Highly Oxygenated Meroterpenoids from Fruiting Bodies of the Mushroom Tricholoma terreum

Four new meroterpenoids, terreumols A–D (1–4), with a rare 10-membered ring system, were isolated from the fruiting bodies of Tricholoma terreum. Their structures with absolute stereochemistry were determined by comprehensive spectroscopic methods, as well as single-crystal X-ray diffractions. Compounds 1, 3, and 4 were evaluated for their cytotoxicities against five human cancer cell lines; all of them exhibited inhibitory effects, with IC50 values comparable to those of cisplatin.