Cl-PEG6-acid

Cl-PEG6-acid is a polyethylene glycol–based PROTAC linker building block designed to connect a ligand-bearing warhead to an E3-recruiting element while supporting solubility, conformational flexibility, and controlled spatial presentation. Its functional handles enable robust conjugation strategies commonly used in targeted protein degradation workflows. The following sections describe the linker’s structure and practical reactivity considerations in detail.

Structure: Cl-PEG6-acid comprises a PEG oligomer backbone bearing a terminal acid functionality and a chloro substituent at the terminus. The structure features ether linkages along the PEG chain, with a carboxylic acid group suitable for amide formation and a chloride that can serve as an electrophilic leaving group.

Reactivity: This linker is well suited for PROTAC assembly via nucleophilic substitution or subsequent carboxyl activation chemistry. The chloro terminus can react with nucleophiles under conditions that promote chloride displacement, while the carboxylic acid can be converted to activated intermediates (for example, acid chlorides, activated esters, or coupling-agent–mediated species) to form amide bonds with amine-containing ligands. Typical approaches use dry polar organic solvents and base to drive coupling while minimizing side reactions.