Preparation d'esters par deshydrogenation d'alcools primaires en phase liquide catalysee par l'oxyde de cuivre - observations preliminaires

Linear primary alcohols with at least 7 carbon atoms are quite quantitatively transformed in esters, by CuO, at temperatures > 170°, without air in liquid phase. Preponderant influence of carbon in position 2 is evidenced. In the same conditions lactones are obtained from diols, and benzylic alcohols undergoes, by hydride transfer, a disproportionation into toluene, benzaldehyde and water.     

Two-Photon Absorption and Cell Imaging of Fluorene-Functionalized Epicocconone Analogues

Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro-fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium-catalyzed carbonylation reaction, allowing the construction of the β-keto-dioxinone key intermediate. Two-photon absorption cross-section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle-like structures around the nucleus.     

Amine capture strategy for peptide bond formation by means of quinolinium thioester salts

A new and unprecedented exploitation of quinolinium thioester salts 2 in peptide bond formation is reported. These synthetic tools were assessed during the preparation of a number of dipeptides 3a-f obtained in good yields with complete stereochemical integrity. A sequential mechanism related to a prior amine capture strategy is well-established. Additionally, a tripeptide 3g was prepared according to a "safety-catch" approach, thus demonstrating the important potential of these new synthetic tools in the design of new safety-catch linkers exploitable in Solid-Phase Peptide Synthesis (SPPS).     

Linear programming solutions and distance functions under α-returns to scale

This note generalizes analytical relationships among activity variables of Dataenvelopment analysis models previously derived in a previous article by theauthors of this note. We relax the assumption of constant returns to scale byshowing that the key results hold under a weaker assumption of homogeneity. Weuse the notion of α-returns to scale to extend the analysis tostrictly increasing and decreasing returns, covering now the whole range ofreturns to scale for multi-output homogenous technologies.     

PegPhos: a monodentate phosphoramidite ligand for enantioselective rhodium-catalysed hydrogenation in water

A BICOL derived monodentate phosphoramidite ligand gives ee's up to 89% in the enantioselective Rh-catalysed hydrogenation of N-acyl dehydroalanine using water as the solvent.     

Trefoil Symmetry IV: Basic Enhanced Superspace for the Minimal Vector Clover Extension

We construct a differential representation and covariant derivatives of the minimal vector clover extension of the Poincaré algebra. In analogous way as in the supersymmetric case, there arises an enhanced superspace which allows to define superfields. The action of group transformations on such superfields determines a representation out of which the covariant derivatives are obtained.     

Economic value of greenhouse gases and nitrogen surpluses: Society vs farmers’ valuation

Livestock supply must challenge the growth of final demand in the developing countries. This challenge has to take into account its ecological effects since the dairy and livestock sectors are clearly pointed out as human activities which contribute significantly to environmental deterioration. Therefore, livestock activity models have to include desirable and undesirable outputs simultaneously. Using this perspective, we implement a Data Envelopment Analysis model to evaluate shadow prices of outputs under contradictory objectives between the society and the farmers. We show that farmers are able to reduce pollution significantly if society accepts to balance farmers’ opportunity cost. Finally, we observe that initial levels of the CO₂ tax implemented in European countries are in line with farmers’ valuation while the current level of the CO₂ tax tends to reach the value of pollution targeted by the society.     

Cationic polymerization of isobutyl vinyl ether initiated with the system aluminium trichloride/ethyl acetate,in toluene solution

The cationic polymerization of isobutyl vinyl ether initiated with the title system apparently has some features of a living polymerization (linear increase of number average molecular weight M̄_n with conversion). However, evidence is given for the occurrence of a transfer reaction resulting in the increase of the number of macromolecules, and this even for relatively low molecular weights.