ENANTIOMERIC COMPOSITION OF GRANDISOL AND GRANDISAL PRODUCED BY PISSODES STROBI AND P-NEMORENSIS AND THEIR ELECTROANTENNOGRAM RESPONSE TO PURE ENANTIOMERS

Grandisol (cis-2-isopropenyl-1-methylcyclobutaneethanol) and its corre sponding aldehyde, grandisal, were previously isolated and identified as aggregation pheromone components for Pissodes strobi (Peck) and P. nemorensis Germar, but the enantiomeric ratios produced by these insec ts were not previously determined. We isolated grandisol and grandisal from males of both P. strobi and P. nemorensis. The insect-produced g randisol was derivatized with trifluoroacetic anhydride, and the enant iomeric composition was determined by gas chromatography on an optical ly active cyclodextrin glass capillary column. The insect-produced gra ndisal was first reduced to grandisol before derivatization. P. nemore nsis produced nearly 100% (1R,2S)-grandisol and nearly 100% (1S,2R)-gr andisal. P. strobi produced 99% (1R,2S)-grandisol and approximately 60 % (1R,2S)-grandisal. In electroantennogram (EAG) studies with live P. nemorensis and P. strobi, no significant differences were found betwee n the responses of males and females to racemic grandisol, racemic gra ndisal, or the 1R,2S and 1S,2R enantiomers of grandisol and grandisal, which is consistent with previous assertions that these compounds are aggregation pheromones. Although no studies to date with P. strobi ha ve demonstrated a behavioral response to grandisol and grandisal, P. s trobi antennae detected all enantiomers of grandisol and grandisal tes ted in EAG tests. The antennae of P. nemorensis responded significantl y more to (1R,2S)grandisal than to (1S,2R)-grandisal, despite producin g only (1S,2R)-grandisal.