Directed Evolution of an Feᴵᴵ-Dependent Halogenase for Asymmetric C(sp³)-H Chlorination

By using structure-guided directed evolution, the substrate scope of the FeII and a‑ketoglutarate dependent halogenase Wi‑WelO15 from Westiella intricata HT-29-1 was engineered to enable chemo-, regio- and diastereoselective chlorination of unactivated C(sp3)-H bonds using NaCl as chlorine source. While FeII dependent enzymes are often oxygen sensitive, variants of this halogenase could be screened in lysates under aerobic conditions. The new biocatalysts offer a sustainable approach for mild, late-stage chlorination on mg-scale of non-natural hapalindoles containing a ketone instead of an isonitrile functionality, thereby unlocking them for preparative biocatalysis.