Phomeroids A and B: two novel cytotoxic meroterpenoids from the deep-sea-derived fungus Phomopsis tersa FS441

Phomeroids A (1) and B (2), two novel meroterpenoids representing two types of skeletons, together with one known homologous analogue (3) were isolated from the deep-sea-derived fungus Phomopsis tersa FS441. Phomeroid A is the first example of tropolonic sesquiterpenes consisting of a highly fused 6/6/11/6/5/5 ring system, while phomeroid B is the first example of meroterpenoids featuring an unusual 7/6/11/6-5 spiral core skeleton. All of them showed considerable cytotoxicity against the tested cell lines, and their biosynthetic pathways were also discussed.