Periconiastone A, an Antibacterial Ergosterol with a Pentacyclo[8.7.0.01,5.02,14.010,15]heptadecane System from Periconia sp. TJ403-rc01.

Periconiastone A (1), an ergosterol with an unprecedented pentacyclo[8.7.0.01,5.02,14.010,15]heptadecane system, was isolated from Periconia sp. TJ403-rc01. Its structure was assigned by extensive spectroscopic analyses and quantum-chemical 13C NMR and ECD calculations. A vinylogous α-ketol rearrangement and an aldol condensation reaction during biosynthesis were proposed as key steps for the formation of 1. Compound 1 showed antibacterial activity against Gram-positive S. aureus and E. faecalis with MIC values of 4 and 32 μg/mL, respectively.