Submitted to: Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2001
Publication Date: N/A
Interpretive Summary: Dangerous diseases such as Lyme disease, Nile fever, malaria and encephalitis that are transmitted by mosquitoes, sandflies, ticks and chiggers have become of increasing concern to the general public and the U. S. Department of Defense. A compound called number 220 was known to be a reasonably effective repellent against the blood-feeding arthropods. It was known that 220 was a mixture of four spatially different molecules, but it was not known which molecules were responsible for the observed repellent activity. Therefore, purified forms of each of the four molecules were synthesized and tested to find out which form was the most potent repellent. Tests with mosquitoes showed two spatial forms of 220 were 180 to 310 percent more repellent than the other forms. By using the highly active forms it will be possible for commercial industry and the Department of Defense to formulate new repellents with greater levels of protection against disease.
Technical Abstract: Racemic 1-[3-cyclohexen-1-ylcarbonyl]-2-methylpiperidine effectively repels blood-feeding arthropods such as mosquitoes, chiggers and ticks. The compound contains two asymmetric carbon atoms and the racemate consists of 4 stereoisomers. Quantitative mosquito bioassays using Aedes aegypti showed that (1S,2S) and (1R,2S) configurations were 2.8-3.1 and 1.6-1.8 times more effective, respectively, than the other 2 stereoisomers in reducing mosquito bites. (1S,2S) was 2.5 more repellent than the racemate. Biological data show that an interaction of the (2S)2-methylpiperidine configuration with a repellent receptor system in Ae. aegypti is apparently most important to repellent activity. Nuclear magnetic resonance spectra and molecular mechanics calculations for the stereoisomers provided insight into the conformation of the 2'S group. Results indicate that enhanced repellent effects can be realized through formulation of the most active stereoisomers of the compound.