L-Phenylalanine tert.butyl ester hydrochloride is a phenylalanine-derived amino acid ester in which the carboxyl group is converted to a tert-butyl ester while the amino group remains protonated as the hydrochloride salt. The molecule bears a benzyl side chain typical of phenylalanine, and the tert-butyl ester masks the carboxyl functionality to modulate polarity and chemoselectivity during handling and coupling steps. As an amino acid ester hydrochloride, it is used as a protected/derivatized phenylalanine building block for peptide-related synthesis and for preparing more complex amino acid and peptide derivatives where controlled reactivity of the carboxyl group is required.
CAT No: CP01638
CAS No:15100-75-1
Synonyms/Alias:15100-75-1;H-Phe-OtBu.HCl;(S)-tert-Butyl2-amino-3-phenylpropanoatehydrochloride;H-PHE-OTBUHCL;L-Phenylalaninetert-butylesterhydrochloride;tert-Butyl3-phenyl-L-alaninatehydrochloride;Phe-OtBu.HCl;ST50320126;75898-47-4;Tert-ButylL-PhenylalaninateHydrochloride;PubChem13012;H-Phe-OtBuhydrochloride;L-Phenylalaninet-ButylEsterHydrochloride;C13H19NO2.HCl;KSC491O3N;78080_ALDRICH;P0881_SIGMA;SCHEMBL237074;Jsp002891;CHEMBL1222003;78080_FLUKA;CTK3J1736;FDMCEXDXULPJPG-MERQFXBCSA-N;MolPort-003-939-036;L-Phenylalaninet-butylesterHCl
L-Phenylalanine tert.butyl ester hydrochloride is the hydrochloride salt of L-phenylalanine bearing a tert-butyl ester at the carboxyl terminus, retaining the L-stereogenic center of the amino acid side chain. The molecule combines a protected carboxyl functionality with a free amino group under salt conditions, and the benzyl side chain provides an aromatic handle for π-stacking interactions and electrophile/oxidation-compatible chemistry. The tert-butyl ester motif is acid-labile, enabling controlled deprotection to regenerate the carboxylic acid for peptide coupling or downstream functionalization. The presence of the hydrochloride counterion influences solubility and handling in peptide synthesis workflows, while the aromatic ring supports incorporation into peptidomimetics and SAR-focused analog series.
1. Peptide Synthesis
L-Phenylalanine tert.butyl ester hydrochloride is applied in peptide building block preparation where an L-phenylalanine residue with a removable carboxyl protecting group is required. The tert-butyl ester strategy supports orthogonal protection logic by allowing selective ester cleavage under acidic conditions to form a carboxylic acid suitable for amide-bond formation. The maintained L-configuration at the α-carbon supports stereochemically consistent incorporation into sequences via standard coupling chemistries for protected amino acids. The aromatic side chain then becomes a structural element for hydrophobic packing and conformational effects in peptide scaffolds, enabling systematic generation of peptide libraries and analogs.
2. Side-Chain Functionalization
L-Phenylalanine tert.butyl ester hydrochloride is used as a chiral aromatic amino acid intermediate for side-chain derivatization in synthetic organic chemistry. The benzyl aromatic ring can be transformed through electrophilic substitution, halogenation, or oxidative functional group interconversions to generate substituted phenylalanine derivatives while preserving the amino acid stereocenter. The tert-butyl ester can remain as a protected carboxyl handle during side-chain modification, reducing competing reactions at the acid functionality. Downstream, deprotection yields a carboxylic acid for coupling into peptides, conjugates, or peptidomimetic fragments, supporting structure-activity relationship studies that correlate aromatic substitution patterns with molecular recognition.
3. Chiral Amino Acid Intermediate
L-Phenylalanine tert.butyl ester hydrochloride serves as a chiral amino acid intermediate for stereoselective synthesis of enantiopure derivatives and protected amino acid chemistry. The L-configuration at the α-carbon is preserved through the ester-protected stage, supporting downstream conversion into N- or C-terminal modified building blocks after appropriate deprotection and functional group interconversions. The hydrochloride salt form can be leveraged for controlled reactivity of the amino group during protection/deprotection sequences, improving compatibility with multi-step manufacturing routes. The resulting carboxylic acid regeneration from the tert-butyl ester enables formation of activated derivatives for peptide coupling, esterification, or further derivatization into industrially relevant fine chemicals.
4. Bioconjugation Chemistry
L-Phenylalanine tert.butyl ester hydrochloride is suitable for biomolecule modification workflows where an amino acid-derived aromatic motif is incorporated into conjugation handles. The protected carboxyl group can be deprotected to generate a carboxylic acid for coupling to amines, hydrazides, or other nucleophiles, enabling the construction of amide-linked conjugates. The aromatic side chain can support noncovalent recognition and can be used as a scaffold for attaching linkers that later introduce functional groups such as dyes, affinity tags, or reactive moieties. The L-stereochemistry helps maintain consistent spatial presentation of the amino acid unit within conjugate architectures used in chemical biology and analytical reagent development.
5. Pharmaceutical Intermediate Preparation
L-Phenylalanine tert.butyl ester hydrochloride is applied as a process-relevant intermediate in the synthesis of peptide-like fragments and chiral building blocks used in pharmaceutical manufacturing. The tert-butyl ester protection enables route design where carboxyl functionality is masked during earlier steps, then unmasked to furnish a carboxylic acid for coupling into larger intermediates. The amino acid framework supports conversion into activated species for amide bond formation, supporting the assembly of peptidomimetic or constrained analogs that retain stereochemical integrity. The aromatic phenylalanine side chain provides a common motif for fragment elaboration, supporting downstream fine chemical synthesis and controlled intermediate generation in multi-step production sequences.
6. Analytical Research Standards
L-Phenylalanine tert.butyl ester hydrochloride can be used to prepare analytical standards and reference materials for amino acid and peptide method development. The defined L-stereochemistry and the ester-protected carboxyl group support reproducible derivatization pathways that generate predictable chromatographic or mass spectrometric signatures. The tert-butyl ester can be converted to the corresponding acid form to create matched reference compounds used for calibration and method verification in amino acid profiling and peptide analysis. The aromatic side chain provides a stable structural feature that supports consistent detection behavior across derivatization and analytical workflows, linking amino acid chemistry to applied analytical research.
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