Ipsenol and ipsdienol, pheromones of Ips bark beetles

Professor Jean-Pierre Vitd s bioassay revealed (S)-lll to be bioactive also as the aggregation pheromone of Ips grandicollis, while (R)- V was neither bioactive nor inhibitory.114 

In the case of ipsdienol (112), the stereochemistry-bioactivity relationship is much more complicated and interesting. My first synthesis of (/ )-(—)-ipsdienol (112 ) in 1976 from (fC j-glyccraldchyde allowed the assignment of S-configuration to (+)-ipsdienol isolated by Silverstein.115 Our second synthesis to provide both the enantiomers of ipsdienol employed the enantiomers of malic acid as starting materials.113 That synthesis, however, was lengthy and yielded the final products of 90% ee due to the partial racemization in the course of the synthesis. 

Later biological studies on the enantiomers of ipsdienol revealed the following interesting facts. Ips paraconfusus employs (S )-(+)-112 as the pheromone, while Ips calligraphus and Ips avulsus use (R)-(—)-112. Ipspini in New York employs a mixture of (R)-112 and (S)-112 = 32-56 68-44, while that in California uses a mixture of (R)-112 and (S)-112 = 89-98 11-2. Thus, different enantiomers are employed by different species or subspecies. 

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