One-pot synthesis of chalcone epoxides—A green chemistry strategy

Waste minimization is a very important aspect of an environmentally benign protocol. A one-pot consecutive process has been developed for chalcone epoxide synthesis that allows compounds to be prepared without having to isolate and purify the intermediates. The strategy utilizes consecutive Claisen Schmidt condensation and epoxidation reactions to prepare chalcone epoxides from substituted benzaldehydes and acetophenones in good yields.     

Investigation of the reactions of 2-hydrazino-benzimidazoles with β-diketones: Synthesis of 2-(3,5-disubstituted- 1H-pyrazol-1-yl)benzimidazoles

Reaction of 2-hydrazinobenzimidazoles with β-diketones in neutral and acidic media revealed that 2-(3,5-disubstituted-1H-pyrazol-1-yi)benzimidazoles are formed in the former case, whereas hydrazones are obtained in acidic medium. Further the alkylation of > NH of the title compound was investigated. Characterisation of these products have been done by elemental analysis, ir, pmr, ¹⁹F nmr, ¹³C nmr and mass spectral studies.     

A proposed common spatial pharmacophore and the corresponding active conformations of some peptide leukotriene receptor antagonists

Summary Molecular modeling studies were carried out by a combined use of conformational analysis and 3D-QSAR methods to identify molecular features common to a series of hydroxyacetophenone (HAP) and non-hydroxyacetophenone (non-HAP) peptide leukotriene (pLT) receptor antagonists. In attempts to develop a ligand-binding model for the pLT receptor, the Apex-3D program was used to identify biophoric structural patterns that are common to 13 diverse sets of compounds showing different levels of biological activity. A systematic conformational analysis was carried out to obtain sterically accessible conformations for these flexible compounds. Apex-3D was then utilized to propose common biophoric regions based on the selection of one of several conformations (MOPAC-minimized AM1) from each compound's data set that best fits the biophoric pattern and the resulting superimposition with all the other data-set compounds. Apex-3D identified three common biophoric features important for activity: one as the hydroxyl, acetyl, carbonyl and carboxyl groups, which mimic the acid-binding region of an agonist, the other as the hydrogen-bond donating site, and the third part is represented by a plane in which lipophilic aromatic groups align. The structure-activity relationships were then assessed by using the 3D-QSAR model. A common biophore model is proposed from the Apex-3D analysis which may be useful in designing new pLT antagonists. Molecular volumes and electrostatic potential similarities were also calculated in order to obtain the important structural requirements for the activity.     

Conserved Hydrogen Bonded Tartrate Frameworks: Inclusion of Amines and Implications for Second Harmonic Generation

A series of anilinium cations with various functional groups as substituents has been chosen to form salts with l-tartaric acid and d-dibenzoyl tartaric acid. The salts show second harmonic generation activities comparable to urea. The tartrate frameworks provide conformationally rigid hydrogen bonded frameworks for the incorporation of these cations. The SHG activity of these salts appear to depend upon the type of framework provided by the tartrate anions, which in turn decides the orientation of the cations.     

Selectivity analysis of 5-(arylthio)-2,4-diaminoquinazolines as inhibitors of Candida albicans dihydrofolate reductase by molecular dynamics simulations

A series of 5-(arylthio)-2,4-diaminoquinazolines are known as selective inhibitors of dihydrofolate reductase (DHFR) from Candida albicans. We have performed docking and molecular dynamics simulations of these inhibitors with C. albicans and human DHFR to understand the basis for selectivity of these agents. Study was performed on a selected set of 10 compounds with variation in structure and activity. Molecular dynamics simulations were performed at 300 K for 45 ps with equilibration for 10 ps. Trajectory data was analyzed on the basis of hydrogen bond interactions, energy of binding and conformational energy difference. The results indicate that hydrogen bonds formed between the compound and the active site residues are responsible for inhibition and higher potency. The selectivity index, i.e the ratio of I₅₀ against human DHFR to I₅₀ against fungal DHFR, is mainly determined by the conformation adapted by the compounds within the active site of two enzymes. Since the human DHFR active site is rigid, the compound is trapped in a higher energy conformation. This energy difference between the two conformations E mainly governs the selectivity against fungal DHFR. The information generated from this analysis of potency and selectivity should be useful for further work in the area of antifungal research.     

