Ald-Ph-PEG2-NH-Boc is a specialized bifunctional linker featuring an aldehyde group attached to a phenyl ring, connected via a PEG2 spacer to an NH-Boc protected amine. It serves as a protecting group for amines in peptide synthesis, ensuring selective reactions during peptide bond formation, and is particularly useful in solid-phase peptide synthesis (SPPS) for building complex peptides. The Boc (tert-butyloxycarbonyl) group offers stability under acidic conditions for controlled deprotection. In bioconjugation, the reactive aldehyde enables the attachment of PEG chains to biomolecules, such as proteins or antibodies, via imine or oxime formation with amines or hydrazides, improving solubility and stability. The protected amine allows subsequent modifications. This reagent is also applied in drug delivery systems to enhance the pharmacokinetic properties of therapeutic agents.