Title: Aspertaichunol A, an Immunomodulatory Polyketide with an Uncommon Scaffold from the Insect-Derived Endophytic Aspergillus taichungensis SMU01

Abstract: Aspertaichunol A (1), a polyketide with a novel scaffold, was isolated from the medicinal insect (Periplaneta americana)-derived endophytic Aspergillus taichungensis SMU01. Its structure was assigned on the basis of spectroscopic data and quantum chemical computational methods. Notably, 1 possesses an uncommon tricyclo[6.2.0.0^2,6]decane motif and an unusual bridgehead double bond (anti-Bredt system). A plausible biosynthetic pathway, involving a key intramolecular [2+2] cycloaddition and a reductive cyclization, is postulated. Finally, the immunomodulatory activity of 1 at 20 nM was evaluated by promoting Th9 cell differentiation from naive CD4⁺CD62L⁺ T cells.