Hydroxy-PEG2-t-butyl ester

This Hydroxy-PEG2-t-butyl ester is a PEG-based, cleavable linker building block designed to support PROTAC assembly and tuning of physicochemical properties. Its PEG segment helps modulate solubility and conformational flexibility, while the tert-butyl ester motif provides a chemically addressable handle for downstream coupling and controlled deprotection strategies. The linker is well suited for constructing targeted protein degradation molecules, where linker architecture can influence effective ternary complex formation and overall degradative performance. The structure and reactivity considerations are described in detail below.

Structure: The linker comprises a short polyethylene glycol spacer terminated by a hydroxy group and capped as a tert-butyl ester. It contains ether linkages within the PEG chain, an ester carbonyl, and an alcohol functionality, providing a polar, flexible scaffold with hydrogen-bonding capability.

Reactivity: The hydroxy terminus can be used for standard PROTAC linker functionalization via esterification or ether-forming coupling, typically under mild base/activator conditions compatible with PEG. The tert-butyl ester can be cleaved by acid-mediated deprotection to regenerate the carboxylic acid for subsequent amide or ester bond formation. Common approaches use coupling reagents such as carbodiimides with suitable additives, employing polar aprotic solvents.