Aspertaichunol A, an Immunomodulatory Polyketide with an Uncommon Scaffold from the Insect-Derived Endophytic <i>Aspergillus taichungensis</i> SMU01.

Aspertaichunol A (<b>1</b>), a polyketide with a novel scaffold, was isolated from the medicinal insect (<i>Periplaneta americana</i>)-derived endophytic <i>Aspergillus taichungensis</i> SMU01. Its structure was assigned on the basis of spectroscopic data and quantum chemical computational methods. Notably, <b>1</b> 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 <b>1</b> at 20 nM was evaluated by promoting Th9 cell differentiation from naive CD4⁺CD62L⁺ T cells.