Bis-PEG4-acetic acid

Bis-PEG4-acetic acid, provides a hydrophilic, flexible polyethylene glycol-based spacer architecture that supports efficient conjugation between targeting ligands and E3 ligase recruiters. Its PEG-derived segment can enhance solubility and reduce non-specific interactions, while the acetic acid termini enable robust functionalization for building degraders. Detailed structural and synthetic guidance are provided below to support experimental PROTAC assembly and optimization.

Structure: Bis-PEG4-acetic acid is a PEGylated, bifunctional linker featuring ether-rich polyethylene glycol segments connected to acetic acid functional groups. It contains multiple C–O ether linkages and terminal carboxylic acid moieties, offering conformational flexibility and strong hydrogen-bonding capacity, which together influence solubility and linker behavior in aqueous PROTAC formulations.

Reactivity: The carboxylic acid termini are suitable for standard PROTAC linker coupling strategies, including amide bond formation via activation of the acid followed by reaction with an amine-functional ligand or intermediate. Common activation approaches use carbodiimide coupling systems with suitable additives, typically in polar aprotic or mixed aqueous media. The flexible PEG scaffold can facilitate productive conjugation by maintaining local mobility during coupling.