Diaporisoindoles A–C: Three Isoprenylisoindole Alkaloid Derivatives from the Mangrove Endophytic Fungus Diaporthe sp. SYSU-HQ3

Diaporisoindoles A (1) and B (2), two novel isoprenylisoindole alkaloids, and an unusual diisoprenylisoindole dimer diaporisoindole C (3), together with a precursor tenellone C (4) were all isolated from the endophytic fungus Diaporthe sp. SYSU-HQ3. The absolute configurations of 1–4 were elucidated by spectroscopic analysis, X-ray diffraction, and quantum chemical calculations. Diaporisoindole A (1) and tenellone C (4) exhibited inhibitory activity against Mycobacterium tuberculosis protein tyrosine phosphatase B with IC₅₀ values of 4.2 and 5.2 μM.