Activeester
An active ester is an ester of a carboxylic acid in which the leaving group is highly activated, making the carbonyl more susceptible to nucleophilic attack than that of a standard ester. Activation of the carboxyl group creates an intermediate that undergoes rapid acyl transfer to nucleophiles such as amines or alcohols, forming amide or ester bonds under relatively mild conditions. This activated character is the basis for widespread use in synthetic and bioconjugation chemistry.
Common activating groups include N-hydroxysuccinimide (NHS), p-nitrophenol, and pentafluorophenol derivatives. NHS esters are among the most
Applications include peptide and protein synthesis, antibody–drug conjugation, small-molecule bioconjugation, and surface or polymer labelings. They