New trifluoropropanone sulfides as highly active and selective inhibitors of insect juvenile hormone esterase

A series of α,α′-bis(2-oxo-3,3,3-trifluoropropylthio)alkanes was synthesized by the alkylation of the appropriate α,α′-alkanedithiol with 3-bromo-1,1,1-trifluoropropan-2-one. The compounds were tested for in vitro inhibition of insect juvenile hormone esterase (JHE), electric eel acetylcholinesterase (AChE), porcine carboxylesterase, and yeast lipase. Inhibition of hemolymph JHE from fifth instar larvae of the cabbage looper, Trichoplusia ni (Hübner) (Lepidotera: Noctuidae), was in the nanomolar range for many compounds. The inhibition of the other three enzymes was only moderate in comparison to JHE. The inhibition of JHE was compared to carbon chain length, differing heteroatoms, and presence of methyl side-chains. The most effective compound was 1,1,1,16,16,16-hexafluoro-4,13-dithiahexadecane-2,15-dione (I₅₀: 8.2 × 10^-10 M). The kinetics of inhibition were found to be time-dependent against both JHE and AChE enzymes using representative compounds of both high and low inhibitory potential. Second-order inhibition velocity constants were determined and found to be in agreement with the I₅₀ values.