Two New Eudesmane‐Type Sesquiterpene from Clonostachys sp. Y6‐1and Their Cytotoxic Activity

Abstract Two undescribed eudesmane‐type sesquiterpenoids together with four known compounds were isolated from Clonostachys sp. Y6‐1 associated. Their chemical structures were unambiguously determined by NMR, mass spectrometry, and 13 C‐NMR calculation as well as DP4+ probability analyses. The absolute configurations of compounds 1 and 2 were determined by ECD calculation and X‐ray single‐crystal diffraction methods. Furthermore, all isolates were evaluated for in vitro cytotoxic activities against MCF‐7, HCT‐116, MDA‐MB‐231, and SW620 cancer cells. Among them, bioactivity evaluation of compound 5 revealed that weak activity (IC 50 =66.55±0.82 μM) against SW620.