Catalyse biomimétique avec des foldameres a structure heliocidale comportant des motifs oligo-(thio)urées

Resumo

Bioinspired Catalysis using Oligourea Helical FoldamersCatalysis and folding are two closely interwoven notions in Nature particularly among enzymes, and by extension can be applied tosynthetic catalysts designed by chemists. Artificial monomers have been created for two decades to synthesize new oligomeric molecular architectures with a high propensity to fold, which are called foldamers. In many systems, folded structure is stabilized by a strong hydrogenbonding network, in a similar way to biopolymer structures. These folded backbones may provide significant advantages as catalyst as they could offer cooperativity in ligand binding, a greater stabilization of charged intermediates and then a minimization of entropic cost of the transition state binding. They constitute a class of potential organocatalysts which deserves more investigation. Organocatalysis is an area of strong interest nowadays because of the lower toxicity of the catalysts and meta free procedures, their modularity and easiness to handle them.But generally high loading (5-20 mol%) are needed to perform chemical transformations with good yields and good stereoselectivities. The synergistic effect brought by the well-defined structures of foldamers through the strong hydrogen-bonding network can be in favour of a decrease of the catalyst loading.