Amino-PEG6-propionic acid

This amino-PEG6-propionic acid linker is designed to provide a hydrophilic, flexible spacer for assembling PROTACs, enabling efficient spatial presentation of ligands to target proteins and E3 ligases. Its PEG-based architecture supports favorable solubility and reduced nonspecific interactions, while the terminal amino and carboxylic acid functionalities enable robust, modular conjugation strategies. The detailed structural and reactivity considerations are provided below.

Structure: The linker comprises a poly(ethylene glycol) segment terminated by an amino group and a propionic acid moiety, connected through stable carbon–nitrogen and carbon–oxygen linkages. Its ether-rich PEG backbone confers conformational flexibility, water compatibility, and multiple hydrogen-bonding sites that influence PROTAC solubility and ligand spacing.

Reactivity: The terminal carboxylic acid can be activated for amide-bond formation with amine-bearing ligands or handles, commonly via carbodiimide-mediated coupling or activated ester approaches. The amino group can participate in nucleophilic acyl substitution after appropriate activation. Reactions are typically performed under anhydrous or controlled-moisture conditions with suitable bases and coupling reagents to minimize side reactions and preserve linker integrity during PROTAC synthesis.