Olefination of 3-diazopiperidin-2-one

New conditions have been developed for the olefination of diazo compounds catalysed by methyl trioxorhenium. The new system is suitable for unreactive diazo compounds and its utility is demonstrated by the olefination of 3-diazopiperidin-2-one with a range of aromatic, heterocyclic and alkylaldehydes.     

Novel nucleoside analogues via direct attack of carbon : Nucleophiles on nucleosides containing epoxy-sugars

Direct ring-opening of the epoxide ring in 1-(5′-$\text{O}$-trityl-2′,3′-anhydro-β-D-lyxo-furanosyl) uracil (1) by lithium acetylide or vinylmagnesium bromide/cuprous iodide affords the corresponding 5′-$\text{O}$-trity]-3′-$\text{C}$-substituted-3′-deoxy-$\text{ara}$-uridine species.     

Transition-metal-free synthesis of primary to tertiary carboxamides: A quick access to prodrug-pyrazinecarboxamide

One-pot expedient and direct carbamoylation of heterocyclics is described. The transformation is realized via direct dehydrogenative aminocarbonylation of heterocyclic compounds under transition-metal-free conditions. This method is regioselective and the protocol is proved to be scalable on a gram scale. Further, the therapeutically useful antitubercular agent pyrazinecarboxamide is successfully synthesized by employing this protocol.     

Acyl/aroyl Meldrum’s acid as an enol surrogate for the direct organocatalytic synthesis of α,β-unsaturated ketones

The operationally simple, robust and straightforward organocatalytic protocol is developed for the synthesis of E-selective α,β-unsaturated ketones. The method utilizes simple and easily accessible starting materials such as Meldrum’s acid, carboxylic acid, aldehyde and simple bifunctional amine catalyst. The tandem organocatalytic process utilizes acyl/aroyl Meldrum’s acid as an enol surrogate for the effective Doebner-Knoevenagel type condensation reactions. A wide variety of aldehydes, carboxylic acids and base sensitive functional groups are well tolerated under the mild reaction conditions.     

Composition-dependent crystallization behavior of copolyperoxides from methyl methacrylate and 4-vinylbenzyl stearate

To study the composition-dependent crystallization behavior of copolyperoxides, herein a series of copolymers were prepared by varying the ratios of methyl methacrylate (MMA) and 4-vinylbenzyl stearate (VBS) under 100 psi oxygen pressure using AIBN as an initiator at 50°C in toluene. Both ¹³C NMR and electron impact mass spectroscopy (EI-MS) approved an alternative placement of either of the monomer and peroxy (–O–O–) links throughout the polymer chain. Thermal stability of the resulting copolyperoxides was investigated by thermogravimetric analysis (TGA) and the degradation fragments have been recognized from EI-MS study. In addition, differential scanning calorimetry (DSC) displayed an endothermic peak as well as an exotherm associated with the melting of the side chain crystalline domains and degradation of –O–O– links in the polymer main chain, respectively. Furthermore, DSC thermograms unveiled a systematic decrease of the crystalline melting temperature (T_m) with the enhancement of MMA content in the copolymers. Small angle X-ray scattering (SAXS) revealed the existence of lamellar morphology (depends on VBS content in the copolyperoxide) in the synthesized polyperoxide materials, further supported by atomic force microscopy (AFM) analysis showing a layered fibrillar assembly with multiple heights of the lamella. The significant crystalline nature of the polyperoxides was further evidenced from the appearance of lattice fringes in the transmission electron microscope (TEM) micrographs. The crystalline morphology with birefringent texture was further evidenced from the polarized optical microscopy (POM) study. Thus, the present study reported the effective variation of crystalline behavior in copolyperoxide materials with the incorporation of MMA units in the copolyperoxide chains.     

Mathematical modelling and dynamic response of a multi-straight-line path tracing flexible robot manipulator with rotating-prismatic joint

In this study, mathematical modelling and dynamic response of a flexible robot manipulator with rotating-prismatic joint are investigated. The tip end of the flexible robot manipulator traces a multi-straight-line path under the action of an external driving torque and an axial force. Considered robot manipulator consists of a rotating prismatic joint and a sliding flexible arm with a tip mass. Flexible arm is assumed to be an Euler–Bernoulli beam carrying an end-mass. Equations of motion of the flexible manipulator are obtained by using Lagrange’s equation of motion. Effect of rotary inertia, axial shortening and gravitation is considered in the analysis. Equations of motion are solved by using fourth order Runge–Kutta method. Numerical simulations obtained by using a developed computer program are presented and physical trend of the results are discussed.     

