Biocatalytic synthesis of n-n and c-n heterobiaryl atropisomers - proposal summary atropisomerism is a type of chirality that arises from restricted rotation about a bond

Introduction of atropisomerism to small-molecule drug candidates can improve potency, selectivity, and adme (absorption, distribution, metabolism, and excretion) properties. An underexplored class of atropisomers are heterobiaryl atropisomers featuring an n-n or c-n atropisomeric axis. These classes of atropisomers have demonstrated potent pharmaceutical properties. However, as compared to c-c atropisomers, there are relatively few enantioselective methodologies for their synthesis. Most strategies rely on the derivatization of substrates already containing the n-x bond (where x = n or c). An underexplored approach is the direct coupling of two heteroarene fragments that form the n-x bond atroposelectively. However, known methods require the pre- functionalization of starting materials, thereby limiting the generality of these strategies. Nature, on the other hand, synthesizes heterobiaryl atropisomers by a direct oxidative coupling, wherein an n-h and x-h bond undergo direct conversion into an n-x bond under mild reaction conditions. Flavin- dependent aromatic hydroxylases (fdah) are an enzyme class with demonstrated n-n and c-n coupling reactivity. The research outlined in this proposal will draw upon this known reactivity to develop general strategies for the synthesis of n-n and c-n heterobiaryl atropisomers. Towards this goal, i will employ bioinformatic techniques to develop a library of fdah enzymes to explore this unique coupling reactivity. From the reactivity profile of this fdah enzyme library, i will identify features of these enzymes that contribute to the site-selectivity of this oxidative coupling approach. Employing both enzyme library reactivity profiling and protein engineering, i will develop atroposelective n-n and c-n biocatalytic coupling strategies. The methods developed herein will provide access to a class of medicinally relevant atropisomers that are difficult to obtain by other approaches.