Amino-PEG5-propionic acid

Amino-PEG5-propionic acid is a PEG-based linker building block designed for constructing PROTACs and other targeted protein degradation conjugates. Its hydrophilic, flexible spacer character supports productive ternary complex formation by improving solubility and reducing steric constraints between the target-binding ligand and the E3 ligase moiety. The amino and carboxylic acid functionalities enable modular coupling strategies, making it valuable for assembling degraders in a stepwise, research-oriented workflow. Detailed structural and reactivity considerations are provided below.

Structure: The linker comprises a polyethylene glycol chain terminated with an amino group and a propionic acid functionality, providing a flexible, water-compatible scaffold. It contains ether linkages within the PEG segment and a carboxylic acid group capable of hydrogen bonding and ionic interactions, alongside an amine for covalent attachment chemistry.

Reactivity: The amino group can be used for amide-bond formation with activated carboxylic acids (for example, via common peptide-coupling reagents) or for coupling to carboxyl-activated ligand derivatives. The carboxylic acid can be converted to activated esters or acylating intermediates under standard coupling conditions. Reactions are typically performed in polar aprotic solvents with base to promote nucleophilic acyl substitution, proceeding through acyl-activation and amide/ester bond-forming steps.