Fmoc-protected 2-(2-hydroxyethoxy)ethylamine (Fmoc-HEEA), a specialty building block used as a hydrophilic spacer in peptide synthesis, bioconjugation, and pharmaceutical development. The Fmoc group protects the primary amine, providing stability during multi-step reactions and enabling selective deprotection under mild basic conditions (e.g., piperidine in DMF). The 2-(2-hydroxyethoxy)ethyl chain mimics PEG, enhancing water solubility of peptides, conjugates, and bioactive compounds for improved biochemical compatibility.