Biological Activities of the Analogs of the Aggregation Pheromone of Tribolium castaneum(Coleoptera : Tenebrionidae)

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Abstract
The biological activities of 7 optically active analogs of the aggregation pheromone of T. castaneum stereoselectively synthesized from (R)-(+)-citronellic acid (100% e.e. [enantiomeric excess]) and/or (S)-(-)-2-methyl-1-butanol (93% e.e.) were tested and compared with those of their corresponding racemates and the 4 optical isomers of the pheromone. the 4S-analogs showed no activity at doses of not less than 1000 ng; all 4R-analogs were active at 1.0-1000 ng, especially (4R, 8RS)-4,8-dimethyldecanal (VII) had strong activity showing a 40.3% of attractiveness at a dose of 1.0 ng. Th 8S-analog was repellent. The presence of the 4R methyl group was indispensable for the activity. The aggregation activities of the 2 optical isomers of the pheromone, (4R, 8R)- and (4R, 8S)-4,8-dimethyldecanals were tested in various mixtures of them. A (8:2) mixture was most active and significant difference even at a dose of 0.1 ng, which was about 10 times more attractive than (4R, 8R)-isomer alone. The (4R, 8S)-isomer had no activity at doses of not less than 10 ng when used alone. The (4R, 8S)-isomer acted as a synergist. This suggested the possibility that the natural pheromone of T. castaneum might be a mixture of (4R, 8R)- and (4R, 8S)-isomers.