4-Bromo-L-Phenylalanine is a naturally occurring amino acid derivative in which the phenylalanine side chain bears a bromine substituent at the para (4-) position, retaining the amino acid backbone with an α-amino group and a carboxyl group. The molecule is specified as the L stereochemical form and features a benzyl side chain that contains the aryl bromide functionality, which can participate in halogen-directed chemical transformations while remaining compatible with peptide-related handling of the amino and carboxyl groups. In synthesis and chemical biology workflows, it is employed as a halogenated phenylalanine building block for preparing peptides and analogues, supporting structure-activity studies, and providing a chemically addressable handle for subsequent conjugation or labeling strategies.
CAT No: CP11201
CAS No:24250-84-8
Synonyms/Alias:4-BROMO-L-PHENYLALANINE;24250-84-8;(s)-2-amino-3-(4-bromophenyl)propanoic acid;L-4-Bromophenylalanine;(2S)-2-amino-3-(4-bromophenyl)propanoic acid;h-phe(4-br)-oh;L-p-Bromophenylalanine;Phenylalanine, 4-bromo-;MFCD00063062;l-4-bromophe;L-Phenylalanine, 4-bromo-;P-BROMO-L-PHENYLALANINE;P-BROMOPHENYLALANINE;SCHEMBL44832;IS_4-BROMO-PHENYLALANINE;PEMUHKUIQHFMTH-QMMMGPOBSA-N;AKOS010398002;AC-5856;CS-W009177;FB37986;GS-6454;4BF;BP-20585;HY-34597;DS-012234;4-Bromo-L-phenylalanine, >=98.0% (NT);NS00052242;EN300-217027;Q27454571;634-793-5;
4-Bromo-L-Phenylalanine is a halogenated, proteinogenic L-amino acid featuring a para-bromo substituent on the phenyl side chain, making it a practical aromatic building block for chemical biology and peptide/bioconjugation workflows. The aryl bromide provides a robust handle for downstream derivatization via cross-coupling and related electrophilic aromatic substitution-compatible chemistry, while the stereochemistry and free amino acid functionality keep it aligned with standard peptide assembly and analytical reference use. Researchers commonly select this scaffold when they need an aromatic group that can be selectively functionalized after incorporation into peptides or small molecules.
1. Peptide Synthesis Building Block
4-Bromo-L-Phenylalanine is used as an amino acid building block for preparing peptides that require a chemically addressable aromatic side chain. Peptide synthesis groups incorporate this residue to introduce a para-bromo functionality that can later be transformed into diversified aryl motifs through coupling-based modification strategies, enabling rapid structure-activity or structure-property exploration in custom peptide manufacturing and academic peptide chemistry. Because the residue is L-configured and matches the steric and backbone preferences of phenylalanine derivatives, it integrates naturally into peptide sequences where an aromatic side chain is needed but further side-chain elaboration is planned.
2. Bioconjugation Via Aryl Coupling
4-Bromo-L-Phenylalanine supports chemical biology workflows where an aryl bromide is used as a site-selective functionalization handle after peptide or small-molecule assembly. Researchers use this amino acid to install a reactive aromatic handle that can be converted into substituted aryl linkers for conjugation strategies, including coupling to aryl-containing tags, affinity handles, or reporter-bearing fragments. This approach is particularly useful when the conjugation chemistry must be performed on a defined residue position within a peptide scaffold rather than relying on less controlled modification of native side chains.
3. Medicinal Chemistry SAR Intermediates
4-Bromo-L-Phenylalanine is frequently selected in medicinal chemistry and peptidomimetic development programs as a versatile intermediate for generating bromo-activated aromatic analogs and for building libraries of substituted phenylalanine derivatives. Medicinal chemistry teams use the para-brominated aromatic ring as a modular starting point for diversification, allowing systematic variation of aryl substitution patterns while retaining the amino acid stereochemical identity in peptide-like scaffolds. This makes the reagent valuable for preparing analog panels used in structure-activity relationship studies and for downstream synthesis of aryl-functionalized intermediates.
4. Analytical Reference For Halogenated Amino Acids
4-Bromo-L-Phenylalanine is used as a reference material and calibration component in analytical method development targeting halogenated amino acid species. Analytical chemistry laboratories employ it to validate retention behavior, confirm identity in LC-MS workflows, and support quantitation or qualitative screening when brominated aromatic amino acids are expected as process impurities, degradation products, or labeled/unlabeled standards in research-grade assays. The defined para-bromo substitution provides a distinctive mass signature and chemical identity that is useful for establishing robust analytical performance for this class of compounds.
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