Acetyl-L-Leucine is an N-acetylated derivative of the proteinogenic amino acid leucine, featuring an isobutyl side chain typical of the hydrophobic branched alkyl class. The molecule bears a carboxamide formed by acetylation of the amino group while retaining the carboxylic acid functionality, and the stereocenter at the alpha carbon is specified as L by the product name. As an amino acid derivative, it is used in peptide and amide chemistry as a protected/blocked leucine analogue for controlling chemoselectivity at the nitrogen and for preparing further leucine-containing intermediates in solution-phase or solid-phase synthesis workflows.
CAT No: CP01304
CAS No:1188-21-2
Synonyms/Alias:N-Acetyl-L-leucine;1188-21-2;acetyl-L-leucine;Ac-Leu-OH;N-Acetylleucine;(S)-2-Acetamido-4-methylpentanoicacid;N-acetyl-Leu;N-acetyl-leucine;n-acetyl-L-leucin;(2S)-2-acetamido-4-methylpentanoicacid;Leucine,N-acetyl-,L-;UNII-E915HL7K2O;acetylleucine;(S)-2-Acetylamino-4-methyl-pentanoicacid;CHEBI:17786;WXNXCEHXYPACJF-ZETCQYMHSA-N;MFCD00065131;SBB017526;CAS-1188-21-2;(2S)-2-(acetylamino)-4-methylpentanoicacid;DSSTox_CID_25870;DSSTox_RID_81188;DSSTox_GSID_45870;L-Acetylleucine;NCGC00094935-01
Acetyl-L-Leucine is an N-acetylated derivative of L-leucine, retaining the branched isobutyl side chain characteristic of leucine while converting the amino group into a stable amide. This structural change makes it less reactive as a free amino acid building block, while preserving the leucine carbon skeleton for use as a defined reference compound in chemical, analytical, and biomolecular studies. Because it is a small, well-defined amino acid derivative with a single carboxylic acid and an N-acetyl group, it is frequently used where controlled leucine chemistry is needed without introducing a free primary amine.
1. Analytical Reference Standards
Acetyl-L-Leucine is used as a defined analytical standard for method development and validation in LC-MS and related workflows that monitor amino acid derivatives, peptide fragments, or acylated metabolites. Researchers commonly include it in calibration and qualification sets when distinguishing N-acetylated leucine species from free leucine or other closely related isomers and derivatives, particularly in targeted profiling of small-molecule nitrogenous metabolites. Its fixed N-acetyl functionality provides a consistent mass signature and chromatographic behavior, supporting robust identification and quantitation in complex matrices such as biological extracts or reaction mixtures.
2. Peptide Fragment Controls
Acetyl-L-Leucine is applied as a peptide-fragment model and control compound in studies that evaluate acylated amino-termini, proteolysis readouts, or the behavior of leucine-containing motifs under chemical or enzymatic conditions. In peptide chemistry workflows, it can serve as a benchmarking compound for how N-acetylated leucine units respond in analytical detection, helping interpret signals arising from terminally modified peptides or hydrolysis products. Its N-acetyl group also makes it useful for distinguishing terminal acylation effects from those associated with free amino groups during assay development and sample interpretation.
3. Metabolic and Biochemical Profiling
Acetyl-L-Leucine is frequently used in metabolic research and biochemical profiling as a stable, defined leucine derivative for tracking or validating the presence of N-acetylated leucine species in experimental samples. Metabolism-focused laboratories use it to support targeted assays that discriminate acylated amino acid forms from parent amino acids, improving confidence when reporting changes in small-molecule composition during enzymatic incubations, cell-based experiments, or extraction-based studies. Its leucine-derived side chain ensures relevance to leucine-centric panels, while the N-acetyl modification provides a chemically distinct reference for interpreting acylation-related signals.
4. Pharmaceutical Intermediate Characterization
Acetyl-L-Leucine is used in pharmaceutical intermediate development and specialty chemical manufacturing contexts as a characterization compound for leucine-derived intermediates and acylated building blocks. Process development teams and analytical chemists may employ it as a structural reference for confirming identity and purity of related N-acylated species, especially when monitoring reaction mixtures where acylation state matters for downstream conversion steps. Because the molecule is a single, unambiguous N-acetyl leucine derivative, it supports consistent method transfer and impurity profiling when developing or optimizing synthetic routes that involve amino-acid acyl intermediates.
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