An approach towards the oxidation of 2-amino-4H-chromenes to 2-imino-2H-chromenes

A novel method for the synthesis of 2-imino-2H-benzo[h]chromenes via the sequential addition of N-chlorosuccinimide and triethylamine to 2-amino-4H-benzo[h]chromenes has been established. This reaction protocol represents an efficient synthetic strategy to form iminochromene derivatives under mild reaction conditions, which utilizes readily accessible aminochromenes as starting materials and tolerates a wide range of substrates.     

Phytochemical constituents from dietary plant Citrus hystrix

Chemical investigation of the fruit peel of dietary plant Citrus hystrix offered two new flavones 5,6,4′-trihydroxypyranoflavone I and 5,4′-dimethyl-6-prenylpyranoflavone XIII besides 11 known compounds. The structures of all compounds were elucidated with the aid of suitable analytical methods like 1D, 2D-NMR, mass and single crystal X-ray analysis. An X-ray crystal study of compound II was done for the first time and the compounds I–VI, XI and XII are hitherto not reported from this plant. Biological studies revealed that compound I found to have a good antidiabetic and antiacetylcholinesterase activities meanwhile compounds II, III and V showed a significant free radical scavenging ability as well as antioxidant capacity. In addition, compounds I, IV, V and VI showed cytotoxicity against U87, A549 and MCF-7 cells. Overall, the new compound I showed valuable bioactive properties. Due to insufficient quantity of compound XIII, biological studies were not done.     

Molecular recognition in bisurea thermoplastic elastomers studied with pyrene-based fluorescent probes and atomic force microscopy

Fluorescence spectroscopy and atomic force microscopy (AFM) measurements using bisurea-pyrene probes show that they are randomly dispersed in the hard blocks of thermoplastic elastomers with matching bisurea groups, whereas they phase separate from polymers with non-matching or no bisurea groups.     

Synthesis, growth and characterization of a new nonlinear optical material: 4-phenylpyridinium hydrogen squarate (4PHS)

A novel organic non-linear optical organic single crystal of 4-phenylpyridinium hydrogen squarate (4PHS) has been synthesized and successfully grown from aqueous solutions by slow evaporation solution growth method. In the present investigation the title compound has been synthesized by taking equimolar quantity of 4-phenylpyridine and squaric acid and mixed thoroughly using double distilled water as the solvent. The prepared concentrated solution was placed in an undisturbed condition, and then the solution was periodically inspected. The good quality single crystals have been harvested in a time span of 3 weeks. Then the grown crystal was characterized as single crystal XRD, differential thermal analysis, thermogravimetric analysis, FTIR, UV-vis-NIR, SHG, (1)H NMR and (13)C NMR analyses, respectively. The observed results from the characterization analyses show its suitability for NLO applications when compared with some of the existing organic crystals. The relative second harmonic generation of this grown crystal was found to be five times higher than that of KDP crystal. The UV cut-off wavelength and decomposition temperature of this grown crystal were also comparatively better. (1)H NMR and (13)C NMR spectroscopic studies were employed to elucidate the structure of the grown specimen.     

Synthesis, growth, structural, spectroscopic and optical studies of a new semiorganic nonlinear optical crystal: L-valine hydrochloride

Single crystals of a new semiorganic nonlinear optical (NLO) material, L-valine hydrochloride (LVHCl), having dimensions up to 20 mm x 6 mm x 4 mm have been grown by slow evaporation solution growth technique. Single crystal X-ray diffraction studies confirm that the grown crystal belongs to the monoclinic system. The functional groups presented in the crystal were confirmed by Fourier transform infrared (FTIR) technique. Optical transmission spectrum shows very low absorption in the entire visible region. Differential thermal and thermogravimetric analyses confirmed that the crystal is stable up to 211 degrees C. The powder second harmonic generation (SHG) efficiency of LVHCl is 1.7 times efficient as potassium dihydrogen phosphate (KDP).     

