TCO-PEG12-acid

TCO-PEG12-acid contains a TCO moiety and a terminal carboxylic acid. The terminal carboxylic acid readily reacts with primary and secondary amine under EDC, DCC, HATU or other amide coupling conditions to form a stable amide bond. This reagent can react with tetrazine-containing compounds to form a stable covalent bond without the catalysis of Cu or elevated temperatures. The inverse-electron demand Diels-Alder cycloaddition reaction of TCO with tetrazines is the fastest bioorthogonal reaction with exceptional selectivity. The PEG spacer increases the aqueous solubility of the resulting compound.