Resolution of epoxydienes by reversed-phase chiral HPLC and its application to stereochemistry assignment of mulberry looper sex pheromone

Resolution of insect pheromonal cis-epoxydiene racemates derived from (Z,Z,Z)-3,6,9-trienes was examined with a reversed-phase chiral HPLC column. The results showed that a Chiralcel OJ-R column was suitable for separating the enantiomers having a C-17-C-23 unsaturated straight chain except for 9,10-epoxydienes with a C-21-C-23 chain. To determine the absolute configuration of the separated enantiomers, each of the optically active epoxydienes was hydrogenated over Pd-BaSO4 and its behavior was examined on this chiral column by cochromatography with the corresponding chiral epoxy compound having a saturated chain, which was prepared via a Sharpless epoxidation reaction. This analysis showed that the dextrorotatory C-17-C-23 3,4- and 6,7-epoxydienes and C-17-C-20 9,10-epoxydienes with shorter R(t)s possess (3S,4R)-, (6S,7R)-, and (9R,10S) configurations, respectively, and the levorotatory enantiomers with longer R(t)s possess the opposite configuration. An abdominal tip extract of the mulberry looper Hemerophila artilineata Butler (Lepidoptera: Geometridae: Ennominae), included (9S,10R)-(Z,Z)-cis-9,10-epoxy-3,6-octadecadiene as a main sex pheromone component. The synthetic (9S,10R)-9,10-epoxydiene, rather than its antipode, elicited strong antennal and behavioral responses from the male moths in electrophysiological and field tests.