Azido-PEG6-propionic acid

Azido-PEG6-propionic acid is a polyethylene glycol-based PROTAC linker building block that incorporates an azide handle for bioorthogonal conjugation and a terminal carboxylic acid for controlled attachment to targeting ligands or warheads. Its flexible PEG spacer can help modulate effective reach and local concentration in ternary complex formation. The following sections describe its structure and practical reactivity considerations for PROTAC assembly.

Structure: The molecule features a PEG chain providing conformational flexibility, terminated by an azide functional group and a carboxylic acid. It contains ether linkages within the PEG segment and a terminal azide suitable for click-type reactions, along with an aliphatic propionic acid motif for coupling chemistry.

Reactivity: The azide group is typically used in copper-catalyzed azide–alkyne cycloaddition or related azide-compatible conjugation strategies to connect partners bearing an alkyne. The carboxylic acid enables amide-bond formation via activated ester or coupling reagent workflows. Reactions are commonly performed under inert or controlled conditions with polar aprotic solvents, and copper catalysis is selected based on substrate stability and downstream compatibility.