Microsphaerones A and B, Two Novel γ-Pyrone Derivatives from the Sponge-Derived Fungus Microsphaeropsis sp.

Two new metabolites, microsphaerones A (1) and B (2), were identified from the EtOAc extract of the culture of an undescribed fungus of the genus Microsphaeropsis, isolated from the Mediterranean sponge Aplysina aerophoba. Compounds 1 and 2 represent the first examples of γ-pyrone derivatives of the fungal genus Microsphaeropsis. The structures of the compounds were elucidated on the basis of comprehensive spectral analysis (1H, 13C, 1H−1H COSY, HMQC, and HMBC NMR, as well as low- and high-resolution ESI and EIMS experiments). The (S)-2-methylsuccinic acid moiety present in 1 was established by GC−MS analysis of a hydrolysis product.