HO-Pr-PEG3-Pr-OH

HO-Pr-PEG3-Pr-OH, is a polyethylene glycol-based diol designed to serve as a flexible spacer between targeting and E3 ligase-binding modules. Its ether-rich backbone supports conformational mobility and can help tune effective intramolecular geometry for ternary complex formation. The hydroxyl termini enable straightforward functionalization routes, making it well suited for constructing degraders through linker–warhead coupling strategies. Detailed structural and reactivity considerations are provided below.

Structure: The linker comprises a PEG3 segment featuring repeating ether units, terminating in primary alcohol functionalities. It contains flexible C–O and C–C connectivity that promotes solvated conformations, while the terminal hydroxyl groups provide hydrogen-bonding capacity. Overall, it is a hydrophilic, conformationally adaptable spacer compatible with common organic synthesis conditions.

Reactivity: The primary alcohol termini are suitable for standard PROTAC assembly reactions such as esterification, ether formation, or conversion to activated derivatives for subsequent coupling. Typical approaches use carbodiimide-mediated ester formation or nucleophilic substitution with appropriately activated electrophiles, often under anhydrous or controlled-moisture conditions. Solvents such as polar aprotic media and alcohol-compatible bases are commonly employed to preserve PEG integrity and maintain coupling efficiency.