Azido-PEG3-alcohol

Azido-PEG3-alcohol is a polyethylene glycol-based linker bearing a terminal azide and a hydroxyl handle, enabling modular synthesis of PROTAC constructs through orthogonal functional-group chemistry. Its PEG character supports solubility and spatial flexibility, while the azide provides a bioorthogonal “click” handle for efficient conjugation to complementary alkynyl partners. The hydroxyl group further facilitates downstream derivatization, making this linker well-suited for assembling targeted protein degradation reagents. Detailed structural and reactivity considerations are provided below.

Structure: The linker consists of an ethylene glycol repeat unit terminated by an azide and a primary alcohol, connected through ether linkages characteristic of PEG scaffolds. It contains an azide functional group and a hydroxyl group capable of hydrogen bonding, with a flexible, polar backbone that enhances aqueous compatibility.

Reactivity: The terminal azide is designed for copper-catalyzed azide–alkyne cycloaddition with terminal alkynes to form stable triazole linkages, a widely used strategy in PROTAC assembly. Typical conditions employ a Cu(I) source generated in situ, with suitable ligands to control copper speciation, in polar organic/aqueous solvent mixtures. Alternative strain-promoted azide–alkyne cycloaddition can be used when copper-free conjugation is preferred.