Chirality of Israeli pine bast scale, Matsucoccus josephi (Homoptera: Matsucoccidae) sex pheromone

The absolute configuration of the sex pheromone of the Israeli pine bast scale, Matsucoccus josephi, was determined as (2E,5R,6E,8E)-5,7-dimethyl-2,6,8-decatrien-4-one, designated here as R-E with 10% (2E,5S,6E,8E)-5,7-dimethyl-2,6,8-decatrien-4-one, designated as S-E. The chirality of the quantitatively minor Z isomer was (2E,5R,6Z,8E)-5,7-dimethyl-2,6,8-decatrien-4-one-(R-Z ). Chiral assignments were made by comparative gas chromatographic (GC) analysis of natural M. josephi pheromone with stereoselectively synthesized stereoisomers on a chiral Cyclodex-B column, which separated the enantiomers with baseline resolution. In gas chromatographic-electroantennographic detection (GC-EAD) analysis of the racemic Z and E isomers, the latter elicited the stronger antennal response by male M. josephi. In GC-EAD of all four stereoisomers, employing the chiral column, R-E was the most active stereoisomer. In field tests R-E attracted 10 times more males of M. josephi than did S-E. The racemic E/Z pheromone mixture, containing all four stereoisomers in approximately equal amounts, attracted as many male M. josephi as did an equivalent amount of R-E, indicating that the other stereoisomers are not inhibitory. The same keto-diene moiety with the same chiral center and configuration in all three known Matsucoccidae sex pheromones implies a common biosynthetic pathway and phylogenetic relationships