This compound is the hydrochloride salt of (S)-methyl 2-amino-6-{[(9H-fluoren-9-yl)methoxy]carbonylamino}hexanoate, a derivative of L-lysine with selective protection. The Fmoc group orthogonally protects the ε-amino side chain, the α-amino group is unprotected (as HCl salt for stability), and the carboxylic acid is esterified as a methyl ester. It is used in peptide synthesis, particularly solution-phase approaches or as an intermediate for incorporating lysine residues where side-chain protection is needed without α-amino blocking. The Fmoc can be deprotected under mild basic conditions (e.g., piperidine in DMF) to reveal the side chain for further modification or coupling, while the ester provides handling stability. Applied in research laboratories for developing therapeutic peptides, biochemical probes, and diagnostic agents, its (S)-chirality ensures stereochemical integrity in biologically active structures.