Total Synthesis of Selligueain A, a Sweet Flavan Trimer

The first total synthesis of selligueain A (4), a plant-derived sweet polyphenol, has been achieved. The key step was the de novo synthetic approach to the selectively protected epiafzelechin unit 10, which was divergently converted to three flavan units 7, 8, and 9. These components were combined by an orthogonal activation and annulation method, enabling assembly of the characteristic trimeric structure with single and double interflavan linkages.