QSAR modelling and structural aspects concerning synthetic heterocycles with larvicidal activity against Aedes aegypti

Structural Chemistry - In this paper, we present a quantitative structure–activity relationships modelling for two series of heterocyclic synthetic compounds with larvicidal activity against...     

Novel regulation of aflatoxin B1 biosynthesis in Aspergillus flavus by piperonal

The present study investigated its inhibitory role in aflatoxin (AF) biosynthesis. Treating only AFB1- and B2-producing Aspergillus flavus with piperonal completely inhibited AFB1 production with high sclerotial formation, resulting in 20-fold higher AFG2 production. On the other hand, benzodioxole and eugenol suppressed AFB1 production without AFG formation, while methyleugenol showed potent inhibition of AFB1 production with slight production of AFG1. These results indicate that natural products may change aflatoxin biosynthesis, and highlight a novel regulation of AFG2 production by piperonal. It is the first report for chemical regulation on AFG2 production in non-AFG producing-aspergilli.     

Generation of single-crystalline domain in nano-scale silicon pillars by near-field short pulsed laser

We observe laser-induced grain morphology change in silicon nanopillars under a transmission electron microscopy (TEM) environment. We couple the TEM with a near-field scanning optical microscopy pulsed laser processing system. This novel combination enables immediate scrutiny on the grain morphologies that the pulsed laser irradiation produces. We find unusual transformation of the tip of the amorphous or polycrystalline silicon pillar into a single crystalline domain via melt-mediated crystallization. On the basis of the three-dimensional finite difference simulation result and the dark field TEM data, we propose that the creation of the distinct single crystalline tip originates from the dominant grain growth initiated at the apex of the non-planar liquid–solid interface. Our microscopic observation provides a fundamental basis for laser-induced conversion of amorphous nanostructures into coarse-grained crystals.     

Chemoselective Hydrogenation of Unsaturated Peroxides

Chemoselective hydrogenation of unsaturated monoperoxyketals provides new methodology for the synthesis of saturated and allyl hydroperoxides.     

On the Local Convergence Analysis of the Gradient Sampling Method for Finite Max-Functions

The gradient sampling method is a recently developed tool for solving unconstrained nonsmooth optimization problems. Using just first-order information about the objective function, it generalizes the steepest descent method, one of the most classical methods for minimizing a smooth function. This study aims at determining under which circumstances one can expect the same local convergence result of the Cauchy method for the gradient sampling algorithm under the assumption that the problem is stated by a finite max-function around the optimal point. Additionally, at the end, we show how to practically accomplish the required hypotheses during the execution of the algorithm.     

Investigation on the Beckmann rearrangement reaction catalyzed by porous solids: MAS NMR and theoretical calculations

In the last years, ‘in situ’ solid-state NMR has been applied to investigate the Beckmann rearrangement of oximes into amides using zeolites and mesoporous materials of different structure containing Brønsted acids or silanol groups as active sites. DFT methods have been applied to model the geometry of the complexes resulting from adsorption of reactants, reaction intermediates and products on clusters representing the zeolite centers, and their ¹⁵N and ¹³C NMR chemical shift calculated theoretically. This article reviews the results reported in the bibliography on the Beckmann rearrangement of various oximes (acetophenone oxime, cyclohexanone oxime and cyclododecanone oxime) mainly using ‘in situ’ ¹⁵N NMR spectroscopy and theoretical calculations, and are compared with those obtained by ‘in situ’ infrared spectroscopy. The combination of experiment and theory has been shown to be very useful for the interpretation of the NMR spectra and the identification of the species present at different reaction temperatures.     

Microwave-Assisted Direct Synthesis of 4H-1,2,4-Benzothiadiazine 1,1-Dioxide Derivatives

Abstract

We describe a rapid and convenient methodology for the preparation of diverse 3-aryl and 3-trifluoromethyl 4H-1,2,4-benzothiadiazine-1,1-dioxides in a one-pot microwave-promoted reaction between 2-aminobenzenesulfonamides and benzaldehydes, trifluoroacetic acid or benzoic acids.

GRAPHICAL ABSTRACT