Amino-PEG4-t-butyl acetate (CAS No. 864680-64-8) is an amino-containing polyethylene glycol derivative with the molecular formula C₁₄H₂₉NO₆ and a molecular weight of 307.38. Its structure consists of a tetraethylene glycol (PEG4) chain linking an amine group (NH₂) to a t-butyl ester moiety (COOtBu), combining hydrophilic and hydrophobic properties. It is typically produced via chemical synthesis, where precise coupling of the amine and t-butyl ester groups is achieved by controlling reaction conditions, resulting in a purity of over 95%. In drug development, this compound serves as a linker for modifying peptides, proteins, or small-molecule drugs to enhance solubility and stability. In bioconjugation, its short-chain characteristics enable precise spatial separation between molecules, making it suitable for precision experiments such as fluorescence resonance energy transfer (FRET).