S-Benzyl-L-cysteine

A variant of this procedure is provided by the preparation of S-benzyl-l-cysteine (Expt 5.206). The required thiolate salt is prepared by the reductive cleavage with sodium in liquid ammonia of the disulphide linkage in the amino acid, (S)-cystine, and is alkylated in situ with benzyl chloride. The preparation of this S-benzyl derivative constitutes a method of protection of the thiol grouping in cysteine. 

The a-proton of the external aldimine is then abstracted by a basic residue Bi and the quinonoid intermediate is formed (Fig. 9.13, III). The rate constants of formation of the quinonoid intermediate from L-tryptophan and S-benzyl-L-cysteine are estimated be 940 and 47.6 sec-1, respectively this demonstrates a drastic effect of the leaving group on labilization of the a-proton.78 ... 

Experiment 5.206 S-BENZYL-l-CYSTEINE [L-2-Amino-3-(benzylthio)-propanoic acid]... 

C12H15N03S N-acetyl-S-benzyl-L-cysteine 19542-77-9 25.00 i.2094 2 24300 C12H17NO 1 -benzy -4-hydroxypiperidine 4727-72-4 23 1 0422 31... 

C13H14CI203 ciprofibrate 52214-84-3 25.00 1.2743 2 26136 C13H17N03S N-acetyl-S-benzyl-L-cysteine methyl ester 77549-14-5 25.00 1.1837 2... 

Cl 5H1608 7-(beta-D-glucopyranosyloxy)-2H-1-benzopyran 93-39-0 25.00 1.3267 2 28630 C15H21N04S boc-S-benzyl-L-cysteine 5068-28-0 25.00 1.1782 2... 

Ripp SE, Overby EIT, Phllpot RM, Elfarra AA. Oxidation of cysteine S-conjugates by rabbit liver microsomes and cDNA-expressed flavin-containing mono-oxygenases studies with S-(l,2-dichlorovinyl)-E-cysteine, S-(l,2,2 trichlorovinyl)-Ecysteine, S-allyl-E-cysteine, and S-benzyl-L-cysteine. Mol Pharmacol 1997 51 507-515. 

C20H211N2O3S2, S-Benzyl-L-cysteinyl-S benzyl-L-cysteine, 41B, 555 C20H28N2O5, t-Butoxycarbonyl-L-prolylsarcosine benzyl ester, 46B,... 

Cystine peptides. Glycyl-S-benzyl-L-cysteine in refluxing liq. NHg treated with Na until the blue color persists for ca. 2 min., NHg removed in vacuo, the crude product dissolved in boiled, Ng-satd. water, filtered, a soln. of 1,2-diiodoethane in acetone added, shaken 5 min., extracted with ether, and the aq. layer neutralized with trifluoroacetic acid bis-glycyl-L-cyslin. Y 81%. F. e. and 1,2-dihalides as reagents s. F. Weygand and G. Zumach, Z. Naturf. 17b, 807 (1962). 

Tissue extracts which exhibit little acetylation in contrast to slices actively deacetylate mercapturic acids (Bray and James, 19f30). Kidney extracts are more active than liver. The deacetylase content of extracts of rat, rabbit, and guinea pig liver were roughly equivalent but varied with the type of substituent on the sulfur. For example, the rabbit dc-acetylase activity toward jV-acetyl-S-benzyl-L-cysteine was low, w hereas toward iV-acetyI- S-butylcysteine it w as high. Bray and James concluded that there is little to support the view that tiie failure of the guinea pig to excrete significant amounts of mercapturic acids is due to the deacetylase activity of its tissues. Probably the failure is in part in the acetylation process and in part due to convemion of the S-substituted cysteines into other metabolism products. 

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