N-(acid-PEG3)-N-bis(PEG3-azide)

This acid-PEG3-based linker, N-(acid-PEG3)-N-bis(PEG3-azide), is designed to enable modular PROTAC assembly through azide-functional handles while retaining solubility and flexible spacer behavior. Its PEG-rich architecture supports efficient conjugation and can help maintain productive ternary complex formation by reducing steric constraints. The following sections describe its structural features and practical reactivity considerations for linker-mediated PROTAC synthesis in research settings.

Structure: The linker consists of an acid-terminated PEG3 segment connected to a tertiary nitrogen that bears two PEG3-azide arms. It is characterized by ether-rich PEG chains, an amide linkage to the acid fragment, and terminal azide functional groups suitable for bioorthogonal coupling. Overall, it is expected to be highly polar and water-compatible.

Reactivity: The PEG3-azide groups support azide–alkyne cycloaddition for constructing PROTACs, typically using copper(I) catalysis or copper-free variants depending on substrate sensitivity. Reaction conditions are generally mild and performed in appropriate polar solvents to maintain PEG solubility. Mechanistically, the azide undergoes cycloaddition with a complementary alkyne to form a stable triazole linkage, enabling controlled attachment of targeting ligands and warheads.