PEG4-bis(phosphonic acid diethyl ester)

PEG4-bis(phosphonic acid diethyl ester) is a PEG-based bifunctional linker designed for constructing PROTACs that require controlled spacing between ligands and efficient conjugation handles. Its flexible ethylene glycol segment supports favorable conformations for ternary complex formation, while the bis(phosphonate) motif enables robust chemical attachment strategies. The molecule is intended for researchers seeking reproducible linker architecture in targeted protein degradation workflows;

Structure: The linker contains an ethylene glycol (PEG) chain providing conformational flexibility, connected to a bis(phosphonate) core bearing diethyl ester functionalities. It features P–O ester bonds and ether linkages, with polar, hydrogen-bond-accepting oxygen atoms that promote solubility and stable covalent incorporation into larger conjugates.

Reactivity: The diethyl phosphonate esters can be transformed into more reactive phosphonic acid derivatives via ester hydrolysis under aqueous acidic or basic conditions, enabling subsequent coupling to electrophilic partners. For PROTAC assembly, researchers typically use stepwise conjugation: first functionalize the phosphonate handle, then perform ligand coupling through established phosphonate–electrophile or phosphonate–metal-mediated strategies, selecting solvents compatible with PEG stability and minimizing conditions that promote unwanted hydrolysis or side reactions.