Azido-PEG5-Br

Azido-PEG5-Br is a bifunctional polyethylene glycol linker designed for modular assembly of PROTACs, enabling efficient conjugation between a ligand and a targeting warhead. Its combination of a terminal azide and a brominated handle supports orthogonal “click-ready” coupling strategies and flexible linker positioning, which can help tune solubility and effective ternary complex formation. The following sections describe the linker’s structure and the practical reactivity considerations for PROTAC construction in detail below.

Structure: The linker contains a PEG ether backbone that provides conformational flexibility and hydrophilicity, terminating in an azide group and a bromide-bearing site. It features ether linkages along the chain and a terminal azide suitable for bioorthogonal cycloaddition, with a halide functionality for substitution chemistry.

Reactivity: The azide group is well suited for copper-catalyzed azide–alkyne cycloaddition with alkyne-functional partners under standard click conditions, typically using Cu(I) sources and compatible aqueous/organic solvent mixtures. The bromide handle can participate in nucleophilic substitution or related coupling workflows to install the linker onto electrophilic or nucleophilic intermediates. Careful choice of solvent, base, and copper control helps minimize side reactions and preserve sensitive ligands.