Phosphane-based cyclodextrins as mass transfer agents and ligands for aqueous organometallic catalysis.

The replacement of hazardous solvents and the utilization of catalytic processes are two key points of the green chemistry movement, so aqueous organometallic catalytic processes are of great interest in this context. Nevertheless, these processes require not only the use of water-soluble ligands such as phosphanes to solubilise the transition metals in water, but also the use of mass transfer agents to increase the solubility of organic substrates in water. In this context, phosphanes based on a cyclodextrin skeleton are an interesting alternative since these compounds can simultaneously act as mass transfer agents and as coordinating species towards transition metals. For twenty years, various cyclodextrin-functionalized phosphanes have been described in the literature. Nevertheless, while their coordinating properties towards transition metals and their catalytic properties were fully detailed, their mass transfer agent properties were much less discussed. As these mass transfer agent properties are directly linked to the availability of the cyclodextrin cavity, the aim of this review is to demonstrate that the nature of the reaction solvent and the nature of the linker between cyclodextrin and phosphorous moieties can deeply influence the recognition properties. In addition, the impact on the catalytic activity will be also discussed.

How cyclodextrins can mask their toxic effect on the blood-brain barrier.

The toxicity of monosubstituted n-alkyldimethylammonium-beta-cyclodextrins (DMA-C(n)-CD with n=2, 4 and 12) towards endothelial cells of an in vitro model of the blood-brain barrier (BBB) was evaluated and compared to that of the native beta-CD. DMA-C(12)-CD was found to be non-toxic below 10mM due to the self-inclusion of the alkyl chain in the CD cavity. A high percentage of passage (30%) of DMA-C(12)-CD through the endothelial cells has been measured.