Tos-PEG3-CH2COOtBu

Tos-PEG3-CH2COOtBu is a PEG-based PROTAC linker building block designed to connect targeting ligands to E3 ligase binders through a flexible, hydrophilic spacer. Its ether-rich PEG segment helps tune linker solubility and conformational freedom, which can improve productive ternary complex formation. The terminal carboxylate functionality enables robust conjugation strategies commonly used in targeted protein degradation workflows.

Structure: The molecule features a tosyl-protected PEG chain terminating in a methylene carboxylate ester. It contains aromatic sulfonate functionality, multiple ether linkages, and a tert-butyl ester group. These elements confer polarity, flexibility, and chemical stability under standard organic synthesis conditions.

Reactivity: The tosyl group and ester handle support common PROTAC assembly routes, including nucleophilic substitution or ester activation followed by coupling to amine-bearing or hydroxyl-bearing partners. Typical approaches use base-mediated transformations and standard coupling chemistries for ester-to-amide or ester-to-ester link formation. Suitable conditions rely on inert atmospheres when needed, polar aprotic solvents, and careful control of temperature to preserve PEG integrity and avoid unwanted side reactions.