Transformation of Aromatic Feedstocks into Value-Added Products via Biocatalytic Primary Amination

Abstract Aromatic compounds derived from fossil and biomass feedstocks represent an abundant class of chemical precursors whose selective functionalization remains a longstanding challenge. Here, we report the engineering of hemoprotein biocatalysts that enable both enantioselective aminative dearomatization and regioselective aryl C(sp2)–H primary amination of planar aromatic substrates. These transformations proceed under mild, aqueous conditions and use hydroxylamine as an inexpensive and readily available amine donor. Starting from a protoglobin variant having basal activity, directed evolution─guided by high-throughput HPLC-MS analysis and next-generation sequencing─uncovered biocatalysts that yielded either enantiomer of dearomatized naphthalenones bearing primary α-tertiary amines or primary aryl amines. Subtle repositioning of phenylalanines within the active site proved sufficient to invert enantioselectivity, and a key proline substitution enabled promiscuous activity toward C(sp2)–H primary amination. Reaction engineering and condition optimization bolstered the synthesis of aminated products from phenolic and naphtholic substrates (up to 1300 TTN), including a motif generated from lignin valorization. Together, this work establishes engineered protoglobin hemoproteins as a platform for biocatalytic primary amination and provides new starting points for the selective transformation of abundant aromatic feedstocks into value-added products.