N-(Azido-PEG2)-N-Boc-PEG3-Boc

This PROTAC linker, N-(Azido-PEG2)-N-Boc-PEG3-Boc, is designed to provide a flexible polyethylene glycol (PEG)-based spacer that supports productive ternary complex formation in targeted protein degradation workflows. Its azide handle enables robust bioorthogonal conjugation to ligands, while one Boc-protected amine and one tert-butyl ester-protected carboxylic acid offer controlled functional-group availability for stepwise assembly. The resulting modularity facilitates the synthesis of degraders with tunable linker length and polarity. Detailed structural and reactivity considerations are provided below.

Structure: The linker contains PEG ether segments providing conformational flexibility and hydrophilicity, together with one Boc-protected amine and one tert-butyl ester-protected carboxylic acid. An azide-bearing substituent serves as a reactive handle. The molecule features ether linkages along the PEG backbone, one Boc carbamate, and one tert-butyl ester.

Reactivity: The azide group is suitable for copper-catalyzed azide–alkyne cycloaddition or strain-promoted azide–alkyne coupling, enabling attachment to alkyne-functional targeting ligands under standard bioorthogonal conditions. Under appropriate acidic deprotection conditions, the Boc group reveals an amine and the tert-butyl ester reveals a carboxylic acid, providing two distinct handles for subsequent coupling. Solvent systems commonly used for PEG-linker chemistry support stepwise assembly and purification.