Stereoselective construction of the tricyclic core of neoliacinic acid

The tricyclic core of the plant-derived sesquiterpene natural product neoliacinic acid was synthesized using a novel synthetic strategy. The pivotal synthetic transformations are construction of the key bicyclic ether-bridged intermediate by sequential deployment of metal carbenoid C−H insertion and ylide-forming reactions and installation of the lactone portion of neoliacinic acid by an acid-catalyzed intramolecular ring-opening reaction of an epoxide with a carboxylic acid

Multiple solvent signal presaturation and decoupling artifact removal in 13C{1H} nuclear magnetic resonance

International audienceThe analysis by proton-decoupled carbon-13 nuclear magnetic resonance spectroscopy of samples dissolved in solvents presenting strong multiple resonances can be facilitated by the suppression of these resonances by multisite presaturation. The advantage drawn from this operation is the elimination of the possible artifacts that arise from the solvent signals in non-optimized decoupling conditions. Solvent presaturation was implemented on glycerol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,3-butanediol with at least 94 % on-resonance efficiency and a bandwidth of less than 50 Hz measured at 50 % signal intensity decrease. The experimental measurement of the signal suppression bandwidth leads to unexpected selectivity profiles for close-frequency resonances. Computer resolution of the Bloch equations during multisite presaturation provide an insight into the origin of the observed profile perturbations

Green microparticles based on a chitosan/lactobionic acid/linoleic acid association. Characterisation and evaluation as a new carrier system for cosmetics

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