Allyl-PEG4-OH

Allyl-PEG4-OH is a polyethylene glycol-based PROTAC linker featuring an allyl terminus and a terminal hydroxyl group, designed to provide aqueous compatibility, conformational flexibility, and efficient spacing between ligand modules. Its ether-rich backbone supports favorable solubility and reduced nonspecific interactions, while the allyl functionality enables orthogonal conjugation strategies commonly used in targeted protein degradation workflows. The following points describe the structure and practical reactivity considerations in detail below.

Structure: The linker consists of an ether-linked PEG chain terminated by an allyl group and a primary alcohol. It contains multiple ether oxygen atoms that confer hydrophilicity and hydrogen-bonding capacity. The allyl moiety provides an alkene handle, while the PEG segment offers flexible, solvated conformations.

Reactivity: The allyl group can be engaged through allyl-functionalization chemistries such as transition-metal-catalyzed coupling or radical-mediated transformations, enabling attachment to complementary PROTAC fragments under standard organic synthesis conditions. The terminal hydroxyl group supports derivatization to activated intermediates (for example, ester or ether formation) using coupling reagents and appropriate bases. Solvent choice typically favors compatibility with PEG ethers, and mild conditions are preferred to preserve linker integrity during PROTAC assembly.