L-Proline methyl ester hydrochloride is a protected/protonated amino acid ester derived from L-proline, featuring a pyrrolidine ring side chain characteristic of the proline class and a methyl ester at the carboxyl terminus. The molecule contains a secondary amine within the pyrrolidine ring that is present as a hydrochloride salt, while the carboxyl group is esterified as a methyl ester, removing the free carboxylic acid functionality. As an amino acid ester salt, it is used as a substrate or intermediate in peptide and amide bond construction and in solution-phase or solid-phase synthesis workflows where controlled handling of the carboxyl functionality and amine salt form are required.
CAT No: CP01723
CAS No:2133-40-6
Synonyms/Alias:L-Prolinemethylesterhydrochloride;2133-40-6;H-Pro-OMe.HCl;MethylL-prolinatehydrochloride;(S)-methylpyrrolidine-2-carboxylateHydrochloride;Methyl(2S)-pyrrolidine-2-carboxylateHydrochloride;MFCD00012708;methyl(2S)pyrrolidine-2-carboxylate,chloride;AC1MBYCG;PubChem10887;H-L-PRO-OMEHCL;UNII-7LWL7P890M;SCHEMBL51792;KSC206E7R;287067_ALDRICH;7LWL7P890M;81740_FLUKA;CTK1A6278;HQEIPVHJHZTMDP-JEDNCBNOSA-N;MolPort-000-005-027;Prolinemethylesterhydrochloride;BB_NC-2036;methyl(S)-prolinatehydrochloride;L-prolinmethylesterhydrochloride;CS-M0706
L-Proline methyl ester hydrochloride is the hydrochloride salt of L-proline methyl ester, combining a chiral pyrrolidine-containing amino acid framework with a methyl-esterified carboxyl group. The stereogenic center at the proline alpha carbon is retained in the L-configuration, enabling stereocontrolled synthesis of peptide and peptidomimetic motifs. Protonation of the amino functionality as the hydrochloride provides practical handling and can modulate nucleophilicity during coupling or derivatization steps, while the ester carbonyl serves as a protected carboxyl equivalent for downstream transformations. The cyclic secondary amine and ester group together support selective functional group interconversions that are compatible with amino acid derivative chemistry and chiral intermediate preparation.
1. Protected Amino Acid Synthesis
L-Proline methyl ester hydrochloride supports protected amino acid synthesis and chiral intermediate preparation for peptide building block workflows by presenting a carboxyl group in methyl-ester form and an amino functionality as a salt. The L-configured proline stereocenter and the pyrrolidine nitrogen enable controlled progression from ester activation to amide formation, while the hydrochloride form can be managed to balance salt stability with reactivity during coupling chemistry. Ester-based carboxyl protection facilitates C-terminal handling, and subsequent ester hydrolysis or transesterification can regenerate the free acid for peptide coupling strategies. Downstream, the compound can be converted into N-protected proline derivatives or used as a chiral precursor for assembling proline-containing fragments in synthetic organic chemistry and process chemistry intermediate streams.
2. Peptide Coupling Chemistry
L-Proline methyl ester hydrochloride is applicable to peptide coupling chemistry as a proline-based C-terminal equivalent that can be converted into activated carboxyl forms prior to amide bond construction. The methyl ester provides a defined electrophilic carbonyl handle for standard peptide coupling sequences, while the cyclic secondary amine in the pyrrolidine ring participates in stereochemically consistent incorporation of proline into growing peptide chains. Salt formation as the hydrochloride can influence base selection and reaction conditions when generating coupling-ready derivatives, supporting reproducible handling in automated synthesis workflows. Resulting proline-containing peptides and peptide fragments can be used for research-grade structure-activity relationship studies, peptidomimetic scaffold generation, and biochemical assay development where proline stereochemistry and conformational constraints matter.
3. Chiral Building Block Development
L-Proline methyl ester hydrochloride functions as a chiral amino acid intermediate for asymmetric and stereocontrolled synthesis programs that require a defined L-proline configuration. The rigid pyrrolidine ring and ester-protected carboxyl group allow selective derivatization at the nitrogen or conversion of the ester into other functional groups that retain stereochemical integrity. N-alkylation, N-protection strategies, or ester transformation to acid derivatives can be designed to feed subsequent steps such as fragment assembly, side-chain functionalization, or heterocycle precursor generation. Downstream products include stereochemically defined proline analogs and chiral intermediates suitable for fine chemical synthesis and pharmaceutical intermediate preparation where consistent stereochemical outcomes are required.
4. Side-Chain Functionalization
L-Proline methyl ester hydrochloride enables side-chain functionalization and amino acid derivatization routes by leveraging the pyrrolidine nitrogen and ester carbonyl as reactive sites. The cyclic secondary amine can be functionalized through protection, alkylation, or controlled oxidation/reduction sequences depending on the targeted proline analog, while the methyl ester can be hydrolyzed to the corresponding acid or converted into alternative carboxyl derivatives for further coupling. The presence of the L-stereocenter supports formation of conformationally constrained derivatives used in peptidomimetic construction and molecular design studies. Resulting functionalized proline derivatives can serve as intermediates for generating libraries of amino acid analogs, supporting SAR studies and chemical biology research focused on backbone-recognition effects.
5. Pharmaceutical Intermediate Preparation
L-Proline methyl ester hydrochloride is suitable for pharmaceutical intermediate preparation and process chemistry intermediate development where proline-derived fragments are incorporated into larger synthetic targets. The esterified carboxyl group provides a controlled form for downstream conversion into amide-forming acids or activated derivatives, and the hydrochloride salt form can be leveraged for handling and reproducible material management during multistep synthesis. The chiral pyrrolidine scaffold supports stereochemically defined incorporation into drug-like motifs and can be carried through synthetic sequences that require retention of L-configuration. Industrially, the compound can be used as a feedstock for producing proline-based building blocks, including N-protected proline derivatives and C-terminal acid equivalents used in specialty chemical production and chemical manufacturing supply chains.
6. Analytical Standards And Derivatization
L-Proline methyl ester hydrochloride can be employed in analytical research and derivatization workflows as a reference material and chemical handle for method development involving proline-containing matrices. The defined stereochemistry and ester/amine functionality allow it to participate in derivatization strategies that distinguish amino acid forms, support chromatographic method tuning, and enable calibration for chiral or functional group-specific detection. Ester-to-acid conversion and N-protection transformations can generate related standards that mirror sample processing steps in peptide and amino acid analysis. Broader use in applied product development includes supporting quality control-oriented analytical reference preparation for amino acid derivative synthesis, peptide building block characterization, and intermediate verification in biochemical research supply contexts.
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