Racemic 9-hydroxy-10-oxo-12(Z),l5(Z)-octadecadienoic acid [(±)-KODA] was synthesized via a coupling reaction between a diyne and an epoxide derived from methyl oleate as a key step. An optically active 9R-KODA was also synthesized by enantioselective lipase-catalyzed esterification of an allyl alcohol. Both synthetic (±)-KODA and 9R-KODA showed remarkable flower-inducing activity in Pharbitis nil.