Bromo-PEG5-alcohol

Bromo-PEG5-alcohol is a polyethylene glycol (PEG)-based linker designed for modular synthesis of PROTACs, providing a flexible, hydrophilic spacer that can improve effective ternary complex formation and reduce steric constraints between the target-binding ligand and the E3 ligase recruiter. Its terminal bromo functionality enables reliable functional-group interconversion, while the terminal alcohol supports further derivatization for conjugation. Detailed structural and reactivity considerations for PROTAC linker assembly are provided below.

Structure: This linker is built from an ether-rich PEG chain terminated by a primary alcohol and a bromo substituent. It contains multiple C–O ether bonds that confer flexibility and water compatibility, with a terminal carbon bearing both hydroxyl and bromine functionalities suitable for stepwise chemical modification.

Reactivity: The bromo group can participate in nucleophilic substitution to install PROTAC-compatible handles, typically using nucleophiles under conditions that favor substitution over elimination. The terminal alcohol can be activated or converted via standard coupling strategies (for example, esterification or ether formation) to connect to ligand fragments. Common approaches employ polar aprotic solvents and base-assisted conditions, with reaction monitoring by chromatography or NMR to ensure clean conversion.