Substrate-directed novel direct amidation of resin-bound amino acids

In peptide drug discovery, the C-terminal structure of peptide compounds is crucial for enhancing the affinity with target proteins and for optimizing the compound's dynamics and physical properties. In conventional solid-phase synthesis, two steps are necessary to modify the C-terminal structure: cleavage from the resin and subsequent amidation involving activation of the resulting carboxylic acid. This process can potentially lead to racemization of the C-terminal amino acid side chain. To address this issue, we developed a novel method that, in the presence of a Ta catalyst, directly allows amines to react with amino acid-loaded resins, thereby accomplishing both resin cleavage and amidation in a single step.