H-Gln-OtBu · HCl

H-Gln-OtBu · HCl is a hydrochloride salt of the tert-butyl ester of L-glutamine, presenting an amino acid framework with a side-chain amide (glutamine side chain) and a protected carboxyl group as the OtBu ester. The molecule bears a stereogenic center at the α-carbon, enabling stereochemically defined incorporation into peptide sequences and chiral intermediate synthesis. Protonation as the HCl salt stabilizes the free amine under handling conditions, while the tert-butyl ester and amide functionality provide orthogonal reactivity patterns for controlled deprotection and subsequent coupling chemistry. The side-chain amide can participate in hydrogen-bonding and can be selectively transformed into derivatized glutamine analogs, making the compound a practical amino acid ester intermediate for peptide building block preparation and downstream functionalization.

1. Protected Amino Acid Chemistry

H-Gln-OtBu · HCl is used in protected amino acid synthesis where the tert-butyl ester masks the C-terminal carboxyl functionality and the side-chain amide remains available for controlled derivatization. Protonated amino functionality supports handling and can be converted into peptide-coupling-ready forms under standard amide-forming conditions, while the ester protection strategy supports orthogonal deprotection relative to other protecting groups. Side-chain amide hydrogen-bonding can be leveraged to tune solubility and reactivity during intermediate preparation. Downstream, H-Gln-OtBu · HCl can serve as a chiral glutamine-derived building block for preparing protected glutamine derivatives and peptide-ready intermediates used in fine chemical synthesis.

2. Peptide Synthesis

H-Gln-OtBu · HCl is applied as a glutamine-containing peptide building block precursor in peptide coupling workflows, where the defined α-stereochemistry supports stereochemically consistent chain assembly. The OtBu ester provides a C-terminal protection mode that can be removed to generate a carboxylate for subsequent transformations or to align with fragment condensation strategies. The side-chain amide of the glutamine residue can be retained for native glutamine incorporation or modified to produce glutamine analogs that maintain hydrogen-bonding motifs in peptide scaffolds. The hydrochloride salt form can facilitate salt-state control during coupling and purification steps, enabling formation of glutamine-containing peptides and peptide fragments for biochemical research and SAR studies.

3. Chemical Biology Labeling

H-Gln-OtBu · HCl is relevant to chemical biology and biomolecule modification workflows that require glutamine-derived handles for conjugation chemistry and affinity tagging strategies. The side-chain amide can be converted into functional derivatives through established transformations that preserve the glutamine backbone geometry while introducing reactive or recognition elements. The protected ester and protonated amine support stepwise synthesis of conjugatable intermediates, including amino acid ester intermediates that can be advanced toward peptide conjugates or linker-bearing analogs. Downstream use includes preparation of glutamine-based probes, substrate mimics, and molecular recognition reagents used to interrogate binding interactions and protein-ligand recognition patterns in biochemical research.

4. Peptidomimetics And SAR

H-Gln-OtBu · HCl is utilized in peptidomimetic construction and structure-activity relationship studies where glutamine's side-chain amide geometry contributes to hydrogen-bonding and conformational preferences. The compound's chiral amino acid core supports incorporation into analog libraries, while the OtBu ester protection enables controlled conversion to carboxylate or activated derivatives for scaffold assembly. Side-chain amide chemistry can be adapted to generate constrained or substituted glutamine analogs that probe the role of polar interactions in receptor or enzyme recognition. Resulting derivatives can be used to build SAR-focused series, supporting fragment-based molecular design and iterative optimization of peptide-like binding motifs.

5. Process Chemistry Intermediate

H-Gln-OtBu · HCl is suitable for process chemistry intermediate preparation where amino acid ester protection and salt-state control support manufacturable handling and downstream conversion. The tert-butyl ester protection strategy can be integrated into multistep routes to access glutamine-derived protected acids, activated intermediates, or peptide coupling partners while maintaining stereochemical integrity at the α-center. The side-chain amide can be carried through manufacturing steps with predictable reactivity under orthogonal protection/deprotection regimes, enabling controlled derivatization toward specific product forms. Industrially, the compound can be employed as a chiral amino acid building block precursor for specialty chemical production, including the synthesis of protected glutamine derivatives and glutamine-containing intermediates used in peptide and peptidomimetic manufacturing workflows.

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