Azido-PEG8-propionic acid

Azido-PEG8-propionic acid is a polyethylene glycol (PEG)-based linker bearing an azide handle and a terminal carboxylic acid, enabling modular assembly of PROTACs through orthogonal chemistries. Its flexible PEG scaffold helps tune solubility, linker length, and conformational freedom, while the azide group serves as a reliable functional handle for bioorthogonal conjugation. The terminal acid further supports stable coupling to targeting or E3-ligand moieties. Detailed structural and reactivity considerations are provided below.

Structure: The molecule consists of a PEG ether backbone terminated by an azide substituent and a propionic acid functionality. It features ether linkages, an azide functional group, and a carboxylic acid capable of forming amide or ester derivatives. The flexible, polar PEG segment promotes aqueous compatibility.

Reactivity: The azide group is typically used in copper-catalyzed azide–alkyne cycloaddition or strain-promoted azide–alkyne cycloaddition to connect PROTAC fragments under mild, bioorthogonal conditions. The carboxylic acid is commonly activated for amide bond formation using standard coupling chemistries (e.g., carbodiimide-based systems) in polar organic solvents with controlled pH. Reaction design should consider PEG-mediated solubility and minimize side reactions by maintaining appropriate reagent purity and stoichiometry.