Reactions Of Auronofin ((1-Thio-β-D-Glucopyranose 2,3,4,6-Tetraacetato-S)(Triethylphosphine)Gold(I) In Aqueous Hydrochloric-Acid

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Inorganic Chemistry


Auranofin ((1-thio-β-D-glucopyranose 2,3,4,6-tetraacetato-S)(triethylphosphine)gold(I)) is an orally active drug for the treatment of rheumatoid arthritis. Auranofin reacts with HCl in aqueous solution and in 50% methanol/water to form chloro(triethylphosphine)gold(I) (ClAuPEt₃) and with ClAuPEt₃ to form a thiolate-bridged dinuclear gold complex with two gold triethylphosphine moieties bound to a single thioglucose ligand ((μ-1-thio-β-D-glucopyranose 2,3,4,6-tetraacetato-S:S)bis(triethylphosphine)digold(I) chloride). The thermodynamics and kinetics of these reactions have been studied in water and in 50% methanol/water. The equilibrium constants for the formation of ClAuPEt₃ are 4.6 X 10⁻⁴ M⁻¹ in water and 2.0 X 10⁻³ M⁻¹ in 50% methanol/water while the equilibrium constant for the formation of the thiolate-bridged digold complex is 1.2 X l0³ (water), 1.3 X l0² (50% methanol/water), and 0.7 X l0² (95% methanol). The kinetics for the formation of the thiolate-bridged digold complex are too rapid to be observed by ordinary mixing techniques, but the chloride replacement of tetraacetylthioglucose could be studied via the stopped-flow method. For the reaction at 25 °C in 1.0 M Cl⁻, k_obsd = 385[H⁺] in the mixed-solvent medium and k_obsd = 210[H⁺] + 4.3 X 10⁵ [HTATG] in water in the presence of excess tetraacetylthioglucose.

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