L-cysteine derivatives

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

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

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>. 

Schlaad et al. [34] produced a biohybrid polymeric amphiphile by free-radical addition of an L-cysteine derivative onto a 1,2-PB with 40 repeat units (Fig. 7a). The zwitterionic polymer could be dispersed into very acidic (pH < 2.3) or basic (pH > 9) aqueous solutions under the formation of vesicles. As shown by DLS and SAXS in solution, the vesicles were about 250 nm in diameter and had a multilamel-lar structure with a lamellar spacing of about 7 nm. 

The first example of a plant steroid conjugated with an amino-acid (see Table of New Compounds) has been reported and glutathione and L-cysteine derivatives of 2-hydroxy-oestradiol have been described. ... 

Controlled acid-catalyzed degradation of the proanthocyanidins in grape seeds with L-cysteine as the capture nucleophile, gave a series of mono-, di-, and tri-meric-L-cysteine complexes. The flavan-3-ol adducts included the L-cysteine derivatives (173), (174), and (175) of epicatechin (3), catechin (2), and epigallocatechin, respectively. The dimers comprise the derivatives of procyanidin B-2 (176) and its C-ring... 

Fluoro-3-nitropyridine also reacts with the thiol function. Cysteinyl peptides react quantitatively with this reagent in a few minutes, whereas the reaction with amino groups is much slower. S-3-Nitropyridyl-L-cysteine derivatives show an absorption maximum at about 365 nm. In the CD spectra, a positive Cotton effect is centered at about the same wavelength. When thiol and amino moieties are in suitable relative positions (free L-cysteine), they react as a common functional group, but the Cotton effects are separated sufficiently (at 365 and 425 nm, respectively) and are both diagnostic of the configuration of cysteine residues. 

Several L-cysteine derivatives carry alkyl or related substituents at the S-atom. They occur at the oxidation level of sulfides or of sulfoxides (alliins. Table 46). The substances are aliphatic or have a cyclic structure, like cycloalliin. Several products are dimeres, cf. the formula of djenkolic acid. 

Table 46. Some naturally occurring S-substituted L-cysteine derivatives and sulfoxides...

L-Cysteine derivatives Taurine, hypo taurine (D 11.1) Urine... 

L"Cysteine derivatives Coenzyme A (D 11) Cosubstrate of carboxylic acid activating enzymes pantothenic acid, a constituent of coenzyme A, is a vitamin for animals... 

L-Cysteine derivatives Ii-Arginine derivatives Isoquinoline alkaloids... 

L-Cysteine derivatives cis-Propanethial S-oxide (D 11.2) Smell of onion... 

Starkenmann C., Niclass Y., Troccaz M. Nonvolatile S-alk(en)ylthio-L-cysteine derivatives in fresh onion (Allium cepa L. cultivzi). Journal of the Agricultural and Food Chemistry, 59 9457-9465 (2011). 

Yamazaki Y., Iwasaki K., Yagihashi A. Distribution of eleven flavour precursors, S-alk(en)yl-L-cysteine derivatives, in seven Allium vegetables. Food Science and Technology Research, 17 55-62 (2011). 

Kamber [92] reports that in contrast to S-benzhydryl phenyl thioether [79], S-benzhydryl-L-cysteine derivatives are oxidatively cleaved to the extent of about 20% by iodine in methanol. It is likely, however, that the S-trityl group can be removed with iodine without disturbing S-benzhydryl groups in... 

A potential problem in the coupling of S-acyl or S-alkoxy-carbonyl-L-cysteine derivatives to other -blocked amino acids is S - iV-acyl migration which results from the presence of the free amino group on the S-acyl cysteine residue. The mechanism for S - -N-dicy m ation has been disj ussed by Barnett and Jenks [145]. Patchornik et al. [8] noted that S- iV-acyl miration occurred when the free base of (60) was prepared and the low yields of S-benzoyl-L-cysteine peptides such as (61) were traced to the formation of (62), produced by S- -N-benzoyl migration during the coupling step [89, 146]. Similar difficulties have been noted in solid-phase synthesis [120]. Problems of this type may have also been encountered in the... 

Hartung, J., Kneuer, R., and Spehar, K., Photoreactions of N-alkoxy-4-(p-chlorophenyl)thiazole-2(3H)-thiones with L-cysteine derivatives in aqueous solutions, /. Chem. Soc., Chem. Commun., 799, 2001. 

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