Bicyclophosphorothionate antagonists exhibiting selectivity for housefly GABA receptors
摘要:
2,6,7-Trioxa-1-phosphabicyclo[2.2.2]octane 1-sulfides (bicyclophosphorothionates) with various C1-4 alkyl groups at the 3- and 4-positions were synthesized and tested for their ability to compete with [H-3]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB), a non-competitive antagonist of gamma-aminobutyric acid (GABA) receptors, for specific binding to rat-brain and housefly-head membranes, and for their insecticidal activity against houseflies. Among the 3,4-substituted analogues, 20 compounds were selectively active for housefly GABA receptors versus rat GABA receptors. The 3-alkyl groups of C-3 length and the 4-alkyl groups of C-4 length were tolerated in housefly receptors, whereas such bulky substituents were deleterious in rat receptors. The 4-isobutyl-3-isopropyl analogue was the most potent in housefly receptors (IC50 = 45.2 nM), and tert-butylbicyclophosphorothionate (TBPS), with the 4-tert-butyl group and no 3-substituent, was the most potent in rat receptors (IC50 = 62.2 nM). Their receptor selectivities (rat IC50/housefly IC50) were 52 and 0.038, respectively. The insecticidal activity (LD50) of 20 active analogues was well correlated with their potency (IC50) in inhibiting [H-3]EBOB binding to housefly-head membranes (r = 0.93). The results obtained in the present study indicate that the introduction of appropriate alkyl groups into the 3- and ii-positions of bicyclophosphorothionate leads to non-competitive antagonists with increased affinity and selectivity for housefly ionotropic GABA receptors versus rat GABAA receptors. (C) 1999 Society of Chemical Industry.
Bicyclophosphorothionate antagonists exhibiting selectivity for housefly GABA receptors
摘要:
2,6,7-Trioxa-1-phosphabicyclo[2.2.2]octane 1-sulfides (bicyclophosphorothionates) with various C1-4 alkyl groups at the 3- and 4-positions were synthesized and tested for their ability to compete with [H-3]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB), a non-competitive antagonist of gamma-aminobutyric acid (GABA) receptors, for specific binding to rat-brain and housefly-head membranes, and for their insecticidal activity against houseflies. Among the 3,4-substituted analogues, 20 compounds were selectively active for housefly GABA receptors versus rat GABA receptors. The 3-alkyl groups of C-3 length and the 4-alkyl groups of C-4 length were tolerated in housefly receptors, whereas such bulky substituents were deleterious in rat receptors. The 4-isobutyl-3-isopropyl analogue was the most potent in housefly receptors (IC50 = 45.2 nM), and tert-butylbicyclophosphorothionate (TBPS), with the 4-tert-butyl group and no 3-substituent, was the most potent in rat receptors (IC50 = 62.2 nM). Their receptor selectivities (rat IC50/housefly IC50) were 52 and 0.038, respectively. The insecticidal activity (LD50) of 20 active analogues was well correlated with their potency (IC50) in inhibiting [H-3]EBOB binding to housefly-head membranes (r = 0.93). The results obtained in the present study indicate that the introduction of appropriate alkyl groups into the 3- and ii-positions of bicyclophosphorothionate leads to non-competitive antagonists with increased affinity and selectivity for housefly ionotropic GABA receptors versus rat GABAA receptors. (C) 1999 Society of Chemical Industry.