A. Lattes

Dendritic Catanionic Assemblies: In vitro Anti‐HIV Activity of Phosphorus‐Containing Dendrimers Bearing Galβ1cer Analogues

Two series of water‐soluble dendritic catanionic assemblies, acting as multisite analogues of galactosylceramide (Galβ1cer), have been prepared with the goal of blocking HIV infection prior to the entry of the virus into human cells. Trifunctional and hexafunctional cinnamic acid‐terminated dendrimers have been synthesized from phosphorus‐containing dendrimers bearing aldehyde end groups. A classical acid–base reaction performed in water between acid‐terminated dendrimers and stoichiometric amounts of N‐hexadecylamino‐1‐deoxylactitol (3) provided the expected catanionic assemblies. Antiviral assays on these supramolecular entities confirmed the crucial roles both of multivalency effects and of lipophilicity on the biological activity of Galβ1cer analogues. Moreover, correlation between in vitro tests and molecular modeling highlights the specific influence of the assembly shape on the anti‐HIV efficiency, with the tri‐ and hexafunctional cored dendrimers, both decorated with 12 sugar moieties, exhibiting IC50 values of 1.1 and 0.12 μM, respectively.

Waterless microemulsions. 2. Use of formamide in place of water in the preparation of large monophasic areas of perfluorinated microemulsions

Abstract Formamide is highly suited for the production of perfluorinated microemulsions since: 1. —Perfluorinated surfactants are soluble in formamide 2. —Perfluorinated alcohols (good cosurfactants for perfluorinated oils due to their high solubility in these iols) are also slightly soluble in formamide but not in water. Such waterless perfluorinated microemulsions have quite similar structures to their aqueous counterparts since percolation and Winsor systems have been observed. We are now undertaking a study of these microemulsions as reaction media for oxidative reactions.

Corrosion inhibition study of a carbon steel in acidic media containing hydrogen sulphide and organic surfactants

Inhibition of the corrosion of a carbon steel (0.4% C) by 2-hexadecyl imidazoline and 2-hexadecyl imidazole has been evaluated by electrochemical techniques and correlated with surface tension measurements. Plots of inhibitor efficiency versus surfactant concentration produce S-shaped curves which are assumed to represent adsorption isotherms. A sharp increase in slope was observed at concentrations below the critical micellar concentration. This increase in slope is accounted for by changes in conformation of the adsorbed molecules: horizontal orientations (with respect to the surface) at lower concentrations reflecting cathodic behaviour and perpendicular orientations at the higher concentrations reflecting mixed cathodic and anodic behaviour. At increasing concentrations the inhibitory effect remained constant, suggesting complete saturation of the surface in a bilayered arrangement. Electrochemical impedance measurements, carried out for concentrations greater than the critical micellar concentration, corroborate this assumption: the inhibitors form a thick but adherent micellar film which acts as a diffusion barrier.

Formamide, a water substitute in micelles and microemulsions xxx structural analysis using a diels-alder reaction as a chemical probe

Abstract We recently demonstrated that it is possible to prepare waterless microemulsions by replacing water with formamide. Using the Diels-Alder reaction between methyl acrylate and cyclopentadiene as a chemical probe, we were able to explore the monophasic areas of both ionic and non-ionic surfactant solutions in formamide. Discontinuities in reaction selectivity indicate the presence of structured phases.

Optimization of the enzymatic synthesis of amino acid esters. Reaction in polyphasic medium

Abstract N-acetyl-L-Tyrosine Ethyl Ester (ATEE) was synthesized from N-acetyl- l -Tyrosine and ethanol, with immobilized chymotrypsin as catalyst. For this purpose, a biphasic liquid reaction mixture consisting of an organic chloroform phase and an aqueous phase was used. This system allows the shift of the reaction equilibrium towards ATEE synthesis by achieving continuous ATEE extraction in the organic phase. Synthesis rates of up to 90% were obtained by optimizing the reaction conditions and controlling the pH of the aqueous phase.

