International audienc

After seminal Tsuji-Trost reactions (palladium catalyzed allylation of nucleophiles via π-allyl intermediates as electrophiles), the idea of reversal reactivity of π-allyl intermediates (i.e. π-allyl as nucleophiles) has been stated since the eighties. Thanks to different transition metal sources and the modification of their electronic environment through the use of additives and ligands, such 'reactivity switch' of π-allyl intermediates proved its powerfulness allowing high control in regio-, diastereo- and enantio-selectivities. These methodologies have thus emerged as efficient methods in the catalytic enantioselective allylation of carbonyl compounds and imines with a deep impact on natural product and/or drug elaboration. This tutorial review highlights the concept of 'umpoled' reactivity of π-allyl intermediates, relying on selected recent examples.

A survey was performed using a sample of pregnant women selected at one of the biggest test centres in the Paris area. These women were serologically screened for toxoplasmosis between October 1981 and September 1983 (according to the prevention protocol for congenital toxoplasmosis established by the French health ministry). The prevalence rate of specific antibodies for toxoplasmosis was estimated from the 1074 women who were tested for the first time during the study. The prevalence rate among pregnant women in the Paris area was derived by direct standardization according to age and geographical origin. A standardized prevalence rate of 71% +/- 4% among French women, of 51.4% +/- 5% among immigrant women and a global adjusted prevalence rate of 67.3% +/- 3% for pregnant women in the Paris area was found. An incidence rate of 1.6% was estimated for the 2216 non-immune pregnant women included in the sample. There is no significant difference between the probabilities of seroconversion among French and immigrant women (2.3% +/- 1% and 1.6% +/- 0.8% respectively). Comparison of the data with previous study results show a decrease in the prevalence rate of specific antibodies for toxoplasmosis in the Paris area over the last 20 years that cannot be explained by changes in age and geographical origin. No data were available to support an aetiological hypothesis for a decrease in toxoplasma transmission to humans. Since immigration and a decrease in toxoplasma transmission to humans has led to a larger population of women at risk of infection during pregnancy in France, it is therefore important to perform studies to investigate risk factors and markers of acquired toxoplasmosis during pregnancy in order to improve the prevention of congenital toxoplasmosis.

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Owing to their significant abundance in natural products, chiral beta,beta'-disubstituted alpha-amino acids remain an important synthetic objective. Emphasis has been focused in this critical review on the great diversity of enantio- and diastereoselective methodologies to reach these highly functionalized compounds. The oldest and cutting edge synthetic methods are described in parallel with the synthesis of many relevant biologically active targets (224 references).

SummaryNew functional monomers bearing a methacrylate, a bisphosphonate function and, for most, an internal carboxylate group, were prepared for incorporation into copolymers with adhesive or anticorrosive properties. Methanolysis of some trimethylsilyl bisphosphonate esters not only deprotects the desired bisphosphonate function but also regioselectively cleaves the alkyl ester function without affecting the methacrylate ester.