Efficient synthesis of 3-aminocyclobut-2-en-1-ones: squaramide surrogates as potent VLA-4 antagonists

A novel series of uniquely functionalized 3-aminocyclobut-2-en-1-ones has been prepared by facile condensation of a variety of cyclobuta-1,3-diones with a phenylalanine-derived primary amine. These systems subsequently lend themselves to substitution at C-2 by reaction with a variety of electrophilic reagents including N-halosuccinimides, sulfenyl chlorides, and Eschenmoser's salt. Compounds from this novel series are potent antagonists of VLA-4. [reaction: see text]     

First zeolite carbon replica with a well resolved X-ray diffraction pattern

The present study demonstrates that for the nanocasting process with zeolites, a careful choice of the zeolite structure type (EMT) allows the formation of faithful carbon replica exhibiting up to three well resolved XRD peaks.     

Local energy decay for the damped wave equation

We prove local energy decay for the damped wave equation on R^d${\mathbb{R}}^d$. The problem which we consider is given by a long range metric perturbation of the Euclidean Laplacian with a short range absorption index. Under a geometric control assumption on the dissipation we obtain an almost optimal polynomial decay for the energy in suitable weighted spaces. The proof relies on uniform estimates for the corresponding “resolvent”, both for low and high frequencies. These estimates are given by an improved dissipative version of Mourre's commutators method.     

Elimination versus ring opening: a convergent route to alkylidene-cyclobutanes

Functionalized alkylidene-cyclobutanes have been prepared from 2-fluoropyridinyl-6-oxy precursors derived from vinyl cyclobutanols by a radical addition-elimination process. A wide range of functional groups is tolerated, and the alkylidene-cyclobutanes can be further elaborated into cyclopentanones. The limitation of this approach resides in the competition with opening of the cyclobutane ring.     

Synthesis and electrochemical studies of LiMn1−xCuXO4 cathode material

LiMn_1.8Cu_0.2O₄ was investigated in order to improve the electrochemical properties of LiMn₂O₄. We report the synthesis and characterization of materials prepared by solid-state reaction. The structural properties evaluated by the X-ray diffraction and vibrational spectroscopy show that a single phase was formed. Conductivity of LiMn_1.8Cu_0.2O₄ cathode is found to be 8×10⁻⁶ S/cm at 25 °C. The cyclic voltammetry data shows the reversibility of the electrode material. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

Preparation and characterization of LiCo1−yCryO2 oxides

We report the synthesis, characterization and electrochemical properties of LiCo_0.85Cr_0.15O₂ samples. Powders prepared by wet-chemistry using the poly(vinyl alcohol) gel technique exhibit a well-defined layered structure. We describe the evolution of the local environment of cations when the precursor is heat treated at 750 °C in air. Electrochemical features of Li//LiCo_0.85Cr_0.15O₂ cells show a reversible capacity of 125 mAh/g for the first charge-discharge cycle. Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000.     

Singularités des courants d'Ahlfors

We prove that an algebraic curve charged by a current coming from an entire curve is rational or elliptic. This answers a question by M. P?un.