H-D-His(3-Me)-OH

H-D-His(3-Me)-OH is a deuterated, stereochemically defined histidine derivative featuring a deuterium-labeled amino acid backbone and a 3-methyl-substituted imidazole side chain. The structure contains a free carboxylic acid and a protected/deuterated amino functionality (H-D indicates the deuterium incorporation at the amino position), while the imidazole ring provides a pH-dependent, metal-coordinating heteroaromatic functionality. The 3-methyl substitution modulates side-chain sterics and electronic distribution, which can influence hydrogen-bonding patterns and coordination behavior during peptide coupling or biochemical recognition. As a chiral amino acid variant used as an isotope-enabled building block, it functions as a controlled intermediate for amino acid derivatization, peptide construction, and mechanistic studies where isotopic labeling and side-chain tuning are required.

1. Isotope-Labeled Peptide Synthesis

H-D-His(3-Me)-OH supports isotope-enabled peptide building block preparation for mechanistic studies in peptide chemistry and chemical biology. The free carboxylic acid and deuterium-labeled amino position enable incorporation into peptide chains via standard peptide coupling strategies after appropriate activation, while the imidazole N atoms participate in coordination and hydrogen-bonding interactions that are often central to peptide folding and binding. The 3-methyl imidazole substituent can be used to tune side-chain microenvironment effects without removing the core histidine reactivity. Downstream peptide analogs prepared from this amino acid can serve as labeled substrates in mass spectrometry-based studies of binding, proteolysis, or reaction pathways, linking amino acid structure to observed isotopic signatures.

2. Chemical Biology Labeling

H-D-His(3-Me)-OH is suitable for chemical biology workflows that require site-specific labeling of histidine-like motifs. The imidazole side chain offers a defined heteroaromatic handle for metal-assisted interactions and for designing conjugates that rely on imidazole coordination or pH-dependent protonation states. The deuterium incorporation at the amino position can be exploited to distinguish labeled species in quantitative LC-MS experiments, while the 3-methyl substitution helps control steric accessibility around the imidazole ring. Conjugation-ready derivatives generated from the carboxylic acid and amino functionality can be used to probe biomolecular recognition, map interaction surfaces, or track incorporation of modified amino acid residues in protein or peptide constructs.

3. Peptidomimetic SAR Studies

H-D-His(3-Me)-OH can be applied in peptidomimetic construction and structure-activity relationship studies where histidine side-chain geometry and electronics are systematically varied. The imidazole ring with a 3-methyl substituent provides a controlled modification of steric bulk and electronic density, which can affect hydrogen-bonding networks and metal-binding pharmacophores in peptide-like scaffolds. The amino acid backbone, bearing a deuterium label, enables synthesis of analog series that can be monitored by isotope-resolved analytical methods to correlate structural changes with physicochemical or binding readouts. Peptidomimetic libraries derived from this labeled histidine analog can guide SAR mapping while maintaining a consistent amino acid framework for comparative studies.

4. Process Chemistry Intermediate

H-D-His(3-Me)-OH functions as a chiral amino acid intermediate for fine chemical synthesis and process-oriented preparation of isotope-enabled building blocks. The presence of a free carboxylic acid supports conversion to activated intermediates for peptide coupling or for downstream ester/amide formation in manufacturing routes, while the imidazole heterocycle can be protected or chemoselectively handled depending on the selected protecting-group strategy. The deuterium label is compatible with industrial isotope-manufacturing workflows that require stable incorporation without altering the core functional group set. Industrial use can include supplying labeled amino acid derivatives for research-grade peptide reagents, isotope-traceable standards, and intermediate feedstocks used in multi-step synthesis of labeled biomolecule analogs.

5. Analytical Reference Standards

H-D-His(3-Me)-OH is suitable for analytical research as an isotope-enabled reference material for histidine-containing species. The deuterium incorporation and 3-methyl imidazole substitution create a distinguishable mass signature and side-chain-specific fragmentation pattern that can improve identification confidence in LC-MS/MS workflows. The free carboxylic acid and imidazole functionality support preparation of calibration standards, derivatized analogs, or internal standards that reflect histidine side-chain chemistry under relevant analytical conditions. Use in analytical method development and validation can extend to monitoring incorporation of labeled histidine residues in peptides, tracking degradation products, and supporting quantitative studies of amino acid transformations during synthesis or formulation development.

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