N'-Boc-L-2,4-diaminobutyric acid methyl ester hydrochloride is a protected derivative of the non-proteinogenic amino acid L-2,4-diaminobutyric acid (L-Dab). It features a tert-butoxycarbonyl (Boc) group protecting the side-chain amine and a methyl ester protecting the carboxylic acid, making it a versatile building block for peptide synthesis. This compound is primarily used as a key intermediate in the synthesis of peptides and peptidomimetics, particularly those requiring the incorporation of the Dab residue. The Dab side chain, with its additional amino group, is crucial for introducing positive charge, hydrogen bonding, or serving as a site for further chemical modification. It finds significant application in the research and development of bioactive peptides, including antimicrobial peptides (AMPs) and enzyme inhibitors. As a Boc-protected amino acid ester, it is a stable, crystalline solid suitable for standard solid-phase peptide synthesis (SPPS) or solution-phase coupling strategies. Its protected functional groups allow for selective deprotection and sequential chain elongation, making it a valuable reagent in medicinal chemistry and chemical biology for constructing complex molecular architectures.