New Phthalides and Isochromanone Derivatives from the Deep‐Sea‐Derived Fungus <i>Penicillium bialowiezense</i> A3

Two new phthalide derivatives, namely bialowalides A (1) and B (8), and one new isochromanone analogue biourgalide C (11), together with 8 known phthalides (2-7, 9, and 10) as well as two known isochromanones (12 and 13) were discovered from the EtOAc extract of the deep-sea-derived fungus Penicillium bialowiezense A3. The structures were resolved on the basis of extensive spectroscopic analyses (NMR and HRESIMS data), in association with the modified Mosher's method and ECD data for the determination of the absolute configurations. All isolated secondary metabolites (1-13) were tested their antiviral activities against the SARS-CoV-2 trVLP pseudovirus at a concentration of 25 μM. As a result, compounds 1, 5, 11, and 12 exhibited the inhibitory effects against the luminescence at 46.2 %, 39.6 %, 45.5 %, and 48.8 %, respectively.