Azido-PEG8-C1-NHS ester

Azido-PEG8-C1-NHS ester is a bifunctional polyethylene glycol-based PROTAC linker designed to connect a primary amine-bearing targeting ligand to an azide-functional handle for subsequent conjugation. Its PEG spacer improves aqueous solubility and provides conformational flexibility, which can help maintain productive ternary complex formation in targeted protein degradation workflows. The azide enables orthogonal “click” coupling, while the NHS ester supports efficient amide-bond formation with amines. Detailed structural and reactivity considerations are provided below.

Structure: The linker contains a PEG chain terminating in an azide group and a carboxylic acid activated as an N-hydroxysuccinimide ester, enabling stable storage of the electrophile. It features ether linkages along the PEG backbone and forms an azide-functional terminus suitable for azide–alkyne cycloaddition.

Reactivity: The NHS ester reacts with primary amines to form amide bonds under mildly basic aqueous or mixed solvent conditions, typically using buffering systems compatible with NHS chemistry. The azide is retained for later bioorthogonal conjugation via copper(I)-catalyzed or strain-promoted azide–alkyne cycloaddition. Select solvents and catalysts that preserve azide integrity and minimize side reactions such as hydrolysis of the activated ester.