Synthesis and analysis of zingerone analogues as fruit fly attractants

Fruit fly species have a devastating impact on food production in Australia and other countries. With new restrictions on the use of certain organophosphate insecticides, other control methods, such as male annihilation technique (MAT), will be more important for crop protection. MAT depends on effective male lures to attract pests to toxicants. Zingerone is a natural product that is attractive to males of Bactrocera jarvisi, a species that responds only weakly to other lures. In a step towards more effective lures, a series of zingerone analogues were synthesised and characterised. Many analogues were synthesised by an Aldol-hydrogenation synthetic route. Volatility is considered an important factor in lure attraction and the measurement of the volatility of the analogues by differential scanning calorimetry showed that fluorinated compounds have a 7-10-fold greater vapour pressure than corresponding non-fluorinated compounds. Unexpectedly, the acetyl and formyl esters of zingerone were half as volatile as zingerone. Electroantennography experiments with B. tryoni and B. jarvisi indicated that fluorinated compounds generally produce a greater response and the two species have vastly different preferences for the methylenedioxy moiety. Limited laboratory cage bioassays conducted with B. tryoni indicated that some of the fluorinated compounds tended to elicit a positive response.