L-Isoleucine is a proteinogenic, aliphatic amino acid featuring a branched side chain (sec-butyl-like) attached to the α-carbon, with both amino and carboxyl groups on the same molecule. The molecule is present as the L stereoisomer, bearing a primary amino group and a carboxylic acid that can exist as zwitterions under aqueous conditions, enabling formation of peptide bonds through its amino functionality and controlled reactivity of the carboxyl group during synthesis. L-Isoleucine is used as a defined building block for peptide and protein chemistry, including incorporation into peptides in solid-phase or solution-phase synthesis and as a reference material for amino acid analysis and derivatization-based analytical workflows.
CAT No: CP01205
CAS No:73-32-5
Synonyms/Alias:l-isoleucine;Isoleucine;73-32-5;(2S,3S)-2-Amino-3-methylpentanoicacid;(S)-Isoleucine;(S,S)-Isoleucine;2S,3S-Isoleucine;L-(+)-Isoleucine;erythro-L-Isoleucine;2-Amino-3-methylvalericacid;L-Ile;iso-leucine;alpha-Amino-beta-methylvalericacid;ISOLEUCINE,L-;Isoleucine(VAN);Valericacid,2-amino-3-methyl-;Isoleucinum[Latin];Isoleucina[Spanish];L-Norvaline,3-methyl-,erythro-;Aceticacid,amino-sec-butyl-;Norvaline,3-methyl-;(2S,3S)-alpha-Amino-beta-methyl-n-valericacid;Pentanoicacid,2-amino-3-methyl-;(2S,3S)-alpha-Amino-beta-merthylvalericacid;CCRIS5229
L-Isoleucine is a naturally occurring L-amino acid with an aliphatic side chain bearing a stereogenic carbon, giving the molecule a defined chiral identity that is preserved in peptide incorporation. The structure contains a primary amino group and a carboxylic acid, enabling salt formation, acid-base control, and standard peptide coupling chemistry after appropriate protection. L-Isoleucine participates in transamination and catabolic pathways in biochemical systems, while its side-chain branching supports hydrophobic packing in peptides and protein environments. As a chiral, non-aromatic amino acid, it serves as a reliable building block for protected amino acid synthesis, stereochemically controlled derivatization, and downstream conversion into peptide analogs and industrial intermediates.
1. Peptide Synthesis
L-Isoleucine is used in peptide building block preparation and solid-phase or solution-phase peptide coupling workflows where an L-configured amino acid residue is required for stereochemical fidelity. The amino and carboxyl functionalities enable conversion into N-protected, C-activated forms for amide bond formation, while the branched side chain can influence coupling conditions and subsequent deprotection selectivity. Incorporation of the intact L-stereocenter and side-chain topology supports the formation of peptides with defined hydrophobic character and conformational preferences. L-Isoleucine-derived residues are therefore applied for generating peptide libraries, reference standards, and sequence-defined intermediates in synthetic peptide chemistry.
2. Protected Amino Acid Chemistry
L-Isoleucine is commonly transformed into N-protected amino acid derivatives to control chemoselectivity during multistep synthesis, including orthogonal strategies for N- and carboxyl protection. The primary amine can be protected using acyl or carbamate protecting groups, while the carboxyl group can be maintained as an acid, ester, or activated derivative depending on the coupling format. The stereogenic centers in the backbone and side chain support stereochemically consistent incorporation into peptides and enable reliable downstream deprotection to regenerate the free amino acid. L-Isoleucine thus functions as a practical chiral starting material for protected amino acid synthesis, peptide coupling readiness, and process chemistry intermediate preparation.
3. Chemical Biology And SAR Studies
L-Isoleucine is applied in chemical biology and structure-activity relationship studies as a component for designing peptide mimetics and amino acid substitutions that probe hydrophobic interactions and backbone recognition. The branched aliphatic side chain provides a handle for modulating steric bulk and hydrophobic surface area without introducing aromatic or heteroatom functionality. Side-chain derivatization can be used to generate analogs for receptor-binding studies, enzyme substrate mapping, or conformational probing where the L-configuration is retained to maintain biological relevance of stereochemistry. L-Isoleucine-based analogs can be employed to construct focused SAR panels and to support mechanistic studies in peptide and peptidomimetic chemistry.
4. Bioconjugation Chemistry
L-Isoleucine is suitable for bioconjugation workflows where amino acid residues are incorporated into linker peptides or used to generate functional handles after controlled derivatization. The carboxyl group and amino functionality can be converted into activated intermediates for amide coupling to biomolecule scaffolds, while protection strategies prevent cross-reactivity during multi-component conjugation. Side-chain functionalization can be introduced through chemically addressable transformations that preserve the L-stereochemical identity of the amino acid residue. L-Isoleucine-derived conjugation intermediates support preparation of labeled peptides, affinity reagents, and biomolecule-modified constructs used in biochemical research and analytical development.
5. Pharmaceutical Manufacturing Intermediates
L-Isoleucine is used as a chiral feedstock and intermediate in pharmaceutical manufacturing contexts that require amino acid-derived building blocks for peptide-like active ingredients or formulation-related components. The amino acid's defined stereochemistry supports consistent incorporation into protected amino acid derivatives and peptide intermediates used in controlled synthetic routes. Carboxyl activation and N-protection enable manufacturing-compatible coupling steps that minimize epimerization risk when appropriate conditions and protecting-group strategies are selected. L-Isoleucine therefore serves as a practical starting material for fine chemical synthesis and amino acid intermediate preparation aligned with industrial peptide chemistry.
6. Industrial Bioprocessing and Fermentation Inputs
L-Isoleucine is relevant to industrial bioprocessing as a fermentation-derived amino acid input and as a component in nutrient formulations that support microbial production of value-added chemicals. The molecule's zwitterionic character and well-defined L-configuration make it suitable for incorporation into defined media and for downstream conversion into protected derivatives used in specialty chemical manufacturing. Amino acid chemistry downstream of fermentation often includes derivatization to esters, protected forms, or activated intermediates for coupling and polymer-related modifications. L-Isoleucine thus functions as an industrially meaningful amino acid starting point that bridges bioprocess supply with chiral intermediate production for applied chemistry.
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