Propargyl-PEG8-NHS ester

Propargyl-PEG8-NHS ester is a PEG-based linker designed for efficient conjugation in PROTAC workflows, enabling the modular assembly of bifunctional degraders. Its NHS-ester functionality supports robust amide-bond formation with primary amines on targeting ligands, while the terminal propargyl group provides a chemically addressable handle for orthogonal coupling strategies. These features facilitate reliable linker installation, improved solubility, and flexible spatial control between recognition and recruitment elements; detailed structural and reactivity considerations are provided below.

Structure: The linker contains an NHS-activated ester attached to a polyethylene glycol chain, terminating in a propargyl (alkyne) group. It features an amide-forming NHS ester, ether-rich PEG segments, and a terminal carbon–carbon triple bond for subsequent bioorthogonal functionalization. The PEG backbone contributes hydrophilicity and conformational flexibility.

Reactivity: The NHS ester reacts with primary amines under mildly basic aqueous conditions to form stable amide bonds, typically using controlled pH buffers to preserve NHS reactivity. The propargyl handle enables orthogonal coupling approaches commonly used for PROTAC assembly, such as copper-catalyzed azide–alkyne cycloaddition or related alkyne click chemistries, depending on partner functionality. Solvent systems are chosen to balance amine accessibility and alkyne compatibility, with catalysts and ligands selected to minimize side reactions.