Zinkkomplexe von Aminosäuren und Peptiden, 4. Zinkkomplexe von Peptiden mit C‐terminalem Cystein

Zinc Complexes of Amino Acids and Peptides, 4. ‐ Zinc Complexes of Peptides with C‐terminal Cysteine The cysteine derivatives N‐Ac‐Cys, N‐Ac‐Gly‐Cys, N‐Ac‐Ala‐Cys, and N‐Ac‐Gly‐Gly‐Cys with unprotected SH and CO2H functions (LH2) were prepared by the mixed anhydride method. Their reactions with basic zinc carbonate resulted in the formation of complexes Zn(LH)2 which were converted by KOH to complexes K2[ZnL2]. Potentiometric titrations revealed ZnL and [ZnL2]2− as the major solution species. By pD‐dependent NMR measurements (1H, 13C) in D2O carboxylate coordination in acidic solution and carboxylate and thiolate coordination in neutral and basic solution was identified.