess one oxygen atom in their rings. Coumarins are classified as multifunctional scaffold and are used as anti-oxidant reagents, anti-inflammatory, anti-microbial, anti-fungal, anti-HIV active, analgesic, anti-histaminic, insecticides, dyes, herbicides, sensitizers, perfumes, cosmetics and food additives. Due to their diverse applications in industrial and pharmaceutical fields, many chemists have given significant interest to these compounds. Herein, the review highlights various methods for the synthesis and interactions of coumarin moiety as one of the most efficient categories of heterocycles.

Quantum chemical study on the interaction of arginine with silica surface

The structure and energy characteristics of structures formed during arginine adsorption on silica surface from aqueous solution were studied by the density functional theory (B3LYP) method using a valence-split basis set 6-31++G(d,p) within the continuous solvent model (PCM) and supermolecular approximation. The equilibrium structural and energy parameters of the protonated arginine molecule in the gas phase dependent on the location of the hydrogen atom are considered including those of two possible zwitterions. The structure of the arginine ion Н2А+, which is formed when a proton attaches to a molecule or zwitterion of a given amino acid, has been elucidated. To determine the deprotonation constant of the carboxyl group in an acidic medium, the complexes of the arginine molecule (AH32+) in the state with undissociated and deprotonated carboxyl groups are considered. The simulation of the acid medium was performed by taking into account the interaction with two hydrated HCl ion pairs, which provided the protonation of the a-amino group and the nitrogen atom of amino group within the guanidine group. In the study on the interaction of an arginine molecule with silica surface in an aqueous medium, complexes containing a Si8O12(OH)7O– ion with a deprotonated silanol group, six water molecules, and an arginine molecule with a deprotonated carboxyl group were considered. It has been found that the arginine molecule is most likely to be adsorbed on slica surface with formation of hydrogen bonds between the hydrogen atoms of the a-amino group and the oxygen atom of the deprotonated silanol group. In this case, the formation of a hydrogen bond between the oxygen atom of the carboxyl group and the hydrogen atom of the neighboring silanol group is possible. Slightly less likely is adsorption of arginine molecules due to interaction of the guanidine group with silanol groups of the surface. According to the calculated data, the adsorption of the zwitterionic form of the arginine molecule from the aqueous solution is equally likely to occur due to interaction of silanol groups of silica surface with both the carboxyl group and the guanidine group.

Synthesis of sp2-Iminosugar Selenoglycolipids as Multitarget Drug Candidates with Antiproliferative, Leishmanicidal and Anti-Inflammatory Properties

sp2-Iminosugar glycolipids (sp2-IGLs) represent a consolidated family of glycoconjugate mimetics encompassing a monosaccharide-like glycone moiety with a pseudoamide-type nitrogen replacing the endocyclic oxygen atom of carbohydrates and an axially-oriented lipid chain anchored at the pseudoanomeric position. The combination of these structural features makes them promising candidates for the treatment of a variety of conditions, spanning from cancer and inflammatory disorders to parasite infections. The exacerbated anomeric effect associated to the putative sp2-hybridized N-atom imparts chemical and enzymatic stability to sp2-IGLs and warrants total α-anomeric stereoselectivity in the key glycoconjugation step. A variety of O-, N-, C- and S-pseudoglycosides, differing in glycone configurational patterns and lipid nature, have been previously prepared and evaluated. Here we expand the chemical space of sp2-IGLs by reporting the synthesis of α-d-gluco-configured analogs with a bicyclic (5N,6O-oxomethylidene)nojirimycin (ONJ) core incorporating selenium at the glycosidic position. Structure–activity relationship studies in three different scenarios, namely cancer, Leishmaniasis and inflammation, convey that the therapeutic potential of the sp2-IGLs is highly dependent, not only on the length of the lipid chain (linear aliphatic C12 vs. C8), but also on the nature of the glycosidic atom (nitrogen vs. sulfur vs. selenium). The ensemble of results highlights the α-dodecylseleno-ONJ-glycoside as a promising multitarget drug candidate.

Modeling the Liquid Phase Exfoliation of Graphene in Polar and Nonpolar Solvents

Exfoliation is a promising technique to obtain graphene from graphite. The search for suitable exfoliation solvents is currently underway. The quality of the solvents used for spontaneous exfoliation is determined by a simple thermodynamic model. The model shows that the solvation energy of the organic solvents is higher for NMP (-177.37 mJ m-2) than other nonpolar solvents. It also shows that the solvation energy is correlated with sheet deformation and surface excess. Four groups of effective solvents are identified, including amine-, sulfoxide-, halogen-benzene-based solvents, in addition to cyclic structures with the oxygen atom. One can predict and screen potential solvents for spontaneous graphene exfoliation based on the reported mechanism.

Recent Progress in the Synthesis of Isoxazoles

: Isoxazole derivatives are aromatic five-membered ring heterocyclic compounds with one oxygen atom and one nitrogen atom at adjacent positions. These compounds have a broad spectrum of applications in medicinal chemistry, such as antimicrobial, anticancer, antitumor, antitubercular, analgesic, anti-inflammatory, antidepressant, and anticonvulsant activities and some of them are well-known drugs for the treatment of various diseases in the market. The use of this class of compounds in agriculture as herbicides, insecticides have been widely reported. In organic materials, these compounds have been applied as semiconductors, single-walled nanotubes, liquid crystals, chiral ligands, scaffolds for peptidomimetics, dyes, and high-temperature lubricants. Isoxazole derivatives also play an important role in organic synthesis because they can be converted into several important synthetic units such as β-hydroxy ketones, γ-amino alcohols, α,β-unsaturated oximes, β-hydroxy nitriles, α-hydroxy-β-diketones, and β-dicarbonyl compounds. Due to such a wide range of applicability, the synthesis of isoxazole derivatives has attracted intensive research from chemists. This review will focus on considerable studies on the synthesis of isoxazoles which date back from 2012.