A New Secondary Metabolite from Alternaria Alternata : Structure Elucidation and Total Synthesis of Altenuic Acid IV

A putative intermediate in the biosynthesis of altenuic acids I–III was isolated from Alternaria alternata in the 1950ies and a sample survived over the decades. This resorcylic lactone named altenuic acid IV is a composite of a resorcylic and a muconic acid. Its structure was confirmed by NMR spectroscopy and by total synthesis. Altenuic acid IV was here obtained starting with 2‐bromo‐4,6‐dimethoxybenzene and 4‐methylbenzene‐1,2‐diol with a total yield of 20 %. The synthesis was achieved in ten steps where the longest sequence consists of seven steps. Key steps were an oxidative ring opening of a bromocresol furnishing a bromomuconate and its Suzuki coupling with a resorcylate‐derived boronate.