5. Synthesis of chiral pesticides

Safety and efficacy dictate that as far as possible, closely targeted products should be marketed, leading to the separation of stereoisomers. Methods for obtaining enantiopure molecules are now available. A reaction is stereospecific when the configuration of the product is related to that of the reactant. For two enantiomers, applied to each of them, it leads from one to the enantiomeric product of the one obtained with the other. For two diastereoisomers E and Z, applied to each of them, it leads from one to the product with a different configuration to that obtained from the other. A reaction is stereoselective when it leads to stereoisomers in different proportions. Cost, regulations and the product's ecological image are the main factors driving manufacturers' choices. Three production strategies have been selected.