Bromo-PEG5-propionic acid

Bromo-PEG5-propionic acid is a PEG-based, bromo-functional linker designed for modular assembly of PROTACs, enabling reliable spatial separation between a ligand and an E3-recruiting or target-binding moiety. Its ether-rich PEG scaffold supports favorable solubility and conformational flexibility, while the bromo group provides a practical handle for controlled bond formation. The following sections describe the linker’s structure and the reactivity options typically used to build PROTAC architectures.

Structure: The linker features a polyethylene glycol chain containing repeating ether units, terminated with a bromo substituent and a propionic acid functionality. It contains C–Br and C–O ether bonds, along with a carboxylic acid capable of hydrogen bonding and ionic interactions. Overall, it is a polar, flexible scaffold.

Reactivity: The bromo terminus is commonly used for nucleophilic substitution or related coupling strategies, where the bromo group serves as a leaving group under appropriate conditions. Carboxylic acid can be activated for amide or ester formation via standard coupling chemistries, often using carbodiimide-based activators and compatible bases. Solvents such as polar aprotic media are frequently employed to promote substitution and minimize side reactions.