Second-generation artificial hydrogenases based on the biotin-avidin technology:: Improving selectivity and organic solvent tolerance by introduction of an (R)-proline spacer

We report on our efforts to create efficient artificial metalloenzymes for the enantioselective hydrogenation of N-protected dehydroamino acids using streptavidin as host protein. Introduction of an (R)-proline spacer between the biotin anchor and the diphosphine moiety affords a versatile ligand Biot-(R)-Pro-1 which displays good (S)-selectivities in the presence of streptavidin (91% ee). The resulting artificial metalloenzyme [Rh(Biot-(R)-Pro-1)(COD)](+) subset of WT-Sav displays increased stability against organic solvents.