Inhibition of insect juvenile hormone esterase by α,β-unsaturated and α-acetylenic trifluoromethyl ketones

A series of β,β-disubstituted-α,β-unsaturated and β-substituted-α-acetylenic fluoroketones have been prepared and assayed as inhibitors of insect juvenile hormone esterase from the cabbage looper, Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae). The most potent inhibitors of each series, 4-methyl-1,1,1-trifluorododec-3-en-2-one 3 and 1,1,1-trifluorododec-3-yn-2-one 15, were also assayed as in vivo inhibitors of juvenile hormone esterase. None of the new compounds assayed were more effective inhibitors than structurally analogous α-thioalkyl substituted trifluoropropanones. The acetylenic series were uniformly more potent inhibitors than the unsaturated series of fluoroketones. The difluoroketone derivatives of the most potent inhibitors were markedly less active. This study clearly reveals that the S atom of α-thioalkyl substituted fluoroketone inhibitors has a more complex function than simply mimicking the site of unsaturation in the natural substrate.