Analgesic and antimicrobial studies of some 2,4-dichloro-5-fluorophenyl containing arylidenetriazolothiadiazines

2,4-Dichloro-5-fluorophenyl containing 7-arylidenetriazolothiadiazines were obtained by the reaction of 4-amino-3-(2,4-dichloro-5-fluorophenyl)-5-mercapto-1,2,4-triazole with 2,3-dibromo-1,3-diarylpropan-1-ones, and also by the reaction of 4-amino-3-(2,4-dichloro-5-fluorophenyl)-5-mercapto-1,2,4-triazole with α-bromopropenones in the presence of a base. The structure of the 7-arylidenetriazolothiadiazines was confirmed by an alternative synthesis. A plausible mechanism for the formation of 7-arylidenetriazolothiadiazines is proposed. All newly synthesized compounds were screened for their analgesic and antimicrobial activities. Compounds bearing 4-chlorophenyl or 3,4-methylenedioxyphenyl moieties at position 7 of the arylidenetriazolothiadiazines showed excellent analgesic activity. Arylidenetriazolothiadiazines carrying a phenyl, 4-chlorophenyl, 4-methylphenyl, 3,4-dimethoxyphenyl, and 2,4-dichlorophenyl moieties at position 7 showed excellent antibacterial and antifungal activities. Correspondence: Mari Sithambaram Karthikeyan, Department of Chemistry, Mangalore University, Mangalagangothri 574199, Karnataka, India.     

金属含量对Ni-Pd/H-Y上正癸烷加氢异构化反应活性和产物选择性的影响

在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.     

Large scale free energy calculations for blind predictions of protein–ligand binding: the D3R Grand Challenge 2015

We describe binding free energy calculations in the D3R Grand Challenge 2015 for blind prediction of the binding affinities of 180 ligands to Hsp90. The present D3R challenge was built around experimental datasets involving Heat shock protein (Hsp) 90, an ATP-dependent molecular chaperone which is an important anticancer drug target. The Hsp90 ATP binding site is known to be a challenging target for accurate calculations of ligand binding affinities because of the ligand-dependent conformational changes in the binding site, the presence of ordered waters and the broad chemical diversity of ligands that can bind at this site. Our primary focus here is to distinguish binders from nonbinders. Large scale absolute binding free energy calculations that cover over 3000 protein–ligand complexes were performed using the BEDAM method starting from docked structures generated by Glide docking. Although the ligand dataset in this study resembles an intermediate to late stage lead optimization project while the BEDAM method is mainly developed for early stage virtual screening of hit molecules, the BEDAM binding free energy scoring has resulted in a moderate enrichment of ligand screening against this challenging drug target. Results show that, using a statistical mechanics based free energy method like BEDAM starting from docked poses offers better enrichment than classical docking scoring functions and rescoring methods like Prime MM-GBSA for the Hsp90 data set in this blind challenge. Importantly, among the three methods tested here, only the mean value of the BEDAM binding free energy scores is able to separate the large group of binders from the small group of nonbinders with a gap of 2.4 kcal/mol. None of the three methods that we have tested provided accurate ranking of the affinities of the 147 active compounds. We discuss the possible sources of errors in the binding free energy calculations. The study suggests that BEDAM can be used strategically to discriminate binders from nonbinders in virtual screening and to more accurately predict the ligand binding modes prior to the more computationally expensive FEP calculations of binding affinity.     

Optical,magnetic and photocatalytic properties of magnetically separable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-doped ZnO and pristine ZnO nanospheres

This work focussed on the optical, magnetic and photocatalytic properties of sol–gel-synthesized Fe₃O₄-doped ZnO nanospheres and was compared with pristine ZnO nanospheres. The crystalline phase of Fe₃O₄-doped ZnO nanospheres was studied with X-ray diffraction analysis and was well matched with standard pattern. Surface morphology was studied with HR-SEM images and EDAX spectrum. Furthermore, elemental mapping analysis was carried out to confirm the presence of Fe₃O₄ phase in Fe₃O₄-doped ZnO nanospheres. FT-Raman spectral studies show that a strong intense peak at 670 cm^?1 indicates the presence of Fe₃O₄ in Fe₃O₄-doped ZnO nanospheres. The mean crystallite size of Fe₃O₄-doped ZnO nanospheres was 34 nm as calculated by Debye–Scherrer’s formula which confirmed with HR-TEM image. The SAED pattern shows the presence of (100), (101), (102) and (202) of ZnO phase and (400) of Fe₃O₄ phase, confirming the crystalline nature of Fe₃O₄-doped ZnO nanospheres. The vibrating sample magnetometer (VSM) result shows that Fe₃O₄-doped ZnO nanospheres possess superparamagnetic nature and the composite nanospheres are magnetically separable. The optical properties have been studied by diffuse reflectance spectroscopy and time-resolved photoluminescence spectra. Implantation of Fe₃O₄ in ZnO nanospheres modifies the UV absorption edge, and it displays near-band gap emission and deep-level emission. The photocatalytic activity of Fe₃O₄-doped ZnO nanospheres studied against rhodamine B dye is found higher than that of pristine ZnO nanospheres which shows that Fe₃O₄-doped ZnO nanospheres are a promising photocatalyst.