Azide-PEG3-Tos

This Azide-PEG3-Tos linker is designed for modular PROTAC synthesis, providing an azide handle for bioorthogonal conjugation and a PEG-based spacer to support productive ternary complex formation. Its tosylate-derived leaving group enables efficient functional group interchange under standard organic conditions, facilitating rapid assembly of targeted degradation constructs. The following sections describe its structure and practical reactivity considerations in detail.

Structure: The linker contains a PEG3 ethylene glycol spacer that imparts conformational flexibility and hydrophilicity, coupled to an azide functional group and a tosylate moiety. Key features include ether linkages within the PEG chain and an aryl sulfonate ester, with an azide suitable for click-type transformations.

Reactivity: The azide group is compatible with copper-catalyzed azide–alkyne cycloaddition or strain-promoted azide–alkene cycloaddition, enabling attachment to alkyne-bearing ligands under mild, bioorthogonal conditions. The tosylate portion can act as an activated leaving group for nucleophilic substitution, typically using polar aprotic solvents and appropriate nucleophiles to install PROTAC-forming connection points. Reaction design should prioritize maintaining linker integrity and minimizing azide side reactions.