Contrôle de la chiralité axiale à l’aide d’arynes et en absence de métaux de transition

International audienceThe modular construction of enantioenriched biaryl derivatives is presented. This approach is based on (a) an almost quantitative access to polybrominated precursors via a transition metal-free aryl-aryl coupling, the ARYNE-coupling, (b) the regioselective introduction of a traceless chiral auxiliary (an enantiopure para-tolylsulfinyl group), (c) the chemoselective functionalization of this auxiliary and (d) subsequent regioselective functionalization of the remaining bromine atoms without any racemization during these steps. Next, the atropo-selective coupling of in situ generated arynes and aryllithiums bearing various chiral auxiliaries (tert-butylsulfoxide, para-tolylsulfoxide, tartrate-derived chiral diethers and oxazolines) is described and applied to the formal synthesis of (-)-steganacin. La construction modulaire de dérivés biaryliques énantioenrichis est présentée. Cette approche est basée sur (a) un accès quasi quantitatif aux précurseurs polybromés via un 2 couplage aryle-aryle sans métaux de transition, le couplage ARYNE, (b) l'introduction régiosélective d'un auxiliaire chiral (un groupe para-tolylsulfinyl énantiopur), (c) la fonctionnalisation chimiosélective de cet auxiliaire et (d) la fonctionnalisation régiosélective subséquente des atomes de brome restants sans racémisation au cours de ces étapes. Ensuite, le couplage atropo-sélectif à l'aide d'arynes générés in situ et d'aryllithiums portant divers auxiliaires chiraux (tert-butylsulfoxyde, para-tolylsulfoxide, diéthers dérivés du tartrate et des oxazolines chirales) est décrit et appliqué à la synthèse formelle de la (-)-stéganacine

Transition-Metal-Free Synthesis of a Known Intermediate in the Formal Synthesis of (-)-Steganacin

International audienceThe formal synthesis of both enantiomers of a natural axially chiral biaryl, steganacin is reported. The previously developed atropo-diastereoselective coupling of an aryne and an aryllithium (the 'ARYNE coupling') allows for this synthesis. In each step, the axial configuration of the biaryl could be maintained. The key intermediate of literature was accessed without using transition metals, demonstrating the interest of the ARYNE coupling as a complement or an alternative to transition metal-catalyzed couplings

Madagascan day geckos (Phelsuma spp.) exhibit differing responses along a gradient of land-use change

Madagascar is a key priority for global conservation efforts, as much of its diverse and highly endemic biota is threatened by deforestation. Despite this threat, there are limited data on the responses and tolerances of herpetofaunal species to landscape change. This study investigated the response of Madagascan day geckos (Phelsuma spp.) to deforestation in Nosy Be, Madagascar. We selected six sites along a gradient of land-use change: two in Sambirano rainforest (“Forest”), two in secondary, fragmented forest (“Fragment”), and two in agricultural plantations (“Orchard” and “Cropland”). We conducted a series of time-constrained searches at each site. The mean encounter rate of Phelsuma geckos (geckos detected per person/hour) was greater in agricultural sites than Forest sites, but no difference was detected between Forest and Fragment or Fragment and agricultural areas. Three species were encountered more frequently in agricultural land than forested sites, but this was not true for Phelsuma seippi, an endangered species on the IUCN Red List. These results suggest that adaptive, generalist species may benefit from anthropogenic land-use change, whereas specialist species will suffer. Our study emphasizes the importance of extending research beyond the borders of protected forests to include anthropogenically disturbed areas

UDRIVE: the European naturalistic driving study

UDRIVE is the first large-scale European Naturalistic Driving Study on cars, trucks and powered two wheelers. The acronym stands for “European naturalistic Driving and Riding for Infrastructure & Vehicle safety and Environment”. Naturalistic driving can be defined as a study undertaken to provide insight into driver behaviour during every day trips by recording details of the driver, the vehicle and the surroundings through unobtrusive data gathering equipment and without experimental control. Data collection will take place in seven EU Member States. Road User Behaviour will be studied with a focus on both safety and environment. The UDRIVE project follows the steps of the FESTA-V methodology, which was originally designed for Field Operational Tests. Defining research questions forms the basis of the study design and the specification of the recording equipment. Both will be described. Although the project has yet to start collecting data from drivers, we consider the process of designing the study as a major result which may help other initiatives to set up similar studies

Prisoner's Dilemma cellular automata revisited: evolution of cooperation under environmental pressure

We propose an extension of the evolutionary Prisoner's Dilemma cellular automata, introduced by Nowak and May \cite{nm92}, in which the pressure of the environment is taken into account. This is implemented by requiring that individuals need to collect a minimum score $U_{min}$, representing indispensable resources (nutrients, energy, money, etc.) to prosper in this environment. So the agents, instead of evolving just by adopting the behaviour of the most successful neighbour (who got $U^{msn}$), also take into account if $U^{msn}$ is above or below the threshold $U_{min}$. If $U^{msn}<U_{min}$ an individual has a probability of adopting the opposite behaviour from the one used by its most successful neighbour. This modification allows the evolution of cooperation for payoffs for which defection was the rule (as it happens, for example, when the sucker's payoff is much worse than the punishment for mutual defection). We also analyse a more sophisticated version of this model in which the selective rule is supplemented with a "win-stay, lose-shift" criterion. The cluster structure is analyzed and, for this more complex version we found power-law scaling for a restricted region in the parameter space.Comment: 15 pages, 8 figures; added figures and revised tex

Efficacité de la thérapie par ondes de choc extracorporelles dans les tendinopathies rebelles.

Cet article présente notre expérience de l'utilisation d'un appareil délivrant des ondes de choc extra-corporelles dans le traitement des tendinopathies chroniques chez des sportifs, ce nouveau type de traitement utilisé en orthopédie du sport depuis le début des années 1990 a été appliqué chez 55 patients souffrant de tendonopathies chroniques entrainant des symptômes douloureux et une incapacité à la pratique sportive. Les manifestations duraient depuis 4 mois au moins et tous les patients avaient arrêté le sport lors de la consultation initiale, 4 à 6 séances de traitement ont été nécessaires pour obtenir chez 50 de nos patients une diminution significative des douleurs (p &lt; 0.01) et une reprise satisfaisante de l'activité physique (p &lt; 0,01). Chez 5 patients ce traitement a été inefficace. Les auteurs considèrent que ce nouveau traitement semble efficace lors des tendinopathies chroniques. Cependant, des investigations complémentaires sont nécessaires pour améliorer les connaissances quant au mécanisme d'action de la thérapie Nous n'avons observé aucun effet secondaire grave