Enantiocomplementary Synthesis of Tetrahydrofurans by Engineered Halohydrin Dehalogenases

Chiral tetrahydrofurans are prevalent structural motifs in biologically active compounds, approved drugs and natural products, but relevant enantiocomplementary synthesis remains underdeveloped. In this study, wild type halohydrin dehalogenase HheC from Agrobacterium radiobacter AD1, was first discovered to enable the intramolecular substitution of δ-halohydrins for the formation of tetrahydrofurans but with unsatisfied activity and stereoselectivity. Through structure-guided protein engineering, two completely enantiocomplementary variants T134M and P84L/W139A of HheC were obtained for the synthesis of tetrahydrofurans by the kinetic resolution of δ-halohydrins (both giving products with up to 99% e.e., E>200). This research unveiled the halohydrin dehalogenases’ catalytic ability to form chiral cyclic ethers larger ring size than three-membered epoxides, which has hitherto been unexplored, and provided an enzymatic synthesis access to valuably enantiocomplementary tetrahydrofurans.