Alterbrassicicene A, a Highly Transformed Fusicoccane-Derived Diterpenoid with Potent PPAR-γ Agonistic Activity from Alternaria brassicicola

Alterbrassicicene A (1), a fusicoccane-derived diterpenoid with an unprecedented framework, together with two known biosynthetic intermediates (2 and 3), were characterized from Alternaria brassicicola. The absolute structure of 1 was assigned by extensive spectroscopic analyses and quantum chemical calculations. Compound 1 represents a newly transformed monocyclic carbon skeleton of a highly functionalized diterpenoid bearing unique dihydro-2(3H)-furanone and 2-cyclopenten1-one motifs. Compound 1 was the first fusicoccane-derived diterpenoid functioning as a potent PPAR-gamma agonist (EC50 = 744.1 nM).