K. Eiter
Oct 1, 1974
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0
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Journal
Biochemical Society Transactions
Abstract
After the discovery and isolation of lO-E,12-Z-hexadecadien-l-ol ‘bombycol’ by Butenandt et al. (1959, 1961a,b) and the h a 1 constitution classification and synthesis by Truscheit & Eiter (1962), not only of bombycol itself, but also of the other theoretically possible 10,12-hexadecadienols-(l), it was possible, initially by applying Butenandt’s method of determining the attractant unit in ng/ml, to make a quantitive statement about the biological activity (attractiveness) of a sex attractant on the corresponding insect. The attractant units of O.ooO1-0.1 ag/ml which could be well reproduced with bombycol, corresponded mathematically to concentrations of several hundreds to thousands of bomycol molecules/ml, which led to numerous problems at an early stage, particularly with respect to the absolute values of attractant units of, for instance, synthesized geometric isomeric 10,12-hexadecadien-l-ols that are considerably less effective than bombycol itself. These effects could not only be attributed to properties of the substance, but also to admixtures of bombycol molecules, perhaps originating from spontaneous rearrangement or because the selected methods of synthesis were not specific enough. Only the development of an analytic technique similar to the tracer method in nuclear chemistry could yield a solution to these problems, as the classical methods of gas chromatography, g.1.c. and use of 13C spectroscopy or mass spectroscopy did not allow any statements to be made about trace admixtures of geometric isomers. The electroantennagram method, developed by Schneider & Hecker (1956) and enhanced by Priesner (1973) by taking into consideration the electroantennagram-characteristic curves, permits investigation of the effects of sex attractants at the receptor sites. It has to date been used to determine the concentrations of, e.g. bombycol, in Bombyx moriat thereceptor site, and thesevalues were substantially different from those obtained by the original glass-rod method of Butenandt et ul. (1959, 1961a,b). With the electroantennagram method, the concentrations exceed, by several powers of ten, those obtained with the AUSo method (AUS0 is the equivalent term to LDS0 in toxicology). Applications of the electroantennagram method to the discovery of new pheromones have frequently led to spurious results, for example (f)-cis-gyplure, (+)-cis-gyplure, (+)-trans-gyplure, gyptol from Lymuntria dispar, propylures from Pectinophora gossypiella S., 2,2-dimethyl-3-isopropylidenecyclopropyl propionate from Periplaneta urnericana (American cockroach) (Jacobson, 1961), as well as the pheromone from Carpocupsa pomonella, which was detected by Roelofs et al. (1971) as 8-EJ0-E-dodecadien-1-01 on the basis of electroantennagram investigations after separation by gas chromatography, not discovered at all by McDonough et al. (1969, 1972) on reinvestigation of the codling moth but determined as active pheromone 7-methyl-3-propyl-2,2,6E-decadien-1-01, a constitution that did not correspond in n.m.r. spectra to an attractant synthesized stereospecifically; the correct constitution will therefore probably be 7methyl-3-propyl-2E,6Z-decadien-l-ol (Cook, 1973). We are currently engaged in our own investigations into new syntheses of disparlurs and gossyplures, taking into account the stereochemistry and the discovery of the erroneous use of inhibitory and masking effects ,which were used as arguments in biological quarters at the very time when the first insect-pest pheromones were available for characterization and when these earlier papers proved to be fundamentally incorrect in important respects. These earlier misleading developments are the reason why it is impossible at present to state whether or not sex attractants can be utilized technically as a method of environmentally positive pest control.