ALKYLATIVE EPOXIDE REARRANGEMENT - A STEREOSPECIFIC APPROACH TO CHIRAL EPOXIDE PHEROMONES

The alkylative rearrangement of 1,2-epoxy-3-alkanol tosylates is applied to the synthesis of chiral epoxide pheromones. Attack at the terminal carbon atom of epoxy tosylates by lithioacetylenes and cyclization of the intermediate tosyloxy alcohols produces internal epoxides in high yield. The method is stereospecific: threo-epoxy tosylates give eL's-epoxides, and erythro-epoxy tosylates yield trans-epoxides. Several diastereomerically pure epoxides were prepared in high optical purity from chiral pool intermediates derived from sugars. Pheromone components prepared include (+/-)-cis-epoxyalkene 20 and both enantiomers of cis-epoxy diene 16, a female sex pheromone component of a number of lepidopteran species. These results demonstrate that alkylative rearrangement of 1,2-epoxy-3-alkanol tosylates complements existing methods for stereoselective synthesis of epoxides, including the Payne rearrangement and Sharpless epoxidation.