52-90-4

Basic information

• Product Name: L-Cysteine
• Synonyms: (R)-2-Amino-3-mercaptopropanoic acid;3-mercapto-l-alanin;alpha-amino-beta-mercaptopropionicacid;alpha-Amino-beta-thiolpropionic acid;alpha-amino-beta-thiolpropionicacid;Cystein;half-cysteine;L-Alanine, 3-mercapto-
• CAS NO: 52-90-4
• Molecular Formula: C₃H₇NO₂S
• Molecular Weight: 121.16
• EINECS: 200-158-2
• Product Categories: API intermediates;Cysteine [Cys, C];Amino Acids;Amino Acids and Derivatives;alpha-Amino Acids;Antioxidant;Biochemistry;Nutritional Supplements;L-Amino Acids;Amino Acids;amino
• Mol File: 52-90-4.mol
• Article Data: 240

Chemical Properties

• Melting Point: 220 °C (dec.)(lit.)
• Boiling Point: 293.9 °C at 760 mmHg
• Flash Point: 131.5°C
• Appearance: White/Solid
• Density: 1.197 (estimate)
• Refractive Index: 8.8 ° (C=8, 1mol/L HCl)
• Storage Temp.: Store at RT.
• Solubility: H2O: 25 mg/mL
• PKA: 1.92(at 25℃)
• Water Solubility: 280 g/L (25 ºC)
• Sensitive: Air Sensitive
• Stability: Stability Stable, but may be air sensitive. Incompatible with oxidizing agents, bases.
• Merck: 14,2781
• BRN: 1721408
• CAS DataBase Reference: L-Cysteine(CAS DataBase Reference)
• NIST Chemistry Reference: L-Cysteine(52-90-4)
• EPA Substance Registry System: L-Cysteine(52-90-4)

Safety Data

• Hazard Codes: Xn,Xi
• Statements: 22-36/37/38-20/21/22
• Safety Statements: 36-37/39-26-24/25
• WGK Germany: 3
• RTECS: HA1600000
• F: 10-23
• TSCA: Yes
• Hazardous Substances Data: 52-90-4(Hazardous Substances Data)

Usage

Description

L-Cysteine is a sulfur-containing non-essential amino acid that plays a crucial role in protein synthesis, detoxification, and various metabolic functions. It is one of the 20 natural amino acids and is found in beta-keratin, which is the main protein in nails, skin, and hair. L-Cysteine is important for collagen production, skin elasticity and texture, and is a component of the antioxidant glutathione.

Uses

Used in Pharmaceutical Industry:
L-Cysteine is used as a precursor in the pharmaceutical industry for the treatment of various health conditions. It is used as an antidote for hepatitis, liver poisoning, radiopharmaceutical poisoning, antimony poisoning, and allergic diseases. L-Cysteine also has a role in preventing radiation damage and is used in the treatment of bronchitis and phlegm, particularly in the form of acetyl L-cysteine methyl ester salt.
Used in Food Industry:
L-Cysteine is used as a bread improver, nutritional supplement, antioxidant, and color fixative. It is used in the baking industry as a dough conditioner, breaking the disulfide bonds of gluten, which lowers the viscosity of the dough and increases its elasticity. It is also used in natural fruit juices to prevent oxidation of vitamin C and to prevent fruit juice from becoming brown. Additionally, L-Cysteine is used as a processing aid for baking, an additive in cigarettes, and in the preparation of meat flavors.
Used in Cosmetics Industry:
L-Cysteine is used in the cosmetics industry for its skin benefits, including the treatment of eczema, urticaria, freckles, and other skin diseases. Its products are widely used in medicine, food, and cosmetics. In cosmetics, it is mainly used as a component in cosmetic water, perm solution, anti-sun cream, and other skin care products.
Used in Biochemical Research:
L-Cysteine is used in biochemical research and as a reagent for the receptor agonists of NMDA glutamate. It is also a popular target for site-directed labeling experiments to investigate biomolecular structure and dynamics.
Used in Personal Care Industry:
L-Cysteine is used for permanent wave applications, predominantly in Asia, where it helps break up the disulfide bonds in the hair's keratin. It is also a component of the skin's natural moisturizing factor and can help normalize oil gland secretion due to its sulfur content.
Industrial Sources:
The majority of L-cysteine is obtained industrially by hydrolysis of poultry feathers or human hair. Synthetically produced L-cysteine, compliant with Jewish Kosher and Muslim Halal rules, is also available, albeit at a higher price. The synthetic route involves fermentation utilizing a mutant of E. coli.

