A rapid access to chiral alkylidene cyclopentenone prostaglandins involving ring-closing metathesis reaction

A synthesis of the alkylidene cyclopentenone prostaglandin TEI 9826 has been realized. The synthesis involved the preparation of the chiral 1,5-diene 8 using a stereoselective Claisen rearrangement from the allylic alcohol 6 giving the ester 7 after vinylation. Then a key RCM reaction allowed the preparation of the cyclopentenol 9 which, after oxidation, gave the cyclopentenone 10, precursor of the prostaglandin.     

Monte Carlo versus molecular dynamics simulations in heterogeneous systems: an application to the n-pentane liquid-vapor interface

The Monte Carlo (MC) and molecular dynamics (MD) methodologies are now well established for computing equilibrium properties in homogeneous fluids. This is not yet the case for the direct simulation of two-phase systems, which exhibit nonuniformity of the density distribution across the interface. We have performed direct MC and MD simulations of the liquid-gas interface of n-pentane using a standard force-field model. We obtained density and pressure components profiles along the direction normal to the interface that can be very different, depending on the truncation and long range correction strategies. We discuss the influence on predicted properties of different potential truncation schemes implemented in both MC and MD simulations. We show that the MD and MC profiles can be made in agreement by using a Lennard-Jones potential truncated via a polynomial function that makes the first and second derivatives of the potential continuous at the cutoff distance. In this case however, the predicted thermodynamic properties (phase envelope, surface tension) deviate from experiments, because of the changes made in the potential. A further readjustment of the potential parameters is needed if one wants to use this method. We conclude that a straightforward use of bulk phase force fields in MD simulations may lead to some physical inconsistencies when computing interfacial properties.     

Experimental study of the frequency response of electrochemical split probes to transversal velocity fluctuations

An experimental investigation of the frequency response of electrochemical probes to transversal velocity fluctuation is reported. The study has been focused on wall shear stress for a modulated flow due to an oscillating cylinder along its own axes since the wall shear stress has been first numerically determined for this flow. Results indicate that a frequency response correction to probe outputs is required and that this correction depends on the amplitude of fluctuations.List of symbols A total area of the electrode - A _i area of the part i of the electrode - a amplitude of oscillation - C concentration - c fluctuation of concentration - D cylinder diameter - D diffusion coefficient - h dimensionless velocity normal to the wall - H transfer function modulus - K _i transfer coefficient - l electrode length - n frequency - S wall shear - S fluctuation of the wall shear - U mean value of the fluid velocity far from the wall - u streamwise component of the fluid velocity - spanwise component of the fluid velocity (along the cylinder axis) - w component of the fluid velocity perpendicular to the wall - x direction of the mean flow - y direction parallel to the cylinder axis - z direction perpendicular to the wall - v kinematic viscosity - dimensionless distance perpendicular to the wall (z) - dimensionless distance (x) - phase shift - azimuthal angle - modulation frequency     

Access to New Endoperoxide Derivatives by Electrochemical Oxidation of Substituted 3‐Azabicyclo[4.1.0]hept‐4‐enes

A series of substituted 3‐azabicyclo[4.1.0]hept‐4‐ene derivatives were prepared and analysed by cyclic voltammetry. Preparative aerobic electrochemical oxidation reactions were then carried out. Three original endoperoxides were isolated, characterised and subjected to antimalarial and cytotoxicity activity assays.