Catalytic oxidation of α-pinene by transition metal using t-butyl hydroperoxide and hydrogen peroxide

The allylic oxidation of α-pinene 1 was investigated using various catalytic systems. By a proper choice of the latter, the reaction can be directed toward the selective synthesis of verbenol 2 or verbenone 3. High yield into verbenone was achieved under mild conditions with copper salts as catalysts and t-butyl hydroperoxide (TBHP) as oxidant. On the other hand, when Pd(acac)₂ was used with hydrogen peroxide, verbenol was obtained as the main product.     

Microtubule‐Binding R3 Fragment from Tau Self‐Assembles into Giant Multistranded Amyloid Ribbons

Tau protein and its fragments self‐assemble into amyloid fibrils in the presence of polyanions, such as heparin. By combining microscopy, scattering, and spectroscopy techniques, we studied the aggregation of the 26‐mer Tau‐derived peptide alone, Tau_306–327, the third repeat fragment (R3) of the microtubule‐binding domain. We show that: i) the sole Tau_306–327 can self‐assemble into amyloid fibrils without the need of aggregation‐promoting polyanions; ii) the resulting structures consist of surprisingly large, well‐ordered 2D laminated flat ribbons, with a log‐normal distribution of the lateral width, reaching the unprecedented lateral size of 350 nm and/or 45 individual protofilaments, that is, the largest amyloid laminated structures ever observed for Tau or any other amyloidogenic sequence. Our results provide insight into the molecular determinants of Tau aggregation and open new perspectives in the understanding of the assembly of amyloid fibrils and β‐sheet‐based biomaterials.     

Pricing Occupation-Time Options in a Mixed-Exponential Jump-Diffusion Model

In this short paper, in order to price occupation-time options, such as (double-barrier) step options and quantile options, we derive various joint distributions of a mixed-exponential jump-diffusion process and its occupation times of intervals.     

Convergence in law for certain additive functionals of symmetric stable processes under strong topology

We give some limit theorems of certain additive functionals for symmetric stable process of index $1<\alpha ?2$ in anisotropic Besov space. These results generalize those obtained by Eisenbaum (1997) and by Csaki et al. (2002). To cite this article: M. Ait Ouahra, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Preferential oxidation of CO in H2 over highly loaded Au/ZrO2 catalysts obtained by direct oxidation of bulk alloy

The intimate mixture of a skeletal gold structure with ZrO2 nanoparticles obtained simply by oxidation of Au(0.5)Zr(0.5) alloy at room temperature turns out to be an efficient catalyst for the selective oxidation of CO in the presence of hydrogen.     

A Multifunctional Photochromic Light-Modulating Polymer Film

Russian Journal of General Chemistry - The results of the authors’ studies on development of a multilayer photochromic sun-protective energy-saving polymer film able of reversibly changing...     

4-Aminopyrimidine libraries from the Ugi-Smiles reaction of thiouracil

The Ugi-Smiles reaction of S-benzyl thiouracil have been exploited in several three-step sequences for the preparation of aminopyrimidine libraries with high diversity. After the 4-component coupling, oxidation of the thioether to sulfone is followed by displacement of the latter by various carbon-centered nucleophiles (cyanide, malonate, boronic acids) or amines. The efficiency of the whole sequence was further demonstrated with one-pot procedures.     

Photochromic properties of modified nanodiamonds

A functionalization of the surface of detonation nanodiamonds by photochromic spirocompounds from the classes of spiropyrans and spirooxazines has been carried out for the first time. A comparative study of the interaction of nanodiamonds with positive and negative potential is performed by the spectral–kinetic method, which shows the possibility of surface modification by only functionalized molecules of spirocompounds with the formation of surface proton complexes. This is confirmed by the hypsochromic shift of the absorption bands of the photoinduced merocyanine forms of adsorbed molecules of spirocompounds and by the decrease of the speed of their dark relaxation to the initial state in the presence of nanodiamonds with a negative potential.     

Suites récurrentes linéaires : terme général et idempotents

In this Note, we show essentially two results. The first one consists in showing that the algebra of linear recurrence sequences is the direct sum of two sets. The second result consists in giving a characterisation of the idempotents of this algebra.