Pyrrospirones K–Q, Decahydrofluorene-Class Alkaloids from the Marine-Derived Fungus Penicillium sp. SCSIO 41512

Seven new decahydrofluorene-class alkaloids, pyrrospirones K–Q (1–7), together with six known analogues (8–13) were isolated from the marine-derived fungal strain Penicillium sp. SCSIO 41512. Their structures were determined by extensive spectroscopic analysis, and their absolute configurations were established by single-crystal X-ray diffraction analysis and quantum chemical calculations of electronic circular dichroism spectra. Compounds 1 and 3 possess a novel decahydrofluorene-class alkaloid skeleton with a 6/5/6/8/5/6/13 and a 6/5/6/5/6/13 polycyclic system, respectively. Biologically, 13 displayed significant inhibitory activity against protein tyrosine phosphatases CD45, TCPTP, SHP1, and PTP1B with IC50 values of 8.1–17.8 μM, and 1, 2, 5, 8–10, 12, and 13 showed antibacterial activity against six pathogens. Their structure–activity relationship is also discussed.