Mal-PEG1-bromide

Mal-PEG1-bromide is a PEG-based bifunctional linker reagent designed for constructing PROTACs through reliable nucleophilic substitution and subsequent conjugation steps. Its electrophilic bromide handle enables efficient attachment to appropriate nucleophiles, while the maleimide functionality supports selective coupling to thiol-containing ligands. This combination helps researchers build targeted protein degraders with controlled linker properties and practical synthetic accessibility. Detailed structural and reactivity considerations are provided below.

Structure: Mal-PEG1-bromide contains a short polyethylene glycol segment that provides hydrophilicity and conformational flexibility, linked to a maleimide moiety and a terminal bromide. It features an alkyl bromide electrophile and a maleimide double-bond system suitable for thiol addition, with stable ether connectivity along the PEG chain.

Reactivity: The bromide group is suited to substitution reactions with nucleophiles under conditions commonly used for alkyl halide functionalization, typically in polar aprotic or mixed solvents with base to promote nucleophile formation. The maleimide reacts selectively with thiols via a Michael-type addition to form a stable thioether linkage. For PROTAC assembly, thiol-bearing targeting ligands are typically coupled to the maleimide after installing the appropriate partner at the bromide position, minimizing side reactions by controlling pH and avoiding competing thiols.