Propargyl-PEG6-COOtBu

Propargyl-PEG6-COOtBu is a polyethylene glycol-based PROTAC linker designed to provide a flexible, water-compatible spacer between targeting and recruiting ligands while incorporating a terminal alkyne handle for orthogonal conjugation. Its PEG segment supports favorable solubility and reduced aggregation, which can improve the practical handling of large conjugates. The protected carboxylate functionality enables controlled downstream derivatization, making this linker suitable for constructing targeted protein degraders.

Structure: The linker contains a PEG chain that confers conformational flexibility and hydrophilicity, terminating in a propargyl (alkyne) group and a tert-butyl-protected carboxylate. It features ether linkages along the PEG backbone, an alkyne carbon–carbon triple bond, and ester/alkyl protecting group chemistry at the carboxyl terminus.

Reactivity: The terminal alkyne enables bioorthogonal conjugation strategies such as copper-catalyzed azide–alkyne cycloaddition or related alkyne-alkene coupling approaches, typically performed under conditions compatible with PEG-containing substrates. The tert-butyl ester can be deprotected under standard acidolysis to reveal a free carboxylic acid for amide or ester formation. Common coupling methods use carbodiimide-based activation with amine partners, often in polar organic solvents, optionally with base to promote efficient bond formation.