Title: Monomeric Streptavidin Artificial Metalloenzymes for the Development of Novel Reaction Methodologies
Description: Reliable design of artificial metalloenzymes (ArMs) to access transformations not observed in nature remains a long-standing and important challenge. We report that a monomeric streptavidin (mSav) Rh(III) ArM permits asymmetric synthesis of α,β-unsaturated-δ-lactams via a tandem C-H activation and [4+2] annulation reaction. These products are readily derivatized to enantioenriched piperidines, the most common N-heterocycle found in FDA approved pharmaceuticals. Embedding a Rh cyclopentadienyl (Cp*) catalyst in the active site of mSav results in improved stereocontrol and a seven-fold enhancement in reactivity relative to the isolated biotinylated Rh(III) cofactor. With the goal of using protein engineering to improve the activity of monomeric streptavidin (mSav) ArM complexed to Rh(III), we also report computational calculations that demonstrate the effects of modifying the secondary coordination sphere. These findings have allowed us to engineer a more active mutant G49A that provides up to 67 more TON compared to WT mSav ArM.

Directed evolution techniques, when applied to ArMs, allows us to mimic the natural selection process and thereby dramatically increase the TON of the ArM. This technology has been used to develop an artificial aminobrominase with up to 2587 TON.