Functional Biosynthetic Stereodivergence in a Gene Cluster via a Dihydrosydnone N -oxide

Chirality features a critical role in the biochemistry of life and often only one enantiomeric series is observed (homochirality). Only few natural products have been obtained as racemates, e.g. the quorum-sensing signal valdiazen produced by Burkholderia cenocepacia H111. In this study, we investigated its biosynthetic gene cluster and discovered that both the enantiomerically pure ( R )–fragin and the racemic valdiazen are obtained from the same pathway. This stereodivergence is based on the unusual heterocycle dihydrosydnone N -oxide intermediate, as evident from gene knockout, stable isotope feeding experiments, and mass spectrometry experiments. Both non-enzymatic racemisation via keto-enol tautomerisation and enzyme-mediated dynamic kinetic resolution were found to be crucial to this stereodivergent pathway. This novel mechanism underpins the production of configurationally and biologically distinct metabolites from a single gene cluster. Our findings highlight the intricate design of an intertwined biosynthesis pathway, providing a deeper understanding of microbial secondary metabolism related to microbial communication.