Propargyl-PEG4-acid

Propargyl-PEG4-acid is a PEG-based PROTAC linker designed to provide aqueous solubility, conformational flexibility, and a chemically addressable handle for modular assembly. Its propargyl functionality enables bioorthogonal-style conjugation strategies, while the terminal carboxylic acid supports stable amide formation with targeting ligands. These features facilitate efficient construction of targeted protein degraders and help tune linker length and attachment chemistry for controlled ternary complex engagement.

Structure: The linker contains a polyethylene glycol segment providing a hydrophilic, flexible backbone, connected to a propargyl group and a terminal carboxylic acid. It features an alkyne carbon–carbon triple bond, ether linkages within the PEG chain, and a carboxylic acid functionality suitable for acyl-derivatization.

Reactivity: The propargyl group is well suited for alkyne-reactive conjugation approaches commonly used in PROTAC synthesis, including copper-catalyzed azide–alkyne cycloaddition under standard organic solvent systems. The carboxylic acid can be activated for amide coupling with amine-bearing ligands using coupling reagents and base in polar aprotic media. Select conditions that preserve sensitive functional groups and maintain linker solubility during assembly.