Amino acids

L-cysteine, also known as cysteine, is a non-essential amino acid of the human body. Amino acids are protein components and protein is the material basis of life. Ranging from human to microorganism, all consist of protein. Protein is composed of peptides, and peptide chain is composed of amino acids. Different proteins are composed of peptide chains in different order and length. Genes related to heredity are in fact amino acid chains in different orders. L-cysteine is closely related to cysteine, and two molecules of cysteine can form a cysteine. Cysteine is relatively unstable and easy to become cysteine. Cystine can also re-generate cysteine. These two both are sulfur-containing amino acids, which affect the formation of skin and can be used for detoxification. L-cysteine is present in keratin, which is the major protein that makes up nails, toenails, skin and hair. L-cysteine can help the production of collagen, and can maintain the skin's elasticity and texture. It is also related to the protein of digestive enzymes, and cysteine can supply –SH group to many important enzymes, such as succinate dehydrogenase and lactate dehydrogenase. L-cysteine is mainly used in the field of cosmetics, medicine and food. In cosmetics, it can be used for the preparation of perm essence, sunscreen, hair-restoring perfume and other nourishing hair essence. In the field of medicine, it is mainly used for the preparation of methyl cysteine, ethyl cysteine, acetyl cysteine, cysteine methyl ester, cysteine ethyl ester as well as comprehensive amino acid preparations and other drugs. Cysteine can be used as protective agent for radiation damage. In food, L-cysteine can be used as bread fermentation aid (ripening agent), stabilizer of milk powder and fruit juice antioxidants and nutrition of pet food and so on. The above information is edited by andy of lookchem.

health benefits

L-cysteine is an important precursor for antioxidants such as glutathione – a product metabolized in the liver. Glutathione is essential for the breakdown of toxins in the body, such as alcohol. L-cysteine is also the precursor for other important antioxidants that help ward off cancer by decreasing the incidence of cell mutation. Cancer is caused by the replication of genetic mistakes (mutations) that go unnoticed by the cell’s recognition system. In healthy cells, mutations are caught and denatured before replication continues. If mutations are not caught, then the on/off mechanisms that monitor cell formation may be disrupted allowing uncontrolled proliferation of cells into tumors. A healthy cell rich in amino acids such as L-cysteine, has a better chance of sensing and discarding such mutations. L-cysteine benefits can also include improved heart and circulatory system health. Inflammation plays a key role in heart health. The inflammation response causes a cascade of events to bring fluids, proteins and cells to damaged tissues. Some of these substances carried in an inflammatory response are sticky and can get stuck on the walls of arteries. The presence of L-cysteine has been found to directly regulate this adhesion of sticky substances to the walls of arteries and therefore has a positive effect on the health of our hearts. figure 1: L-Cysteine 500mg, 100 Tablets

Cysteine Metabolism

Cysteine is a sulfur-containing amino acid that constitutes protein. It has an ionized mercapto side chain and is hydrophobic. However, it is unstable in neutral pH or alkaline pH in the air, and its aqueous solution can automatically convert into cysteine . Although cystine does not belong to the list of amino acids composing protein, but in the process of protein conformation, it can generate by oxidizing the SH group of two close cysteine, so many protein molecules in the body contain cystine. The formation of cystine disulfide bond makes the protein conformation more stable. Of course, if the cystine is reduced, it can also produce two molecules of cysteine. The importance of cysteine as a protein component is to give the active protein a free SH group, for example, the active centers of some proteases (papain, bromelain) and glyceraldehyde phosphate dehydrogenase all regard SH group as their function base. The metabolic pathway of cysteine carbon skeleton is mainly to form pyruvate and generate oxaloacetate through carboxylation for gluconeogenesis, so cysteine belongs to the glucogenic amino acid, or to change into acetyl-CoA and come into the tricarboxylic acid cycle for complete oxidization. There may be three ways for cysteine transforming into pyruvate. Non-protein nitrogenous compounds synthesized or part-synthesized by cysteine include taurine, peroxydihydroxyethylamine, coenzyme A and glutathione.

