S-(2-Pyrimidinyl)- and S-(2-(4,6-dimethylpyrimidinyl))-1,1,3,3-tetramethylthiouronium hexafluorophosphates: novel reagents for in situ peptide coupling

Two new reagents for in situ peptide coupling based on the 2-mercaptopyrimidine core have been developed. The readily prepared thiouronium salts were found to promote both peptide and segment coupling efficiently with low racemization/epimerization levels.