Propargyl-PEG5-amine

Propargyl-PEG5-amine is a polyethylene glycol–based linker bearing a terminal propargyl group and a primary amine, enabling modular assembly of targeted protein degradation constructs. Its flexible PEG segment supports solubility and conformational adaptability, while the reactive propargyl handle facilitates bioorthogonal conjugation strategies commonly used in PROTAC workflows. The terminal amine provides an additional functional site for coupling to ligands or scaffolds. The following sections describe its structure and practical reactivity considerations in detail below.

Structure: The linker comprises a PEG ether backbone that confers flexibility and hydrophilicity, terminated by a primary amine and a propargyl (alkyne) functionality. It contains ether linkages, a carbon–carbon triple bond in the propargyl group, and an amine capable of forming salts or participating in amide-forming reactions.

Reactivity: The terminal alkyne supports copper-catalyzed azide–alkyne cycloaddition or strain-promoted azide–alkyne cycloaddition, enabling efficient conjugation to azide-bearing PROTAC components under mild conditions. The primary amine can be used for amide coupling to carboxylic acid–functional ligands using standard coupling chemistries, typically requiring activation of the acid and an appropriate base. Solvent choice often favors compatibility with both PEG solubility and the selected coupling strategy.