Aurovertins from a Marine-Derived Penicillium Species and Nonenzymatic Reactions in Their Formation

Six new aurovertins (1–6) and a new citreoviridin derivative (7), together with six known analogues (8–13), were isolated from the marine-derived Penicillium sp. OUCMDZ-5930. Their structures were determined based on detailed spectroscopic analysis and ECD calculations. The putative nonenzymatic formation from citreoviridin to various aurovertins was presented, which was confirmed by chemical transformations. These results provide new insights into the formation mechanism of the 2,6-dioxabicyclo[3.2.1]octane ring system present in aurovertin-type natural products.