Ammosamides: Structures of Cell Cycle Modulators from a Marine-Derived Streptomyces Species

From the ocean: Ammosamides A (1) and B (2) were isolated from a marine‐derived Streptomyces species collected in the Bahamas. The structures of these chlorinated tricyclic pyrroloquinoline alkaloids were solved using X‐ray crystallographic techniques. Ammosamide A (1) was shown to contain an unusual thio‐γ‐lactam ring. Both metabolites show specific nanomolar cytotoxicity against selected cancer cell lines.