Total Synthesis of Altenusin and Alterlactone

Abstract

The resorcylic lactone alterlactone, a mycotoxin produced by alternaria sp., was synthesized for the first time. The total synthesis was achieved in nine steps with 69% yield starting with acetal-protected phloroglucinic acid and 6-bromopiperonal, where the longest linear sequence consists of five steps. Key step is a ­Suzuki coupling used for the construction of the central biaryl bond. When the final deprotection with cleavage of benzyl ethers (yielding unprotected alterlactone) was performed in a less polar solvent the biaryl mycotoxin altenusin was obtained.