Sterhirsutins A and B, Two New Heterodimeric Sesquiterpeneswith a New Skeleton from the Culture of Stereum hirsutumCollected in Tibet Plateau.

Twonew heterodimeric sesquiterpenes, sterhirsutins A (1)and B (2), and two new sesquiterpenes, hirsutic acidsD–E (3and 4), were identified fromthe culture of Stereum hirsutum. The absolute configurationsin 1and 2were confirmed by single-crystalX-ray diffraction experiments and electronic circular dichroism (ECD)calculations. Compounds 1and 2are likelybiosynthesized from a hirsutane-type sesquiterpene and α-humuleneby a hetero-Diels–Alder cycloaddition. Compounds 1–4showed cytotoxicity against K562 and HCT116cell lines. [ABSTRACT FROM AUTHOR]