PERFLUORINATED MOTH PHEROMONES - SYNTHESIS AND ELECTROPHYSIOLOGICAL ACTIVITY

Perfluoroalkyl analogs of pheromone constituents were synthesized and responses from male antennal olfactory receptor neurons from three moth species were recorded during stimulation by these analogs. In each analog, the hydrophobic terminus, either a butyl or hexyl substituent on the (Z)-alkenyl chain, was replaced with a perfluorobutyl (Pfb, C4F9) or perfluorohexyl (Pfh, C6F13) moiety. Perfluoroalkyl analogs were more volatile than their hydrocarbon analogs, showing a decrease in gas chromatographic retention time by two to four methylene equivalents (Kovàts retention indices). Specialist neurons of male Heliothis zea responded to a 0.02-μg dose of (Z)-11-hexadecenal (Z11-16:Al) and a dose of 200 μg of Pfb-Z11-16:Al with similar spike discharge rates. The HS(a) neurons of Trichoplusia ni responded to a dose of 0.02 μg of Z7-14:OAc and a dose of 10 μg of Pfb-Z7-12:Ac with similar discharge rates. The same difference in sensitivity to Pfb-Z7-12:OH and Z7-12:OH was observed for the responses of the HS(b) neuron and for the responses of theNS(a) neurons to Pfb-Z9-14:Ac and Z9-14:Ac. Sensilla of Diatraea grandiosella similarly showed 100- to 1000-fold greater sensitivity to Z9-16-Al and Z11-16:Al than to Pfh-Z9-16:Al and Pfb-Z11-16:Al. Thus, replacement of terminal alkyl groups with perfluoroalkyl groups in pheromone components produced biologically active compounds with increased volatility and displaced electrophysiological response profiles. Because of the diminished receptor cell sensitivity, we suggest that the binding of the fluorinated analogs to a putative receptor is reduced as a result of less favorable interaction between the hydrophobic protein binding site and the more rigid and more polar perfluoroalkyl moiety. © 1990 Plenum Publishing Corporation.