Penerpenes A–D, Four Indole Terpenoids with Potent Protein Tyrosine Phosphatase Inhibitory Activity from the Marine-Derived Fungus Penicillium sp. KFD28

Four unusual indole-terpenoids, penerpenes A–D (1–4), along with two known ones paxilline (5) and emindole SB (6), were isolated from the marine-derived fungus Penicillium sp. KFD28. The absolute structures of 1–4 were elucidated on the basis of spectroscopic data and ECD spectra analysis along with quantum ECD calculations. Compounds 1 and 2 showed potent inhibitory activity toward protein tyrosine phosphatases (PTP1B and TCPTP). Plausible biosynthetic pathways of compounds 1–4 are proposed.