2-Aryl-5-tert-butyl-1,3-dithianes and their S-oxidation products: structure-activity relationships of potent insecticides acting at the GABA-gated chloride channel
1992
Wacher, V.J. | Toia, R.F. | Casida, J.E.
2-(4-Bromophenyl)-, 2-(4-ethynylphenyl)-, and 2-phenyl-5-tert-butyl-1,3-dithianes were prepared as their cis and trans isomers. Oxidation with m-chloroperoxybenzoic acid or permanganate yielded 12 S-oxidation products in each aryl series. The relative potencies of the dithianes and their oxidation products for both topical toxicity to houseflies and inhibition of [35S]-tert-butylbicyclophosphorothionate binding to mouse brain membranes are generally ethynylphenyl > bromophenyl > phenyl. The 2-axial and 2-equatorial isomers, except for the monosulfoxides, are usually of similar potency at the receptor and to houseflies pretreated with piperonyl butoxide (PB) synergist. Monosulfoxides with the trans arrangement of the 2-aryl group and the S==O bond are more potent as receptor blockers, while the cis isomers are more toxic to PB-synergized houseflies. Maximum potency is always attained with the monosulfone; e.g., with cis- and trans-2-(4-ethynylphenyl)-5-tert-butyl-1,3-dithiane 1,1-dioxide the housefly LD50 is 0.6, micrograms/g alone or 0.01-0.02 micrograms/g with PB and the [35S]TBPS receptor IC50 is 1 nM. Studies with [3H]ethynylbicycloorthobenzoate and housefly brain membranes further indicate that the dithianes and their S-oxidation products act at the GABA-gated chloride channel.
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