Production methods

1. Tin granule reduction method. Dissolve cystine in dilute hydrochloric acid and filtrate. Add tin granules into the filtrate and heat for reflux of 2h. Dilute the reducing solution with water and remove the residual tin particles. Saturate the diluted solution with hydrogen sulfide and filtrate. Wash the residue with a small amount of water and combine the washing liquor with filtrate. Then concentrate the mixture under reduced pressure, cool for crystallization, filtrate and dry to obtain L-cysteine hydrochloride. 2. Electrolysis reduction method. Add distilled water, hydrochloric acid, cystine into the electrolytic tank and dissolve under stirring. Maintain at 50℃ until the electrolysis to the end. Add hydrogen sulphide to pass through the resultant electrolytic solution for several hours and filtrate. Decolorize the filtrate with activated carbon, filtrate and concentrate under reduced pressure. Cool for crystallization, filtrate and then dry to give L-cysteine hydrochloride. 3. Use L-cysteine hydrochloride as raw materials. Neutralize L-cysteine hydrochloride with alkali and obtain L-cysteine after further purification. 4. Heat the hair (or animal hair, feathers) with hydrochloric acid for 6~8h and then hydrolyze. Remove the hydrochloric acid by vacuum distillation. Add activated carbon for decolorization, Filtrate and neutralize with ammonia to obtain L-cystine crude crystals. And then dissolve with ammonia solution for recrystallization. Next dissolve with hydrochloric acid again and perform electrolytic reduction. The resultant electrolytic solution is concentrated, cooled for crystallization and dried to obtain the product.

synthesis

Cysteine can be prepared in three ways: 1, extraction method: process the hair (or feather powder) into cystine, dissolve in hydrochloric acid, and then obtain L-cysteine hydrochloride by electrolysis or the reduction of tin and hydrochloric acid Methods for Extracting Cysteine from Hair 2, synthesis method: the current industrial applications include β-chloroalanine method, α-bromo-methyl acrylate and Degussa method. Use α-chloroacrylic acid methyl ester and thiourea as raw materials to firstly synthesize DL-2-aminothiazoline-4-carboxylic acid and then carry out asymmetric hydrolysis under the action of Pseudomonas aeruginosa enzyme to obtain the product. Use methyl α-bromo-acrylic acid as raw materials to react with methyl thioacetamide and form 2-methyl-thiazoline-4-carboxylic acid methyl ester. The product can be obtained after?? further hydrolysis. α-methyl bromoacrylate method: use chloroacetaldehyde as raw materials to react with sodium bisulfate and form α-hydroxy-β-chloro ethanol sodium sulfonate [2]. [2] and ammonium hydroxide react to form α-amino-β-chlorosulfonate [3]. [3] and sodium hydride react to obtain α-amino-β-chloropropionitrile[4]. After the hydrolysis of [4], β-chloroalanine [5] is generated. Then [5] and ammonium thiosulfate react and hydrolyze to form DL-cysteine precipitation. And L-cysteine can be finally obtained after further desalination. 3, enzymatic method (Ajinomoto method): use α-chloro acrylic acid methyl ester and thiourea as raw materials to firstly synthesize DL-2-aminothiazoline-4-carboxylic acid (DL-ATC). L-cysteine is produced by the asymmetric hydrolysis of DL-ATC in the presence of the three enzymes of thermophilic thiazole pseudomonas bacteria.

physiological effects

Cysteine can help the detoxification of the body. It is the best free radical scavenger combined with selenium and vitamin E. Cysteine is also the precursor of glutathione, which is capable of binding with poisonous substances for detoxication in the liver. It can protect the liver and brain from the damage of cigarettes, alcohol and drugs. Since cysteine is more soluble than cystine, it is easier for cysteine to be used by the body to treat various diseases. Vitamin B6 is required for in vivo cysteine synthesis. Cysteine can not be synthesized in the presence of chronic conditions, so people with chronic diseases need a higher dose of cysteine, for example, 3 times a day for 1 month. The patients with rheumatoid arthritis, vascular sclerosis or cancer need to supplement cysteine. Cysteine can also assists people to accelerate recovery after surgery and burns. It can form complexes with heavy metals, and enhance iron absorption. These two amino acids can also accelerate the use of fat and formation of muscle. Cysteine can clears mucus in the respiratory tract, so it can treat bronchitis, emphysema and tuberculosis. Cysteine (or acetyl-linked acetylcysteine) can be used to prevent the side effects in cancer chemotherapy or radiation therapy. It can also increase the level of glutathione in lung, kidney, liver and bone marrow, so it has anti-aging effects, for example, it can reduce the incidence of age spots. Cysteine can inactivates insulin. Therefore, patients with diabetes can not take cysteine. Genetic cystinuria can result in cystine stones, so people with genetic cystinuria can not take these two amino acids.