A proposed model of Mycobacterium avium complex dihydrofolate reductase and its utility for drug design

A homology model of Mycobacterium avium complex dihydrofolate reductase (MAC DHFR) was constructed on the basis of the X-ray crystal structure of Mycobacterium tuberculosis (Mtb) DHFR. The homology searching of the MAC DHFR resulted in the identification of the Mtb DHFR structure (PDB 1DF7) as the template for the model building. The MAC enzyme sequence was aligned to that of the Mtb counterpart using a modified Needleman and Wunsch methodology. The initial geometry to be modeled was copied from the template, either fully or partially depending on whether the residues were conserved or not, respectively. Using a randomized modeling procedure, 10 independent models of the target protein were built. The cartesian average of all the model structures was then refined using molecular mechanics. The resulting model was assessed for stereochemical quality using a Ramachandran plot and by analyzing the consistency of the model with the experimental data. The structurally and functionally important residues were identified from the model. Further, 5-deazapteridines recently reported as inhibitors of MAC DHFR were docked into the active site of the developed model. All the seven inhibitors used in the docking study have a similar docking mode at the active site. The network of hydrogen bonds around the 2,4-diamino-5-deazapteridine ring was found to be crucial for the binding of the inhibitors with the active site residues. The 5-methyl group of the inhibitors was located in a narrow hydrophobic pocket at the bottom of the active site. The relative values of the three torsion angles of the inhibitors were found to be important for the proper orientation of the inhibitor functional groups into the active site.     

Electrogeneration of Hg(+) in the presence of tryptophan

In the presence of l-tryptophan, a one-electron oxidation of mercury takes place at the dropping mercury electrode at 0.265 V vs. SCE in 0.1M potassium nitrate. The electrogeneration of the monomeric Hg(+) ion has been established by a.c. polarography, cyclic voltammetry and ultraviolet spectroscopy. A paramagnetic Hg-trp compound has been electrochemically synthesized and characterized.     

Wave propagation in a micropolar fluid contained in a visco-elastic membrane

The aim of the paper is to investigate the propagation of a pulse in a micropolar fluid contained in a visco-elastic membrane. It was undertaken with a view to study how closely we can approximate the flow of blood in arteries by the above model. We find that for large Reynolds number, the effect of micropolarity is hardly perceptible, whereas for small Reynolds numbers it is of considerable importance.     

Aurivillius family of layered perovskites,BiREWO6 (RE = La,Pr, Gd,and Dy): Synthesis,characterization, and photocatalytic studies

The present work deals with the synthesis, characterization, and photocatalytic studies of layered perovskites belonging to Aurivillius family. Layered perovskites of various chemical compositions, BiREWO₆ (RE = La, Pr, Gd, and Dy), were synthesized by an ethylene glycol–assisted sol–gel method. These materials were characterized by X-ray diffraction, scanning electron microscopy–energy dispersive spectroscopy (EDS), Fourier transform infrared, Raman, and ultraviolet–visible diffuse reflectance techniques. The composition of all these materials was obtained from EDS. The unit cell lattice parameters were attained from Rietveld refinement program, Fullprof.2k, by refining the d-lines of BiREWO₆. The band gap energy of these samples was obtained from the Kubelka–Munk plot. The photocatalytic activity of all the samples was evaluated by photodegradation of methylene blue. The mechanistic degradation pathway of methylene blue was studied using radical quenchers.     

Chemoprofiling and Solamargine Estimation from a Few Solanum Species Used as ‘Brihati’ and Its Market Samples Using a Validated High-Performance Thin-Layer Chromatography Method

JPC – Journal of Planar Chromatography – Modern TLC - An ingredient of ‘Dasamoola’ and ‘Laghupanchamoola’ group of drugs, the source of ‘Brihati’ has...