Complexation of captopril with gold(I) and its exchange reactions with thiomalate and cyanide

Abstract

Captopril {Hcap, 1-[(2S)-3-mercapto-2-methylpropionyl]-L-proline} with gold(I) forms a 1 : 1 crystalline complex [Au(cap)]. The exchange reactions of thiomalate and cyanide with [Au(cap)] have been studied using ¹³C NMR spectroscopy. It is found that [Au(cap)] forms a very high-molecular-weight polymer compared to gold(I) thiomalate. Thiomalate and CN^– both bind to [Au(cap)], however, as expected, CN^– binds more strongly. When ¹³CN^– was added to [Au(cap)] solution, ¹³C NMR resonances due to [Au(cap)(¹³CN)]^–(two isomers containing cis or trans cap) and [Au(¹³CN)₂]^– were observed. Evidence is presented which shows that the cis isomer of [Au(cap)(¹³CN)]^– is more stable than the trans.