Cubebenes

The third component of the elm bark beetle pheromone (p T 4) is a-cubebene (34) which the beetle takes from the tree. Simple disconnections lead to ketone (35). What disconnection would you suggest next ... 

This approach has been used in two published syntheses of cubebene, though there is a problem in that control over the stereochemistry has not yet been perfected. 

Sampling time 60 min extraction temperature 80°C. Monoterpenes a-pinene, p-myrcene, a-phellandreneand limonene sesquiterpenes a-cubebene, a-copaene, p-elemene, p-caryophyllene, a-humulene, y-muurolene, p-eudesmene and caryophyllene oxide diterpenes cembrene A and isoincensole acetate. 

Figure 12.3 GC/MS (a) and THM GC/MS (b) curves of aged dammar. Peak assignments 2, a cubebene 3, copaene 4, ft bourbonene 8,10 12, cadinane type pyrolysis fragments 14 16, cadinene type pyrolysis fragments 17, calamanene type pyrolysis fragments 18 21, unidentified sesquiterpenoids 22, dammaradienone 23, dammaradienol 24, nor a amyrone 25, 28 nor olean 17 en 3 one 26, dammarenolic acid methyl ester 27, oleanonic acid 28, hydroxydammarenone 29, oleanonic aldehyde 30, ursonic acid methyl ester 31, ursonic aldehyde 32, nor (3 amyrone 34, 20,24 epoxy 25 hydroxy 3,4 seco 4(28) dammaren 3 oic acid methyl ester 35, 20,24 epoxy 25 hydroxy dammaren 3 one 36, dammaradienol...

Citronellol n-Decanal Ethyl butanoate 6-Methyl-5- a-p-Cubebene... 

The elm bark beetle pheromone contains three compounds multistriatin, the alcohol 12 and a-cubebene 13. At first we shall consider simple molecules like 12 but by the end of the book we shall have thought about molecules at least as complex as multistriatin and cubebene. 

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. 

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