Asymmetric total synthesis of AK-toxins

A practical total synthesis of AK-toxins (AK-toxin I, ; II, ), host-specific toxins against the Japanese pear, has been achieved in 10% total yield, starting from the key intermediate . The (2E,4Z,6E)-conjugated triene system was successfully constructed by the use of the Stille coupling reaction between the (E,Z)-bromodiene () and (E)-stannylacrylate (). The (E,Z)-configuration of was established with excellent geometrical purity by palladium-catalyzed stereoselective hydrogenolysis of gem-dibromide (), which was derived from via the Wittig–Horner reactions.