Oxepin Formation in Fungi Implies Specific and Stereoselective Ring Expansion

Oxepinamides are fungal oxepine-pyrimidinone-ketopiperazine derivatives. In this study, we elucidated the biosynthetic pathway of oxepinamide D in Aspergillus ustus by gene deletion, heterologous expression, feeding experiments, and enzyme assays. We demonstrated that the cytochrome P450 enzymes catalyzed highly specific and stereoselective oxepin ring formation.