L-Cysteic acid monohydrate is a naturally occurring, proteinogenic amino acid derivative in the cysteine family featuring a thiol-oxidized side chain that is converted to a sulfonic acid group, along with a free amino group and a carboxyl group on the alpha carbon. The molecule bears a strongly acidic sulfonate functionality on the side chain and exists as a monohydrate, which can influence its solubility and handling in aqueous peptide-chemistry and analytical workflows while retaining the amino and carboxyl functional groups for coupling chemistry. L-Cysteic acid monohydrate is used as a defined amino acid building block for preparing cysteic acid-containing peptides and for structure-function studies where a permanently oxidized sulfur substituent is required, as well as for analytical method development and calibration materials involving sulfonate-bearing amino acid motifs.
CAT No: CP00610
CAS No:23537-25-9
Synonyms/Alias:L-Cysteicacidmonohydrate;23537-25-9;UNII-VN8X20T18R;(R)-2-Amino-3-sulfopropanoicacidhydrate;(R)-2-Amino-3-sulfopropionicacid;L-CysteicAcidHydrate;beta-Sulfo-L-alanine;C3H9NO6S;cysteinesulfonicacidhydrate;Cysteicacidmonohydrate,l-;SCHEMBL1157749;VN8X20T18R;30170_SIGMA;CTK3J4525;L-2-Amino-3-sulfopropionicacid;L-Cysteicacidmonohydrate[MI];MolPort-003-929-596;PCPIXZZGBZWHJO-DKWTVANSSA-N;L-Alanine,3-sulfo-,monohydrate;MFCD00149544;Alanine,3-sulfo-,monohydrate,l-;AKOS016011092;L-Alanine,3-sulfo-,hydrate(1:1);AK122208;KB-53169
L-Cysteic acid monohydrate contains a canonical L-amino acid backbone bearing a side-chain sulfonic acid group, providing a strongly anionic, highly polar functional motif that remains chemically informative across aqueous and mixed-solvent peptide chemistry. L-Cysteic acid monohydrate is present as the zwitterionic amino acid salt form with a carboxylic acid and an additional sulfonic acid functionality, enabling controlled ion-pairing, salt formation, and predictable reactivity under acid-base conditions. The stereochemical integrity at the α-carbon supports stereodefined incorporation into cysteine-derived chemical architectures, while the sulfonate group can participate in derivatization, activation, or protective-group strategies tailored to preserve the side-chain during coupling steps. As a research-grade amino acid derivative and biochemical intermediate, it functions as a chemically stable, water-compatible precursor for generating sulfonated amino acid derivatives, peptide analogs, and downstream functional molecules.
1. Peptide Coupling Chemistry
L-Cysteic acid monohydrate finds application in peptide coupling chemistry where a defined L-amino acid scaffold with a carboxylic acid and sulfonic acid side chain enables construction of sulfonated peptide building blocks for aqueous-compatible synthesis. The α-amino group and carboxyl functionality can be managed through N-protection and carboxyl activation strategies, while the sulfonate can be preserved as an anionic handle or selectively masked depending on the coupling sequence. Peptide coupling workflows can incorporate cysteic-acid-derived residues to generate peptide analogs that model oxidized cysteine states or introduce persistent negative charge for conformational and solubility control. Downstream derivatives include sulfonated peptides used as standards, mechanistic probes, and scaffold components in peptide science and synthetic methodology studies.
2. Chemical Biology Probes
L-Cysteic acid monohydrate supports chemical biology research by providing a stereodefined, highly polar amino acid motif that can serve as a taggable or charge-modulating unit in biomolecule modification. The side-chain sulfonic acid group enables robust ionic interactions and can be used to tune binding behavior in peptide-protein or peptide-receptor interaction studies without relying on labile functionalities. Functionalization of the carboxyl and amino groups can be used to generate labeled conjugates, affinity reagents, or immobilizable linkers that remain stable in aqueous buffers. Sulfonated amino acid derivatives derived from this starting material can then be applied in biochemical research intermediate preparation, molecular recognition studies, and analytical reagent development.
3. Protein Engineering Studies
L-Cysteic acid monohydrate is suitable for protein engineering studies that require defined incorporation of cysteine-oxidation mimics or persistent anionic side-chain analogs into peptide and protein fragments. The L-configuration at the α-carbon provides stereochemical control when used to generate amino acid derivatives that can be incorporated into engineered sequences via compatible peptide synthesis routes. The sulfonate side chain can participate in electrostatic patterning and can be retained through synthesis to maintain charge distribution in the resulting constructs. Resulting sulfonated peptide fragments and proteinogenic analogs can serve as tools for probing structure-function relationships, binding-site electrostatics, and post-translational modification modeling.
4. Amino Acid Derivatization Intermediates
L-Cysteic acid monohydrate serves as a biochemical research intermediate for amino acid derivatization, leveraging its dual acid functionality to access a range of protected amino acid derivatives and sulfonated building blocks. The presence of both carboxyl and sulfonic acid groups enables selective activation, salt formation, and orthogonal protection schemes that can be designed to withstand peptide coupling conditions. N-protection of the amino group and controlled handling of the sulfonate can yield intermediates for generating sulfonamide, sulfonate esters, or sulfonyl-containing amino acid analogs used in synthetic organic chemistry. Downstream utility includes preparation of chiral sulfonated intermediates, process-relevant fine chemical building blocks, and analytical standards for verifying sulfonated amino acid transformations.
5. Pharmaceutical Intermediate Preparation
L-Cysteic acid monohydrate can be applied in pharmaceutical intermediate preparation where a highly polar, anion-stabilized amino acid unit is used to construct fragment-like motifs for medicinal chemistry and formulation-oriented chemistry. The sulfonic acid side chain enables incorporation of strong ionic character into peptidomimetic structures, while the α-amino and carboxyl groups support conversion into protected derivatives compatible with stepwise synthesis. Protective-group strategies can be aligned with peptide coupling chemistry to generate sulfonated scaffolds that can be further elaborated into conjugates, linkers, or charged pharmacophore fragments. Industrially, this functionality can translate into manufacturing routes for sulfonated intermediates used in specialty chemical production and downstream API-adjacent synthesis planning.
6. Process Chemistry And Specialty Production
L-Cysteic acid monohydrate is relevant to process chemistry and specialty chemical production due to its water-compatible, strongly acidic functionality that can simplify handling in aqueous or mixed-solvent manufacturing steps. The stable sulfonate group supports conversion into industrially useful derivatives such as sulfonated amino acid building blocks, immobilization reagents, or ionic intermediates that can be carried through multi-step synthesis with predictable acid-base behavior. The stereodefined α-carbon enables consistent generation of L-configured downstream products for peptide analog construction and chiral intermediate supply chains. Resulting derivatives can serve as inputs for fine chemical synthesis, industrial biocatalysis feedstocks where charge-stable amino acid motifs are required, and broader amino acid derivatization programs in applied product development.
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