Spectaterpenoids A–G, Sesterterpenoids with Unprecedented Polycyclic Ring System from Aspergillus spectabilis

Spectaterpenoids A-G (1-7), seven novel sesterterpenoids with five distinct skeleton types, along with one known analogue (8), were characterized from Aspergillus spectabilis. Notably, compound 1 was a nitrogenous sesterterpenoid possessing an unprecedented 5/3/8/6/5-fused pentacyclic system, while compounds 2 and 3 feature a novel 5/5/8/6/6/5-fused hexacyclic scaffold. Compounds 4 and 5 represent the first examples possessing a five-membered lactam bridge connecting C-5 and C-20 in variecolin derivatives. Plausible biosynthetic pathways for 1-8 were proposed.