N-(Propargyl-PEG2)-N-Boc-PEG3-t-butyl ester

This PROTAC linker can be used as a flexible, solubilizing polyethylene glycol (PEG) spacer in targeted protein degradation conjugation workflows. Its protected functional groups enable controlled, stepwise conjugation to ligands while maintaining chemical stability during synthesis and purification. The following sections describe the linker’s structural features and practical reactivity considerations for constructing PROTACs in a research setting.

Structure: The linker contains PEG-based ether segments that impart conformational flexibility and improved aqueous compatibility. It also includes a propargyl handle and a Boc-protected amine, along with an ester functionality. The structure features ether linkages, an ester carbonyl, and an alkyne suitable for selective coupling strategies.

Reactivity: The propargyl group provides a terminal alkyne handle for copper-catalyzed azide–alkyne cycloaddition (CuAAC) with azide-bearing partners; strain-promoted azide–alkyne cycloaddition (SPAAC) requires a strained alkyne partner such as DBCO or BCN rather than an ordinary terminal alkyne. Boc protection supports amine handling during multi-step synthesis, with deprotection typically performed under standard acidolysis conditions to reveal a reactive amine. The ester can be incorporated or transformed using conventional ester-chemistry tactics (e.g., activation or nucleophilic substitution) to install the final linker–ligand connectivity.