HO-PEG21-OH

HO-PEG21-OH is a polyethylene glycol-based bifunctional linker designed for constructing PROTACs through reliable, modular conjugation chemistry. Its PEG-rich backbone provides a flexible, hydrophilic spacer that can improve the effective reach and conformational adaptability between the ligand-binding warhead and the E3-recruiting element. This product is commonly used to tune linker length and polarity in targeted protein degradation workflows, and the following points describe its structure and practical reactivity considerations in detail below.

Structure: HO-PEG21-OH is a linear PEG diol featuring terminal hydroxyl groups connected by repeating ether units. The structure is dominated by flexible C–O–C linkages, offering high polarity and strong hydrogen-bonding capacity. As a result, it typically exhibits good solubility in aqueous and mixed organic media and behaves as a hydrophilic spacer.

Reactivity: The terminal alcohols enable PROTAC linker installation via standard hydroxyl-reactive transformations, such as activation to form leaving groups followed by nucleophilic substitution with complementary functional groups on ligands. Common approaches include converting alcohols to activated esters or carbonates, or using coupling strategies compatible with amines or carboxylic acids. Selection of mild bases, appropriate solvents, and temperature control is important to preserve ligand integrity and minimize side reactions during conjugation.