DL-δ-Hydroxylysine HCl

DL-δ-Hydroxylysine HCl is a hydrochloride salt form of DL-δ-hydroxylysine, an amino acid derivative featuring a lysine backbone with a stereogenic center at the α-position and an additional stereogenic/functional site at the δ-hydroxyl-bearing side chain. The molecule contains a primary amino group and a carboxylic acid functionality (present as the salt-associated carboxylate/acid pair depending on medium), together with a side-chain hydroxyl that can participate in hydrogen bonding and can be selectively protected or activated for further transformations. The DL designation indicates a racemic mixture at the α-chiral center, which can be leveraged for method development, derivatization screening, and non-stereospecific intermediate preparation. The salt form improves handling and can facilitate controlled conversion into protected amino acid derivatives or activated building blocks for peptide coupling and downstream chemical synthesis.

1. Protected Amino Acids

DL-δ-Hydroxylysine HCl is used in protected amino acid synthesis workflows where the α-amino group and δ-hydroxyl require orthogonal protection strategies. The side-chain hydroxyl can be protected as an ether or ester while the amine is commonly converted to an N-protecting group compatible with peptide coupling conditions, enabling stepwise deprotection without side-chain scrambling. The carboxylic acid functionality can be transformed into peptide-ready activated forms or amino acid ester intermediates, supporting C-terminal incorporation into sequences. The resulting protected derivatives serve as intermediates for peptide building block preparation, amino acid derivatization studies, and process chemistry intermediate generation where controlled functional group reactivity is required.

2. Peptide Synthesis

DL-δ-Hydroxylysine HCl is applicable to peptide synthesis and peptidomimetic construction where hydroxyl-bearing lysine residues are incorporated as functional side-chain motifs. The molecule's lysine-like primary amino group and δ-hydroxyl enable coupling chemistry at the α-carboxylate position while preserving the side-chain hydroxyl for later functionalization or selective deprotection. The racemic nature at the α-center can be used for developing coupling and protecting-group strategies, preparing standards, or generating mixed stereochemical peptide libraries for structure-activity relationship studies. Downstream, hydroxyl retention supports formation of peptide analogs that can undergo further side-chain transformations, including derivatization to enable conjugation, crosslinking analogs, or analytical probes.

3. Bioconjugation Chemistry

DL-δ-Hydroxylysine HCl is suitable for chemical biology and bioconjugation routes that require hydroxyl-functional amino acid handles for linker installation. The δ-hydroxyl can be converted into activated intermediates (such as leaving-group derivatives) or protected/activated forms that participate in controlled conjugation chemistry, while the amino and carboxyl functionalities can be used to anchor the building block to biomolecule scaffolds. The hydrochloride salt form supports reproducible handling during derivatization steps and can be converted into N-protected or side-chain-protected analogs to manage chemoselectivity. The resulting conjugation-ready intermediates can be employed to generate labeled peptides, hydroxyl-functional linkers, and amino acid-based constructs for biomolecule modification and analytical research.

4. Protein Engineering Studies

DL-δ-Hydroxylysine HCl serves in protein engineering and chemical protein modification contexts where hydroxylated lysine side chains are modeled or introduced as structural elements. The δ-hydroxyl group provides a hydrogen-bonding and polarity feature that can mimic post-translational hydroxylation patterns in synthetic protein segments or peptide fragments used for binding and recognition studies. The α-amino acid framework supports incorporation into synthetic peptides that can be used as substrates, competitors, or reference materials in enzyme and binding assays, while the side-chain hydroxyl enables subsequent chemical transformation to probe recognition mechanisms. The DL stereochemical mixture can be applied in screening-style studies where method development, assay calibration, or stereochemical independence at early stages is acceptable before selecting a single stereoisomer.

5. Analytical Research Standards

DL-δ-Hydroxylysine HCl is used to prepare analytical standards and derivatization reagents for amino acid profiling, hydroxylated amino acid quantification, and method validation in biochemical analysis. The presence of both an amino functionality and a δ-hydroxyl group supports derivatization schemes that improve detection by mass spectrometry or chromatographic workflows, including formation of stable derivatives for consistent ionization behavior. The hydrochloride salt form can improve reproducibility during sample preparation and can be converted into protected or activated forms to match the chemistry of internal standards. The racemic composition enables robust calibration for total δ-hydroxylysine content, supporting analytical research intermediate development and downstream quality control of peptide or protein hydrolysate workflows.

6. Process Chemistry Intermediate

DL-δ-Hydroxylysine HCl is relevant to process chemistry and fine chemical synthesis as a chiral amino acid intermediate precursor for protected amino acid derivatives and peptide coupling feedstocks. The functional group set, including the α-amino group, carboxylic acid, and δ-hydroxyl, enables planned protection-deprotection sequences and controlled conversion into activated intermediates that can be manufactured at scale. The salt form supports handling in bulk operations, while the DL stereochemistry can reduce stereocontrol requirements when the target application tolerates racemic material or when stereoselective steps occur later in the manufacturing route. The compound can be employed to generate downstream intermediates for specialty chemical production, including hydroxyl-functional linkers, peptidomimetic building blocks, and amino acid-based reagents used across peptide science and industrial chemical manufacturing.

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