| Abstract: | The unique physicochemical properties of a thioamide bond, which is an ideal isostere of an amide bond, have not been fully exploited because of the tedious synthesis of thionated amino acid building blocks. Here, we report a purification‐free and highly efficient synthesis of thiobenzotriazolides of Fmoc‐protected and orthogonally protected 20 naturally occurring amino acids including asparagine, glutamine, and histidine. The near‐quantitative conversion to the respective thioamidated peptides on solid support demonstrates the robustness of the synthetic route. Furthermore, the unaltered incorporation efficiency of thiobenzotriazolides from their stock solution till 48 h suggests their compatibility toward automated peptide synthesis. Finally, utilizing an optimized cocktail of 2% DBU + 5% piperazine for fast Fmoc‐deprotection, we report the synthesis of a thioamidated Pin1 WW domain and thioamidated GB1 directly on solid support. |
