Bis-PEG4-PFP ester

This Bis-PEG4-PFP ester linker is designed for efficient PROTAC assembly, providing two reactive activated-ester handles that can be used to install linkages from targeting ligands and/or E3 ligase binders. Its PEG-based spacer supports solubility and conformational flexibility, which can help maintain productive ternary complex formation. The dual functional nature streamlines synthetic workflows, and the activated PFP ester reactivity is well suited to amide-bond formation under mild, aqueous-compatible conditions.

Structure: The linker consists of a PEG spacer terminated by two pentafluorophenyl ester groups, enabling covalent coupling through amide formation. It contains ether linkages within the PEG chain and ester carbonyls attached to pentafluorophenyl leaving groups, giving a polar, water-compatible scaffold.

Reactivity: The PFP ester groups undergo nucleophilic acyl substitution with primary amines to form stable amide bonds, releasing pentafluorophenol as the leaving group. PROTAC synthesis typically employs amine-containing ligands under buffered or mildly basic conditions, using polar organic/aqueous solvent mixtures to maintain solubility. No special catalysts are generally required; reaction efficiency depends on amine nucleophilicity and controlled stoichiometry to favor selective bis-functional coupling.