Oxalierpenes A and B, Unusual Indole-Diterpenoid Derivatives with Antiviral Activity from a Marine-Derived Strain of the Fungus <i>Penicillium oxalicum</i>.
Zhang YH, Li L, Li YQ, Luo JH, Li W, Li LF, Zheng CJ, Cao F.
Oxalierpenes A and B (<b>1</b> and <b>2</b>), two unusual indole-diterpenoid derivatives, were obtained from the marine-derived fungus <i>Penicillium oxalicum</i>. The absolute configurations of <b>1</b> and <b>2</b> were elucidated by calculated TDDFT ECD and DP4plus methods. Oxalierpene A (<b>1</b>) represents the first indole-diterpenoid derivative with a five-membered ring of 4-hydroxy-5,5-dimethyldihydrofuran-3-one as a side chain. Oxalierpene B (<b>2</b>) has a unique 6/5/6/5/5/6/6/5/5 ring system. Compounds <b>1</b> and <b>2</b> showed antiviral activity against the H1N1 virus and respiratory syncytial virus (RSV), with IC<sub>50</sub> values ranging from 2.8 to 9.4 μM.