In recent years a range of novel amide ligation strategies have been developed, many incorporating sulfur-containing reagents as 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 undergo acyl transfer to generate peptide imides.1,2 Recent progress in this area will be highlighted, including a site-selective ring expansion process and a novel strategy for peptide ligation strategy involving a single atom substitution.