H-Asp(pNA)-OH · HCl is an amino acid derivative of aspartic acid bearing a p-nitroanilide (pNA) substituent on the side chain, classifying it as a functionalized Asp analogue suitable for peptide-related chemistry and analytical labeling. The molecule contains a free α-amino group and a carboxylic acid group while the side-chain functionality is converted to a p-nitroanilide, and the "· HCl" indicates formation of a hydrochloride salt that affects the protonation state of the amine for handling and solubility. In research workflows, this Asp(pNA) derivative is used as a substrate or building block for preparing peptide or amide derivatives that incorporate a chromogenic p-nitroanilide handle for monitoring cleavage or conjugation events in chemical biology and analytical method development.
CAT No: CP26722
CAS No:201732-79-8
Synonyms/Alias:201732-79-8;H-ASP-OHHCL;H-Asp(pNA)-OH.HCl;FT-0697961;L-Asparticacidbeta-4-nitroanilidehydrochloride
H-Asp(pNA)-OH · HCl is a protected amino acid hydrochloride consisting of the L-aspartic acid backbone bearing a p-nitroanilide side-chain functionality at the β-carboxyl position (Asp(pNA) motif). The molecule contains an α-amino group and a side-chain carboxamide linked to a p-nitroaniline chromophore, while the hydrochloride salt form increases handling stability and supports controlled reactivity during peptide coupling or derivative formation. The p-nitroaniline unit provides a strongly electron-withdrawing aromatic system that can participate in spectroscopic monitoring and can be retained through multiple synthetic steps. The presence of defined amino acid functionality makes it suitable for peptide building block preparation, side-chain functionalization strategies, and downstream analytical or mechanistic studies where an Asp-derived chromogenic handle is required.
1. Peptide Synthesis
H-Asp(pNA)-OH · HCl is applied in peptide synthesis workflows where an Asp residue bearing a chromogenic p-nitroanilide side-chain is required as a stable, side-chain-bearing building block. The amino acid framework supports standard peptide coupling chemistry at the α-amino and α-carboxyl positions, while the β-side-chain is already converted to the pNA amide, reducing the need for late-stage side-chain manipulation. The hydrochloride counterion can be managed through base treatment to enable efficient amide bond formation while maintaining the integrity of the p-nitroanilide chromophore. The resulting Asp(pNA)-containing peptides can be used as substrates or probes in peptide chemistry and biochemical research where side-chain-defined chromogenic reporting is beneficial.
2. Enzyme Assays
H-Asp(pNA)-OH · HCl is suitable for enzyme substrate design and mechanistic studies in biochemical research, particularly when a chromogenic p-nitroaniline reporting group is desired. The Asp(pNA) structure places the p-nitroanilide functionality in a defined side-chain context that can be incorporated into peptide or peptidomimetic substrates to monitor cleavage or transformation events by spectrophotometric readout. The amino acid-derived stereochemistry helps maintain recognition by enzyme active sites that discriminate between L- and D-configurations. The hydrochloride salt form supports reproducible handling during substrate synthesis and intermediate preparation for assay libraries.
3. Bioconjugation Chemistry
H-Asp(pNA)-OH · HCl can be employed in bioconjugation chemistry as an amino acid-based intermediate for constructing labeled biomolecule derivatives that retain a chromophoric p-nitroanilide handle. The molecule's functional group set enables conversion into activated derivatives suitable for coupling to amines or other nucleophiles, while the Asp-derived stereocenter can be used to preserve structural fidelity in biomolecular labeling constructs. The p-nitroaniline chromophore enables downstream detection and tracking of conjugates in analytical workflows. The resulting conjugation products can serve as tools for chemical biology studies, including monitoring binding events or tracking biomolecule transformations.
4. Analytical Research Standards
H-Asp(pNA)-OH · HCl is used in analytical research as a reference compound and intermediate for developing chromatographic and spectroscopic methods targeting Asp(pNA) motifs. The p-nitroaniline chromophore provides a strong UV-visible signal that can be exploited for detection of related peptides, degradation products, or reaction intermediates containing the same side-chain functionality. The defined amino acid identity and stereochemistry support method transfer to peptide coupling libraries and stability studies where Asp(pNA) is a recurring structural element. The hydrochloride salt form can improve reproducibility in standard preparation and calibration workflows for analytical monitoring.
5. Process Chemistry Intermediate
H-Asp(pNA)-OH · HCl is applicable as a process chemistry intermediate for fine chemical synthesis routes that require a chiral Asp-derived building block with a preinstalled chromogenic side-chain. The side-chain carboxyl is already converted to the p-nitroanilide, which can simplify manufacturing sequences by reducing the number of protecting-group manipulations at the β-position during peptide building block preparation. The hydrochloride salt form supports controlled handling and can be integrated into scalable derivatization steps that generate coupling-ready forms without altering the pNA chromophore. The resulting downstream derivatives can be manufactured as peptide reagents, assay components, or labeled intermediate materials for industrial and research supply chains.
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