Cysteine derivatives

L-cysteine (derivatives) /5-chloro-DL-alanine + Na2S Cys desulfhydrase Enterobactor cloacae 193... 

D-cysteine (derivatives) 3-chloro-DL-alanine + iNaHS 3-chloro-D-Ala dehydrochlorinase or Pseudomonas putidaE. coli etc ... 

These sulfides are prepared from other sulfur-protected cysteine derivatives by reaction with the sulfenyl chloride, The Npys group can also be introduced directly by treatment of the thiol with NpysCl, ... 

The related serine derived (4S)-4-methoxycarbonyl-3-(l-oxopropyl)-2-thiono-l,3-oxazolidine 11, and the cysteine derived (4A)-4-methoxycarbonyl-3-(l-oxobntyl)-2-thiono-1,3-thiazolidine 13, also serve as efficient chiral auxiliaries in boron- and tin(II)-mediated aldol condensations98. Thus, conversion of 11 into the boron or tin enolate, followed by reaction with 2-methylpropanal affords predominantly one adduct. Subsequent methanolysis and chromatographic purification delivers the syu-methyl ester in 98% ee. 

Figure 28-9. Conversion of homocysteine and serine to homoserine and cysteine. The sulfur of cysteine derives from methionine and the carbon skeleton from serine.

Isab, A.A. and Sadler, P.J. (1982) A carbon-13 nuclear magnetic resonance study of thiol exchange reactions of gold(l) thiomalate ( Myocrisin ) including applications to cysteine derivatives. Journal of the Chemical Society, Dalton Transactions, (1), 135—141. 

Scott Oakes et al. (1999a, b) have shown how adoption of SC conditions can lead to a dramatic pressure-dependent enhancement of diastereoselectivity. In the case of sulphoxidation of cysteine derivatives with rert-butyl hydroperoxide, with cationic ion-exchange resin Amberlyst-15 as a catalyst, 95% de was realized at 40 °C and with SC CO2. By contrast, with conventional solvents no distereoselectivity was observed. Another example is the Diels-Alder reaction of acrylates with cyclopentadiene in SC CO2 at 50 °C, with scandium tris (trifluoromethanesulphonate) as a Lewis acid catalyst. The endoiexo ratio of the product was as high as 24 1, while in a solvent like toluene it was only 10 1. 

Scheme 3.6 L-Cysteine-derived thiazolidine ligands for additions of ZnEt2 to aldehydes.

Scheme 3.27 D-Cysteine-derived C2-symmetric bis-P-amino alcohol ligands for addition of ZnEt2 to benzaldehyde.

In addition, Rowlands has involved chiral sulfoxide-containing ligands for the catalytic addition of McsSiCN to aldehydes. " The ligand structure was based on a phenolic oxazoline scaffold with introduction of the sulfur substituent via cysteine derivatives. The best enantioselectivities of up to 61% ee were obtained with the bulkiest tert-butyl substituted ligand (Scheme 10.42). The effect of the sulfoxide configuration was studied, showing that the use of... 

Scheme 10.61 Borane reduction of acetophenone with D-cysteine-derived bis-P-amino alcohol ligands.

Hydrogen sulfide formation has been demonstrated in pediatric intravenous amino acid solutions used to treat infants with high protein requirements (Decsi and Koletzko 1993). Levels up to 1.96 ppm were found, presumably formed by sulfide liberation from cysteine derivatives during heat sterilization. 

Photocyclization (A = 300nm) of an imidic cysteine derivative 216 results in the formation of regioisomers 217 and 218 in an 81 19 ratio (Equation 25) <2000JOC7151>. 

A range of L-cysteine derivatives bearing a 1,2,4-triazolyl residue on the sulfur atom has been prepared by the asymmetric Michael addition of 4,5-dialkyl-3-mercapto-l,2,4-triazoles to a nickel Schiff base complex. The enantiomeric excesses of the product aminoacids were measured and found to be greater than 98.5% in some cases <2004TA705, 2004RCB932, 2004IZV894>. 

