Rapid Discovery of Antifungal α-Pyrone Analogs from Diaporthe kyushuensis ZMU-48-1 via an HSQC-Based DeepSAT Strategy

Endophytic fungi represent an extensive source of chemically diverse and bioactive polyketides. Herein, an HSQC-based DeepSAT-guided strategy was employed for the scaffold-prioritized isolation of metabolites from Diaporthe kyushuensis ZMU-48-1, an endophyte isolated from Acacia confusa. DeepSAT analysis of the semi-purified fractions identified an α-pyrone chemotype, which facilitated the targeted isolation of thirteen pyranone-type polyketides, including eight previously undescribed analogues, diaporthopyranone A–H (1–8). The structures of the new compounds were rigorously elucidated via comprehensive spectroscopic analysis (1D and 2D NMR and HRESIMS), while their absolute configurations were established by comparing experimental and TDDFT-calculated ECD data. All isolates (1–13) were screened for antifungal activity against nine plant pathogens. While most metabolites were inactive at 200 μg/mL, compound 4 inhibited Alternaria alternata and Valsa mali (MICs = 100 and 80 μg/mL, respectively), and compounds 6 and 8 exhibited selective inhibition against Colletotrichum musae (MICs = 60 and 80 μg/mL). These results expand the pyranone repertoire of the genus Diaporthe and underscore the utility of the HSQC–DeepSAT platform for the streamlined discovery of specific natural product scaffolds.