In recent years a range of novel amide ligation strategies have been developed, many incorporating sulfur-containing reagents such as thioesters and other carboxylic acid surrogates. We recently reported a novel method for peptide synthesis based on the reaction of thioamides with carboxylic acids in the presence of silver(I) to generate isoimides, which can undergo a variety of acyl transfer processes. Recent progress in this area will be highlighted, including novel strategies for macrocyclization and ligation of peptide thioamides.