- Butyrylcholinesterase Inhibitors
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Butyrylcholinesterase inhibitors, their formulation, and their use primarily in the treatment of neurodegenerative diseases. These inhibitors generally are phosphates, phosphonates, phosphinates, and phosphoramidates. These inhibitors can be incorporated
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Paragraph 0118
(2016/08/17)
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- BUTYRYLCHOLINESTERASE INHIBITORS
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Butyrylcholinesterase inhibitors, their formulation, and their use primarily in the treatment of neurodegenerative diseases. These inhibitors generally are phosphates, phosphonates, phosphinates, and phosphoramidates. These inhibitors can be incorporated in pharmaceutical compositions and administered to a patient in therapeutically effective amounts to treat neurodegenerative diseases.
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- Dependence of Transition-state Structure on Nucleophile in the Reaction of Aryl Oxide Anions with Aryl Diphenylphosphate Esters
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Second-order rate constants have been measured for reaction of aryl oxide anions with substituted phenyl diphenylphosphate esters in aqueous media at 25 deg C.The rate constants obey good Broensted type correlations with the pKa of either the leaving group or nucleophile.Both βnuc and βlg values vary substantially with basicity of leaving group and nucleophile, respectively, providing evidence for coupling between bond fission and formation.Attack of phenolate ions on 2,4-dinitrophenyl diphenylphosphate has a βnuc value of 0.12 giving a Kreevoy's tightness parameter value, τ, of 0.18 which is consistent with an 'exploded' transition state for the identity reaction involving 2,4-dinitrophenolate ion as the nucleophile.Transfer of the diphenylphosphinoyl group between 2,4-dinitrophenolate ion nucleophiles has a τ value of 0.28, consistent with an 'exploded' transition state for this reaction also.The identity reaction involving transfer of the diphenylphosphoryl group between phenolates ions has a τ value of 1.20, indicating an almost synchronous process.The data for transfer of the diphenylphosphinoyl and diethylphosphoryl groups between phenolate ion nucleophiles indicates that the identity reaction for the parent phenol has an almost synchronous mechanism for the former phosphinoyl species (τ = 0.92) whereas the latter (τ = 1.45) is almost associative.
- Ba-Saif, Salem A.,Waring, Mark A.,Williams, Andrew
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p. 1653 - 1659
(2007/10/02)
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- Single transition state in the transfer of a neutral phosphoryl group between phenoxide ion nucleophiles in aqueous solution
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The second-order rate constants (kAro) for reaction of substituted phenoxide ions with 4-nitrophenyl diphenyl phosphate obey a linear equation over a range of 18 substituents with pKArOH values spanning the pKa of the leaving 4-nitrophenolate ion: log kArO =0.53pKArOH -6.6. The linear plot is consistent with a mechanism involving a single transition state or a two-step process with a very reactive intermediate with two almost identical transition states for its formation and breakdown; the value of the exponent (0.53) is also not consistent with a regular stepwise process with a discrete intermediate. The symmetrical reaction of 4-nitrophenolate ion with the 4-nitrophenyl ester is slightly imbalanced whereby bond formation does not keep up with bond fission in the transition state; the transition state, therefore, has some phosphorylium ion character. Transfer of the dielhylphosphoryl group between weakly basic oxyanion nucleophiles is probably a concerted process with a transition state with more of the character of the pentacoordinate intermediate than it has in the corresponding diphenylphosphoryl group transfer.
- Ba-Saif, Salem A.,Waring, Mark A.,Williams, Andrew
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p. 8115 - 8120
(2007/10/02)
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