Thioester Hydrolysis Promoted by a Mononuclear Zinc Complex

Abstract

The mononuclear zinc complex [(bpta)Zn](ClO(4))(2).0.5H(2)O promotes the hydrolysis of the thioester PhCH(OH)C(O)SCD(3) when dissolved in CH(3)CN:H(2)O (50:50 buffered at pH 9.0). This reaction results in the formation of a mixture of CD(3)SH and a zinc thiolate complex, the latter of which can be protonated to generate additional CD(3)SH. Kinetic studies revealed an overall second-order reaction with an activation energy that is similar to that found for aqueous OH(-) promoted thioester hydrolysis. These studies represent the first investigation of chemistry relevant to that occurring in the monozinc-containing form of human glyoxalase II.

Transition Metal Mediated Hydrolysis of C–S Bonds: An Overview of a New Reaction Strategy

“…Hydrolysis of thioesters could also be promoted by various metal ions such as Tl 3+ , Hg 2+ , Hg 2 2+ , Ag + , Au 3+ , etc. Such metal ion assisted hydrolysis of thioesters has been studied in detail, and the kinetics and mechanism of such reactions are also available in the literature. − First-row transition metals have also been shown to promote the hydrolysis of thioesters, and examples include hydrolysis of a thioester (PhCH­(OH)­C­(O)­SCD 3 ) by a mononuclear Zn­(II) complex and a binuclear Fe­(III)­Zn­(II) complex, and hydrolysis of hydroxyphenylthioacetic acid S -methyl ester by binuclear Zn­(II)-hydroxide complexes where the binuclear complexes actually dissociate in solution to generate a mononuclear Zn­(II)-hydroxide complex …”

Catalytic Hydrolysis of Thiolates to Alcohols

“…The rate constants for acid-mediated, base-mediated, and pH-independent hydrolysis of S -methyl thioacetate in water have been reported to be 1.5 × 10 –5 M –1 s –1 , 1.6 × 10 –1 M –1 s –1 , and 3.6 × 10 –8 s –1 , respectively, which indicates inhibition of hydrolysis under acidic conditions. Inhibition of thioester hydrolysis in an acidic medium were also reported for ethyl S -trifluoroacetylmercaptoacetate and ethyl trifluorothiolacetate. , The kinetics and mechanism of metal-ion-promoted hydrolysis of thioesters have been investigated in detail, , and reports on the first-row transition-metal-promoted hydrolysis of thioesters are also available in the literature. − In stark contrast to the presence of an appreciable number of literature reports on thioester hydrolysis, reports on the hydrolysis of thiols/thiolates to alcohols and phenols are nonexistent in the literature. The only available examples of C–S bond hydrolysis in the literature involve oxidative hydrolysis processes , to yield oxidized products such as disulfides or sulfonates, along with alcohols (sometimes only as a byproduct) …”