4-Carboxy-L-tryptophan is a naturally occurring amino acid derivative in the tryptophan family, featuring an indole-containing side chain substituted at the 4-position with an additional carboxyl group. The molecule contains both an amino group and a carboxyl group on the alpha carbon, and it is specified as the L stereochemical form, with the extra side-chain carboxyl providing an acidic functionality that can participate in ionic interactions and pH-dependent behavior. In peptide and protein chemistry, it is used as a building block to introduce a tryptophan-like indole motif bearing an extra carboxyl handle, supporting structure-function studies, peptide analog synthesis, and analytical method development for indole-containing amino acid variants.
CAT No: CP24601
4-Carboxy-L-tryptophan is an L-tryptophan derivative bearing an additional carboxyl group on the indole ring, providing a more acidic, highly functionalized aromatic side chain than proteinogenic tryptophan. This extra carboxyl functionality makes it a useful building block for designing peptides and peptide-like molecules with altered charge distribution, hydrogen-bonding capacity, and aromatic microenvironments. In synthetic and analytical workflows, the indole carboxyl group also supports downstream derivatization strategies where controlled polarity and side-chain functionality are required.
1. Peptide Building Block
4-Carboxy-L-tryptophan is used as a specialized amino acid building block for peptide synthesis when an indole-carboxyl side chain is needed to introduce additional negative charge and specific interaction motifs into the peptide sequence. Researchers developing acidic or charge-tuned peptide libraries often select this residue to modulate local electrostatics around an aromatic center, which can be important for structure-activity relationship studies in peptidomimetic development. The compound's L-configuration and amino acid functionality support incorporation into custom peptides through standard peptide assembly workflows, enabling systematic comparison against peptides containing canonical tryptophan or other aromatic residues.
2. Protein Interaction Probes
4-Carboxy-L-tryptophan is also applied in chemical biology and protein science to construct peptide probes that mimic or perturb aromatic binding environments with a defined, carboxylated indole motif. Because the side chain carries an additional acidic group, peptides incorporating this residue can be used to probe how charge and hydrogen-bonding patterns near an indole influence binding to protein pockets, receptors, or binding domains. This approach is commonly used in interaction mapping workflows where researchers need a chemically precise tryptophan analog rather than relying on non-specific aromatic substitutions.
3. Analytical Standards And LC-MS
4-Carboxy-L-tryptophan serves as a reference material for analytical method development and quantitation workflows involving tryptophan-derivative chemistry, including studies that require defined standards for LC-MS characterization of indole-carboxyl-containing species. Analytical chemists and metabolomics-focused groups may employ this compound to validate chromatographic behavior, retention characteristics, and mass spectrometric detection for target analytes or related degradation/derivatization products. Its well-defined structure and amino acid identity make it useful for calibration and method qualification when monitoring aromatic carboxylated metabolites or peptide fragments.
4. Pharmaceutical Intermediate Development
4-Carboxy-L-tryptophan is frequently used as a functionalized amino acid intermediate in medicinal chemistry and specialty synthesis programs that require an indole-carboxyl motif as a key structural element. Process and R&D chemists leverage the additional carboxyl group to enable downstream transformations that introduce polarity or serve as a handle for further derivatization in heteroaromatic scaffolds. This makes the compound relevant to the preparation of tryptophan-derived building blocks and to the synthesis of peptide-inspired small molecules where precise placement of an indole carboxyl group is required for structure-property studies.
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