Preparation

L-Cysteine used to be produced almost exclusively by hydrolysis of hair or other keratins. The amino acid isolated was l-cystine, which was reduced electrolytically to l-cysteine. L-Cysteine has also been prepared from beta-chloro-d,l-alanine and sodium sulfide with cysteine desulfhydrase, an enzyme obtained from, e.g., Citrobacterium freundii. Today, however, the main processes for cysteine production are biological. A direct fermentation process has been developed for the manufacture of l-cystine, using a modified Escherichia coli bacterium. The technology has been extended to prepare other modified l-cysteine analogues. An enzymatic process for l-cysteine has been successfully developed using microorganisms capable to hydrolyze 2-amino-delta2-thiazoline 4-carboxylic acid (ATC) which is readily available from methyl alpha-chloroacrylate and thiourea. A mutant of Pseudomonas thiazolinophilum converts d,l-ATC to l-cysteine in 95% molar yield at product concentrations higher than 30 g/L.

Biological Functions

The cysteine thiol group is nucleophilic and easily oxidized. The reactivity is enhanced when the thiol is ionized, and cysteine residues in proteins have pKa values close to neutrality, so are often in their reactive thiolate form in the cell. Because of its high reactivity, the thiol group of cysteine has numerous biological functions. Precursor to the antioxidant glutathione Due to the ability of thiols to undergo redox reactions, cysteine has antioxidant properties. Cysteine's antioxidant properties are typically expressed in the tripeptide glutathione, which occurs in humans as well as other organisms. Precursor to iron-sulfur clusters Cysteine is an important source of sulfide in human metabolism. The sulfide in iron-sulfur clusters and in nitrogenase is extracted from cysteine, which is converted to alanine in the process. Metal ion binding Beyond the iron - sulfur proteins, many other metal cofactors in enzymes are bound to the thiolate substituent of cysteinyl residues. Examples include zinc in zinc fingers and alcohol dehydrogenase, copper in the blue copper proteins, iron in cytochrome P450, and nickel in the [NiFe]-hydrogenases . The thiol group also has a high affinity for heavy metals, so that proteins containing cysteine, such as metallothionein, will bind metals such as mercury, lead, and cadmium tightly. Roles in protein structure In the translation of messenger RNA molecules to produce polypeptides, cysteine is coded for by the UGU and UGC codons. Cysteine has traditionally been considered to be a hydrophilic amino acid, based largely on the chemical parallel between its thiol group and the hydroxyl groups in the side-chains of other polar amino acids. However, the cysteine side chain has been shown to stabilize hydrophobic interactions in micelles to a greater degree than the side chain in the non-polar amino acid glycine, and the polar amino acid serine .

Synthesis Reference(s)

Chemical and Pharmaceutical Bulletin, 34, p. 869, 1986 DOI: 10.1248/cpb.34.869

Biochem/physiol Actions

NMDA glutamatergic receptor agonist.

Side effects

Cysteine has been proposed as a preventative or antidote for some of the negative effects of alcohol, including liver damage and hangover. It counteracts the poisonous effects of acetaldehyde, which is the major by - product of alcohol metabolism and is responsible for most of the negative aftereffects and long - term damage associated with alcohol use (but not the immediate effects of drunkenness). Cysteine supports the next step in metabolism, which turns acetaldehyde into the relatively harmless acetic acid. In a rat study, test animals received an LD50 dose of acetaldehyde. Those that received cysteine had an 80 % survival rate; when both cysteine and thiamine were administered, all animals survived . There is not yet direct evidence for or against its effectiveness in humans who consume alcohol at normal levels. N-Acetylcysteine N - Acetyl - L - cysteine (NAC) is a derivative of cysteine wherein an acetyl group is attached to the nitrogen atom. This compound is sold as a dietary supplement and used as an antidote in cases of acetaminophen overdose, and obsessive compulsive disorders such as trichotillomania.

Safety Profile

Moderately toxic by ingestion, intraperitoneal, and subcutaneous routes. Experimental reproductive effects. Human mutation data reported. When heated to decomposition fumes of SO and NO.

