Enantioselective Synthesis of the Female Sex Pheromone of the Pink Hibiscus Mealybug, Maconellicoccus hirsutus

The pink hibiscus mealybug, Maconellicoccus hirsutus (Green), is an exotic insect pest and recently invaded Southern California and Florida. The female M. hirsutus releases the 2-methylbutanoate of a novel cyclobutanoid monoterpene alcohol (maconelliol) that together with lavandulyl 2-methylbutanoate constitutes the sex pheromone to attract males from a distance. Enantioselective syntheses of four different stereoisomers of the major component, maconelliyl 2-methylbutanoate 1, from alpha-pinene are reported. Absolute configurations of both naturally occurring maconelliyl 2-methylbutanoate 1 and the minor component, lavandulyl 2-methylbutanoate 2, have been established. Comparison of the analytical data of naturally occurring compounds with those of optically active synthetic isomers proved that both esters show the (R)-configuration at the alcohol and the (S)-configuration at acid moieties.