HO-PEG9-OH

This PEG-based linker is designed to support targeted protein degradation workflows by providing a flexible, hydrophilic spacer that can tune the spatial relationship between a ligand and an E3-recruiting moiety. Its ether-rich backbone and terminal hydroxyl groups facilitate robust synthetic coupling strategies and help improve solubility and handling in PROTAC assembly. The structure and reactivity considerations for constructing PROTACs using this linker are described in detail below.

Structure: HO-PEG9-OH is a poly(ethylene glycol) chain terminated by primary alcohol groups. The linker contains repeating ether linkages that confer conformational flexibility and strong hydrogen-bonding capability. Its hydrophilic, low-interfacial-interaction character supports aqueous compatibility and minimizes aggregation in typical PROTAC preparations.

Reactivity: The terminal hydroxyl groups enable PROTAC-linker construction via standard alcohol functionalization reactions such as ester or ether formation, or conversion to activated intermediates for subsequent nucleophilic substitution. Common coupling approaches rely on dehydrating agents or carbonyl-activating reagents under anhydrous or controlled-humidity conditions, using polar aprotic solvents when appropriate. Reaction progress is typically monitored by chromatographic methods, and mild bases may be used to promote coupling while preserving sensitive functional groups.