(E)-6-NONEN-2-ONE AND (Z)-6-NONEN-2-ONE - BIOSYNTHETIC PRECURSORS OF ENDOBREVICOMIN AND EXOBREVICOMIN IN 2 BARK BEETLES (COLEOPTERA, SCOLYTIDAE)

The ability of (E)- and (Z)-6-nonen-2-one to serve as precursors of the common scolytid pheromones endo- and exo-brevicomin was examined in vivo. When mountain pine beetles (MPB), Dendroctonus ponderosae Hopkins, or western balsam bark beetles (WBBB), Dryocoetes confusus Swaine, were exposed to [6,7-D2](E)-6-nonen-2-one, the endo-brevicomin produced was enriched with two deuterium atoms per molecule (as determined by GC-MS), indicating that (E)-6-nonen-2-one served as a precursor of this pheromone. Similarly, when the beetles were exposed to 14,4-D2](Z)-6-nonen-2-one, the exo-brevicomin produced was enriched with two deuterium atoms per molecule. Evidence in support of biological relevance of the latter observation include: (1) (Z)-6-nonen-2-one was found in the volatiles of male MPBs and WBBBs, indicating that this is a natural metabolite; (2) the exo-brevicomin produced by MPB was shown to be of natural (+) chirality by complexation chromatography; and (3) female WBBBs and MPBs (which are not known to produce exo-brevicomin) produced significantly less exo-brevicomin when exposed to the precursor than did the males.