Used as a hydrophilic linker or spacer in pharmaceutical and bioconjugation chemistry. Its long polyethylene glycol (PEG)-like chain enhances solubility and flexibility when connecting molecules, especially in prodrug design or peptide modification. The terminal tert-butyl ester protects the carboxylic acid during synthesis and can be removed under mild acidic conditions to release the active acid form. Frequently employed in the development of PEGylated compounds to improve pharmacokinetic properties such as circulation time and bioavailability. Also applied in surface functionalization for diagnostics and biosensors due to its stable ether linkages and resistance to oxidation.