A Six‐Oxidase Cascade for Tandem C−H Bond Activation Revealed by Reconstitution of Bicyclomycin Biosynthesis

As a commercial antibiotic, bicyclomycin (BCM) is currently the only known natural product targeting the transcription termination factor rho. It belongs to a family of highly functionalized diketopiperazine (DKP) alkaloids and bears a unique O‐bridged bicyclo[4.2.2]piperazinedione ring system, a C1 triol, and terminal exo‐methylene groups. We have identified and characterized the BCM biosynthetic pathway by heterologous biotransformations, in vitro biochemical assays, and one‐pot enzymatic synthesis. A tRNA‐dependent cyclodipeptide synthase guides the heterodimerization of leucine and isoleucine to afford the DKP precursor; subsequently, six redox enzymes, including five α‐ketoglutarate/Fe 2+ ‐dependent dioxygenases and one cytochrome P450 monooxygenase, regio‐ and stereoselectively install four hydroxy groups (primary, secondary, and two tertiary), an exo‐methylene moiety, and a medium‐sized bridged ring through the functionalization of eight unactivated C−H bonds.