6.8- Dioxabicyclo octane bark-beetle

The U.S. Forest Service scientists in New York have isolated and identified chemical sex attractants used by elm bark beetles that are responsible for transmitting the fungus causing Dutch elm disease. Examples of attractants are 2,4-dimethyl-5-ethyl-6,8-dioxabicyclo [3.2.1] octane (called multistriatin) and 4-methyl-3-heptanol. In field trials an artificially produced mixture of the compounds has proved attractive to the elm bark beetle. 

Figure 6.12 Cyclization reactions of acyclic, unbranched and methyl-branched ketones to bicyclic acetals and cyclic alcohols in bark beetles. (A) Mountain pine beetle, Dendroctonus ponderosae formation of exo-brevicomin [(1 F ,5S,7fl)-(+)-7-ethyl-5-methyl-6,8-dioxabicyclo[3.2.1]octane] from (Z)-6-nonen-2-one (Vanderwel and Oehlschlager, 1992 Vanderwel ef a/., 1992a) ...

B) Western balsam bark beetle, Dryocoetes confusus formation of endo-brevicomin [(1 F ,5S,7S)-7-ethyl-5-methyl-6,8-dioxabicyclo[3.2.1 ]octane] from ( )-6-nonen-2-one (Vanderwel et a/., 1992a) (C) Spruce beetle, Dendroctonus rufipennis formation of frontalin [(1S, 5fl)-(-)-1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane] from 6-methyl-6-hepten-2-one (Perez ef a/., 1996 Francke etai, 1995 Francke and Schulz, 1999) (D) European elm bark beetle, Scolytus multistriatus hypothetical formation of oc-multistriatin [(1 S,2F ,4S,5F )-(-)-2,4-dimethyl-5-ethyl-6,8-dioxabicyclo[3.2.1]octane] from 4,6-dimethyl-7-octen-3-one (Francke and Schulz, 1999) and E The colored... 

Francke W., Schroder F., Kohnle U. and Simon M. (1996a) Synthesis of (lS,2R,5R)-2-ethyl-l,5-dimethyl-6,8-dioxabicyclo [3.2.1] octane, the aggregation pheromone of male beech bark beetle, Taphrorychus bicolor (Col., Scol.). Liebigs Ann. 10, 1523-1527. 

The terpenoid-exocrine theme emphasized by scolytid beetles was again evident when the chemical constitution of the secondary attractant for the smaller European elm bark beetle, Scolytus multistriatus, was elucidated. The aggregation pheromone was identified as a mixture of (-)-4-methyl-3-heptanol, 2,4-dimethyl-5-ethyl-6,8-dioxabicyclo [3.2.1]octane (multistriatin) (XXII), and (-)-a-cubebene (XXIII), a host-derived synergist (70). All three compounds are required for the maximum attraction of beetles. The inactive diastereomers of 4-methyl-3-heptanol and multistriatin did not inhibit the responses of airborne beetles. 

Examples include the alkylated 2,8-dioxabicyclo[3.2.1]octane (aro-brevicomin, 54), 6,8-dioxabicyclo[3.2.1]-octanes (frontalin, 55, and multistriatin, 56), and the 2,9-dioxabicyclo[3.3.1]nonane (57). Brevicomin, frontalin, and multistriatin are important components of the male or female pheromones of several bark beetle species. More recently, several hydroxylated 6,8-dioxabicyclo[3.2.1]octanes, including 58-60, have been identified from the mountain pine beetle, Dendroctonusponderosae Interestingly, frontalin (55) also represents an important component of the Asian elephant s male pheromone (Figure 20). ... 

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