Azido-PEG9-amine

Azido-PEG9-amine is a polyethylene glycol–based linker bearing a terminal azide and a primary amine, designed to enable modular assembly of PROTACs through orthogonal chemistries. Its flexible PEG scaffold improves solubility and provides spatial separation between binding elements, while the azide handle supports bioorthogonal conjugation. The amine functionality further facilitates coupling to activated carboxyl groups or derivatization for subsequent linker exchange. Detailed structural and synthetic considerations are provided below.

Structure: The linker consists of a PEG chain terminated by an azide group and a primary amine. It contains ether linkages typical of PEG, with an azide substituent and an amine for nucleophilic reactivity. The flexible, hydrophilic backbone supports conformational mobility and favorable dispersion in aqueous media.

Reactivity: The azide is commonly used for copper-catalyzed or strain-promoted azide–alkyne cycloaddition to connect PROTAC warheads and ligands under bioorthogonal conditions. The primary amine can be used for amide-bond formation via coupling to activated carboxylic acids, or for forming stable linkages through standard amination/derivatization strategies. Typical workflows employ polar aprotic or aqueous buffers compatible with azide stability, with catalysts and ligands selected to balance coupling efficiency and functional-group tolerance.