Bis-PEG1-C-PEG1-CH2COOH

Bis-PEG1-C-PEG1-CH2COOH, is designed to provide a flexible, water-compatible tether that supports efficient spatial organization between a target-binding ligand and an E3 ligase-recruiting moiety. Its PEG-rich architecture can improve solubility and reduce non-specific interactions, which are often important for maintaining productive ternary complex formation. The linker’s bifunctional connectivity enables straightforward assembly into PROTAC constructs, and the following sections describe its structure and practical reactivity considerations in detail.

Structure: The molecule is a PEG-based, bis-functional linker featuring ether-rich segments that confer conformational flexibility, along with a terminal carboxylic acid for covalent coupling. It contains multiple C–O and C–C connections, with a polar, hydrogen-bonding functional group that supports aqueous compatibility and linker hydration.

Reactivity: The terminal carboxylic acid is suitable for amide-bond formation with primary amines under standard peptide-coupling strategies. Typical approaches use carboxyl-activation reagents and base in polar aprotic solvents, proceeding via formation of an activated ester or acyl intermediate followed by nucleophilic attack by the amine. This enables modular PROTAC synthesis by coupling the linker to amine-bearing ligands while maintaining linker integrity and flexibility.