Tos-PEG3-CH2COOtBu is widely used in organic synthesis and bioconjugation due to its reactive tosyl group and PEG spacer. It serves as a versatile linker for attaching molecules, particularly in the development of prodrugs, targeted drug delivery systems, and bioconjugates. The tosyl group allows for efficient nucleophilic substitution reactions, enabling the attachment of amines, thiols, or other nucleophiles. The PEG spacer enhances solubility and biocompatibility, making it suitable for applications in pharmaceuticals and biomaterials. Additionally, it is employed in peptide synthesis and the modification of biomolecules, such as proteins and antibodies, to improve their stability and pharmacokinetic properties.