3-Aminophenol-PEG4-methyl

This PEG-based linker is designed to connect a protein-binding ligand to an E3-recruiting moiety in PROTAC constructs, providing a flexible, water-compatible spacer that can improve effective intramolecular reach and ternary complex formation. Its ether-rich scaffold helps maintain solubility and can reduce steric constraints near the conjugation sites. The detailed structural and reactivity considerations for building PROTACs with this linker are provided below.

Structure: 3-Aminophenol-PEG4-methyl contains an aminophenol aromatic core linked to a methyl-substituted polyethylene glycol chain. The linker features phenolic and primary amine functionalities, multiple ether linkages, and a terminal methylated PEG segment, yielding a flexible, hydrophilic, and conformationally adaptable spacer suitable for bioconjugation.

Reactivity: The primary amine and phenolic group enable common PROTAC conjugation strategies such as amide or urea formation after activation of a carboxylic acid or isocyanate, and ether/phenol-compatible coupling via activated electrophiles. Typical syntheses use base-promoted coupling in polar aprotic solvents, with carbodiimide-type reagents for carboxyl activation or other standard coupling chemistries, while protecting-group approaches are often employed to preserve chemoselectivity.