Sulfamic acid: a novel and efficient catalyst for the synthesis of aryl-14H-dibenzo[a.j]xanthenes under conventional heating and microwave irradiation

A simple and convenient procedure for the synthesis of aryl-14H-dibenzo[a.j]xanthenes is described through a one-pot condensation of β-naphthol with aryl aldehydes in the presence of sulfamic acid as the catalyst in a solvent-free media using both conventional heating and microwave irradiation.     

Development and Validation of the Chiral HPLC Method for Daclatasvir in Gradient Elution Mode on Amylose-Based Immobilized Chiral Stationary Phase

A selective and specific high-performance liquid chromatography method for the determination of daclatasvir enantiomers has been developed and validated. Various immobilized polysaccharide-based chiral stationary phases were used to define a separation strategy utilizing normal-phase and polar organic chromatography modes. Excellent resolution between daclatasvir and its enantiomer was achieved on amylose tris (3-chlorophenylcarbamate) stationary phase, namely CHIRALPAK ID-3, using binary gradient containing acetonitrile:diethylamine and methanol:diethylamine as the mobile phase. The flow rate of the mobile phases was maintained at 1.0 mL min⁻¹ while the column oven temperature was maintained at 40 °C. The column effluent was monitored by UV detection at 315 nm. In comparison with isocratic method, the binary gradient method offered excellent peak shape and improved resolution between daclatasvir and its enantiomer while maintaining the specificity with diastereomers. The method was found to be precise, accurate, and linear (R ² > 0.999). Limit of detection and limit of quantitation of the enantiomer were found to be 0.083 µg mL⁻¹ as and 0.25 µg mL⁻¹, respectively. Recovery of the enantiomer was found to be in the range of 90 to 112 %.

     

Finite element approximation of a free boundary plasma problem

In this article, we study a finite element approximation for a model free boundary plasma problem. Using a mixed approach (which resembles an optimal control problem with control constraints), we formulate a weak formulation and study the existence and uniqueness of a solution to the continuous model problem. Using the same setting, we formulate and analyze the discrete problem. We derive optimal order energy norm a priori error estimates proving the convergence of the method. Further, we derive a reliable and efficient a posteriori error estimator for the adaptive mesh refinement algorithm. Finally, we illustrate the theoretical results by some numerical examples.     

A method for stabilizing the cis prolyl peptide bond: influence of an unusual n→π interaction in 1,3-oxazine and 1,3-thiazine containing peptidomimetics

The cis/trans isomer ratios of the Xaa-Pyr (Pyr = pyrrolidine) 3° amide bonds are significantly high (∼90% cis) in the novel peptidomimetics where Pyr contains 1,3-oxazine (Oxa) or 1,3-thiazine (Thi) at its 2 position. We find that an unusual n→π_i−1^∗ interaction, selectively stabilizes the cis conformer and the n)(n repulsion destabilizes the trans conformer of these molecules. Both these electronic effects oppose the steric effects in the 3° amide bond. The structural requirements for manifestation of these electronic effects are determined.     

A simple spectrophotometric method for the determination of minoxidil

A simple and sensitive method for the determination of minoxidil using 3-methyl-2-benzothiazolinone hydrazone (MBTH) and Fe(III) as the coloring agent is described. The method is sensitive to permit the determination of 0.5–4.5 μg ml⁻¹ of minoxidil at 500 nm. The accuracy and precision of the method were checked by high-performance liquid chromatography.     

Facile synthesis of novel (1-Aryl/alkyl-1<Emphasis Type="Italic">H</Emphasis>-1,2,3-triazol- 4-yl)methyl-2-bromo-4-methylthiazole-5-carboxylates by Cu(I) catalyzed click reaction

A number of novel thiazole-triazole heterocycles bearing (1-aryl/alkyl-1H-1,2,3-triazol-4-yl)methyl- 2-bromo-4-methylthiazole-5-carboxylates was synthesized through the click reaction. The structure of all new synthesized compounds was established by ¹H and ¹³C NMR spectroscopy and mass spectrometry methods.     

A new strategy for synthesis of 9-benzoyl-4-methylpyrano[2,3-f]chromene-2,8-dione using L-proline as a novel and efficient catalyst

Russian Journal of General Chemistry - We report the high yield synthesis of novel 9-benzoyl-4-methylpyrano[2,3-f]chromene-2,8-dione derivatives obtained by the reaction of...     

Differentiation of human gingival mesenchymal stem cells into neuronal lineages in 3D bioconjugated injectable protein hydrogel construct for the management of neuronal disorder

The success of regeneration attempt is based on an ideal combination of stem cells, scaffolding and growth factors. Tissue constructs help to maintain stem cells in a required area for a desired time. There is a need for easily obtainable cells, potentially autologous stem cells and a biologically acceptable scaffold for use in humans in different difficult situations. This study aims to address these issues utilizing a unique combination of stem cells from gingiva and a hydrogel scaffold, based on a natural product for regenerative application. Human gingival mesenchymal stem cells (HGMSCs) were, with due induction, differentiated to neuronal lineages to overcome the problems associated with birth tissue-related stem cells. The differentiation potential of neuronal lineages was confirmed with suitable specific markers. The properties of mesenchymal stem cells in encapsulated form were observed to be similar to free cells. The encapsulated cells (3D) were then subjected to differentiation into neuronal lineages with suitable inducers, and the morphology and gene expression of transient cells were analyzed. HGMSCs was differentiated into neuronal lineages as both free and encapsulated forms without any significant differences. The presence of Nissl bodies and the neurite outgrowth confirm the differentiation. The advantages of this new combination appear to make it a promising tissue construct for translational application.