TCO-PEG4-amine

TCO-PEG4-amine is a bifunctional, polyethylene glycol–based linker designed for efficient conjugation in PROTAC workflows that employ trans-cyclooctene (TCO) chemistry. Its flexible PEG spacer supports productive spatial presentation of warhead and ligand partners while the terminal amine enables straightforward coupling handles for building targeted protein degraders. The following sections describe its structural features and practical reactivity considerations for PROTAC assembly in research settings.

Structure: TCO-PEG4-amine contains a trans-cyclooctene moiety linked to a PEG spacer terminating in a primary amine. The molecule features ether linkages within the PEG chain and a cyclooctene ring with unsaturation, providing conformational flexibility and improved aqueous compatibility for conjugation.

Reactivity: The primary amine enables amide or urea formation via standard coupling strategies using activated carboxylic acids or isocyanate-type reagents under typical peptide-coupling conditions. Separately, the TCO group is suited to rapid bioorthogonal ligation with tetrazines through an inverse-electron-demand Diels–Alder mechanism, commonly performed in aqueous buffer at neutral pH. Solvent systems are selected to maintain solubility of PEG conjugates and preserve functional group integrity; catalysts are generally those used for amide bond formation when coupling the amine.