Used in pharmaceutical synthesis, particularly in the development of antibody-drug conjugates (ADCs) and other bioconjugation applications. Its structure contains a carboxylic acid group for coupling reactions and a protected amine via the Boc group, allowing for selective deprotection and further functionalization. The triethylene glycol-like spacer provides hydrophilicity and flexibility, improving solubility and reducing aggregation in complex molecules. Commonly employed to link payloads to antibodies or in prodrug design where controlled release and stability are critical. Also utilized in the preparation of PEGylated intermediates for drug delivery systems.