Purification Methods

Purify it by recrystallisation from H2O (free from metal ions) and dry it in a vacuum. It is soluble in H2O, EtOH, Me2CO, EtOAc, AcOH, *C6H6 and CS2. Acidic solutions can be stored under N2 for a few days without deterioration. [For synthesis and spectra see Greenstein & Winitz Chemistry of the Amino Acids (J. Wiley) Vol 3 p1879 1961, Beilstein 4 III 1618, 4 IV 3144.]

Sheep

Cysteine is required by sheep in order to produce wool: It is an essential amino acid that must be taken in as food from grass. As a consequence, during drought conditions, sheep stop producing wool; however, transgenic sheep that can make their own cysteine have been developed.

InChI:InChI=1/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m0/s1

Synthetic route

S-(4-methoxybenzyl)-L-cysteine (2544-31-2) → L-Cysteine (52-90-4)

Conditions	Yield
With trimethylsilyl trifluoromethanesulfonate; methyl-phenyl-thioether In trifluoroacetic acid at 0℃; for 0.5h; Product distribution; New peptide deprotection procedure: hard-soft acid-base concept; the role of soft bases (thioanisole, dimethylsulfide, diphenylsulfide) employed.;	100%
With trifluoroacetic acid In dichloromethane at 20℃; Rate constant;

Boc-cysteine(4-Me-Bn) (61925-77-7) → L-Cysteine (52-90-4)

Conditions	Yield
With phenylthiotrimethylsilane; pertrimethylsilylated Nafion; 3-methyl-phenol; trifluoroacetic acid for 3h;	100%
With ethandithiol; methoxybenzene; thallium(III) trifluoroacetate 1.) trifluoroacetic acid, 0 deg c, 60 min; 2.) 40 deg C, 5 h, pH=7.5 adjusted with 5percent NH4OH;

S-(2,4,6-trimethylbenzyl)-L-cysteine (78221-55-3) → L-Cysteine (52-90-4)

Conditions	Yield
With hydrogen fluoride; methoxybenzene at 0℃; for 0.5h; Product distribution; various time, reagents and temperature;	100%

S-benzyloxymethylcysteine (123043-33-4) → L-Cysteine (52-90-4)

Conditions	Yield
With silver trifluoromethanesulfonate; methoxybenzene In trifluoroacetic acid Product distribution; other reagents;	100%

Z(OMe)-Cys(Ad)-OH*DCHA (103022-01-1) → L-Cysteine (52-90-4)

Conditions	Yield
With trimethylsilyl trifluoromethanesulfonate; methyl-phenyl-thioether In trifluoroacetic acid at 0℃; for 0.5h; Product distribution; New peptide deprotection procedure: hard-soft acid-base concept; the role of soft bases (thioanisole, dimethylsulfide, diphenylsulfide) employed.;	100%
With ethandithiol; methoxybenzene; thallium(III) trifluoroacetate 1.) trifluoroacetic acid, 0 deg c, 60 min; 2.) 40 deg C, 5 h, pH=7.5 adjusted with 5percent NH4OH; Yield given. Multistep reaction;

(2S,4R)-2-methyl-1,3-thiazolidine-2,4-dicarboxylic acid → L-Cysteine (52-90-4) + 2-acetoacetic acid (541-50-4)

Conditions	Yield
With water at 90℃; Column which a srtongly acidic cation exchanger in the H+ form;	A n/a B 99.6%

L-cystine (56-89-3) → L-Cysteine (52-90-4)

Conditions	Yield
With ethandithiol at 40℃; for 5h; pH=7.5 adjusted with 5 percent NH4OH;	98.5%
With ammonia; sodium Reduction;	90%
With hydrogenchloride; tin man verduennt die Loesung, befreit sie mit H2S vom Zinn, verdunstet zur Trockne, loest den Rueckstand in Alkohol und faellt vorsichtig mit Ammoniak;

N-(Carbo-tert-butoxy)-S-tert-butyl-L-cysteine (56976-06-8) → L-Cysteine (52-90-4)

Conditions	Yield
With trimethylsilyl trifluoromethanesulfonate; diphenyl sulfide In trifluoroacetic acid at 0℃; for 0.5h; Product distribution; New peptide deprotection procedure: hard-soft acid-base concept; the role of soft bases (thioanisole, dimethylsulfide, diphenylsulfide) employed.;	97.1%
With ethandithiol; methoxybenzene; thallium(III) trifluoroacetate 1.) trifluoroacetic acid, 0 deg c, 60 min; 2.) 40 deg C, 5 h, pH=7.5 adjusted with 5percent NH4OH; Yield given. Multistep reaction;

