Dassonmycins A and B, Polycyclic Thioalkaloids from a Marine Sponge-Derived Nocardiopsis dassonvillei SCSIO 40065

Two polycyclic thioalkaloides dassonmycins A (1) and B (2) were isolated from Nocardiopsis dassonvillei SCSIO 40065 associated with marine sponge Petrosia sp. Structures of 1 and 2 were elucidated by comprehensive spectroscopic analysis and confirmed by single-crystal X-ray diffraction experiments, to have a 6/6/6/6-fused tetracyclic ring featuring a naphthoquinone­[2,3-e]­piperazine­[1,2-c]­thiomorpholine scaffold. Compound 2 formed a caged core through an additional ether bridge. Both compounds exhibited moderate antibacterial and cytotoxic activities.