Bacterial Cytochrome P450 for Oxidative Halogenated Biaryl Coupling

ABSTRACT

Biaryl motifs are fundamental structural elements in many pharmaceuticals, agrochemicals, and advanced materials. Traditional synthetic approaches for biaryl bond formation often require harsh conditions, costly catalysts, and prefunctionalized starting materials, which limit their efficiency, sustainability, and substrate scope. Enzymatic catalysis offers a more environmentally benign alternative. However, biocatalysts capable of directly coupling halogenated biaryl compounds remain largely underexplored. Here, we report the functional characterization of the marine-derived cytochrome P450 enzyme Bmp7, which catalyzes the formation of halogenated biaryls. We began by defining the product profile of recombinant Bmp7 using its native substrate 2,4-dibromophenol (1) and confirmed the dominant ortho-ortho C-C homocoupled product as MC21-A. Screening a halogenated aromatic substrate library revealed that Bmp7 binds and catalyzes the coupling of 17 halogenated phenols, as evidenced by spectral shift assays, LC-HRMS, HRMS/MS, and GC-MS analyses. Two homocoupled products were structurally confirmed by NMR analysis to possess ortho-ortho C-C linkages. In addition to efficient homocoupling, Bmp7 catalyzed heterocoupling reactions between substrate 1 and 16 other substrates, producing mixtures of homocoupled and heterocoupled halogenated biphenols. X-ray crystallography revealed the binding of two substrate 1 molecules within the active site, while DFT calculations supported a single-radical reaction mechanism, shedding light on the mechanistic basis of the coupling reaction. Together, these findings establish a foundation for future efforts in enzyme engineering and the development of biocatalytic strategies for synthetic applications.