Locustol and its analogues

A new method of synthesis of the locust gregarization pheromone, locustol, is described, the pathway being from guaiacol to acetyl-isoacetovanillone, to isoacetovanillone, to 5-ethylguaiacol. These substances were all checked for their infrared spectra and were bioassayed. Only 5-ethylguaiacol affected chiasma frequency, hopper colour, and the $\text{F}\text{C}$ morphometric ratio, although guaiacol had some effect on chiasma frequency. Hopper and adult faeces, as well as grasshopper faeces, were steamextracted, tested by infrared spectrophotometry and by gas chromatography, and were bioassayed. Only the hopper faeces extract contained the pheromone as well as some isoacetovanillone. In the adult and grasshopper faeces extracts no aromatic substance could be found but the impurities contained, possibly, a mixture of a secondary alcohol, a carboxylic acid, and/or its ester, some of which also occurred in the impure hopper faeces extract. Isovanillin, 5-methylguaiacol, and amylacetate were also bioassayed: they showed no effect on chiasma frequencies, but the latter stimulated the production of a gregaria $\text{F}\text{C}$ ratio in solitaries. A figure is given of the chemical structures of eight substances which are part-analogues of locustol in regard to chiasma frequency, and of eight related substances which are chromosomally inactive but of which amylacetate stimulates the gregaria $\text{F}\text{C}$ ratio and methylformate stimulates the production of black hopper colour in solitaries. A consideration of these structures may aid in solving the chemical action of locustol.