H-Lys(Tos)-OH

H-Lys(Tos)-OH is an Nε-tosyl-protected lysine amino acid bearing the free α-amino and α-carboxylic acid functionalities, with the ε-amino group masked as a tosylamide. The molecule therefore presents a chiral, stereodefined amino acid backbone suitable for peptide coupling at the carboxyl group while maintaining orthogonal selectivity through the tosyl protecting group on the side chain. The tosyl group introduces an aromatic sulfonamide handle that can be removed under controlled conditions, while the side-chain nitrogen remains protected during standard amide bond formation. As a protected amino acid intermediate, H-Lys(Tos)-OH supports downstream synthesis of lysine-containing peptides, lysine side-chain functionalization products, and chiral building blocks for chemical biology and process chemistry.

1. Peptide Synthesis

H-Lys(Tos)-OH supports peptide building block preparation in solid-phase and solution-phase peptide synthesis where lysine side-chain orthogonality is required. The free α-carboxylic acid and α-amino group enable incorporation into peptide chains via standard peptide coupling chemistry, while the Nε-tosyl group suppresses undesired side-chain amide formation and cross-linking during chain assembly. The tosyl protection strategy provides a stable ε-nitrogen that can survive many coupling and deprotection sequences, enabling controlled late-stage unmasking for subsequent lysine functionalization. Lysine-containing peptide analogs, including sequence-defined scaffolds and branched or multivalent constructs, can be generated by using H-Lys(Tos)-OH as the chiral lysine component.

2. Side-Chain Functionalization

H-Lys(Tos)-OH is suitable for side-chain derivatization workflows that rely on orthogonal protection of the lysine ε-amino functionality. The tosylamide serves as a removable protecting group, allowing selective conversion of the lysine side chain into reactive amines for conjugation, further acylation, or attachment of linkers after peptide assembly or in intermediate stages. The presence of the carboxylic acid and α-amino group also enables conversion into activated derivatives for downstream coupling to electrophiles, supporting synthetic routes to functionalized lysine derivatives. The resulting Nε-unprotected lysine intermediates can be applied to generate amine-bearing handles for bioconjugation chemistry, molecular probes, and peptidomimetic scaffolds.

3. Chemical Biology Labeling

H-Lys(Tos)-OH can be employed in chemical biology research where lysine residues provide attachment points for labeling and affinity reagents. The protected ε-amino group helps maintain chemoselectivity during synthesis of peptide probes, protein fragments, or peptide-based ligands, minimizing off-target reactions from the side-chain amine. Controlled deprotection of the tosyl group can generate a primary amine suitable for conjugation to activated esters, aldehyde-derived linkers, or other electrophilic labeling partners under defined conditions. Lysine-bearing probe molecules produced from H-Lys(Tos)-OH can be used to map binding interfaces, study biomolecular interactions, or prepare structured reagents for analytical assays.

4. Pharmaceutical Intermediate Preparation

H-Lys(Tos)-OH is applicable to pharmaceutical intermediate preparation for manufacturing and process development of lysine-containing peptide intermediates and protected amino acid fragments. The Nε-tosyl group provides an industrially relevant orthogonal protection mode that can be carried through peptide coupling steps, reducing variability from side-chain reactivity during multistep synthesis. The chiral amino acid framework supports consistent stereochemical incorporation into peptide sequences, which is important for reproducible downstream transformations into active or investigational peptide-like structures. The compound can be used to design scalable synthetic routes where protected lysine fragments are required before final deprotection and conversion to the desired functional form.

5. Process Chemistry Intermediate

H-Lys(Tos)-OH functions as a chiral amino acid intermediate for process chemistry and fine chemical synthesis, particularly when controlled protection of the lysine ε-amino group is needed. The tosyl protecting group provides stability against many coupling conditions while preserving the ability to perform selective deprotection to reveal the ε-amino functionality when required by the manufacturing sequence. The free α-carboxylic acid and α-amino group allow conversion into protected or activated forms compatible with peptide coupling strategies, supporting intermediate preparation for larger molecule assembly. The resulting lysine-containing intermediates can feed into downstream synthesis of peptidomimetics, polymerizable amino acid derivatives, and other amine-functional products used in industrial chemical manufacturing.

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