Synthesis and field examinations of the sex pheromone of the diamondback moth, Plutella xylostella Linnaeus (Lepidoptera: Plutellidae) in the Mekong Delta of Vietnam
Tác giả: Đinh Thị Chi và Lê Văn Vàng
The diamondback moth (Plutella xylostella) is one of the most destructive pests of cruciferous vegetables in the Mekong Delta of Vietnam. In order to apply sex pheromones as tool for a sustainable management program, the sex pheromone components of P. xylostella, (Z)-11-hexadecenal (Z11-16:Ald), (Z)-11-hexadecenyl acetate (Z11-16:OAc) and (Z)-11-hexadecen-1-ol (Z11-16:OH) were synthesized using a Wittig reaction as a key step, and their attraction activities were evaluated in cabagge fields. The synthesis of the three C16 monoenyl compounds was started from commercialized 11-bromo-1-undecanol. This C11 bromohidrine was converted into the methoxymethyl (MOM) ether and heated with Ph3P. The produced phosphonium salt was treated with NaN(SiMe3)2 to make the corresponding ylide, which was coupled with C5 aldehyde to prepare an MOM ether of the C16 monoenyl alcohol. Its deprotection produced prospected Z11-16:OH (>96% geometric purity) in 42.9% overall yield. Following Pyridinium chlorochromate (PCC) oxidation and acetylation of Z11-16:OH gave Z11-16:Ald and Z11-16:OAc, respectively. In the field, traps baited with a synthetic mixture of Z11-16:Ald, Z11-16:OAc and Z11-16:OH in a ratio of 5:5:1 or 5:5:0.1 caught many P. xylostella males as well as with a virgin female. Furthremore, the field tests confirmed that Z11-16:Ald and Z11-16:OAc were essential components for the attraction, and Z11-16:OH played an auxilary role.