Propargyl-PEG7-NHS ester

Propargyl-PEG7-NHS ester is a polyethylene glycol (PEG)-based linker designed for modular synthesis of PROTACs and other bifunctional degraders. The NHS ester enables efficient conjugation to primary amines on targeting ligands, while the terminal propargyl group provides a versatile handle for orthogonal click-type coupling. This combination supports controlled linker installation, improved solubility, and flexible architecture for assembling targeted protein degradation constructs, with detailed structural and reactivity considerations provided below.

Structure: The linker comprises a PEG chain terminating in an N-hydroxysuccinimide ester and a propargyl (alkyne) functionality. It contains an NHS-activated carboxylate for amide formation and a carbon–carbon triple bond suitable for bioorthogonal coupling. The ether-rich PEG backbone imparts hydrophilicity and conformational flexibility.

Reactivity: The NHS ester reacts with primary amines to form stable amide bonds under mildly basic aqueous buffer conditions, typically using freshly prepared solutions to minimize hydrolysis. The terminal alkyne can be used in copper-catalyzed azide–alkyne cycloaddition or related orthogonal coupling strategies, depending on the partner functionality. Common solvents include aqueous buffers with compatible cosolvents, and catalysts are selected to balance coupling efficiency and functional-group stability.