H-4-Nitro-Phe-OEt · HCl is an amino acid ester hydrochloride derived from 4-nitro-L-phenylalanine, featuring an aromatic phenyl ring bearing a para nitro substituent and an ethyl ester (-COOEt) at the carboxyl terminus. The molecule contains a free amino group in its hydrochloride salt form (-NH2·HCl) and a nitro-functionalized side chain that can participate in electron-withdrawing and hydrogen-bonding interactions, while the esterification masks the carboxyl group relative to the free amino acid. This protected carboxyl functionality is commonly used in peptide and amide synthesis workflows and in chemical biology or analytical labeling contexts where controlled handling of the carboxyl group and the nitro-bearing aromatic side chain are required.
H-4-Nitro-Phe-OEt · HCl is a hydrochloride salt of the ethyl ester of 4-nitrophenylalanine, featuring an L-phenylalanine backbone with a para-nitro substituent on the aromatic ring and an esterified carboxyl group (OEt) paired with an amine hydrochloride for controlled handling. The molecule contains a chiral center at the alpha carbon, enabling stereochemically defined incorporation into peptide and peptidomimetic sequences. The para-nitro group provides an electron-withdrawing handle that can participate in reduction, nucleophilic aromatic substitution under activated conditions, or subsequent derivatization after conversion to a more reactive aniline or related functionalities. The ester and salt-form amine together support peptide-coupling workflows as well as downstream synthetic transformations typical of amino acid ester intermediates.
1. Peptide Synthesis
H-4-Nitro-Phe-OEt · HCl is applied in peptide building workflows where the amino acid ester and protected amine salt state support peptide coupling strategies under standard amide-forming conditions. The alpha-amino functionality, present as an HCl salt, can be deprotonated in situ to enable acylation, while the ethyl ester can be retained for C-terminal derivatization or converted to other terminal forms depending on the target sequence. The para-nitro-substituted phenyl side chain can be carried through coupling steps to maintain an orthogonality handle for later functional group interconversion. Peptide assembly using this chiral aromatic amino acid intermediate enables preparation of nitro-bearing peptide fragments and subsequent analog generation via nitro-to-amino or nitro-based aromatic transformations.
2. Side-Chain Functionalization
H-4-Nitro-Phe-OEt · HCl is suitable for side-chain functionalization programs in synthetic organic chemistry and chemical biology, leveraging the para-nitro group as a tunable reactive motif. The nitro substituent can be converted into an aniline or other nitrogen-containing derivatives to introduce new hydrogen-bonding patterns, altered electronics, and modified reactivity profiles on the aromatic ring. The amino acid ester framework allows controlled downstream conversion of the carboxyl group (for example, to amides or acids) while preserving the stereochemical integrity of the chiral center. Functionalized nitro-derived phenylalanine derivatives generated from this intermediate can be used to build SAR-focused libraries, probe binding interactions, or create molecular tags for subsequent conjugation chemistry.
3. Protected Amino Acid Chemistry
H-4-Nitro-Phe-OEt · HCl is employed as a chiral amino acid ester intermediate in protected amino acid synthesis where the amine hydrochloride form provides a practical handle for sequential protection/deprotection planning. The salt-stabilized amine can be managed to coordinate with coupling reagents and to control chemoselectivity during multi-step syntheses that require selective activation of the ester or conversion to an acid derivative. The ethyl ester enables C-terminal functional group manipulation, supporting preparation of protected C-termini, activation-ready acids, or incorporation into longer peptide fragments. The para-nitro aromatic substituent functions as a chemical "switch" that can be preserved during assembly and later transformed to expand the accessible chemical space of peptide building blocks.
4. SAR Studies
H-4-Nitro-Phe-OEt · HCl is applied to structure-activity relationship studies and molecular design efforts that require defined aromatic side-chain electronics and stereochemical control. The para-nitro group modulates aromatic electron density and can influence conformational preferences and intermolecular interactions when incorporated into peptide-like scaffolds or peptidomimetic constructs. The chiral phenylalanine core enables stereospecific placement of the aromatic functionality, supporting comparative studies across analogs differing in side-chain substitution patterns. Nitro-bearing derivatives produced from this intermediate can serve as precursors for a range of SAR-relevant analogs, including nitro-to-amino converted variants and other aromatic modifications that probe binding determinants.
5. Pharmaceutical Manufacturing
H-4-Nitro-Phe-OEt · HCl is relevant to pharmaceutical manufacturing workflows that require chiral amino acid intermediates for peptide intermediate preparation and fine chemical synthesis. The amino acid ester and amine salt form facilitate integration into scalable synthetic routes where C-terminal handling and amine activation steps are coordinated to minimize side reactions. The aromatic nitro functionality can be carried through intermediate stages and then converted at a later processing step to match the functional group requirements of the final peptide or peptidomimetic intermediate. Downstream utility includes manufacturing of nitro-functionalized building blocks and their conversion into chemically matched derivatives used in controlled synthetic sequences for complex active-molecule precursors.
6. Analytical Research Standards
H-4-Nitro-Phe-OEt · HCl can be used in analytical research and method development as a structurally defined amino acid ester salt standard for chromatographic and spectrometric characterization. The combination of a chiral alpha-amino acid framework with a para-nitro aromatic group provides strong, distinguishable signals that can support tracking of derivatization, coupling consumption, or conversion of nitro-containing intermediates. The ester functionality and salt form enable consistent sample preparation approaches aligned with amino acid ester handling in analytical workflows. Use of this compound as an analytical reference can support verification of stereochemical integrity and functional group transformations during amino acid derivatization and peptide building block synthesis.
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