Biosynthesis of solanapyrone A, a phytotoxin of Alternaria solani

The building blocks and the origin of hydrogen and oxygen atoms in solanapyrone A (1) were determined by incorporation experiments employing sodium [1-13C]-, [1,2-13C2]-, [1-13C, 18O2]-, [1-13C, 2H3]-, [2-13C, 2H3]acetates and [S-13CH3] methionine; the labelling pattern supports the hypothesis that (1) is biosynthesized via the intramolecular Diels–Alder reaction.