Propionates and Acetates of Chiral Secondary Alcohols: Novel Sex Pheromone Components Produced by a Lichen Moth Barsine expressa (Arctiidae: Lithosiinae)

Females of a lichen moth, Barsine expressa (Arctiidae, Lithosiinae), which inhabit Iriomote Island in Japan, were captured by a black-light trap, and the pheromone gland extract was analyzed by gas chromatography (GC) with an electroantennographic (EAG) detector, and by GC coupled with mass spectrometry. The females produced several EAG-active esters, and the mass spectrum of a major component indicated the mixture consists of propionates derived from C₁₇-saturated secondary alcohols, which were inseparable on the capillary GC column. In addition to these main components, the pheromone glands included two acetate derivatives of C₁₇ alcohols, and other propionates of C₁₆ and C₁₅ alcohols. The crude extract was treated with K₂CO₃, and a 1:1 mixture of C₁₇ alcohols with a C₆- or C₇-chain moiety was obtained. The two alcohols were uniformly converted into monodeuterated n-heptadecane by mesylation and succeeding LiAlD₄ reduction. This result revealed a straight-chain structure of the C₁₇ alcohols with the acyl groups located at the 7- or 8-position. Field tests on Iriomote Island showed that the synthetic esters were behaviorally active. A 1:1 mixture of racemic 7-propioxyheptadecane and 8-propioxyheptadecane, which were prepared from the secondary alcohols synthesized by a Grignard coupling reaction, attracted male moths. Furthermore, propionates of the alcohols synthesized enantioselectively by using a hydrolytic kinetic resolution with Jacobsen’s catalyst were evaluated. Only the traps baited with a mixture of the two esters with the same S-configuration significantly attracted B. expressa males. In the Tokyo area, the propionate mixture attracted a closely related species, Barsine aberrans aberrans.