SCHEDULED MAINTENANCE
A carbon-13 nuclear magnetic resonance study of thiol-exchange reactions of gold(I) thiomalate (‘Myocrisin’) including applications to cysteine derivatives
Abstract
Reactions at pH 7 between gold(I) thiomalate and a variety of thiols with pKSH values ranging from 7.6 (thioglucose) to 10.2 (mercaptoacetate) have been studied by 13C n.m.r. spectroscopy. New species [Au(SR)n]1–n, where n appears to be less than 2, are formed and thiomalate is readily displaced, especially by thiols with low pKSH. The latter are in fast exchange with AuI on the n.m.r. time scale. Similar activation parameters have been derived for thiomalate, N-acetyl-L-cysteine, and mercaptoacetate exchange (ΔG‡ 63 kJ mol–1, ΔS‡–145 J K–1 mol–1, EA 22 kJ mol–1)via a line-shape analysis of 13C n.m.r. spectra at different temperatures. Thiol exchange rates increase at high pH, but at low pH 1:1 polymers are more stable than [Au(SR)n]1–n species.
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