L-cystine (56-89-3) → L-Cysteine (52-90-4) + L-Cysteic acid (498-40-8)

Conditions	Yield
With hydrogenchloride; sulfuric acid; hydrogen bromide In water at 45℃; electrolysis (graphite sheets, i = 0.5 A/cm2);	A 94% B n/a
With hydrogenchloride; sulfuric acid; hydrogen bromide In water at 45℃; Product distribution; Mechanism; paired electrosynthesis (graphite sheets, i = 0.5 A/cm2);	A n/a B 94%
With hydrogenchloride at 40℃; Electrolysis;

N-t-butoxycarbonyl-S-acetamidomethyl-L-cysteine (19746-37-3) → L-Cysteine (52-90-4)

Conditions	Yield
With silver tetrafluoroborate; methoxybenzene In trifluoroacetic acid at 4℃; for 1h;	93%

l-cysteine hydrochloride (52-89-1) → L-Cysteine (52-90-4)

Conditions	Yield
In acetone for 1.5h; Heating / reflux;	92%
With pyridine; ethanol durch Faellung;
With ethanol; ammonia durch Neutralisation;
With sodium hydrogencarbonate In water; dimethyl sulfoxide at 20℃;

Boc-Cys-Merrifield resin → L-Cysteine (52-90-4)

Conditions	Yield
With dimethyl ether-poly(hydrogen fluoride) at 0℃; for 1h;	91%

L-thioproline (34592-47-7) → L-Cysteine (52-90-4)

Conditions	Yield
With hydroxylamine hydrochloride	83%
With hydroxylamine hydrochloride In methanol reflux, 120 min, ice bath, 60 min;	82%

rac-cysteine (921-01-7, 3374-22-9, 4371-52-2, 40143-64-4, 40143-66-6, 40143-69-9, 52-90-4) → L-Cysteine (52-90-4)

Conditions	Yield
With porcine kidney D-amino acid oxidase (EC 1.4.3.3.); sodium cyanoborohydride; flavin adenine dinucleotide In phosphate buffer at 37℃;	77%

2(R,S)-D-gluco-(1',2',3',4',5'-pentahydroxypentyl)-thiazolidine-4(R)-carboxylic acid (232617-16-2) → L-Cysteine (52-90-4)

Conditions	Yield
With hydroxylamine hydrochloride In methanol; water for 2.5h; Heating;	74%

(2R,4R)-2-(D-galacto-1,2,3,4,5-Pentahydroxypentyl)-4-thiazolidincarbonsaeure (57918-01-1, 124650-46-0) → L-Cysteine (52-90-4)

Conditions	Yield
With hydroxylamine hydrochloride In methanol for 3h; Heating;	73%

2(RS)-D-manno-(1',2',3',4',5'-pentahydroxypentyl)thiazolidine-4(R)-carboxylic acid (17087-37-5, 17087-38-6, 17205-71-9, 57918-01-1, 85504-88-7, 85504-89-8, 88271-26-5, 88271-27-6, 88271-28-7, 88271-29-8, 88271-30-1, 110270-21-8, 110270-23-0, 110311-43-8, 124650-44-8, 124650-45-9, 124650-46-0, 124650-49-3, 124650-50-6, 124650-51-7, 132338-92-2, 149885-33-6) → L-Cysteine (52-90-4)

Conditions	Yield
With hydrazine hydrate In methanol for 0.5h; Heating;	69%

→ L-cystine (56-89-3)

Conditions	Yield
With 3-bromo-2-(1-hydroxycyclohexyl)[1,2]selenazolo[2,3-a]pyridinium chloride; dihydrogen peroxide In methanol; water at 20℃; for 0.166667h;	100%
With dihydrogen peroxide; sodium iodide In water at 25℃; for 1h; Cooling with ice;	100%
With bis(4-methoxyphenyl)telluride; rose bengal In water; isopropyl alcohol at 0℃; for 0.833333h; Irradiation;	99%

L-Cysteine (52-90-4) + ethylene dibromide (106-93-4) → S,S'-ethanediyl-bis-L-cysteine (14344-49-1)

Conditions	Yield
With sodium hydrogencarbonate In ethanol; water at 70 - 90℃; for 1h;	100%
With sodium hydrogencarbonate	88%

methanol (67-56-1) + L-Cysteine (52-90-4) → L-cysteine methyl ester hydrochloride (18598-63-5)

