Hydroxy-PEG6-t-butyl ester

This Hydroxy-PEG6-t-butyl ester linker is a polyethylene glycol–based, hydroxyl-functional spacer designed for constructing PROTACs and other heterobifunctional degraders. Its PEG character supports solubility and flexible reach between binding modules, while the protected ester functionality enables controlled conjugation strategies. Researchers can leverage this linker to tune linker length, reduce steric constraints, and facilitate stepwise assembly of targeted protein degradation constructs; detailed structural and synthetic considerations are provided below.

Structure: The linker contains a PEG backbone featuring repeating ether units, terminating in a hydroxyl group and a tert-butyl ester. It presents flexible C–O and C–C connectivity, with an ester carbonyl and ether oxygen atoms that promote polarity and hydrogen-bonding capability, improving aqueous compatibility.

Reactivity: The tert-butyl ester can be selectively deprotected under acid-mediated conditions to reveal the corresponding carboxylic acid for subsequent amide or ester coupling to target-binding ligands. The terminal hydroxyl group can participate in standard functionalization routes (for example, activation and nucleophilic substitution) to install electrophiles for PROTAC assembly. Common approaches use coupling reagents and base/solvent systems compatible with PEG stability, with reaction monitoring required to avoid overreaction or linker cleavage.