Microascones, Decahydrofluorene-Class Alkaloids from the Marine-Derived Fungus Microascus sp. SCSIO 41821

Abstract

Eight new decahydrofluorene-class alkaloids, microascones A and B (1 and 2), 2,3-epoxyphomapyrrolidone C (3), 14,16-epiascomylactam B (4), 24-hydroxyphomapyrrolidone A (5), and microascones C−E (6−8), along with five known analogs (9−13) were isolated from the marine-derived fungus Microascus sp. SCSIO 41821. Compounds 1 and 2 have an unprecedented complex macrocyclic alkaloid skeleton with a 6/5/6/5/6/5/13 polycyclic system. Their structures and absolute configurations were determined by spectroscopic analysis, quantum chemical calculations of ECD spectra, and 13 C NMR chemical shifts. Compounds 10−13 showed selective enzyme inhibitory activity against PTPSig, PTP1B, and CDC25B, and 4, 9, and 10 exhibited strong antibacterial activity against seven tested pathogens. Their structure−bioactivity relationship was discussed, and a plausible biosynthetic pathway for 1−8 was also proposed.

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“…SCSIO 41821, obtained from a gorgonian coral, produces a range of decahydrofluorene alkaloids including microascone A 4 with an unprecedented heptacyclic skeleton. 4 Taberdisine A 5 , from the cultivated variety Tabernaemontana divaricata ‘Dwaft’, has a novel bisindole skeleton. 5 Taberdisine A 5 shows insecticidal activity, which may explain the insect resistance of this variety.…”