NHS-Ac-N3

This PROTAC linker, NHS-Ac-N3, is an activated N-hydroxysuccinimide (NHS) ester bearing an azide handle, designed to enable efficient, modular assembly of targeted protein degraders. Its NHS functionality supports rapid coupling to primary amines under mild conditions, while the azide group provides a versatile bioorthogonal “click” handle for subsequent conjugation steps. The combination of controlled reactivity and orthogonal functional groups makes it well suited for constructing heterobifunctional PROTACs, where linker geometry and chemoselectivity directly influence productive ternary complex formation. Detailed structural and reactivity considerations are provided below.

Structure: NHS-Ac-N3 features an NHS-activated ester linked to an acyl group and an azide substituent. The molecule contains amide-forming carbonyl functionality and an electrophilic ester susceptible to nucleophilic attack, alongside an azide moiety suitable for azide–alkyne cycloaddition chemistry.

Reactivity: The NHS ester reacts with primary amines via nucleophilic acyl substitution, forming a stable amide linkage. Typical coupling is performed in aqueous or mixed aqueous buffer systems at near-neutral conditions, using bases such as mild amine bases to promote amine availability while minimizing hydrolysis. The azide can then be carried forward using strain-promoted or copper-catalyzed azide–alkyne cycloaddition, depending on the compatibility of the protein-binding ligands and overall PROTAC assembly workflow.