Pinene and Derivatives for Stereospecific Syntheses of Chiral Monoterpenes

8 a-Pinene and Derivatives for Stereospecific Syntheses of Chiral Monoterpenes 

The production of pure (i )-(-)-linalool involves hydroperoxidation of (].R,2S,5R)-(+)-pinane by air oxygen the pinane enantiomer is obtained by eatalytie hydrogenation of (+)-a-pinene. Another catalytic hydrogenation eonverts the hydroperoxide to (l/ ,2i ,5/ )-(-)-2-pinanol which opens its eyelobutane ring by pyrolytic cycloreversion to the target compound with its pleasant flowery odor, widely used in perfumery instead of bergamot or French lavender. 

Bark beetles of the genus Ips are pests which attack pine and spruce trees. They use ipsdienols as aggregation pheromones, Ips confusus emitting the (5)-(-l-)-, and Ips paraconfusus the (.K)-(-)-enantiomer The beetles receive the myrcenes (section 2.2) occurring in conifers with their food and metabolize them to ipsdienols some evidence for de-novo synthesis by the bugs is also reported. In order to catch the beetles, pheromone traps are supplied with both enantiomers of ipsdienol which are produced from (-l-)-verbenone, a constituent of the Spanish verbena oil (section 2.4.3). This terpenone, also available by oxidation of a-pinene, is isomerized to the enantiomers of 2(10)-pinen-4-one via three steps (reduction, protonation, oxidation). After separation, both enantiomers are reduced by lithiumaluminumhydride. Pyrolytic cycloreversion of the resulting diastereomeric 2(10)-pinen-4-ols provides the enantiomers of ipsdienol 

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