Canadian Forest Service Publications
Synthesis of 9-geranylterpinolene as a mixture of isomers, and synthesis of α- and β-springene, possible kairomones of the beech leaf-mining weevil, Orchestes fagi (L.). 2018. Mayo, P. D.; Silk, P. J.; Abeysekera, S. D.; MaGee, D. I. Synthetic Communications Volume 48, Issue 14
Issued by: Atlantic Forestry Centre
Catalog ID: 40366
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The beech leaf-mining weevil, Orchestes fagi (L.), also known as the beech flea weevil, is a common and widespread pest of beech, Fagus sylvatica L., in its native Europe. It now appears to be well established in Nova Scotia, Canada. We have previously reported the synthesis of 9-geranyl-p-cymene and 9-geranyl-α-terpinene, as they are both found in eclosing beech buds, and have researched the synthesis of other diterpenes that are isomers of 9-geranyl-α-terpinene. We now wish to report a synthesis of the diterpene 9-geranylterpinolene as a mixture of isomers, as a novel diterpene, and as a possible kairomone of O. fagi.
Plain Language Summary
A new-to-chemistry synthesis of 9-geranylterpinolene as a mixture of isomers, which are molecules with the same atoms but different bonding arrangements, is outlined. This molecule is itself an isomer of 9-geranyl-α-terpinene, a compound found in the volatiles of eclosing beech buds. Also, three other molecules that are isomers of 9-geranyl-α-terpinene were synthesized using methods found in the literature; these molecules are trans,trans,trans-α-springene, cis,trans,trans-α-springene, and all trans-β-springene.
Previously, the Silk research group, by examining the volatile organic compounds emitted by eclosing or opening beech tree buds using a technique known as solid phase microextraction (SPME), has shown the presence of two diterpenes (organic molecules having 20 carbons), which were identified as 9-geranyl-α-terpinene and 9-geranyl-p-cymene. The latter molecule was found to be attractive to the beech weevil, thus it is a kairomone: a molecule produced by one species (the beech tree) and detected by, and used to the advantage of, another (the beech weevil, which mates and lays eggs on the newly opened beech buds). Several other unidentifiable diterpenes that are isomers of 9-geranyl-α-terpinene were also found in beech bud volatiles; thus, we directed our efforts toward synthesizing as many isomers of this molecule as possible, with the possibility of testing them as lure treatments for beech weevil in the 2018 field season. To this end, syntheses of 9-geranylterpinolene as a mixture of isomers; trans,trans,trans-α-springene, cis,trans,trans-α-springene, and all trans-β-springene as a three-component mixture and all trans-β-springene in pure form are described in this paper.