Bromo-PEG3-propionic acid

Bromo-PEG3-propionic acid is a PEG-based functional linker designed for constructing PROTACs through controlled conjugation chemistry. Its flexible poly(ethylene glycol) segment supports solubility and spatial separation between ligands, while the bromoalkyl handle enables selective attachment to nucleophilic partners under standard alkylation conditions. The resulting linkers can be used to assemble degraders that retain productive geometry for ternary complex formation. Detailed structural and reactivity considerations are provided below.

Structure: The linker contains a bromoalkyl electrophile attached to a short PEG chain terminating in a carboxylic acid. It features ether linkages within the PEG backbone, an alkyl bromide for substitution, and a terminal carboxylic acid for further derivatization. Overall, it is a polar, flexible molecule with hydrogen-bonding capability.

Reactivity: The bromoalkyl group undergoes nucleophilic substitution with amines or other nucleophiles to form a stable C–N or related C–heteroatom bond, enabling ligand conjugation for PROTAC assembly. Carboxylic acid functionality is compatible with standard activation chemistries (for example, coupling after conversion to an activated ester or acid-derivative). Typical conditions use polar aprotic solvents, base-assisted deprotonation of nucleophiles, and inert atmosphere to minimize side reactions.