Aggregation in formamide solution: reactivity and structure of non-aqueous microemulsions

Abstract Relatively little attention has been paid to molecular aggregation phenomena in structured non-aqueous solvents compared to that devoted to such processes in aqueous media. This paper is a review concerning our work with formamide in place of water. The following observations showed that formamide has sufficient cohesive force to favor molecular aggregation: (1) critical micellar concentrations (c.m.c.) were determined with various ionic and non-ionic surfactants; (2) the phase diagram of CTAB in formamide shows two mesomorphic phases closely resembling those found in aqueous systems; (3) X-ray scattering demonstrated the presence of molecular aggregates, and gave an indication of their structure, and (4) a variety of microemulsions were prepared in formamide. Such non-aqueous microemulsions represent valuable media for synthetic purposes. For example, Diels-Alder reactions, photoamidation of olefins, and the Wacker process can be carried out readily in such media. The observed discontinuities in reaction selectivity indicate the presence of structured phases.

Formamide, a water substitute XIV (1) waterless microemulsions 8. Structural analysis by X-ray scattering of CTAB aggregates in formamide and in the microemulsion system (formamide, CTAB, isooctane, 1-butanol)

X-ray scattering was used to analyse the structures of aggregates of CTAB in various formamide-containing media.Firstly, CTAB micelles were detected in formamide solutions. A spherical micelle model was proposed; at values close to the CMC, smaller micelles were observed in formamide than in water.Secondly, the structure of microemulsions in the isooctane-rich zone of the system (formamide/CTAB=2, isooctane, 1-butanol) was studied by X-ray scattering. The structure was found to be quite different in this zone from that normally observed in aqueous microemulsions. Structures compatible with small filaments of formamide were detected. The results were related to previous measurements of electrical conductivity.

Waterless microemulsions - IV : diels-alder reaction of cyclopentadiene and methylacrylate as a probe of formamide microemulsions

Abstract The use of the Diels-Alder reaction between methyl acrylate and cyclopentadiene as a chemical probe has demonstrated two distinct zones in the formamide microemulsion system. Good selectivity and high yields can be obtained from Diels-Alder reactions in formamide.

Synthesis of new sugar-based surfactants having biological applications : key role of their self-association

Abstract Non-ionic surfactants based on sugars are of interest to both chemists and biochemists. They have potential pharmaceutical (biocompatible formulation) biochemical (extraction of membrane proteins) and medicinal applications; generally these derivatives are not readily synthesized as the starting sugars require protection. We present here routes, avoiding protection of the starting sugars, to new series of surfactants derived from lactose, glucose, gluconic or lactobionic acids. By changing the tail or the hydrophobic body bonded to the sugar heads, we have synthesized sugar-based amphiphilic compounds having (1) one chain, (2) one fluorinated chain, (3) a double chain or (4) two sugar heads (bolaamphiphilic compounds) All these compounds form aggregates in solution: direct, reverse micelles, or vesicles. Fluorinated molecules give gels in aqueous or non-aqueous media. Some of them are interesting products to extract membrane proteins or to formulate solution of hydrophobic acids to realize enzymatic reactions. Finally soluble analogs of Galcer possess activity against both HIV andAspergillus fumigatus, a yeast responsible for opportunistic infections in AIDS patients.

Functionalized Vesicles Based on Amphiphilic Boronic Acids: A System for Recognizing Biologically Important Polyols

We report on a new approach for creating water-soluble functionalized vesicles employing N-alkyl-3-boronopyridinium triflates (alkyl = Me, C12H25, C16H33) as sensors for monosaccharides. The nanoaggregate properties were studied by means of DLS, TEM, high-resolution (1)H NMR, and the solvatochromic dyes Reichardts betaine and Methyl Orange. The vesicles were shown to have 30-200 nm diameters depending on the amphiphile chain length. Diol binding to the vesicles was studied by steady-state fluorescence and UV-vis using Alizarin Red S as a probe in the solution at pH 7.4 in the presence and in the absence of D-glucose and D-fructose. Strong sensing ability of boronic acid functional moieties in the order D-fructose > D-glucose was demonstrated, and apparent binding constants were estimated.