Cysteine‐Free Peptide and Glycopeptide Ligation by Direct Aminolysis

Left to their own devices in a mixed-solvent system, peptides undergo efficient aminolysis with peptide thioesters (see scheme). This ligation method, which does not require coupling reagents, auxiliaries, or an N-terminal cysteine residue, is suitable for a variety of amino acids at the ligation junction. Its effectiveness was demonstrated by the synthesis of a 6.9-kDa section of the cancer-associated MUC1 tandem repeat.