Chetocochliodins A‑I, Epipoly(thiodioxopiperazines) from Chaetomium cochliodes

Nine new epipoly­(thiodioxopiperazine) (ETP) analogues, chetocochliodins A-I (1–9), along with two known ones, chetoseminudins E and C (10 and 11), were purified from the fungus Chaetomium cochliodes. The planar structures and absolute configurations of these new compounds were determined by extensive NMR spectroscopic analysis, CD spectra, and chemical reactions. Shielding effects from the indole on the 3-SCH3/3-OCH3/3-OCH2- groups facilitated the determination of relative configuration of the analogues. Compound 9 was cytotoxic, suggesting the importance of the sulfide bridge for the diketopiperazine bioactivities.