Ac-Orn-OH is an N-acetylated amino acid derivative of ornithine (Orn), featuring a primary amino group and a carboxylic acid (-CO2H) on the side chain-bearing, basic amino acid scaffold. The molecule contains an N-acetyl (Ac) protecting group on the α-amino functionality, while the side-chain terminal amine remains unprotected and can participate in salt formation or nucleophilic reactions under appropriate conditions. As a protected ornithine derivative, Ac-Orn-OH is used as a precursor for preparing more complex amino acid and peptide derivatives, including building blocks where controlled chemoselectivity of the α-amino group is required for stepwise coupling and subsequent functionalization of the side-chain amine.
CAT No: CP27278
CAS No:6205/8/9
Synonyms/Alias:62040-55-5;4-Amino-L-phenylalaninehydrochloride;H-Phe(4-NH2)-OHHCl;p-Amino-L-phenylalaninehydrochloride;ST50320081;(S)-2-amino-3-(4-aminophenyl)propanoicacidhydrochloride;(2S)-2-amino-3-(4-aminophenyl)propanoicacidhydrochloride;P-AMINOPHENYLALANINEHYDROCHLORIDE;EINECS263-388-2;312693-79-1;4-Amino-L-phenylalanineHCl;AminophenylalanineHydrochloride;AC1O596G;SCHEMBL3873365;09193_FLUKA;CTK8B3711;4-Amino-3-phenyl-L-alanineHCl;MolPort-003-925-567;L-4-AminophenylalanineHydrochloride;ANW-42981;KM0570;AKOS015909548;AK-81282;AM008385;AN-39150
Ac-Orn-OH is an N-acetylated ornithine derivative supplied as a free carboxylic acid, featuring the ornithine side chain with a terminal primary amine that remains available for downstream coupling or derivatization. The N-acetyl group provides a defined, non-proteinogenic amino acid building block character that is commonly leveraged to control reactivity at the alpha-amino position during chemical synthesis and analytical workflows. Ac-Orn-OH is therefore used when a protected-like backbone reactivity profile is desired while retaining a functional side-chain handle for conjugation, salt formation, or further functional group installation.
1. Peptide Segment Building
Ac-Orn-OH is used as a defined ornithine-containing building block for constructing peptide segments in solution-phase or automated peptide assembly workflows where the alpha-amino functionality is intentionally masked by N-acetylation. Researchers and custom peptide synthesis groups select this form to introduce ornithine-derived residues with controlled reactivity, enabling subsequent coupling strategies that rely on the side-chain amine as a distinct functional element. This product is particularly relevant for preparing peptides and peptide-like intermediates that require a later-stage side-chain modification or controlled side-chain chemistry rather than immediate full functionalization during assembly.
2. Side-Chain Derivatization Chemistry
Ac-Orn-OH serves as a practical starting material for installing additional functionality onto the ornithine side-chain primary amine, supporting downstream development of tailored amino acid derivatives for chemical biology and materials research. Because the N-acetyl group differentiates the alpha-amino position from the side-chain amine, chemists can selectively target the terminal amine for derivatization, including attachment of protecting groups, linkers, or other substituents used to tune charge density and reactivity. This makes Ac-Orn-OH a convenient reagent when the workflow requires a stable, well-defined amino acid scaffold that can be carried through multiple synthetic steps while preserving a single, chemically accessible functional handle.
3. Bioconjugation Linker Intermediate
Ac-Orn-OH is frequently used in bioconjugation-oriented intermediate development where ornithine's terminal amine provides a handle for coupling to activated carboxylates, electrophilic linkers, or other conjugation chemistries used to generate amine-reactive or amine-bearing conjugates. Protein and polymer chemistry teams value the N-acetylated backbone for providing a controlled starting point that reduces ambiguity in multi-functional coupling sequences, allowing the side-chain amine to be leveraged as the primary attachment site. In this context, Ac-Orn-OH supports preparation of conjugation-ready amino acid components used to build linkers, charge-modulating tags, or modular units for assembling larger bioconjugates.
4. Analytical Reference Derivative
Ac-Orn-OH is also used as an analytical reference derivative in workflows that require ornithine-related standards or calibration compounds for method development and verification in amino acid quantification and related LC-based analyses. Analytical chemistry teams select N-acetylated ornithine forms to match specific derivatization or detection behavior in their assay formats, particularly when distinguishing ornithine species with different amino protection states. The defined structure of Ac-Orn-OH helps support consistent retention and derivatization profiles, making it useful for preparing standards and internal reference materials used during analytical troubleshooting and routine quality checks.
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