Propargyl-PEG3-azide

Propargyl-PEG3-azide is a bifunctional polyethylene glycol (PEG)-based linker designed for modular PROTAC assembly, enabling efficient conjugation between a ligand bearing an azide and a complementary partner bearing a reactive alkyne. Its PEG spacer supports favorable solubility and conformational flexibility, which can help maintain productive ternary complex formation. The molecule is commonly used as a “click” handle in targeted protein degradation workflows, and the following points describe its structure and practical reactivity considerations in more detail.

Structure: The linker contains an azide group and a terminal propargyl (alkyne) functionality connected through a short PEG chain. It features ether-rich segments, enabling hydrophilicity, and carbon–carbon and carbon–heteroatom bonds that support stable conjugation chemistry. The azide and alkyne are positioned for orthogonal bioorthogonal coupling.

Reactivity: Propargyl-PEG3-azide is primarily used in copper-catalyzed azide–alkyne cycloaddition to form a stable triazole linkage. Typical conditions employ a Cu(I-generating system, an appropriate ligand to control copper speciation, and polar solvents compatible with PROTAC components. The reaction proceeds via cycloaddition of the azide and alkyne; careful exclusion of strong reductants and control of copper levels are often used to minimize side reactions and preserve sensitive functional groups.