H-D-His(1-Trt)-OMe · HCl

H-D-His(1-Trt)-OMe · HCl is a protected histidine methyl ester hydrochloride in which the α-amino function is present as an N-protected derivative (D-amino acid configuration) and the imidazole side chain is protected with a trityl-type group at the N1 position. The structure combines an esterified carboxylate (OMe) with a stereodefined chiral center, while the imidazole ring bears a bulky protecting group that modulates nucleophilicity and suppresses undesired side reactions during peptide coupling. The hydrochloride salt form improves handling of the amino ester and can influence solubility and reactivity in organic synthesis. The N- and side-chain protection pattern is designed to preserve the histidine backbone for controlled deprotection and subsequent incorporation into peptide building blocks and histidine-containing analogs.

1. Peptide Synthesis

H-D-His(1-Trt)-OMe · HCl supports peptide coupling workflows in peptide synthesis by providing a protected histidine methyl ester with an N-protected amino group and an N1-trityl-protected imidazole that remains largely inert under typical acylation conditions. The ester functionality enables formation of peptide bonds while maintaining a defined C-terminal handle that can be converted to an amide or further transformed after coupling. The D-stereochemistry at the α-carbon enables stereochemically controlled construction of D-His-containing peptides and can be used to probe stereochemical effects on backbone recognition. Downstream deprotection of the side-chain protecting group and conversion of the ester to the desired C-terminal form can generate histidine-containing peptide fragments compatible with stepwise solid-phase or solution-phase assembly strategies.

2. Unnatural Amino Acid Incorporation

H-D-His(1-Trt)-OMe · HCl functions as a chiral amino acid intermediate for unnatural amino acid incorporation studies where D-histidine stereochemistry is required. The protected imidazole (N1-Trt) reduces competing coordination and side reactions during synthetic steps, while the methyl ester provides a stable carboxylate equivalent for controlled coupling and later functional group adjustment. The combination of stereodefined backbone and orthogonal protection enables preparation of D-His analogs for structure-activity relationship studies, including peptide mimetics that rely on altered stereochemical presentation of the imidazole side chain. The resulting derivatives can be used to generate libraries of histidine-containing analogs for synthetic organic chemistry and biochemical research intermediate preparation.

3. Side-Chain Functionalization

H-D-His(1-Trt)-OMe · HCl is suitable for side-chain functionalization routes that require late-stage unmasking of the histidine imidazole to restore nucleophilicity and hydrogen-bonding capability. The N1-trityl protection strategy can be leveraged to keep the imidazole non-reactive during earlier transformations, then enable selective deprotection to expose the free imidazole for subsequent derivatization such as metal-binding motifs, covalent capture handles, or conjugation-ready functional groups. The methyl ester can also serve as a temporary C-terminal protecting group equivalent that can be converted to an amide, hydrazide, or other downstream derivative depending on the target scaffold. The protected histidine framework therefore supports controlled generation of reactive histidine analogs for chemical biology probes and peptidomimetic construction.

4. Bioconjugation Chemistry

H-D-His(1-Trt)-OMe · HCl can be applied in bioconjugation chemistry workflows where histidine-containing peptide linkers or conjugation handles are required with controlled protection states. The imidazole protection helps prevent premature side reactions during linker synthesis, while the ester-to-amide conversion capability supports attachment of the amino acid residue into peptide-based conjugates. The D-histidine stereochemistry can be used to modulate stability and recognition in conjugated biomolecule constructs, supporting preparation of defined peptide tags and linker segments for analytical and research-grade labeling. Downstream unmasking of the imidazole enables conjugation steps that depend on the histidine side chain as a binding or reactive element within the final bioconjugate scaffold.

5. Pharmaceutical Manufacturing

H-D-His(1-Trt)-OMe · HCl is relevant to pharmaceutical manufacturing and fine chemical production as a protected amino acid intermediate for producing histidine-containing peptide intermediates used in active pharmaceutical ingredient (API) synthesis or peptide-derived process streams. The orthogonal protection pattern (N-protected amino functionality and N1-imidazole protection) supports reproducible peptide coupling chemistry and can reduce impurity formation associated with unprotected imidazole reactivity. The hydrochloride salt form can facilitate handling during industrial-scale intermediate preparation, while the methyl ester provides a controllable C-terminal functionality for conversion into the required amide or peptide bond form. The compound's stereochemical definition enables consistent manufacturing of stereochemically specified D-His-containing fragments used in process chemistry intermediate design and downstream synthetic methodology.

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