Thiol-disulfide exchange reactions contribute to the formation and cleavage of sulfur-sulfur bonds and to redox homeostasis in biological systems. Gold(I) thiolate drugs used for treatment of rheumatoid arthritis are pro-drugs, readily undergoing ligand exchange with endogenous thiols. Gold(I) thiolates can also react with disulfides via thiolate-disulfide exchange. We have been studying factors that influence the kinetics and equilibria of gold(I) mediated thiol-disulfide exchange reactions of the type:R3PAuSR'  +  R�SSR�   ?   R3PAuSR�  +  R'SSR� R3PAuSR'  +  R'SSR�   ?   R3PAuSR�  +  R'SSR' Reaction rates for gold(I) mediated thiolate-disulfide exchange increase in more polar solvents. This is opposite to metal-free, thiol-disulfide exchange reactions, which proceed more slowly as the solvent polarity increases.  Kinetic measurements of phosphine gold(I) thiolate � disulfide exchange are complicated by a side reaction in polar solvents, which produces phosphine oxide (R3PO). Factors affecting this side-reaction will be discussed in light of the formation of phosphine oxide in vivo during gold therapy.

Formation of phosphine oxide during gold(I) mediated thiol-disulfide exchange reactions

243rd National Meeting (2012)

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