(S)-Fmoc-Leu-Leu-OH is a protected dipeptide derivative primarily used in solid-phase peptide synthesis, enabling the stepwise construction of complex peptides with precise stereochemical control. The Fmoc protecting group offers mild base-labile deprotection, ideal for efficient coupling in automated synthesizers. This building block is commonly employed in the synthesis of branched peptides, peptide libraries, and bioconjugates for pharmaceutical, biochemical, and materials research applications. Its dual hydrophobic leucine side chains enhance solubility management in organic solvents during assembly. Additionally, it supports drug discovery platforms and the development of peptide-based therapeutics and nanomaterials.