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 th e 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 configuratio n of the separated enantiomers, each of the optically active epoxydienes wa s hydrogenated over Pd-BaSO4 and its behavior was examined on this chiral c olumn by cochromatography with the corresponding chiral epoxy compound havi ng a saturated chain, which was prepared via a Sharpless epoxidation reacti on. This analysis showed that the dextrorotatory C-17-C-23 3,4- and 6,7-epo xydienes 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 abdom inal tip extract of the mulberry looper Hemerophila artilineata Butler (Lep idoptera: 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 beh avioral responses from the male moths in electrophysiological and field tes ts.