Characterization and Miscibility Dynamics of Dextran-Poly(vinylpyrrolidone)-Water System

Summary: The miscibility behavior and intermolecular interactions among Dextran (Dx) with different molecular weight and Polyvinylpyrrolidone (PVP) blends were studied as dilute aqueous solutions at 25 °C by viscosity method. The intrinsic viscosity and the interaction coefficient were experimentally measured for each polymer-water as well as for Dx-PVP-water systems. These results served for the prediction of miscibility of the Dx/PVP blends with various blend compositions by using , , , , and parameters. Except Dx4/PVP with its all compositions (Dx4 with nominal molecular weight of 110 000), other blend systems are found to be almost miscible. The density measurements of these polymer solutions and their blends were conducted in order to compare with the viscosity findings. Lastly, all Dx with different molecular weight, PVP and their blends were characterized by infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC).     

Diabetes induces compositional, structural and functional alterations on rat skeletal soleus muscle revealed by FTIR spectroscopy: a comparative study with EDL muscle

Diabetes Mellitus (DM) is a metabolic disorder, characterized by abnormally high blood glucose levels due to decreased secretion or effectiveness in function of insulin. Having a role in carbohydrate and lipid metabolism, skeletal muscle is affected by the absence of insulin in diabetic conditions. This current study reports the application of Fourier transform infrared (FTIR) spectroscopy in the determination of macromolecular alterations in streptozotocin (STZ)-induced diabetic rat skeletal Soleus (SOL) muscles, which highlight the promise of this technique in medical research. The results revealed that DM induced several alterations in macromolecular content and structure of slow-contracting SOL muscles. In diabetic SOL muscles, a decrease in the content of lipids, proteins and nucleic acids together with an increase in lipid order was observed. The decrease in the level of unsaturation and acyl chain length of lipids demonstrated the increased lipid peroxidation in DM. There were alterations in protein secondary structure in DM with a decrease in α-helix and β-sheet content of proteins, whereas the content of aggregated β-strands increased, which is generally seen when proteins denature. Besides, the integrity of collagen molecules was found to be decreased, demonstrating the alterations in its triple helical structure in diabetic muscles. Furthermore, the same alterations mentioned above were also observed in diabetic fast-contracting Extensor Digitorum Longus (EDL) muscles. However, having a high content of mitochondria and relying on an oxidative pathway, SOL muscle was found to be more affected by DM.     

Evaluation and discrimination of simvastatin-induced structural alterations in proteins of different rat tissues by FTIR spectroscopy and neural network analysis

Statins are commonly used to control hypercholesterolemia and to prevent cardiovascular diseases. Among the statins, Simvastatin is one of the most frequently prescribed statins because of its efficacy in reducing LDL lipoprotein cholesterol levels, its tolerability, and its reduction of cardiovascular risk and mortality. Conflicting results have been reported with regard to benefits (pleiotropic effects) as well as risks (adverse effects) of simvastatin on different soft and hard tissues. In the current study, Attenuated Total Reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to obtain detailed information about protein conformational changes due to simvastatin therapy of soft tissues namely liver, testis, sciatic nerve and hard tissues such as femur and tibia. Protein secondary structural changes were predicted by intensity calculations from second derivative spectra and neural network (NN) analysis, using the amide I band (1700-1600 cm(-1)) of FTIR spectra. Moreover, based on protein secondary structural differences, hierarchical cluster analysis was carried out in the 1700-1600 cm(-1) region. The results of our study in liver, testis and sciatic nerve tissues revealed that simvastatin treatment significantly decreased alpha helix structure and beta sheet structure at 1638 cm(-1), while increased the anti-parallel and aggregated beta sheet and random coil structures implying a simvastatin-induced protein denaturation in treated groups. Different to soft tissues, the results of hard tissue studies on femur and tibia bones revealed increased alpha helix structure and decreased anti-parallel beta sheet, aggregated beta sheet and random coil structures implying more strengthened bone tissues in simvastatin-treated groups. Finally, the simvastatin-treated and control groups for all soft and bone tissues were successfully differentiated using cluster analysis. According to the heterogeneity values in the cluster analysis of these tissues, the sciatic nerve tissue was found to be the most affected tissue from simvastatin treatment among the studied soft tissues. In addition, the high heterogeneity value implied high secondary structural difference between control and simvastatin-treated groups in tibia bone tissues. These findings reveal that FTIR spectroscopy with bioinformatic analyses such as neural network and hierarchical clustering, allowed us to determine the simvastatin-induced protein conformational changes as adverse and pleiotropic effects of the drug on different soft and hard tissues.