N-Mal-N-bis(PEG4-amine)

This N-Mal-N-bis(PEG4-amine) linker is designed to provide a flexible, hydrophilic PEG-based spacer architecture that can enhance solubility and tune the effective geometry between a target-binding ligand and an E3 ligase recruiter in PROTAC constructs. Its amine functionality enables robust conjugation strategies under commonly used bioconjugation conditions. The features summarized here are described in detail in the following sections, including its structure and practical reactivity for PROTAC assembly.

Structure: The linker contains a malonamide core connected to two PEG4-amine arms, providing a symmetrical, polyether-rich scaffold. It features amide linkages and terminal primary amines, with ether oxygen atoms that confer strong hydrogen-bonding capacity and improved aqueous compatibility.

Reactivity: The terminal primary amines support standard PROTAC linker-to-ligand coupling via nucleophilic substitution or acylation/amide-forming reactions, typically using activated carboxylic acids (e.g., NHS/EDC-type activation) or suitably functionalized electrophiles. Mild base or buffering conditions are commonly employed to maintain amine reactivity while preserving sensitive functional groups. Solvents such as aqueous-organic mixtures are frequently used to balance solubility and reaction kinetics.