Plants of the genus Allium, e.g. garlic Allium sativum), leek Allium amp-eloprasum), and onion Allium cepa), produce a bewildering variety of sulfur compounds. Selenium analogs for some of these have also been found (Section 11.1.3.6). Much work has focused on garlic (contains more than 100 such materials) and onion.56,66,67 Key compounds for formation of the Allium sulfur-containing secondary metabolites are sulfoxides of cysteine derivatives,... 

Mycothiol 43 (Scheme 14) is a complex cysteine derivative isolated from Streptomyces clavuligerus, Mycobacterium bovis, and other mycobacteria. It... 

Cysteine derivatives cysteine base, salts, carbocysteine, acetylcysteine ... 

Isochem has set up a multipurpose electrochemical unit devoted to organic electrosynthesis. The unit located in Pithiviers (France) [115] is dimensioned for the production of 80 tons a year of cystein derivatives, such as cysteine base salts, carbocysteine, acetylcysteine, and thiazolidin carboxylic acids. 

A series of unusual cysteine derivatives were easily resolved on a teicoplanin CSP under RP conditions (Figure 2.20). As it can be observed, the TE CSP shows a good chemo- and enantioselectivity toward a mixture of chemically different pairs. 

Djenkolic acid - cysteine-derived amino 121 acid with nephrotoxicity... 

Exploring a further feature of organotellurium compounds, the bioactivation of an organotellurium cysteine derivative has been evaluated. The results demonstrated that it is bioactivated into its corresponding tellurol. 

Much of the data related to the mechanism of hexachlorobutadiene toxicity indicate that the intermediates produced by modification of the S-1,1,2,3,4-pentachlorodienyl cysteine derivative are responsible for the observed effects on the proximal tubules of the nephrons. The cysteine derivative is formed from the hexachlorobutadiene conjugate in the liver, intestines, and/or kidney through the action of yglutamyl transferase which removes the glutamate from the glutathione tripeptide followed by the action of a peptidase that removes the glycine from the carboxy terminus. 

One or two hexachlorobutadiene metabolites appear to cause some of the compound-induced renal damage (see Section 2.3.5) and are more toxic than the parent compound, causing comparable lesions in the kidneys at lower doses. These active thioacylating metabolites are capable of modifying DNA, as indicated by the isolation of sulfur-containing nucleides from hydrolyzed DNA from renal cells exposed to the hexachlorobutadiene cysteine derivative (Vamvakas et al. 1988b). 

Structures of this type were generated in the reaction of Af-acyloxy-Af-alkoxyamides with thiols. Treatment of Ai-acetoxy-iV-butoxybenzamide (145, R = Bu, = Me) and a series of Ai-benzoyloxy-Ai-benzyloxybenzamides (139) with cysteine derivatives generated disulfides and hydroxamic esters (Section IV.C.3.b, Scheme 24). The intermediate Ai-alkoxy-Ai-thioalkylamides were unstable under the reaction conditions, reacting with a second thiol molecule at sulfur. The reaction of thiols at the anomeric nitrogen of Af-acyloxy-Ai-alkoxyamides has been modelled theoretically and is predicted to be favourable energetically, leading to a stable substitution product ... 

The only available evidence to support this is the fate of intermediates generated from the reaction of A-acyloxy-A-alkoxyamides with cysteine derivatives in methanol described in Section IV.C.3.b. The nucleophilic thiol reacts preferentially at the sulfur atom rather than at nitrogen, generating the hydroxamic ester and the disulfide (Scheme 24). 

Pentachlorothiophenol was formed Iji vitro from S-(PCP)Cys by a C-S lyase enzyme from onion root. This enzyme was active with S-(PCP)Cys, S-(2,M-dinitrophenyl)cysteine, and the cysteine conjugate of propachlor. A C-S lyase from Alblzzla lophanta was previously shown to utilize a broad range of cysteine derivatives (2U). 

Nucleophilic attack at the 5-position of an oxazoline normally proceeds under acidic conditions. For example, in their total synthesis of thiangazole, Wipf and coworkers used thiolacetic acid to convert the trisoxazoline 337 to the S-protected cysteine derivative 338 that was further elaborated to thiangazole through aminol-... 

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