ChemInform Abstract: INSECT SEX ATTRACTANTS

Abstract

The sex attractants described in the literature for certain pests have been incorrectly classified. The corresponding synthetic products, inasmuch as they show any biological activity, are therefore not identical with the genuine pheromones and, in comparison with, for example, attractant units of 'Bombycol', represent at most pheromone mimics. All the inhibition-, maskingand synergism-effects so far described with such artefacts, cannot therefore be regarded as proof of any such biological effects. For those sex attractants which have recently been isolated from pink bollworm moth, (Pectinophora gossipiella S.), and which have also in fact been found in Sitotroga cerealella, such as 7Z, 1 1Z-hexadecadienyl acetate, we were able to develop a new synthesis of three geometrical isomers. By investigating their gas chromatographic behaviour, we have demonstrated the difficulty of separating such isomers (in contrast to previously published results), thus illustrating the problems involved in determining hundreds or thousands of distinct sex attractant molecules in a mixture. The sex attractant of the silk moth Bombyx mon was discovered by Butenandt et al.1 in 1959. The total synthesis of Bombycol (bE, 12Z-hexadecadien-1-ol was first achieved in our laboratory2 and established the complete constitution unambiguously. Since then we have seen that this new class of natural products (designated by P. Karlson as pheromones) is made up of substances with a clearly reproducible biological activity in concentrations which had never been observed prior to the discovery, isolation and total synthesis of Bombycol. The respective values (Figure 1) of 10— 12 and 10—13 tg/ml (say, 10_18 and 10-19 g/ml) given by Butenandt et al.1 and by Truscheit and Eiter2 as an attractant unit (AU) for Bombycol were derived from a test which, according to Butenandt, allowed the quantitative determination of the attractant unit in the laboratory. In this procedure an accurately weighed sample of 1OE, 12Z-hexadecadien-1-ol, or one of its three theoretically possible geometrical isomers (1OZ, 12E-; 1OZ,12Z-; and 1OE,12E-) which were synthesized simultaneously, dissolved in low-boiling light petroleum ether, and a series of dilutions prepared. When a glass rod, after being dipped into the petroleum ether solution, was then held 5 cm away from the antennae of 150 male silk moths, each resting individually on the bottom of a covered beaker, 75 insects (50 per cent) had to show definite buzzing reactions. This test method, admittedly far from satisfactory from the scientific viewpoint, did, however,