HO-PEG5-COOMe

HO-PEG5-COOMe is a PEG-based linker designed to support PROTAC assembly by providing a flexible, water-compatible spacer that can tune effective distance and reduce steric mismatch between the target-binding ligand and the E3 ligase recruiter. Its ether-rich backbone and terminal ester functionality facilitate modular synthesis and subsequent conjugation steps commonly used in targeted protein degradation workflows. Detailed structural and synthetic guidance is provided below.

Structure: This molecule contains a poly(ethylene glycol) ether chain that offers conformational flexibility and hydrophilicity. The terminal methoxy ester introduces an ester carbonyl and a stable linkage suitable for controlled functional transformations. Overall, it features ether oxygen atoms and an ester moiety that influence solubility and reactivity.

Reactivity: The methoxy ester can be converted into more reactive intermediates for PROTAC construction, including ester-to-acid or ester-to-activated ester strategies, depending on the coupling partner. Suitable approaches often involve mild base- or nucleophile-mediated hydrolysis followed by standard amide or ester-forming chemistries. Common conditions use polar organic solvents and aqueous co-solvents, with coupling reagents selected to preserve the PEG chain and avoid degradation of sensitive functional groups.