Azido-PEG3-S-PEG3-azide

Azido-PEG3-S-PEG3-azide is a bifunctional, PEG-based linker designed for modular assembly of PROTACs and other heterobifunctional degraders. Its flexible poly(ethylene glycol) segments help tune linker length and conformational freedom, while the terminal azide groups enable efficient bioorthogonal conjugation. The central thioether provides chemical stability and a defined connection point between PEG arms. Detailed structural and reactivity considerations for PROTAC construction are provided below.

Structure: The molecule contains two terminal azide functional groups connected through PEG3 chains, with a central sulfur-containing linkage. Its ether-rich PEG segments confer flexibility and hydrophilicity, while the azide moieties provide stable handles for click-type coupling. Overall, it behaves as a polar, conformationally adaptable linker suitable for conjugation.

Reactivity: Terminal azides are typically used in copper-catalyzed azide–alkyne cycloaddition or strain-promoted azide–alkyne cycloaddition, enabling formation of stable triazole linkages to complementary alkyne-bearing warheads. For copper-catalyzed variants, reactions are commonly performed in polar organic/aqueous mixtures under inert conditions with standard Cu(I) generation systems. Solvent choice and copper control are important to minimize side reactions and preserve sensitive PROTAC components.