Bioactive natural products and chirality

Mori's synthetic works on bioactive natural products in general and pheromones in particular started about 40 years ago to establish their absolute configurations and also to clarify their stereochemistry-bioactivity relationships. Results indicate that bioactive natural products are not always enantiomerically pure, and the stereochemistry-bioactivity relationships are not simple but complicated. For example, neither (R)- nor (S)-sulcatol, the aggregation pheromone of an ambrosia beetle, is behaviorally bioactive, whereas their mixture is active. In the case of olean, the sex pheromone of the olive fruit fly, its (R)-isomer is active against the males and the (S)-isomer is active against the females. Recent synthesis of two new insect pheromones is discussed to illustrate the modern methods in enantioselective synthesis.