Fmoc-Lys(Alloc)-OH is widely used in peptide synthesis, particularly in solid-phase peptide synthesis (SPPS). It serves as a protected amino acid derivative, where the Fmoc group safeguards the amino terminus, and the Alloc group protects the side chain of lysine. This dual protection allows for selective deprotection, enabling the stepwise construction of peptides with high precision. Its application is crucial in synthesizing complex peptides, especially those requiring orthogonal protection strategies. Additionally, it is employed in the development of peptide-based drugs, biomaterials, and research tools, where controlled lysine modification is essential.