H-D-Phe-OtBu*HCl

H-D-Phe-OtBu*HCl is a chiral, N-acetyl-free D-phenylalanine derivative presented as the tert-butyl ester hydrochloride salt, featuring a D-configured stereocenter at the alpha carbon and a benzyl side chain that supports hydrophobic and aromatic interactions. The molecule contains a protected carboxyl functionality as the OtBu ester, which can be selectively handled under ester-compatible coupling and derivatization conditions while the hydrochloride counterion stabilizes the amino functionality as a salt. The combination of a stereodefined amino acid core and an acid-labile tert-butyl ester enables controlled peptide building block preparation, including downstream conversion to carboxylic acid or activation for amide bond formation. The aromatic ring further supports use in structure-activity relationship studies and in peptidomimetic scaffolds where phenylalanine-like side-chain presentation is required.

1. Protected Amino Acid Chemistry

H-D-Phe-OtBu*HCl is applied in protected amino acid synthesis workflows where a D-phenylalanine stereocenter must be preserved through coupling and intermediate handling. The tert-butyl ester (OtBu) functions as a carboxyl protecting group that can be carried through peptide coupling steps and later converted to the corresponding acid for further functionalization. The hydrochloride salt form provides a practical salt-stabilized amine that can participate in standard peptide coupling chemistry after appropriate base treatment. Downstream use frequently includes preparation of D-Phe-containing protected fragments for solid-phase or solution-phase peptide assembly and for generating stereochemically defined intermediates for fine chemical synthesis.

2. Peptide Synthesis

H-D-Phe-OtBu*HCl serves as a peptide building block precursor for constructing D-phenylalanine-containing sequences in peptide synthesis. The amino acid backbone provides the nucleophilic amine and the ester-protected carboxyl group necessary for controlled transformation into coupling-ready species, while the D-configuration supports incorporation of stereochemically non-native residues. The phenyl side chain enables incorporation into hydrophobic peptide regions and can be used to tune conformational preferences and receptor-binding motifs in peptide analog libraries. The ester protection strategy supports orthogonal deprotection planning, allowing selective unmasking of the carboxyl functionality to enable amide bond formation and subsequent peptide elongation.

3. Peptidomimetics And SAR Studies

H-D-Phe-OtBu*HCl is used in peptidomimetic and structure-activity relationship research where a D-phenylalanine side-chain presentation is required to probe binding selectivity and proteolytic stability trends. The aromatic benzyl group provides a consistent hydrophobic/aromatic pharmacophore, while the D-stereocenter supports systematic stereochemical variation without altering side-chain identity. The protected ester form can be converted into activated carboxylic acid derivatives for scaffold assembly, including formation of amide, ester, or other carboxyl-derived linkages used in analog construction. Downstream applications include generation of stereodefined peptide mimics and SAR-focused intermediate sets for medicinal chemistry and chemical biology campaigns.

4. Chiral Building Block Development

H-D-Phe-OtBu*HCl is suitable for chiral synthesis planning as a stereodefined amino acid intermediate that can feed into broader enantiospecific manufacturing routes. The D-configuration at the alpha carbon makes it a direct chiral input for building blocks where retention of stereochemistry is necessary for downstream stereochemical recognition. The tert-butyl ester provides a handle for orthogonal protection logic, supporting sequential transformations such as conversion to free acid, activation for coupling, or further derivatization into functional intermediates. The hydrochloride salt form can also be leveraged to improve handling consistency during intermediate preparation, enabling reliable transfer into subsequent synthetic steps for chiral fine chemical production.

5. Pharmaceutical Intermediate Preparation

H-D-Phe-OtBu*HCl is employed as an upstream intermediate in pharmaceutical intermediate preparation where D-amino acid motifs are incorporated into peptide-like or constrained small-molecule frameworks. The amino acid architecture supports conversion into activated carboxyl derivatives for amide bond formation with appropriate amine partners, while the ester protecting group supports controlled deprotection scheduling within multi-step synthesis. The phenylalanine side chain can be used to align aromatic pharmacophore elements in drug discovery chemistry and to generate stereochemically defined analogs for downstream process development. The compound's protected functional group pattern supports its use as a chiral input for industrially relevant synthetic sequences requiring stereochemical fidelity and predictable functional group interconversions.

6. Chemical Biology Labeling

H-D-Phe-OtBu*HCl can be applied in chemical biology workflows that require incorporation of D-phenylalanine residues into labeled peptides or probe scaffolds. The protected amino acid form supports stepwise construction of conjugatable intermediates, where the carboxyl group can be unmasked and transformed into coupling-ready derivatives for attachment to linkers, tags, or affinity handles. The aromatic side chain can be used as a structural element in probes designed to engage hydrophobic pockets or to maintain consistent spatial presentation within peptide conjugates. Downstream utility includes preparation of stereochemically defined D-Phe-containing conjugation substrates that integrate into biochemical research reagent sets and analytical assay development.

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