Fmoc-NMe-PEG-NHS ester is a commonly used functional group in drug research and development. It belongs to the class of N-hydroxysuccinimide (NHS) esters and is widely used for conjugation of peptides, proteins, and other biomolecules to various surfaces or drug delivery systems. This ester contains a pegylated spacer and a Fmoc (9-fluorenylmethoxycarbonyl) protecting group that is commonly used in solid-phase peptide synthesis. The Fmoc-NMe-PEG-NHS ester is a popular choice due to its water solubility and mild reaction conditions. It has been extensively used in the development of targeted drug delivery systems and in the synthesis of novel therapeutics.