Synthesis of hydroxy-α-sanshool

Abstract

Hydroxy-α-sanshool was synthesized in a 13% overall yield through eight steps, which included two Wittig reactions that were used to form the carbon skeleton with ethyl 2-oxoacetate and 2 E,4 E-hexadienal being reacted with the appropriate ylides. Impurities in the processes could easily be separated. Ethyl 6-hydroxy-2Z-hexenoate was converted to its E-isomer with catalysis by I2 and 2E,6Z,8E,10E-dodecatetraenoic acid was crystallized from a solution in 1% ethyl acetate in n-hexane.