Conditions	Yield
With thionyl chloride In methanol for 3h; Reflux; Inert atmosphere;	100%
With acetyl chloride at 0℃; for 2h; Reflux;	96%
Stage #1: methanol With acetyl chloride at 0℃; for 0.0833333h; Inert atmosphere; Stage #2: L-Cysteine at 20℃; for 36h; Inert atmosphere;	94%

L-Cysteine (52-90-4) + (R)-2-Amino-3-(4-methoxy-phenylmethanesulfinyl)-propionic acid (73243-09-1) → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide; trifluorormethanesulfonic acid In trifluoroacetic acid at 0℃; for 1h;	100%

L-Cysteine (52-90-4) + cyclohexanecarbaldehyde (2043-61-0) → (2RS,4R)-cyclohexylthiazolidine-4-carboxylic acid (56888-62-1)

Conditions	Yield
In ethanol at 20℃; for 5h;	100%

L-Cysteine (52-90-4) + tin(ll) chloride → bis(cysteinato-OS)tin(IV) dihydrochloride dihydrate

Conditions	Yield
With water In water aq. mixt. of educts allowed to evap. at room temp. over 3 d; dried in vac. at room temp.; elem. anal.;	100%

L-Cysteine (52-90-4) + 2-[N-(tert-butoxycarbonyl)aminomethyl]thiazole-4-carbonitrile (251294-64-1) → (R)-2-(2-tert-butoxycarbonylaminomethyl-thiazol-4-yl)-4,5-dihydrothiazole-4-carboxylic acid (1132667-22-1)

Conditions	Yield
With triethylamine In methanol Reflux;	100%
Stage #1: L-Cysteine; 2-[N-(tert-butoxycarbonyl)aminomethyl]thiazole-4-carbonitrile With triethylamine In methanol Reflux; Stage #2: With hydrogenchloride In water pH=~ 3 - 4;	100%
Stage #1: L-Cysteine; 2-[N-(tert-butoxycarbonyl)aminomethyl]thiazole-4-carbonitrile With water; sodium hydrogencarbonate In N,N-dimethyl-formamide at 20℃; Inert atmosphere; Stage #2: With formic acid; water In N,N-dimethyl-formamide Inert atmosphere;	97%
With triethylamine In methanol at 23℃; for 3h; Reflux;	97%
With triethylamine In methanol for 3h; Reflux;	97%

L-Cysteine (52-90-4) + (2S,4R)-N-allyloxycarbonyl-2-cyano-4-methyl-azetidine (1240490-39-4) → C12H16N2O4S (1240490-42-9)

Conditions	Yield
In methanol at 70℃; for 15h; pH=7; aq. phosphate buffer; Inert atmosphere;	100%

L-Cysteine (52-90-4) + 4-(5-phenyl-3-(selenocyanatomethyl)-1H-pyrazol-1-yl)benzenesulfonamide

Conditions	Yield
With sodium hydroxide In tetrahydrofuran; water at 0 - 20℃; for 12h;	100%

→ (4R)-2-sulfanylidene-1,3-thiazolidine-4-carboxylic acid

Conditions	Yield
With gold; cetyltrimethylammonim bromide; silver nitrate; ascorbic acid at 25℃;	100%

L-Cysteine (52-90-4) + C32H37N7O4S3 → C35H41N7O6S4

Conditions	Yield
With sodium hydrogencarbonate In methanol; aq. phosphate buffer at 70℃; for 4h; pH=5.95;	100%

D-xylose (58-86-6) + L-Cysteine (52-90-4) → C8H14NO6S(1-)*Na(1+)

Conditions	Yield
With sodium hydroxide at 80℃; pH=9.5; Temperature; Flow reactor;	100%

formaldehyd (50-00-0) + L-Cysteine (52-90-4) → (R)-thiazolidine-4-carboxylic acid ; sodium-salt (100208-30-8)

Conditions	Yield
With sodium hydroxide at 80℃; pH=9.5; Temperature; Flow reactor;	100%

L-Cysteine (52-90-4) + (4R,5aS,7aS,7bR)-5,5a,6,7,7a,7b-hexahydro-7b-hydroxy-4-methyl-indeno[1,7-bc]furan-2(4H)-one (133613-71-5) → N-formyl-S-((7bS,3R,4S,5aR,7aR)-7b-hydroxy-4-methyl-2-oxodecahydroindeno[1,7-bc]furan-3-yl)cysteine

