This compound, commonly referred to as Fmoc-PEG-NHS ester, is a specialized reagent used in solid-phase peptide synthesis (SPPS). It consists of an Fmoc-protected amine linked through a long polyethylene glycol (PEG) chain (approximately 12 ethylene glycol units) to an N-hydroxysuccinimide (NHS) active ester. The NHS ester facilitates covalent attachment to amine-functionalized resins, thereby introducing a flexible, hydrophilic PEG linker that significantly improves solubility in organic solvents during synthesis.

This linker is particularly advantageous for the assembly of long-chain or hydrophobic peptides, where traditional resins may cause aggregation or solubility issues. After immobilization on the resin, the Fmoc group is selectively removed under mild basic conditions (e.g., with piperidine), enabling the coupling of the first N-protected amino acid. The compound's high reactivity and selectivity ensure efficient peptide elongation with minimal side reactions. It is widely applied in the production of high-purity peptides for pharmaceutical research, drug development, and biochemical applications.