Methylsulfonylethoxycarbonyl (Msc) and fluorous propylsulfonylethoxycarbonyl (FPsc) as hydroxy-protecting groups in carbohydrate chemistry

The methylsulfonylethoxycarbonyl (Msc) group is presented as a non-lipophilic, base-labile, participating protecting group for carbohydrate alcohols. It can be introduced using Msc-Cl and pyridine and is readily cleaved via β-elimination under mild basic conditions. Its fluorous counterpart, the perfluorooctyl propylsulfonylethoxycarbonyl (FPsc) group, is used in a ‘light fluorous’ trisaccharide synthesis sequence.     

Zinc Hydrogensulfate as an Efficient Catalyst for Preparation of β-Amido Carbonyl Compounds

A one‐pot and efficient three‐component condensation of benzaldehyde derivatives, enolizable ketones or ketoesters, acetyl chloride, and acetonitrile or benzonitrile under ambient conditions in the presence of zinc hydrogensulfate for the synthesis of β‐amido carbonyl compounds is described. The simple experimental procedure, high to excellent yields of products and preparation of diastereoselective β‐acetamido ketoesters are strong features of the presented method.     

Determination of glimepiride in pharmaceutical formulations using HPLC and first-derivative spectrophotometric methods

Two validated analytical methods have been developed to determine glimepiride in pharmaceutical formulations using HPLC and 1st order derivative spectrophotometric techniques. Employing reverse phase HPLC method, the drug was analyzed by pumping a mixture of acetonitrile and 2% formic acid solution, pH 3.5 (80: 20 v/v) through a C₁₈ column (250 × 4.6 mm, 5 μm) and detecting the eluents at 228 nm. The linearity range was found to be 20–140 μg/mL with mean recovery of 100.52 ± 0.33%. The second method was based on the formation of a complex of the drug with 2,3,5-triphenyl-2H-tetrazolium chloride in basic media. 1st order derivative spectrum made it possible to detect the complex at 413.5 nm. The linearity range was found to be 40–160 μg/mL, with mean recovery of 100.33 ± 0.47%. Both the proposed methods can reliably be used for routine analysis of glimepiride in raw material as well as in pharmaceutical formulations. The article is published in the original.     

Peristaltic flow of a Maxwell fluid in a channel with compliant walls

This paper describes the peristaltic motion of a non-Newtonian fluid in a channel having compliant boundaries. Constitutive equations for a Maxwell fluid have been used. Perturbation method has been used for the analytic solution. The influence of pertinent parameters is analyzed. Comparison of the present analysis of Maxwell fluid is made with the existing results of viscous fluid.     

Conditional linearizability criteria for a system of third-order ordinary differential equations

We provide linearizability criteria for a class of systems of two third-order ordinary differential equations that is cubically nonlinear in the first derivative, by differentiating a system of second-order quadratically nonlinear ordinary differential equations and using the original system to replace the second derivatives. The procedure developed splits into two cases: those for which the coefficients are constant and those for which they are variables. Both cases are discussed and examples given.     

A NONLINEAR MICROBEAM MODEL BASED ON STRAIN GRADIENT ELASTICITY THEORY

A micro scale nonlinear beam model based on strain gradient elasticity is developed.Governing equations of motion and boundary conditions are obtained in a variational framework.As an example,the nonlinear vibration of microbeams is analyzed.In a beam having a thickness to length parameter ratio close to unity,the strain gradient effect on increasing the natural frequency is predominant.By increasing the beam thickness,this effect decreases and geometric nonlinearity plays the main role on increasing the natural frequency.For some specific ratios,both geometric nonlinearity and size effects have a significant role on increasing the natural frequency.     

An integrated structure- and pharmacophore-based MMP-12 virtual screening

MMP-12 belongs to a large family of proteases called matrix metalloproteinases (MMPs) that degrades elastin. The main pathologic role of MMP-12 overexpression was suggested to be associated with pathogenesis mechanism of inflammatory respiratory diseases and atherosclerosis. An integrated ligand- and structure-based virtual screening was employed in hope of finding inhibitors with new scaffolds and selectivity for MMP-12. Seven compounds among 18 experimentally tested compounds had a measurable effect on the inhibition of MMP-12 enzyme. Our results demonstrated the applicability of the developed pharmacophore model and selected crystal structure (PDB code: 3F17) to discover new MMP-12 inhibitors. The receptor structure was selected based on cross-docking results. Here, we report the discovery of new class of MMP-12 inhibitors that could be used for lead optimization. For the inhibition of MMP-12, the significance of its interactions with the catalytic residues Glu219 and Ala182 was emphasized through the inspection of the docking poses.     

Synthesis of some new triamide derivatives via Ugi five-component reaction in aqueous solution

Triamide derivatives have been synthesized in good yields in a novel, one-pot, five-component, and efficient process by the reaction of Z-oxazolone, water, primary amines, aldehydes, isocyanides, in the presence of catalytic amount of KAl(SO₄)₂·12H₂O (alum) as a non-toxic, reusable, inexpensive, and easily available reagent via Ugi reaction in aqueous solution.     

Flotation-assisted dispersive liquid–liquid microextraction method for preconcentration and determination of trace amounts of cobalt: Orthogonal array design

A simple, rapid, and efficient flotation-assisted dispersive liquid–liquid microextraction method was developed for preconcentration of trace amount of cobalt(II) ions. In this technique, a mixture of toluene and methanol (20: 80, v/v) was injected through the septum in the bottom of a narrow-bore tube containing cobalt solution. Afterwards, the fine droplets of extraction solvent were formed and cobalt (as 1-nitroso-2- naphtol complex) was collected on the surface of solution by aeration. The effect of different variables on the extraction efficiency of cobalt such as pH of solution, ligand concentration and injection volume was investigated using orthogonal array design. At optimum conditions, the calibration curve was linear over the range of 10–1000 μg/L. The detection limit, relative standard deviation and enrichment factor were 3 μg/L, 3.9% (n = 10) and 120, respectively. The developed method was successfully applied to the determination of cobalt in water and drug samples.     

Application of Krein’s theorem and bifurcation theory for stability analysis of a bladed rotor

This paper considers the stability and eigenvalue analyses for a bladed rotor which goes under cylindrical and conical whirling. The model consists of a group of flexible blades which are modeled by beams and rigid disk on the elastic bearings. The model is a Hamiltonian system which is perturbed by small dissipative forces. Krein’s theorem reveals that the forward whirling mode and the blade collective motion may cause instability when their frequencies cut themselves in the Campbell diagram. An unstable interaction between the blades and the conical whirling is discovered. The eigenmode and eigenvalue evolutions are determined on the stability boundary. The bifurcation analysis is performed by applying multiple scales method around the stability boundary. It is shown that the damping distribution between the blades and the bearings may shift the unstable mode.