L-Homotyrosine.HBr is a free, naturally occurring amino acid derivative in which the phenolic side chain of tyrosine is extended by one methylene to form a para-hydroxyphenethyl group, with an amino group and a carboxyl group on the alpha carbon. The molecule is present as a hydrobromide salt, pairing the basic amino functionality with bromide while retaining the phenolic hydroxyl for hydrogen-bonding and potential derivatization, and the stereochemistry is specified as L. As a salt-form amino acid, it is used as a building block for peptide and peptidomimetic synthesis and for chemical biology and analytical workflows that require a phenolic amino acid side chain with a longer aromatic linker, including labeling strategies and structure-activity studies based on side-chain length and polarity.
L-Homotyrosine.HBr is a chiral amino acid analog of tyrosine in which the side chain contains an extra methylene, giving a phenolic aromatic ring separated from the stereogenic alpha carbon by a longer carbon chain. The structure comprises an L-configured amino acid backbone (α-amino and α-carboxyl functionality) present as a hydrobromide salt, which increases salt stability and water compatibility while maintaining the phenolic hydroxyl for selective derivatization. The phenol can be protected or functionalized to tune reactivity during peptide coupling, while the amino acid framework can be converted into protected amino acid derivatives or activated carboxylic acid forms for amide bond formation. The extended side chain length relative to tyrosine can influence conformational preferences in peptide and protein contexts, making this salt a practical chiral intermediate for stereochemically defined building block preparation.
1. Peptide Synthesis
L-Homotyrosine.HBr supports peptide building block preparation through conversion of the α-carboxyl into activated derivatives and protection of the amino functionality for controlled coupling chemistry. The phenolic side-chain hydroxyl can be masked with an acid-stable or orthogonally removable protecting group to prevent side reactions during N-protection and peptide assembly. The L-stereocenter enables incorporation into linear peptides and peptide fragments where side-chain length affects local geometry and hydrogen-bonding patterns. Downstream, the resulting protected homotyrosine residue can be used to construct peptide analogs for biochemical research and for manufacturing of defined peptide intermediates.
2. Side-Chain Functionalization
L-Homotyrosine.HBr enables amino acid derivatization focused on the phenolic hydroxyl and the extended aromatic side chain for chemical biology and materials-oriented synthesis. Phenol-bearing side chains can be selectively protected, then transformed into aryl ethers, ester derivatives, or handles for further conjugation chemistry after deprotection. The hydrobromide salt form can facilitate handling during protection and activation steps, while the chiral amino acid backbone provides a stable platform for downstream coupling or conversion into activated carboxylic acid intermediates. Resulting functionalized homotyrosine derivatives can serve as intermediates for labeled probes, affinity ligands, and peptidomimetic scaffolds that retain stereochemical fidelity.
3. Chemical Biology Conjugation
L-Homotyrosine.HBr is suitable for chemical biology workflows requiring controlled attachment of aromatic, phenolic side-chain motifs to biomolecules or synthetic scaffolds. The phenolic group can be employed as a reactive handle after appropriate protection strategies, enabling formation of conjugates that preserve the L-configuration of the amino acid residue. Salt formation with hydrobromide can improve solubility during derivatization and can be compatible with stepwise protection-deprotection sequences used to generate bioconjugation-ready intermediates. Downstream applications include preparation of biomolecule labeling reagents, affinity capture tags, and peptide conjugates used to probe molecular recognition and binding interfaces.
4. Protected Amino Acid Chemistry
L-Homotyrosine.HBr functions as a chiral starting material for producing N-protected and C-activated homotyrosine derivatives used in protected amino acid synthesis. The α-amino group can be protected to enable selective peptide coupling, while the α-carboxyl can be transformed into ester or activated acid forms depending on the intended synthetic route. The phenolic hydroxyl requires protecting-group selection aligned with the coupling conditions, allowing orthogonal deprotection to reveal the side-chain functionality at a chosen stage. Prepared protected amino acid intermediates can be used as standardized inputs for automated peptide synthesis, fragment assembly, and fine chemical manufacturing of defined amino acid derivatives.
5. Process Chemistry Intermediate
L-Homotyrosine.HBr can serve as a process chemistry intermediate for industrial fine chemical synthesis where chiral amino acid handling and downstream conversion to peptide-grade building blocks are required. The hydrobromide salt form supports consistent material transfer and can help manage solubility and stability during protection, activation, and purification operations. The combination of an L-amino acid backbone with a phenolic side chain provides multiple orthogonal transformation points, enabling route design that separates N-/C-functionalization from side-chain modification. Downstream, the compound can be converted into protected homotyrosine derivatives and activated intermediates for controlled manufacturing of peptide analogs and stereochemically defined specialty chemicals.
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