New mimics of the acetate function in pheromone-based attraction

Several analogues of (Z)-8-dodecenyl acetate (la), the major pheromone component of the Oriental fruit moth, Cydia molesta, with chloroformate and lactone functional groups in place of the acetate moiety, were synthesized and investigated for their biological activity at four evaluation levels, i.e. by electroantennography (EAG), electrosensillography (ESG), short-range sexual stimulation and activation in the flight-tunnel. We found very strict requirements on the shape as well as on the electron distribution of the acetate group for a productive interaction with the receptor. The behavioral results showed that, among the analogues investigated, the chloroformate lb, alken-4-olide 2a and also dodecyl acetate (lc) possess significant (60-85%) inhibitory activities. Based on electrophysiological evidence demonstrating that (i) only lb is competing with the major pheromone component la for the same receptor sites on the male antennal sensilla, (ii) lc elicits moderate EAG but no ESG responses and (iii) 2a does not produce any electrophysiologicai response at all, three possible inhibitory mechanisms by which these analogues are acting could be distinguished