Azido-PEG4-propargyl

Azido-PEG4-propargyl is a bifunctional polyethylene glycol linker designed for modular PROTAC assembly, enabling efficient conjugation between ligand fragments through orthogonal click-type chemistry. Its PEG-based spacer supports productive linker length and conformational flexibility, which can improve cooperativity in targeted protein degradation workflows. The following sections describe key structural characteristics and practical reactivity considerations for constructing PROTACs using this linker.

Structure: The molecule contains an azide group and a terminal propargyl alkyne connected through a PEG spacer. It features flexible ether linkages typical of polyethylene glycol, with a carbon–nitrogen azide functionality and a carbon–carbon triple bond suitable for bioorthogonal coupling under mild conditions.

Reactivity: PROTAC synthesis commonly employs copper-catalyzed azide–alkyne cycloaddition to join the azide and alkyne partners, forming a stable triazole linkage. Reactions are typically performed under inert or controlled atmospheres using copper(I) sources, with polar organic/aqueous solvent mixtures to maintain solubility. Alternative copper-free strain-promoted variants are used when copper sensitivity is a concern, following established click chemistry principles.