Bromo-PEG2-bromide

Bromo-PEG2-bromide is a PEG-based bifunctional linker designed for constructing PROTACs that require efficient spatial separation and controlled attachment chemistry between a target-binding ligand and an E3-recruiting moiety. Its ether-rich PEG segment improves linker flexibility and aqueous compatibility, while the terminal bromides enable straightforward synthetic elaboration. The following sections describe the linker’s structural features and practical reactivity considerations for PROTAC assembly.

Structure: The linker contains a short poly(ethylene glycol) ether backbone featuring repeating ether oxygen atoms that confer conformational flexibility and polarity. It terminates with reactive bromomethyl groups, providing alkyl bromides suitable for nucleophilic substitution. The molecule is an ether-rich, bifunctional scaffold with polar, water-tolerant character.

Reactivity: Bromo-PEG2-bromide is typically used in PROTAC linker synthesis via nucleophilic substitution of the terminal bromides by amines, thiols, or other nucleophiles. Reactions are commonly performed under anhydrous or low-water conditions using polar aprotic solvents and base to promote nucleophile formation. The mechanism proceeds through alkyl bromide activation followed by SN2 substitution, enabling modular coupling to functionalized ligands under standard organic synthesis conditions.