Atta texana 4-Methyl-3-heptanone

Riley et aK (157) identified S-(+)-4-methyl-3-heptanone as the alarm pheromone of Atta texana and reported that it was 100X more active as an alarm releaser than the unnatural (-)-enantiomer. Similarly, Benthuysen and Blum (158) demonstrated that workers of Pogonomyrmexbadius were more sensitive to the S(+) enantiomer than to the R-(-) enantiomer of this compound, which is the primary alarm pheromone of this species. 

Fig. 15.4 Predicted active spaces of 4-methyl-3-heptanone for workers of Atta texana, 20 s after deposition of 10% of mandibular gland contents, at the point arrowed, on a flat surface in still air. The area of attraction is shaded (compare Figs 15.5 and 15.6) (calculated from data in Moser et aL, 1968).

Methyl-3-heptanone (386a, Scheme 68), the alarm pheromone of the Texas leaf-cutting ant (Atta texana) was synthesized by Riley et al 173, 174) and required resolution of the intermediate, racemic 2-methyl-4-pentenoic acid (384). A convenient synthesis of methyl 4-methylpyrrole-2-carboxylate (392), the trail pheromone of A. texana, has been reported by Sonnet (775) (Scheme 69). Formylation of ester (390) with CUCHOMe and AICI3 gave predominantly the desired 4-formyl derivative (391). 

Riley, R. G., and R. M. Silverstein Synthesis of 5-(-1-)-4-methyl-3-heptanone, the principal alarm pheromone of Atta texana, and its enantiomer. Tetrahedron 30, 1171—1174 (1974). 

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