RAPID AND CONVERGENT ASSEMBLY OF NATURAL BENZO[c]PHENANTHRIDINES BY PALLADIUM/NORBORNENE CATALYSIS

A straightforward total synthesis of a small panel of natural benzo[c]phenanthridines is described. The selective coupling of an aryl triflate with a bromobenzylamine by means of palladium/norbornene joint catalysis and a sequential transfer hydrogenation deliver these alkaloids in one pot. Dihydrophenanthridines initially formed undergo dehydrogenation smoothly while norbornene acts both as a catalyst for their assembly and as a sacrificial olefin in their dehydrogenatio

Effect of summer fire on cursorial spider (Aranei) and beetle (Coleoptera) assemblages in meadow steppes of Central European Russia

Fire is an important structuring force for grassland ecosystems. Despite increased incidents of fire in European steppes, their impact on arthropod communities is still poorly studied. We assessed short-term changes in cursorial beetle and spider assemblages after a summer fire in the meadow steppe in Central European Russia. The responses of spider and beetle assemblages to the fire event were different. In the first post-fire year, the same beetle species dominated burnt and unburnt plots, the alpha-diversity of beetle assemblages was similar, and there were no pronounced changes in the proportions of trophic groups. Beetle species richness and activity density increased in the second post-fire year, while that of the spiders decreased. The spider alpha-diversity was lowest in the first post-fire year, and the main dominants were pioneer species. In the second year, the differences in spider species composition and activity density diminished. The main conclusion of our study is that the large-scale intensive summer fire caused no profound changes in cursorial beetle and spider assemblages of this steppe plot. Mitigation of the fire effect is explained by the small plot area, its location at the edge of the fire site and the presence of adjacent undisturbed habitats with herbaceous vegetation

ANALYSE DES FACTEURS D'ORDRE DES MÉTAUX DE TRANSITION DANS LES PHOSPHURES ET ARSÉNIURES MM'P ET MM'As

Les études magnétiques, par spectrométrie Mössbauer, par diffraction des neutrons et des rayons X sur les composés MM'P et MM'As ont mis en évidence un ordre très marqué des métaux de transition 3d et 4d, qui ne peut s'expliquer simplement que dans une description cristallochimique analogue à celle des oxydes. Les 4 facteurs d'ordre : facteur géométrique, nombre d'électrons d, effets de champ cristallin et transfert électronique s-d sont discutés successivement.The 3d and 4d transition metal ordering in MM'P and MM'As pnictides has been studied by Mössbauer spectroscopy, neutron and X ray diffraction, magnetic measurement. Like in the crystallochemistry of oxides, the order can be correlated with the non metal surrounding of the transition metal site. Four ordering factors : size factor, d electron number, crystalline field and s-d electron transfert are discussed

Identification of irradiation in coded black pepper samples by different physical methods

International audienceThe experiment had been carried out on four black pepper samples coded A, B, C, D. Two physical methods (viscosimetry with two different sample preparation and electron spin resonance) were used to detect irradiated samples. Both viscosimetry preparation methods (10% for heat gelatinization, 8% for non heat gelatinization) showed significant differences in apparent viscosity of coded samples and gave similar results at the examined concentrations. However, heat gelatinization gives greater differences in viscosity between the different samples. All the examined methods showed that sample D was not irradiated, but samples A and C were irradiated. Regarding the results of viscosity measurements sample A and C had to be irradiated at about 8 kGy (according to the calculations of identification number from the literature and our experience). Sample B could have been irradiated at a very low level or long ago according to ESR results, but it was not irradiated according to the results of viscosimetry. Identification of irradiation >8 kGy in black pepper samples is possible using these methods after one month storage at ambient temperature. In well organised conditions all the measurements can be carried out in 3 h. The applied dose for coded black pepper samples were the following: A = 8 kGy, B = 0 kGy, C = 8 kGy, D = 0 kG

Long-term high fructose and saturated fat diet affects plasma fatty acid profile in rats

As the consumption of fructose and saturated fatty acids (FAs) has greatly increased in western diets and is linked with an increased risk of metabolic syndrome, the aim of this study was to investigate the effects of a moderate (10 weeks) and a prolonged (30 weeks) high fructose and saturated fatty acid (HFS) diet on plasma FA composition in rats. The effects of a few weeks of HFS diet had already been described, but in this paper we tried to establish whether these effects persist or if they are modified after 10 or 30 weeks. We hypothesized that the plasma FA profile would be altered between 10 and 30 weeks of the HFS diet. Rats fed with either the HFS or a standard diet were tested after 10 weeks and again after 30 weeks. After 10 weeks of feeding, HFS-fed rats developed the metabolic syndrome, as manifested by an increase in fasting insulinemia, total cholesterol and triglyceride levels, as well as by impaired glucose tolerance. Furthermore, the plasma FA profile of the HFS group showed higher proportions of monounsaturated FAs like palmitoleic acid [16:1(n-7)] and oleic acid [18:1(n-9)], whereas the proportions of some polyunsaturated n-6 FAs, such as linoleic acid [18:2(n-6)] and arachidonic acid [20:4(n-6)], were lower than those in the control group. After 30 weeks of the HFS diet, we observed changes mainly in the levels of 16:1(n-7) (decreased) and 20:4(n-6) (increased). Together, our results suggest that an HFS diet could lead to an adaptive response of the plasma FA profile over time, in association with the development of the metabolic syndrome