Stereocontrolled Synthesis of Dafachronic Acid A, the Ligand for the DAF-12 Nuclear Receptor of <i>Caenorhabditis elegans</i>

An efficient synthetic route to the DAF-12 nuclear receptor ligand of <i>C. elegans</i>, dafachronic acid, is described that starts with the abundant plant sterol β-stigmasterol and proceeds in 37% overall yield. The synthesis establishes the structure of this rare nematode hormone.