DL-Homocitrulline

DL-Homocitrulline is a non-proteinogenic amino acid derivative featuring a ureido functionality on an extended aliphatic side chain, corresponding to a homologated citrulline framework (amino acid backbone with a side-chain urea/ureido group). The molecule contains both an amino group and a carboxyl group, and in the DL (racemic) form it presents a stereogenic center that enables access to both enantiomeric homocitrulline building blocks after resolution or stereoselective downstream transformations. The ureido/urea motif is strongly polar and can participate in hydrogen-bonding and carbonyl/amide-type reactivity, while the amino acid functionality supports peptide coupling, salt formation, and protected-group strategies. As a chiral amino acid intermediate precursor, homocitrulline can be converted into protected derivatives suitable for stepwise peptide construction and into functionalized analogs used for biochemical and synthetic organic chemistry workflows.

1. Peptide Synthesis

DL-Homocitrulline is applied in peptide synthesis as a noncanonical amino acid building block for incorporating ureido-bearing side chains into peptide sequences. The amino acid backbone supports N-protection and C-terminal activation for peptide coupling, while the side-chain ureido group can be managed through orthogonal protection or selective deprotection to preserve coupling compatibility. Racemic stereochemistry can be used for developing coupling conditions, generating preliminary libraries, or serving as a precursor to enantiopure homocitrulline after resolution. Downstream, incorporated homocitrulline residues enable preparation of urea/ureido-rich peptides and peptidomimetic scaffolds that reflect side-chain hydrogen-bonding patterns relevant to peptide science.

2. Chemical Biology Probes

DL-Homocitrulline is used in chemical biology research to generate ureido-functional amino acid analogs for studying molecular recognition and protein-ligand interactions. The ureido group provides a defined hydrogen-bonding and polar interaction handle, while the amino acid framework can be converted into activated esters, amide-forming derivatives, or protected intermediates for conjugation workflows. DL material can serve as a starting point for probe synthesis where stereochemical control is introduced later, enabling side-by-side comparison of enantiomeric effects when resolution is performed. Resulting homocitrulline-containing probes can be applied to biochemical assays, affinity reagent construction, and mechanistic studies that rely on ureido-mediated binding features.

3. Side-Chain Functionalization

DL-Homocitrulline is suitable for side-chain functionalization chemistry because the ureido functionality can undergo controlled derivatization while the amino acid backbone can be protected to direct reactivity. The presence of both amine and carboxyl functionalities supports orthogonal protection strategies that separate peptide-coupling readiness from ureido-group modification, enabling stepwise synthesis of substituted urea/ureido analogs. Racemic stereochemistry can be retained for screening-focused intermediate generation or resolved to access enantiopure derivatives for stereochemistry-sensitive structure-function studies. Functionalized homocitrulline derivatives can then be used to build peptidomimetics, generate SAR-focused analog sets, and prepare downstream intermediates for fine chemical synthesis.

4. Protected Amino Acid Chemistry

DL-Homocitrulline is employed in protected amino acid chemistry as a precursor to N-protected amino acid derivatives and C-terminal activated forms used in controlled peptide assembly. The amino acid backbone enables conversion into common coupling-ready formats, while the ureido side chain can be protected to prevent undesired reactions during carbodiimide- or acyl-transfer-based coupling steps. Orthogonal protection and later deprotection strategies allow the ureido functionality to be revealed at a chosen stage, supporting sequential construction of ureido-containing peptide fragments. The resulting protected homocitrulline intermediates serve as process-compatible inputs for peptide building block preparation and for manufacturing-oriented synthesis of urea/ureido-rich specialty compounds.

5. Pharmaceutical Intermediate Preparation

DL-Homocitrulline is relevant to pharmaceutical intermediate preparation through its role as a chiral amino acid intermediate platform for generating noncanonical amino acid motifs used in medicinal chemistry. The ureido-bearing side chain provides a polar pharmacophore-like element that can be incorporated into peptide-like structures or used to create constrained analogs via derivatization and subsequent coupling. The racemic starting material supports scalable intermediate generation, with enantiomeric enrichment achievable through downstream resolution or stereoselective conversion when required by target structure design. Homocitrulline-derived intermediates can feed into fine chemical synthesis routes for peptidomimetics, SAR libraries, and other specialty molecular scaffolds used in applied drug discovery chemistry workflows.

6. Analytical Standards And Labeling

DL-Homocitrulline is applicable to analytical research as a reference material and derivatization target for quantifying ureido-containing amino acid species in complex matrices. The amino acid structure supports conversion to derivatized forms compatible with chromatographic separation and detector response, while the ureido group provides a consistent functional handle for method development. Racemic material can be used for method calibration and for establishing total homocitrulline signals, with enantiomer-specific characterization enabled by conversion to stereochemically resolved derivatives when needed. Homocitrulline standards and labeled analogs prepared from this scaffold can support quality control of synthetic intermediates, characterization of peptide hydrolysates, and analytical method validation in research and industrial settings.

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