Azido-PEG5-CH2CO2-PFP

This Azido-PEG5-CH2CO2-PFP linker is designed for modular PROTAC synthesis, combining a bioorthogonal azide handle with a reactive activated ester for efficient conjugation to amine-containing ligands. Its PEG-based spacer promotes solubility and conformational flexibility, which can improve productive ternary complex formation. The azide functionality enables orthogonal “click” coupling strategies, while the PFP ester supports rapid linkage under mild conditions.

Structure: The linker contains a PEG-derived polyether chain providing a hydrophilic, flexible spacer, terminated by an azide group and a carboxylate activated as a pentafluorophenyl ester. It features ether linkages, an azide functional group, and an ester carbonyl susceptible to nucleophilic acyl substitution.

Reactivity: The pentafluorophenyl ester reacts with primary amines via nucleophilic acyl substitution, typically using anhydrous or low-water organic solvents with a suitable base to promote acyl transfer. The azide enables copper-catalyzed azide–alkyne cycloaddition or strain-promoted cycloaddition, depending on the partner. For PROTAC assembly, sequential coupling is commonly employed to preserve orthogonality and minimize side reactions.