Amino-PEG9-propionic acid

Amino-PEG9-propionic acid is a polyethylene glycol-based PROTAC linker building block designed to connect ligands while improving solubility and enabling flexible spatial presentation to target proteins and E3 ligases. Its amino functionality supports robust conjugation strategies, and the propionic acid motif provides a handle for stable amide or related linkages. These features make it well suited for constructing degraders with tunable linker length and reduced steric constraints, as detailed in the sections below.

Structure: The linker comprises a PEG ether chain bearing terminal amino and carboxylic acid functionalities, providing a hydrophilic, flexible scaffold. It contains ether linkages within the PEG segment and a carboxylic acid group, enabling formation of amide-type bonds. The terminal amine allows controlled coupling to ligand-derived reactive groups.

Reactivity: The amino and carboxylic acid groups enable PROTAC assembly via amide bond formation using standard peptide-coupling chemistries. Typical approaches employ carboxyl activation (for example, carbodiimide-based systems with an auxiliary nucleophile) followed by coupling to an amine-bearing ligand or PROTAC intermediate. Reactions are commonly performed in polar aprotic solvents under conditions that preserve PEG stability, with pH and temperature optimized to minimize side reactions while maintaining coupling efficiency.