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 sp(3) 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 mu M, 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.