5- Methyl-L-cysteine

Nishimura and coworkers studied the y-radiolysis of aqueous solutions of sulfoxide amino acids. Sulfoxide amino acids are the precursors of the flavors of onions (5-propyl-L-cysteine sulfoxide, 5-methyl-L-cysteine sulfoxide and 5-(l-propenyl)-L-cysteine sulfoxide) and garlic (5-allyl-L-cysteine sulfoxide). In studies on sprout inhibition of onion by y-irradiation it was found that the characteristic flavor of onions became milder. In the y-radiolysis of an aqueous solution of 5-propyl-L-cysteine sulfoxide (PCSO) they identified as the main products alanine, cysteic acid, dipropyl disulfide and dipropyl sulfide. In the radiolysis of 5-allyl-L-cysteine sulfoxide (ACSO) they found that the main products are S-allyl-L-cysteine, cysteic acid, cystine, allyl alcohol, propyl allyl sulfide and diallyl sulfide. The mechanisms of formation of the products were partly elucidated by the study of the radiolysis in the presence of N2O and Br as e, and OH radicals scavengers, respectively. 

Methyl-L-cysteine [1187-84-4] M 135.2, m 207-211°, [from water by adding 4 volumes of EtOH. 

The relative reactivity of the Cbz group lends itself to fine tuning by the simple expedient of introducing substituents onto the aromatic ring. For example, a synthesis of /V-adenylated 5-methyl-L-cysteine sulfoximine 62.1 a potent inhibi-... 

TPL also catalyzes the reverse reaction and may perform other 0 ,/3-elimination and /3-replacement reactions. In addition to L-tyrosine, L- and D-serine, 5-methyl-L-cysteine,. S-ethyl-L-cysteine, 5-(o-nitrophenyl)-L-cysteine, 0-benzoyl-L-serine, ° and /3-chloro-L-alanine also act as substrates for /3-elimination. TPL also catalyzes racemization of alanine. ... 

When sulfur atoms are introduced into the amino acids, the formation of silver-sulfur bonds appears to be of critical importance. The involvement of the other two donor centres, i.e. NH2 and CO2, however, then becomes less clear. It was discovered that reaction of silver nitrate with either Cu or salts of 5-methyl-L-cysteine gave rise to adducts, where the silver... 

Reaction 8, the direct cleavage of L-cystine to produce pyruvate and thiocysteine has been studied in much more detail. An enzyme has been found in a number of Brassica species which cattdyzes the production of pyruvate from L-cystine (Mazelis et al., 1%7). The specificity of this enzyme using six-fold purified B. napobrassica root preparations was limited to L-cystine and 5-methyl-L-cysteine sulfoxide of naturally occurring substrates. The enzyme was completely dependent on added pyridoxal 5 -phosphate. The for L-cystine was 1 vaM and 0.5 pM for pyridoxal phosphate. L-Cysteine was not a substrate but was a competitive inhibitor at low concentrations. This was due to the -SH function since glutathione had the same effect. The Aj for these compounds was 0.15 mM. 

For DMS and DMTS, 5 -methyl-L-cysteine sulfoxide is a precursor action of a C-S lyase enzyme yields methanesulfenic acid, CH3-S-OH, and hence methyl methanethiosulfinate, CH3-SO-S-CH3. Disproportionation reactions yield polysulfides such as DMS. ... 

Similar to the S-allyl-L-cysteine sulfoxide in garlic, the C-S lyase can also catalyze the flavor formation from the 5 -methyl-L-cysteine sulfoxide. Therefore, when garlic is cut or crushed, methyl sulfenic acid and allyl sulfenic acid can be produced from 5 -methyl-L-cysteine sulfoxide and S-allyl-L-cysteine sulfoxide, respectively (Figure 18.5). As sulfenic acids are quite reactive, methyl sulfenic acid and allyl sulfenic acid will quickly form the metiiyl 2-propenethiosulfinate and allyl methaneth-iosulfinate. With the similar reaction to that from diallyl thiosulfinate, these thiosulfinates produce allyl methyl disulfide and allyl methyl trisulfide. 

Contains 0.1-0.36% (usually ca. 0.2%) volatile oil, alliin (5-allyl-L-cysteine sulfoxide), 5-methyl-L-cysteine sulfoxide, enzymes (e.g., alliinase, peroxidase, and myrosinase), ajoenes ( ,Z-ajoene, ,Z-methylajoene, and dimethylajoene), protein (16.8%, dry weight basis), minerals, vitamins (thiamine, riboflavin, niacin, etc.), lipids, amino acids, and others (jiangsu karrer list and horhammer marsh martindale). ... 

Methyl L-cysteine sulfoxide 5 Chem. Ind. (London) I9S6,1428 Acta Oystallogr. 1962,15. 635... 

Condensation of (R)-cysteine methyl ester (85) with monochloroacetone followed by reduction with sodium borohydride yielded (3R,5S)-5-methyl-l,4-thiazane-3-carboxylate (86a) and its (5R)-methyl isomer (86b) in a ratio of 3.1 1 106). The use of (R)-cysteine isopropyl ester instead of the methyl ester (85) gave the corresponding (5S)-methyl isomer (86a) more stereoselectively. 

Urinary metabolites are S-methylthioacetic acid sulfoxide, V-acetyl-.S -methyl-L-cysteine and /-(methylthioacetyl)glycine, which are metabolites of Y-methyl-i-cysteine and 5-methylglutathione. These last two compounds were found after incubation of methyl chloride with rodent liver, kidney and brain homogenates. The methyl group of methyl chloride is metabolized via -methyl-L-cysteine to formate which is found in urine and blood of rats, whereas formaldehyde is found in rat liver microsomes and blood of mice and rabbits (lARC, 1986). 

Chen and Hong [126] found that 5-carboxy methyl-L-cysteine was especially effective for the chelating extraction of lead from contaminated soils. The chelator could be recovered and reused over consecutive runs with no loss in performance. 

C4H10CfNO2S methyl L-cysteine hydrochloride 18598-63-5 25.00 1.2321 2 4080 C4H12N20 N-aminoethyl ethanolamine 111-41-1 0.00 1.2186 2... 

Djenkolic acid (S,S -methyIene-bis-L-cysteine) [498-59-9] M 254.3, m 300-350 (dec), [a]g -65 (c 2, HCl) [See pK of S-methyl-L-cysteine]. Crystallise djenkolic acid from a large volume of water (solubility is 0.5g%). [du Vigneaud Patterson J Biol Chem 114 533 1936, Greenstein Winitz The Chemistry of the Amino Acids J. Wiley, Vol 3 pp 2682, 2687 1961, Beilstein 4 III 1591.] The NJ9 -dibenzoyl derivative crystallises with IH2O from aqueous EtOH with m 87.5-89° [Beilstein 9 III 1171.]... 

Hbsms = 4-mercapto-3,3-methyl-l-= cysteine thiolate psnet = bis(5-... 

Methylcysteine sulfoxide accumulates in certain plants of the Cruciferae and Liliaceae (Thompson, 1967), but could not be detected in several legumes or plants of six other families examined (Fujiwaraet ai, 1958). The compound has been isolated exclusively as (-t-XS-methyl-L-cysteine sulfoxide, suggesting that it is not formed as an artifact by chemical oxidation of 5-methylcysteine. 

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