Abstract
Five new α-pyrones, diaporpyrones G-K (1-5) and three new γ-butenolide derivatives, porbutenolides A-C (6-8), along with seven known compounds (9-15), were isolated from the culture extract of the endophytic fungus Diaporthe sp. CCY4. Their structures were elucidated by comprehensive spectroscopic analysis, including 1D/2D NMR and HRESIMS data. The absolute configurations of 7 and 8 were assigned using electronic circular dichroism (ECD) calculations. All compounds were evaluated for inhibitory activity against ubiquitin-specific peptidase 4 (USP4). Compounds 2, 5, 9, and 13 exhibited significant anti-ubiquitination effects at 40 μM, with 13 showing the most potent inhibition (IC(50) = 20.85 μM).