Efficiency of Industrially Relevant Atropisomeric Diphosphines in Copper-Catalyzed 1,4-Asymmetric Conjugate Addition of Dialkylzincs to Cyclic or Acyclic Enones or Dienones

International audienceIndustrially relevant atropisomeric diphosphines such as 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP), 6,6'-bis(diphenylphosphino)-2,2',3,3'-tetrahydro-5,5'-bi-1,4-benzodioxin (SYNPHOS), and 5,5'-bis(diphenylphosphino)-2,2,2',2'-tetrafluoro-4,4'-bi-1,3-benzodioxole (DIFLUORPHOS) have demonstrated their efficiency in the copper-catalyzed asym. conjugate addn. of various dialkylzincs to α-aryl enones, α-aryl dienones, and cyclic dienones. Excellent 1,4- or 1,6-regioselectivities and enantioselectivities (up to 97% ee) were attained, even with challenging sterically hindered Michael acceptors

Cycloalkyl-based unsymmetrical unsaturated (U2)-NHC ligands : flexibility and dissymmetry in ruthenium-catalysed olefin metathesis.

International audienceAir-stable Ru-indenylidene and Hoveyda-type complexes bearing new unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligands combining a mesityl unit and a flexible cycloalkyl moiety as N-substituents were synthesised. Structural features, chemical stabilities and catalytic profiles in olefin metathesis of this new library of cycloalkyl-based U2-NHC Ru complexes were studied and compared with their unsymmetrical saturated NHC-Ru homologues as well as a set of commercially available Ru-catalysts bearing either symmetrical SIMes or IMes NHC ligands

A Role for Immune Responses against Non-CS Components in the Cross-Species Protection Induced by Immunization with Irradiated Malaria Sporozoites

Immunization with irradiated Plasmodium sporozoites induces sterile immunity in rodents, monkeys and humans. The major surface component of the sporozoite the circumsporozoite protein (CS) long considered as the antigen predominantly responsible for this immunity, thus remains the leading candidate antigen for vaccines targeting the parasite's pre-erythrocytic (PE) stages. However, this role for CS was questioned when we recently showed that immunization with irradiated sporozoites (IrrSpz) of a P. berghei line whose endogenous CS was replaced by that of P. falciparum still conferred sterile protection against challenge with wild type P. berghei sporozoites. In order to investigate the involvement of CS in the cross-species protection recently observed between the two rodent parasites P. berghei and P. yoelii, we adopted our gene replacement approach for the P. yoelii CS and exploited the ability to conduct reciprocal challenges. Overall, we found that immunization led to sterile immunity irrespective of the origin of the CS in the immunizing or challenge sporozoites. However, for some combinations, immune responses to CS contributed to the acquisition of protective immunity and were dependent on the immunizing IrrSpz dose. Nonetheless, when data from all the cross-species immunization/challenges were considered, the immune responses directed against non-CS parasite antigens shared by the two parasite species played a major role in the sterile protection induced by immunization with IrrSpz. This opens the perspective to develop a single vaccine formulation that could protect against multiple parasite species

Inhibitory Effect of TNF-α on Malaria Pre-Erythrocytic Stage Development: Influence of Host Hepatocyte/Parasite Combinations

BACKGROUND: The liver stages of malaria parasites are inhibited by cytokines such as interferon-gamma or Interleukin (IL)-6. Binding of these cytokines to their receptors at the surface of the infected hepatocytes leads to the production of nitric oxide (NO) and radical oxygen intermediates (ROI), which kill hepatic parasites. However, conflicting results were obtained with TNF-alpha possibly because of differences in the models used. We have reassessed the role of TNF-alpha in the different cellular systems used to study the Plasmodium pre-erythrocytic stages. METHODS AND FINDINGS: Human or mouse TNF-alpha were tested against human and rodent malaria parasites grown in vitro in human or rodent primary hepatocytes, or in hepatoma cell lines. Our data demonstrated that TNF-alpha treatment prevents the development of malaria pre-erythrocytic stages. This inhibitory effect however varies with the infecting parasite species and with the nature and origin of the cytokine and hepatocytes. Inhibition was only observed for all parasite species tested when hepatocytes were pre-incubated 24 or 48 hrs before infection and activity was directed only against early hepatic parasite. We further showed that TNF-alpha inhibition was mediated by a soluble factor present in the supernatant of TNF-alpha stimulated hepatocytes but it was not related to NO or ROI. Treatment TNF-alpha prevents the development of human and rodent malaria pre-erythrocytic stages through the activity of a mediator that remains to be identified. CONCLUSIONS: Treatment TNF-alpha prevents the development of human and rodent malaria pre-erythrocytic stages through the activity of a mediator that remains to be identified. However, the nature of the cytokine-host cell-parasite combination must be carefully considered for extrapolation to the human infection

Asymmetric Catalysis with Metal N-Heterocyclic Carbene Complexes

International audienc

Développement de pré-catalyseurs de type hoveyda-grubbs activés et recyclables pour la métathèse d oléfines (synthèse de carbènes N-Hétérocylciques chiraux et utilisation en catalyse asymétrique)

Ce travail traite du développement de nouveaux systèmes catalytiques. Dans une première partie, de nouveaux pré-catalyseurs au ruthénium de type Hoveyda Grubbs II ont été développés pour réaliser des métathèses d oléfines. Suivant la nature de l espaceur permettant l immobilisation sur un support, l activité catalytique et le recyclage ont pu être contrôlés, tout en engendrant une faible contamination des produits au ruthénium. Dans une seconde partie, de nouveaux carbe nes N-hétérocycliques ont été étudiés pour l addition conjuguée asymétrique catalysée au cuivre. L étude des différents groupements des ligands a été réalisée afin d en déterminer l importance dans la réactivité et la sélectivité de cette réaction.This work deals with the development of new catalytic systems. In a first part, new ruthenium-based precatalysts have been developped for olefin metathesis. Depending on the nature of the spacer allowing the immobilization on a support, catalytic activity and recyclability can be controled while generating low contamination in the products. In a second part, new N-heterocyclic carbenes have been studied for copper-catalysed asymetric conjugate addition. A study of the differents groups of these ligands was done to determine their importance for reactivity and selectivity of this reaction.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF