Antiviral Chlorinated Drimane Meroterpenoids from the Fungus Talaromyces pinophilus LD-7 and Their Biosynthetic Pathway.

Ten new drimane meroterpenoids talarines A-J (1-10), along with six known analogues (11-16), were isolated from desert soil-derived fungus Talaromyces pinophilus LD-7. Their 2D structures were elucidated by comprehensive interpretation of NMR and HRESIMS data. Electronic circular dichroism calculation was used to establish their absolute configurations. Compounds 2, 10, and 11 showed antiviral activities toward vesicular stomatitis virus with IC₅₀ values of 18, 15, and 23 nM, respectively. The structure-bioactivity relationship indicated that chlorine substitution at C-5 contributed greatly to their antiviral activities. Finally, we identified a new halogenase outside the biosynthetic gene cluster, which was responsible for C-5 halogenation of the precursor isocoumarin 17 as a tailoring step in chlorinated meroterpenoids assembly.