Spined citrus bug

Hemiacetal 25 [(3 ,4S,l E)-3,4-bis(r-butenyl)tetrahydro-2-furanol] is the male pheromone of the spined citrus bug (Biprorulus bibax). Scheme 38 summarizes Mori s synthesis of 25 [61]. Claisen rearrangement (A B) and lipase-catalyzed asymmetric acetylation [meso-C >(5S,6R)-D] were the two key steps of the synthesis. Further purification of D was executed at the stage of its crystalline derivative E. In this particular case, the unnatural (3S,4R,l E)-25 was as active as the natural (3R,4S,VE)-25. Accordingly, a more efficient synthesis of ( )-25 was achieved by the rearrangement of F, avoiding the use of toxic HMPA [62]. 

R,4S)-dibul-l- enyl- tetrahydrofuran-2-ol H OH Spined citrus bug BiproruUis hibax) M Claisen rearrangement [174]... 

The spined citrus bug (Biprorulus bibax) is a pest of citrus in southern Australia. The major component (74, Figure 4.5) of the male-produced pheromone of B. bibax was isolated and identified by the joint work of James in Australia and Oliver et al. in the USA. Oliver found by chiral GC analysis that the insect produces a single enantiomer of 74. In 1992 I became interested in clarifying the absolute configuration of this pheromone, because Dr. Oliver requested me to do so. 

Bioassays of 74 and 74 in Australia showed them to be equally active as the pheromone. However, B. bibax produces only (3R,4S)-74 as revealed by GC analysis.24 Thus, spined citrus bugs in Australia do not discriminate between the enantiomers of their aggregation pheromone. This is similar to the fact that even a perfumer cannot discriminate between camphor enantiomers. 

I explained this category in the case of the German cockroach pheromone (104), and also discussed the spined citrus bug pheromone [(3/ ,4S)-74], whose opposite enantiomer was as active as the pheromone itself. Females of the maritime pine scale Matsucoccusfeytaudi) use (3.S ,7R)-118 as the sex pheromone. Its OR,1R )-isomcr also showed bioactivity similar to the natural pheromone, while M. feytaudi males responded very weakly to the two other stereoisomers. It therefore seems that only the stereochemistry at C-7 of 118 is important for the expression of pheromone activity.139... 

Suzuki T, Morita K, Ikemiyagi H, Watanabe K, Hiroi K, Katoh T (2006) Synthesis of the hemiacetal pheromone of the spined citrus bug biprorulus bibax utilizing an iridium catalyzed oxidative lactonization. Heterocycles 69 457-461... 

Preparation of half-acetate (5S, 6/ )-11, which was converted to the pheromone of the spined citrus bug. 

Asymmetric acetylation of mcso-diol 10 with vinyl acetate and lipase AK gave (5S,6R)-11 of 88% ee. This was purified by derivatization to 12, which could be recrystallized. The resulting pure 12 was converted to the pheromone of the spined citrus bug (Figure 24.6) [9]. 

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