Azido-PEG3-azide

Azido-PEG3-azide is a polyethylene glycol-based bifunctional linker bearing terminal azide groups, designed to support modular PROTAC assembly through orthogonal “click” chemistry. Its flexible PEG spacer can improve effective reach and conformational adaptability between the target-binding and E3-recruiting elements, while the azide handles enable reliable conjugation under bioorthogonal conditions. The detailed structural and reactivity considerations for PROTAC linker incorporation are provided below.

Structure: Azido-PEG3-azide contains a PEG chain providing a hydrophilic, conformationally flexible scaffold, terminated by azide functional groups. The linker features ether linkages within the PEG backbone and carbon–nitrogen bonds in the azide moieties, supporting stable, nonionic behavior in aqueous media.

Reactivity: The terminal azides are well suited for copper-catalyzed azide–alkyne cycloaddition or strain-promoted azide–alkyne cycloaddition, enabling attachment to alkyne-bearing PROTAC warheads or ligands. Typical preparations use compatible solvents such as aqueous buffers with organic cosolvents, while copper-catalyzed routes may require ligand-stabilized Cu(I) systems to minimize side reactions. Mechanistically, cycloaddition forms a stable triazole linkage without perturbing the PEG spacer.