Conditions	Yield
With triethylamine In d(4)-methanol for 24h;	100%
With triethylamine In methanol at 20℃; for 30h;

L-Cysteine (52-90-4) + 2-[N-(tert-butoxycarbonyl)aminomethyl]thiazole-4-carbonitrile (251294-64-1) → 2-[2-[(tert-butoxycarbonyl)methyl]thiazol-4-yl]-4,5-dihydrothiazole-4-carboxylic acid

Conditions	Yield
With triethylamine In methanol Reflux;	100%

L-Cysteine (52-90-4) + 1,4-benzoquinone-d4 (2237-14-1) → C9H8(2)H3NO4S

Conditions	Yield
In water at 20℃; for 1.16667h; Inert atmosphere;	100%

L-Cysteine (52-90-4) → C6H12N2O4S2*(x)ClH

Conditions	Yield
With hydrogenchloride; Cumene hydroperoxide; tert-butyl (S)-(tetrahydrotellurophen-3-yl)carbamate In dichloromethane; water at 25℃; Flow reactor;	100%

L-Cysteine (52-90-4) + Methoxycarbonylsulfenyl chloride (26555-40-8) → 3-[(methoxycarbonyl)dithio]-L-alanine

Conditions	Yield
In 1,4-dioxane at 0 - 20℃; Inert atmosphere;	100%

L-Cysteine (52-90-4) + nicotinic acid riboside 5'-monophosphate → bis((R)-1-carboxy-2-mercaptoethan-1-aminium)-1-((2R,3R,4S,5R)-3,4-dihydroxy-5-((phosphonatooxy)methyl)tetrahydrofuran-2-yl)pyridin-1-ium-3-carboxylate

Conditions	Yield
In water pH=2 - 2.43; Inert atmosphere; Cooling with ice;	100%

Upstream product

• 56-89-3 cysteine disulfide 
• 56-89-3 L-cystine 
• 143-33-9 sodium cyanide 
• 19538-81-9 N,S-diacetyl-cysteine 
• 91641-78-0 N-benzoyl-cysteine ethyl ester 
• 5680-65-9 2-amino-3-(benzylthio)propionic acid 
• 7732-18-5 water 
• 10034-85-2 hydrogen iodide 
• 922-56-5 meso-lanthionine 
• 600-05-5 2,3-dibromopropionic acid 
• 498-59-9 S,S'-methylenebis(cysteine) 
• 7664-93-9 sulfuric acid 
• 7218-04-4 N-Acetylcysteine 
• 29581-98-4 N,N'-diformyl-L-cystine 

Downstream Products

• 89299-66-1 (RS)-2-amino-3-<(2-chloroethyl)sulfanyl>propanoic acid hydrochloride 
• 50727-80-5 S,S'-butanediyl-di-L-cysteine 
• 6367-98-2 (-)-(2R)-2-amino-3-(2-hydroxyethylsulfanyl)propanoic acid 
• 4134-56-9 S-n-Butyl-L-cysteine 
• 17885-24-4 S-ethylmercapto-L-cysteine 
• 76305-78-7 S,S'-hexanediyl-di-L-cysteine 
• 444-15-5 5-hydroxybarbituric acid 
• 98025-31-1 S-(1,1,2-trichlorovinyl)-L-cysteine 
• 34317-61-8 S-phenyl-L-cysteine 
• 104640-54-2 S-((Ξ)-1-carboxy-ethyl)-L-cysteine 
• 4746-41-2 S-<(S)-1-carboxyethyl>-(R)-cysteine 
• 109819-52-5 N,S-bis-[(2,4,5-trichloro-phenoxy)-acetyl]-cysteine 
• 75-07-0 acetaldehyde 
• 921-01-7 D-cysteine 

Relevant articles and documents

A novel and environmentally friendly colorimetric method for detection of cystine in human urine using unmodified gold nanoparticles

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Biogenesis of Hydrogen Sulfide and Thioethers by Cystathionine Beta-Synthase

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Developing potent backbone cyclic peptides bearing the shared epitope sequence as rheumatoid arthritis drug-leads

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Synthesis method of DL-cysteine

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Dehalogenation of Halogenated Nucleobases and Nucleosides by Organoselenium Compounds

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