H-2,5-Diiodo-His-OH · HCl is a halogenated, free amino acid derivative based on the histidine scaffold, bearing iodine substituents at the 2- and 5-positions of the imidazole ring and present as the hydrochloride salt. The molecule contains an imidazole side chain with two iodine atoms, along with an amino group and a carboxylic acid (as the salt form), where the added halogens increase mass and alter electronic properties relevant to spectroscopic and analytical behavior. It is used as a chemically defined building block for peptide and protein labeling studies, for the incorporation of iodinated histidine analogues into synthetic targets, and for analytical method development where halogenated aromatic/heteroaromatic motifs provide distinct detection characteristics.
CAT No: CP26159
CAS No:105158-70-1
Synonyms/Alias:H-2,5-Diiodo-His-OH.HCl;105158-70-1
H-2,5-Diiodo-His-OH · HCl is a hydrochloride salt of a diiodinated histidine derivative in which the imidazole-bearing amino acid framework retains the stereogenic relationship of the histidine backbone while bearing iodine atoms at the 2- and 5-positions of the imidazole ring. The structure presents a free carboxylic acid and an imidazole heterocycle that can participate in metal coordination, hydrogen bonding, and acid-base equilibria, while the heavy iodine substituents increase polarizability and enable radiolabeling or halogen-based derivatization strategies. Salt formation with HCl improves handling of the basic imidazole functionality and supports reproducible reactivity in peptide coupling and downstream transformations. The diiodinated aromatic-like heterocycle also functions as a chemically addressable handle for selective substitution, cross-coupling, and analytical detection in amino acid and peptide chemistry workflows.
1. Peptide Synthesis
H-2,5-Diiodo-His-OH · HCl supports peptide building block preparation in peptide coupling chemistry where histidine's imidazole can be protected or selectively left functional depending on the coupling strategy. The carboxylic acid and amino functionality enable conversion to activated derivatives for amide bond formation, while the diiodinated imidazole ring provides a stable, halogenated motif that can survive standard peptide assembly conditions with appropriate protection planning. Incorporation into peptide sequences can be applied to generate halogenated histidine-containing analogs for mechanistic studies, binding studies, and structure-activity relationship (SAR) investigations. Downstream deprotection and selective cross-coupling at the 2,5-iodo positions can further expand the accessible peptide analog space for synthetic methodology and library synthesis.
2. Chemical Biology Probes
H-2,5-Diiodo-His-OH · HCl is suitable for chemical biology research requiring a heteroaromatic amino acid motif that can be tracked or functionalized for biomolecular interaction studies. The imidazole ring, bearing two iodine atoms, provides a chemically distinct recognition element that can be used for targeted conjugation or for introducing heavier atoms into peptides used as probes in binding assays and structural characterization. Salt-stabilized handling of the basic side chain facilitates reproducible incorporation into labeled peptides and enables subsequent derivatization routes such as halogen substitution or coupling to introduce reporter groups. The resulting iodinated histidine-containing constructs can serve as intermediates for probe generation, molecular recognition studies, and imaging-compatible labeling workflows.
3. Protein Engineering Labels
H-2,5-Diiodo-His-OH · HCl can be applied in protein engineering and protein labeling contexts where histidine analogs are incorporated as side-chain-modified residues to tune local coordination chemistry and spectroscopic detectability. The diiodinated imidazole retains the histidine-like coordination motif while adding two halogen substituents that can influence electron density and enable subsequent chemical modification at defined positions. The free carboxylic acid and amino functionality support conversion into protected forms for controlled incorporation into peptide segments used as protein fragments or engineered domains. Downstream functionalization of the 2,5-iodo sites can generate protein or peptide conjugates for analytical characterization, interaction mapping, and structure-informed modification of biomolecular surfaces.
4. Radiochemistry And Imaging Intermediates
H-2,5-Diiodo-His-OH · HCl is relevant to radiochemistry and imaging-adjacent research workflows where iodine substitution patterns on an amino acid scaffold support radioiodination strategies. The presence of two iodine atoms on the imidazole ring provides a structural basis for isotope exchange, radiolabel incorporation, and formation of iodinated peptide derivatives that can be used as tracers in biochemical assays. The hydrochloride salt form helps maintain consistent handling of the basic imidazole during labeling and subsequent conjugation steps. The iodinated histidine motif can be carried through peptide synthesis to generate radiolabeled or iodine-enriched intermediates for downstream assay development and analytical method validation.
5. Cross-Coupling Peptidomimetics
H-2,5-Diiodo-His-OH · HCl enables synthetic organic chemistry routes to peptidomimetics and heteroaryl-substituted analogs through its two aryl iodides on the imidazole ring. The diiodinated heterocycle functions as a direct coupling handle for palladium-catalyzed cross-coupling or related halogen-metal exchange chemistry, allowing stepwise diversification of the imidazole substitution pattern while retaining the amino acid backbone for peptide or scaffold assembly. The carboxylic acid functionality supports conversion to protected amino acid derivatives suitable for sequential coupling and fragment assembly in peptidomimetic construction. The resulting diversified histidine analogs can be used to build SAR-focused libraries, generate conformationally tuned scaffolds, and supply chemically defined intermediates for fine chemical synthesis.
6. Pharmaceutical Intermediate Preparation
H-2,5-Diiodo-His-OH · HCl can be employed as a defined chiral amino acid intermediate in pharmaceutical intermediate preparation where halogenated heteroaromatic residues are used to access specialized peptidic or peptidomimetic motifs. The amino acid backbone with a free carboxylic acid and a basic imidazole side chain supports conversion into protected amino acid derivatives and controlled coupling partners for downstream amide formation. The 2,5-diiodo substitution pattern provides an iodine-rich handle for diversification steps that may be used to generate analogs with altered physicochemical properties or binding profiles in medicinal chemistry programs. The compound's salt form supports reproducible handling in process chemistry settings where consistent acid-base behavior and predictable functional group reactivity are required for intermediate manufacturing routes.
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