Hydroxy-PEG2-C2-sulfonic acid

Hydroxy-PEG2-C2-sulfonic acid is a polyethylene glycol-based PROTAC linker building block designed to provide aqueous compatibility, conformational flexibility, and a hydrophilic handle for conjugation strategies. Its sulfonic acid functionality supports robust chemical attachment to partner ligands while maintaining solubility during targeted protein degradation workflows. The features and synthetic compatibility of this linker make it useful for constructing bifunctional degraders, and the following points describe its structure and reactivity in detail below.

Structure: The linker comprises a short PEG segment bearing a terminal hydroxy group and a tethered sulfonic acid substituent. It contains ether linkages within the PEG chain and a sulfonic acid group capable of strong hydrogen bonding and ionic interactions, supporting high hydrophilicity and water-phase behavior.

Reactivity: The sulfonic acid group can be leveraged for salt formation and, where appropriate, for activation or coupling routes that connect ligands through robust linkages. Common PROTAC assembly approaches employ nucleophilic substitution or ester/amide-forming chemistry using activated derivatives of the hydroxyl functionality. Solvent systems that support PEG solubility (such as polar aprotic media or buffered aqueous mixtures) and mild base conditions are typically used to preserve sensitive functional groups during stepwise conjugation.