Organic synthesis and chemical ecology.

The roles of organic synthesis in chemical ecology are discussed, with many examples. The structure, including the absolute configuration, of a semiochemical (signal substance) can be established by enantioselective synthesis. Only through synthesis can a semiochemical be obtained in an amount sufficient for decisive biological evaluation. Rigorous enantioselective synthesis of semiochemicals to provide their pure enantiomers has shown that they are not always enantiomerically pure. Synthesis of the stereoisomers of semiochemicals has clarified their structure-bioactivity relationships to reveal the unprecedented diversity in the stereochemical aspects of pheromone communications.