Trichosterol A, a unique 6/6/6/5/6-fused steroid–alkaloid hybrid with bioherbicidal activity from Trichoderma koningiopsis

Abstract

Naturally occurring steroids constitute a class of pharmacologically privileged scaffolds, owing to their rigid tetracyclic frameworks and well-defined stereochemistry, which have served as the basis for numerous clinically important drugs. In this study, four steroidal derivatives (1–4) were isolated from the endophytic fungus Trichoderma koningiopsis, which was obtained from the gut of a centipede collected in our Tongji campus. Remarkably, trichosterol A (1) represents the first naturally occurring steroid–alkaloid hybrid featuring a rare 6/6/6/5/6-fused pentacyclic skeleton incorporating an unusual 1,2-oxazine moiety. The structure of compound 1 was unambiguously determined by detailed NMR spectroscopic analysis and single-crystal X-ray diffraction. A plausible biosynthetic pathway for compound 1 is proposed. Furthermore, compound 1 exhibited notable herbicidal activity against Medicago sativa (alfalfa), suggesting its potential as a promising lead compound for the development of natural bioherbicides.