Total Synthesis of Valerenic Acid, a Potent GABAAReceptor Modulator

The first total synthesis of the sesquiterpenoid valerenic acid, a constituent of Valeriana officinalis, is described. The compound is a potent modulator of the GABA(A) receptor and may thus be useful in the treatment of various dysfunctions of the central nervous system. The synthesis is enantio-, diastereo-, and regiocontrolled and utilizes an enyne-RCM, a metal-coordinated Diels-Alder reaction, a hydroxy-directed Crabtree hydrogenation, and a Negishi methylation as key steps.