Asymmetric Hydrogenation And Hydroformylation Catalyzed By Artificial Metalloenzyme

Artificial metalloenzymes(ArMs)are versatile hybrids of homogeneous and enzymatic catalysts,which are created by incorporation of abiotic catalytic cofactors into functionalized protein scaffolds modified and evolved via chemistry and molecular chemistry.Along with the rapid development of biologic technology,construction and applications in organic synthesis of ArMs attract extensive attention.In this dissertation,two kinds of ArMs based on supramolecular interactions and covalent bond have been employed in the asymmetric hydrogenation of 2-phenylacrylic acid or hydroformylation of styrene.Firs of all,a series of supramolecular ArMs have been designed via introducing different biotinylated bidentate phosphine rhodium complexs into the cavity of commercial host(strept)avidin protein,which depends on the high affinity of(strept)avidin for biotin.?-Phenylacrylic acid was chosen as model substrate and hydrogenation was selected as model reaction to investigate the catalytic activity and stereoselectivity of these ArMs.ArMs screening and reaction optimization revealed that full conversion and good ee value(up to 73%)were obtained with catalyzed by biotin-avidin ArM.These ArMs were generated in a simple way and were resistant to denaturation,on the other hand,large amount of proteins were added during hydrogenation.Moreover,the stereoselectivity of these ArMs remains to be improved.Subsequently,similar supramolecular biotin-streptavidin ArMs for hydroformylation of styrene have been generated by a combination of biotinylated bidentate phosphine rhodium complexs and streptavidin expressed in Escherichia coli.We hypothesized that AutoDock theoretical result was instructive to the evolution of biotin-streptavidin ArMs.Pivotal intermediates were selected as ligands while streptavidin as a receptor to conduct AutoDock calculation.With computing result analysed and pre-estimated,we began to evolve ArMs via site-directed mutagenesis of amino acids and adjusting the location of cofactor in protein cavity.A comparison of theoretical result and catalytic performance of upgraded biotin-streptavidin ArMs demonstrated that AutoDock calculation is a feasible method for the evolution of ArMs.Though these biotin streptavidin ArMs exhibited regioselectivity in some degree,poor catalytic activity and stereoselectivity of hydroformylation were obtained under the reaction conditions.Finally,a series of novel ArMs based on covalent binding between catalytic chlorosubstituted phosphine rhodium complex and HaloTag protein expressed in Escherichia coli have been designed for the asymmetric hydrogenation of ?-phenylacrylic acid.After preliminary screening of reaction conditions,35% conversion and 9% ee value were obtained.