Frontalin structure

R=OH). With less polar chloride substituents, however, the RhuA dia-stereoselectivity is reduced and a considerable fraction of the FucA configurated product (40%) is also formed. Interestingly, alkaline cyclization in the latter occurs with an inverse preference to furnish 177, which contains the enantiomeric bicyclic [3.2.1] structure shared by the FruA product 175 as well as by (S)-( — )-frontalin 178, the aggregation pheromone of the southern pine beetle Dendroctonus frontalis. 

First identified in Asian elephants during a headspace analysis of volatiles collected from secretions of the musth temporal gland of adult males,156 frontalin (52) is a bicyclic ketal, which is structurally reminiscent of the male mouse priming pheromone component 3,4-dehydro-ara-brevicomin (37). Frontalin (52), Z-7-dodecen-l-yl acetate (51), was already known because of its chemosensory role in the insect world it is an aggregation pheromone in bark beetles.157 Interestingly, the ratio of the two enantiomers of frontalin (52) changes with age and stage of musth and elicits different behavioral responses.158... 

Synthesis of those insect aggregation pheromones having bridged structures may have important economic consequences. Multistriatin (120) is an aggregation pheromone of a European elm bark beetle. A stereoselective synthesis "" has been reported from tartaric acid. A delightfully simple synthesis " of frontalin (121), a pheromone of the pine beetle, is by photolysis of heptane-2,6-dione in methanol-titanium chloride. We also note further photochemical studies... 

Here is an example. The pheromone frontalin is a remarkable compound used by both insects and by elephants to attract a mate. Its structure and H NMR spectrum are shown below. 

Abstract Compounds with a 1,2-, 1,4- and 1,6-dioxygen pattern and related bifunctional structures are presented. Disconnection of the internal bonds results in illogical synthons because of the mismatch of charges in the patterns with an even number of C atoms between the functional groups. Three-membered heterocyclic rings are presented as an important class of illogical nucleophiles in the retrosyn-thesis of the 1,2-difunctional pattern. Retrosynthesis of the 1,6-dicarbonyl pattern by reconnection and rctro-Birch reduction of the aromatic building block is related to chemoselective Birch reduction and ozonolysis in the synthetic route. The retrosynthesis and synthesis of salbutamol and asymmetric synthesis of —)-frontalin are presented. 

Figure 4.12. Molecular structures of (-F)- and (—)-frontalin Figure 4.13. Molecular structures of D- and L-luciferin Figure 4.14. Molecular structures of d- and L-cysteine...

Similar calculations of the charges on the oxygen atoms of multi-striatin gave values very close to those of endo- and xo-brevicomin. The substantially greater negative charge on the oxygen atoms of frontalin is not apparent from a comparison of the structures of these compounds. 

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