Acetyl-L-leucine (N-acetyl-L-leucine) is an N-acylated derivative of the branched-chain amino acid L-leucine, with the formal IUPAC name (2S)-2-acetamido-4-methylpentanoic acid and molecular formula C8H15NO3. The molecule features an acetamide moiety on the α-amino group, a terminal carboxylic acid, and a hydrophobic isobutyl side chain, preserving the chiral (S) configuration at the α-carbon. This combination of a polar amide and carboxylate functionality with a nonpolar side chain affords a balanced amphipathic profile and moderate polarity, reflected in its topological polar surface area (TPSA) of 66.4. These structural features make the compound a useful, structurally defined model for probing how N-acylation modulates the properties of amino acids in solution and in complex matrices.

As a small, well-characterized N-acyl amino acid, acetyl-L-leucine is suitable for use as a reference material or test analyte in chromatographic and spectroscopic method development. The presence of both an amide and a carboxylic acid enables predictable ionization behavior in acid–base and mass spectrometric workflows, while the branched hydrophobic side chain supports studies on retention behavior in reversed-phase and mixed-mode systems. Its defined stereochemistry allows investigations into chiral recognition, separation, and derivatization strategies for amino acid derivatives. The compound is therefore valuable in research focused on peptide and amino acid chemistry, physicochemical profiling, and analytical method optimization for N-acylated amino acid species.