Used in peptide synthesis as a protecting group for amines, enabling selective deprotection during solid-phase peptide synthesis. It is particularly valuable in the synthesis of complex peptides and biomolecules due to its stability under acidic conditions and ease of removal under basic conditions. The PEG4 spacer enhances solubility in aqueous and organic solvents, facilitating reactions in diverse environments. Additionally, it finds application in bioconjugation, where it serves as a linker to attach functional groups or biomolecules, improving the efficiency of drug delivery systems and diagnostic probes. Its versatility makes it a key reagent in pharmaceutical research and development.