Armochaetoglobins K–R, Anti‐HIV Pyrrole‐Based Cytochalasans from Chaetomium globosum TW1‐1

Eight rare pyrrole‐based cytochalasans, termed armochaetoglobins K–R (1–8), along with three known analogues (9–11), were isolated from the solid culture broth of Chaetomium globosum TW1‐1, a symbiotic fungus derived from the medicinal terrestrial arthropod Armadillidium vulgare. Their structures were elucidated using a combination of spectroscopic analysis, a single‐crystal X‐ray diffraction experiment, and an electronic circular dichroism (ECD) calculation. Compounds 4–8 represent the first examples of chaetoglobosin‐type cytochalasans with an sp3 methine carbon at C‐18. All of the isolates were evaluated for their anti‐HIV activities in vitro, and compounds 2–4, 7, 8, and 10 showed significant anti‐HIV activities, with EC50 values ranging from 0.11 to 0.55 μM, and selectivity index (SI) values ranging from 12.33 to 75.42. A plausible biosynthetic pathway was proposed to explain the origin of the pyrrole ring.