An Efficient and Facile Synthesis of Quinoxaline Derivatives Catalyzed by KHSO4 at Room Temperature

Summary. A facile synthesis of quinoxaline derivatives catalyzed by KHSO₄ in very high yields at room temperature is reported.     

Selective Acetylation of Alcohols and Amines with Ethyl Acetate in the Presence of H<Subscript>6</Subscript>[PMo<Subscript>9</Subscript>V<Subscript>3</Subscript>O<Subscript>40</Subscript>] as the Catalyst

Summary. Acetylation of various alcohols and benzyl amine was tested in the presence of H₆[PMo₉V₃O₄₀], a mixed addenda heteropolyacid, in ethyl acetate under reflux condition. Phenols and anilines are not affected under the reaction conditions. Selective transestrification of alcohols can be achieved in the presence of phenol and aniline derivatives using this method.     

Using a Natural Surfactant for Synthesize of NiO and CuO Nanostructures via Simple and Fast Microwave Approach

NiO and CuO nanostructures were synthesized successfully via simple and fast microwave approach. Olive oil was chose as surfactant for stabilizing nanostructures. Different parameters such as microwave time and power and olive oil concentration were investigated on product size and morphology. The products were characterized with X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometry analysis.     

Solvent‐Free Chemoselective Synthesis of 1,1‐Diacetates Catalyzed by Cu(NO3)2 · 3H2O

1,1‐Diacetates have been synthesized by the reaction of a variety of aldehydes with acetic anhydride in the presence of cupric nitrate as catalyst under solvent‐free conditions. Ketones were not converted to the corresponding diacetates under these conditions.     

The Effects of Food on Cannabidiol Bioaccessibility

Cannabidiol (CBD) is a hydrophobic non-psychoactive compound with therapeutic characteristics. Animal and human studies have shown its poor oral bioavailability in vivo, and the impact of consuming lipid-soluble CBD with and without food on gut bioaccessibility has not been explored. The purpose of this research was to study the bioaccessibility of CBD after a three-phase upper digestion experiment with and without food, and to test lipase activity with different substrate concentrations. Our results showed that lipase enzyme activity and fatty acid absorption increased in the presence of bile salts, which may also contribute to an increase in CBD bioaccessibility. The food matrix used was a mixture of olive oil and baby food. Overall, the fed-state digestion revealed significantly higher micellarization efficiency for CBD (14.15 ± 0.6% for 10 mg and 22.67 ± 2.1% for 100 mg CBD ingested) than the fasted state digestion of CBD (0.65 ± 0.7% for 10 mg and 0.14 ± 0.1% for 100 mg CBD ingested). The increase in bioaccessibility of CBD with food could be explained by the fact that micelle formation from hydrolyzed lipids aid in bioaccessibility of hydrophobic molecules. In conclusion, the bioaccessibility of CBD depends on the food matrix and the presence of lipase and bile salts.     

Formation of a Ligand‐Assisted Complex of Two RNA Hairpin Loops

The hairpin structure is one of the most common secondary structures in RNA and holds a central position in the stream of RNA folding from a non‐structured RNA to structurally complex and functional ribonucleoproteins. Since the RNA secondary structure is strongly correlated to the function and can be modulated by the binding of small molecules, we have investigated the modulation of RNA folding by a ligand‐assisted formation of loop–loop complexes of two RNA hairpin loops. With a ligand (NCT6), designed based on the ligand binding to the G–G mismatches in double‐stranded DNA, we successfully demonstrated the formation of both inter‐ and intra‐molecular NCT6‐assisted complex of two RNA hairpin loops. NCT6 selectively bound to the two hairpin loops containing (CGG)₃ in the loop region. Native polyacrylamide gel electrophoresis analysis of two doubly‐labeled RNA hairpin loops clearly showed the formation of intermolecular NCT6‐assisted loop–loop complex. Förster resonance energy‐transfer studies of RNA constructs containing two hairpin loops, in which each hairpin was labeled with Alexa488 and Cy3 fluorophores, showed the conformational change of the RNA constructs upon binding of NCT6. These experimental data showed that NCT6 simultaneously bound to two hairpin RNAs at the loop region, and can induce the conformational change of the RNA molecule. These data strongly support that NCT6 functions as molecular glue for two hairpin RNAs.     

Diastereoselective synthesis of pyrrolo[1, 2-c]imidazoles using chiral thiohydantoins,malononitrile, and aldehydes and evaluation of their antioxidant and antibacterial activities

Diastereoselective synthesis of pyrrolo[1,2-c]imidazoles is reported from three-component reaction of chiral thiohydantoins, aldehydes, and malononitrile in the presence of NEt₃. The antioxidant properties of the obtained products were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Among the products, compound 4l possessing NH₂ and NH groups and bromine atom at 4-position of the aromatic ring displayed the highest antioxidant activity (90%). Also, their antibacterial activities were explored against gram-positive and gram-negative bacteria using disc diffusion method. Among the synthesized compounds, 4a with chlorine atom at para position of the aromatic ring, and methyl group (the smallest alkyl group) at 7-position, displayed the best antibacterial activity against the tested gram-positive bacteria.     

Modification of an implicit approach based on nonstandard rules for structural dynamics analysis

The present study aims to modify a recently suggested implicit approach consisted of the approximate Euler method and closed-form exponential mapping (herein referred to as the Liu scheme) for the dynamic analysis of structures. Such modification has been developed based upon nonstandard rules. The equation of motion is formulated in the augmented dynamic space to apply the exponential mapping as a group preserving scheme. The formulation of the proposed method involves the hyperbolic sine and cosine functions. The method is therefore prone to divergence due to the behavior of the hyperbolic functions in structures with a high ratio of stiffness to mass. In the present study, to consider the properties of the structural equation into the formulation of the time step size and thereby avoid the divergence, a parameter, known as stability parameter, is thus derived from the exact solution of the equation of motion based on nonstandard rules. Embedding this parameter into the proposed method improves its stability. Afterward, for evaluating the performance of the proposed method, it is applied to several structures with different loading patterns while implemented in programing environment of the Matlab software. The results are compared to those of several commonly used numerical methods in structural applications. It is found that the proposed method has acceptable convergence and accuracy, and low time consumption compared to several commonly used methods. Furthermore, its stability is guaranteed by embedding the stability parameter into the proposed method.