Enantiomeric α-pyrone derivatives with immunosuppressive activity from Talaromyces adpressus

Five pairs of undescribed enantiomeric α-pyrone derivatives (±)-adprepyrones A-E (±1-±5), together with an unreported congener adprepyrone F (6), and 6-[(E)-3-Hydroxyprop-1-enyl]-4-methoxy-5-methyl-2-pyrone (7), recently reported as synthetic compound, were isolated from the fungus Talaromyces adpressus. Their structures with absolute configurations were elucidated by HRESIMS, 1D and 2D NMR, electronic circular dichroism calculations, and single-crystal X-ray diffraction analyses. (±)-Adprepyrone A (±1) possesses an unreported carbon skeleton formed by the fusion of an α-pyrone derivative with nicotinamide. Compounds (+)-2, (±)-4, (±)-5, and 7 showed moderate inhibitory activity against concanavalin A (ConA)-induced T lymphocyte proliferation with IC₅₀ values ranging from 8.9 to 19.8 μM.