Catalytic Asymmetric Torgov Cyclization: A Concise Total Synthesis of (+)‐Estrone

An asymmetric Torgov cyclization, catalyzed by a novel, highly Brønsted acidic dinitro‐substituted disulfonimide, is described. The reaction delivers the Torgov diene and various analogues with excellent yields and enantioselectivity. This method was applied in a very short synthesis of (+)‐estrone.     

Kinetics and efficiency displayed by supported and suspended TiO2 catalysts applied to the disinfection of Escherichia coli

TiO₂-mediated photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including photoelectrochemical conversion, self-cleaning surfaces, and especially water purification systems. The dimensionality of the structure of a TiO₂ material can affect its properties, functions, and more specifically, its photocatalytic performance. In this work, the photocatalytic inactivation of Gram-negative Escherichia coli using three photocatalysts, differing in their structure and other characteristics, was studied in a batch reactor under UVA light. The aim was to establish the disinfection efficiency of solid TiO₂ compared with that of suspended catalysts, widely considered as reference cases for photocatalytic water disinfection. The bacterial inactivation profiles obtained showed that: (1) the photoinactivation was exclusively related to the quantity of photons retained per unit of treated volume, irrespective of the characteristics of the photocatalyst and the emitted light flux densities; (2) across the whole UV light range studied, each of the photocatalytic solids was able to achieve more than 2 log bacterial inactivation with less than 2 h UV irradiation; (3) none of the used catalysts achieved a total bacterial disinfection during the treatment time. For each of the catalysts the quantum yield has been assessed in terms of disinfection efficiency, the 2D material showed almost the same performance as those of suspended catalysts. This catalyst is promising for supported photocatalysis applications.     

NMR studies of interactions of new CB2 cannabinoid receptor ligands with cyclodextrins hosts. Correlation with micellar electrokinetic chromatography and reversed phase high performance liquid chromatography

Three selective CB₂ cannabinoid receptor ligands have recently been discovered to be promising anti-inflammatory agents but their low water solubility hinder their per os administration. The popularity of the cyclodextrins, from a pharmaceutical standpoint lies on their ability to interact with poorly water-soluble drugs and improve their solubility. Herein, three experimental approaches for calculating the stability constant of complexes between the selective CB₂ ligands and either the β-CD or the HP-β-CD, were tested: nuclear magnetic resonance, micellar electrokinetic chromatography and high performance liquid chromatography in reversed phase. In NMR studies the calculated K values were relatively high and were between 1486 and 3571 M^?1 with β-CD. With HP-β-CD they were between 1203 and 2650 M^?1. Concerning the two others techniques the K values were found lower. In MECK studies with β-CD they were between 308 and 792 M^?1 and with HP-β-CD between 124 and 764 M^?1. Finally in RP-HPLC studies with β-CD, they were between 539 and 1144 M^?1 and with HP-β-CD between 196 and 396 M^?1. These calculated constants suggest that a complexation phenomenon occurs. A model for inclusion of one of the CB₂ ligands in the β-CD was then proposed from molecular modeling studies.     

Formation of a Single-Crystal Aluminum-Based MOF Nanowire with Graphene Oxide Nanoscrolls as Structure-Directing Agents

An innovative strategy is proposed to synthesize single-crystal nanowires (NWs) of the Al³⁺ dicarboxylate MIL-69(Al) MOF by using graphene oxide nanoscrolls as structure-directing agents. MIL-69(Al) NWs with an average diameter of 70±20 nm and lengths up to 2 μm were found to preferentially grow along the [001] crystallographic direction. Advanced characterization methods (electron diffraction, TEM, STEM-HAADF, SEM, XPS) and molecular modeling revealed the mechanism of formation of MIL-69(Al) NWs involving size-confinement and templating effects. The formation of MIL-69(Al) seeds and the self-scroll of GO sheets followed by the anisotropic growth of MIL-69(Al) crystals are mediated by specific GO sheets/MOF interactions. This study delivers an unprecedented approach to control the design of 1D MOF nanostructures and superstructures.     

Gold(III) π-Allyl Complexes

Gold(III) π-complexes have been authenticated recently with alkenes, alkynes, and arenes. The key importance of Pd^II π-allyl complexes in organometallic chemistry (Tsuji–Trost reaction) prompted us to explore gold(III) π-allyl complexes, which have remained elusive so far. The (P,C)Au^III(allyl) and (methallyl) complexes 3 and 3′ were readily prepared and isolated as thermally and air-stable solids. Spectroscopic and crystallographic analyses combined with detailed DFT calculations support tight quasi-symmetric η³-coordination of the allyl moiety. The π-allyl gold(III) complexes are activated towards nucleophilic additions, as substantiated with β-diketo enolates.     

Oligosaccharides: Defense Inducers,Their Recognition in Plants,Commercial Uses and Perspectives

Plants have innate immune systems or defense mechanisms that respond to the attack of pathogenic microorganisms. Unlike mammals, they lack mobile defense cells, so defense processes depend on autonomous cellular events with a broad repertoire of recognition to detect pathogens, which compensates for the lack of an adaptive immune system. These defense mechanisms remain inactive or latent until they are activated after exposure or contact with inducing agents, or after the application of the inductor; they remain inactive only until they are affected by a pathogen or challenged by an elicitor from the same. Resistance induction represents a focus of interest, as it promotes the activation of plant defense mechanisms, reducing the use of chemical synthesis pesticides, an alternative that has even led to the generation of new commercial products with high efficiency, stability and lower environmental impact, which increase productivity by reducing not only losses but also increasing plant growth. Considering the above, the objective of this review is to address the issue of resistance induction with a focus on the potential of the use of oligosaccharides in agriculture, how they are recognized by plants, how they can be used for commercial products and perspectives.     

Nanoparticles from vesicle polymerization: Characterization and kinetic study

The polymerization of isodecyl acrylate (ISODAC) in vesicles made from an anionic surfactant—sodium di-2-ethylhexyl phosphate (SEHP)—and from water is studied by ¹H-NMR, transmission electron microscopy, and quasielastic light scattering. High polymerization rates and high conversion rates are achieved with both water-soluble initiator, K₂S₂O₈ (potassium persulfate), and oil-soluble initiator, AIBN (azoisobisbutyronitrile). ISODAC is probably located inside the vesicle bilayer(s) because of its high hydrophobicity. Particles stable at room temperature with a mean diameter of about 50 nm are obtained. Kinetic orders of ISODAC polymerization are determined and the characterization of the resulting particles during and after polymerization are studied. © 1996 John Wiley & Sons, Inc.