4-Nitro-D-Phenylalanine is a non-proteinogenic, aromatic amino acid derivative featuring a D-configured α-amino acid backbone with a phenyl side chain substituted by a nitro group at the para (4-) position. The molecule contains both an amino functional group and a carboxylic acid functional group, with the electron-withdrawing nitro substituent imparting distinct polarity and aromatic reactivity compared with unsubstituted phenylalanine. In chemical biology and peptide chemistry, it is used as a substrate analog and building block for preparing labeled or structure-activity study peptides where the para-nitro aromatic functionality provides a spectroscopic handle and a site for further derivatization.
CAT No: CP16102
CAS No:56613-61-7
Synonyms/Alias:BOC-CIT-ONP;56612-88-5;C17H24N4O7;6292AH;ZINC71788014;Boc-L-Citrulline4-nitrophenylester;AM003430;4-NITROPHENYL(2S)-2-[(TERT-BUTOXYCARBONYL)AMINO]-5-(CARBAMOYLAMINO)PENTANOATE
4-Nitro-D-Phenylalanine is a D-configured, non-proteinogenic phenylalanine analog bearing a para-nitro group on the aromatic side chain. This electron-withdrawing nitro functionality makes it a useful aromatic handle in chemical biology and medicinal chemistry workflows where controlled incorporation of a non-natural amino acid is required. Researchers commonly use it as a stereochemically defined building block for peptide and peptidomimetic construction, as well as an aromatic motif for downstream derivatization and analytical characterization.
1. Peptidomimetic Building Blocks
4-Nitro-D-Phenylalanine is used by peptide chemistry groups to introduce a D-amino acid residue with a para-nitro aromatic side chain into peptidomimetics and modified peptide scaffolds. Its non-proteinogenic nature supports structure-activity relationship studies where researchers compare backbone stereochemistry and side-chain electronics across closely related analogs. The nitro-substituted phenyl group provides a chemically distinct aromatic environment that can be tracked by chromatographic behavior and mass spectrometry, supporting iterative library synthesis and SAR optimization in academic and industrial peptide discovery settings.
2. Medicinal Chemistry SAR Probes
4-Nitro-D-Phenylalanine serves medicinal chemistry teams as a defined aromatic substituent for SAR probing in peptidomimetic and constrained peptide-like series. The para-nitro group introduces a strong electronic perturbation relative to unsubstituted phenylalanine, enabling systematic evaluation of how aromatic electronics influence binding interactions and overall molecular recognition in vitro assay panels. Because the compound is stereochemically specified as the D enantiomer, it is particularly useful when researchers design analogs to examine stereochemical effects on conformation and structure-property relationships during lead optimization.
3. Chemical Biology Labeling Handles
4-Nitro-D-Phenylalanine is applied in chemical biology workflows that require an aromatic nitro functionality as a chemical handle for post-incorporation modification or analytical tracking. Teams use it to build peptides or peptide fragments containing a stable, easily detectable aromatic motif that can be leveraged during downstream derivatization strategies and characterization by LC-MS. This makes the reagent useful for mapping synthetic intermediates, verifying sequence incorporation in modified peptide constructs, and supporting experiments where a non-natural aromatic side chain is needed to distinguish engineered material from reference peptides.
4. Analytical Reference Standards
4-Nitro-D-Phenylalanine is also used as an analytical reference material for method development and verification in workflows involving non-natural amino acid-containing peptides. Analytical chemists employ it to confirm retention behavior, ionization response, and fragmentation patterns for LC-MS characterization of peptide synthesis mixtures and final products. Its defined stereochemistry and para-nitro substitution help researchers establish unambiguous identification criteria when monitoring incorporation of D-amino acid residues and when quantifying or verifying synthetic building blocks during quality control of research-grade peptide materials.
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