S- L-cysteine

Figure 7.2. The variation of peak currents with scan number for the electrocatalytic oxidation of cysteine on a GCE modified with [(CN)2RhPc] . Scan rate = lOOmV s L Cysteine concentration = 0.03 mol dm. (Reproduced with permission from Ref. [13] Figure 7.2).

The rate of uptake of labelled cysteine into proteins has been extensively used as an indicator of the metabolic activity of tissues. S-L-cysteine administered to mice was found to be preferentially incorporated into growing hair follicles and claws. In other forms of epithelia the rate of... 

Many hormones are rich in cysteine and the tissues in which they accumulate can be easily recognized by a marked uptake of S-L-cysteine. For instance, mature virgin mice, mature mice of both sexes and castrated males display a S-labelled juxtamedullary X-zone in the brain, whereas normal adult male mice do not . The neurosecretory system of the earthworm markedly accumulates cysteine- S The neurosecretory cells of rapidly developing female locusts and females in the second gonotropic cycle take up cysteine- S at a greater rate than either newly emer d or slowly developing females . 

Woodward s total synthesis of cephalosporin C begins with L-cysteine (48) which establishes the chiral center at C-7. The cis geometry at C-6,7 is achieved in intermediate (49) which is cyclized to (50) by treatment with triethylaluminum. The dihydrothiazine ring is constructed by Michael addition to the condensation product of trichloroethyl glyoxylate... 

Cystamine dihydrochloride, S,5-(L,L)-Cystathionine, Cysteamine, Cysteamine hydrochloride, ( )-Cysteic acid, S-Cysteic acid (H2O), L-Cysteine hydrochloride (H2O), ( )-Cysteine hydrochloride and L-Cystine, Cytidine, see entries in Chapter 6. 

Therapeutic Function Mucolytic expectorant nasal antiinfective Chemical Name S-(carboxymethyl)-L-cysteine Common Name —... 

Thereby the S-carboxymethyl-L-cysteine precipitates out in crystalline form. The product is filtered off with suction, well stirred in 500 ml of water, again filtered with suction and dried in a vacuum at 70°C. The yield is 92% based on L-cysteine. 

S,N-Ditrityl-L-cysteine diethylamine selt L-Tyrosine lower alkyl ester L-lsoleucine lower alkyl ester Benzyl-L-proline hydrochloride L-Leucine lower alkyl ester Ammonia Hydrogen chloride Glycine lower alkyl ester... 

S,N-Ditrityl-L-cysteine diethylamine salt Oxytocin Dodecyl bromide... 

Nishimura and coworkers57-59 studied the y-radiolysis of aqueous solutions of sulfoxide amino acids. Sulfoxide amino acids are the precursors of the flavors of onions (S-propyl-L-cysteine sulfoxide, S-methyl-L-cysteine sulfoxide and S-(l-propenyl)-L-cysteine sulfoxide) and garlic (S-allyl-L-cysteine sulfoxide). In studies on sprout inhibition of onion by /-irradiation it was found that the characteristic flavor of onions became milder. In the y-radiolysis of an aqueous solution of S-propyl-L-cysteine sulfoxide (PCSO)57,58 they identified as the main products alanine, cysteic acid, dipropyl disulfide and dipropyl sulfide. In the radiolysis of S-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 N20 and Br- as eaq - and OH radicals scavengers, respectively. 

In the case of ACSO it was found also that N20 addition reduces the yield of S-allyl-L-cysteine (ACS), indicating that this product is formed by eaq - but not by OH radicals. As a result it can be expected that KBr addition will not reduce the ACS yield. It was found that KBr not only does not reduce the yield of ACS, but it rather increases i ts formation. This is explained as due to ACS formation by reaction of eaq" with ACSO, and its disappearance by reaction with OH radicals to give back ACSO as it is known for the reaction with sulfides. The authors suggest the same reactions for PCSO and PCS (propyl-L-cysteine) although the yield of PCS was not determined. 

The observation that in the case of PCSO there is no formation of propanol while allyl alcohol is formed from ACSO agrees with the resonance stabilization of the allyl radical60 and hence weaker bond for S-allyl than for S-propyl. The yield of allyl alcohol from irradiation of ACSO is considerably greater than that from S-allyl-L-cysteine, probably due to energy delocalization by the four p electrons of the S atom. 

In contrast with irradiation of ACSO and PCSO, where volatile products were formed (sulfides, disulfides and alcohols), no volatile products were formed in the radiolysis of aqueous solutions of S-(cis- l-propenyl)-L-cysteine. Here the authors found that reactions of OH" radicals are responsible for the formation of propyl-1-propenyl sulfides (cis and trans). 

In aqueous solutions at pH 7, there is little evidence of complex formation between [MesSnflV)] and Gly. Potentiometric determination of the formation constants for L-Cys, DL-Ala, and L-His with the same cation indicates that L-Cys binds more strongly than other two amino acids (pKi ca. 10,6, or 5, respectively). Equilibrium and spectroscopic studies on L-Cys and its derivatives (S-methyl-cystein (S-Me-Cys), N-Ac-Cys) and the [Et2Sn(IV)] system showed that these ligands coordinate the metal ion via carboxylic O and the thiolic 5 donor atoms in acidic media. In the case of S-Me-Cys, the formation of a protonated complex MLH was also detected, due to the stabilizing effect of additional thioether coordination. ... 

S-[2-nitro-l-(2-thienyl)ethyl]-N-tert-butoxycorbonyl-L-cysteine (VII)... 

S-ACETAMIDOMETHYL-L-CYSTEINE HYDR0C HL0RIDE,59, 190 N-( 2-Acetamido-3-phenylpropionyl)-pyrrolidine, 59, 52 Acetanilide, 59, 52... 

Benzyloxycarbonyl-O-rerf-butyl-L-seryl-S-rcri-butyl-L-cysteine rerf-butyl ester, 59, 161... 

REMOVAL OF N -BENZYLOXYCARBONYL GROUPS FROM SULFUR-CONTAINING PEPTIDES BY CATALYTIC HYDROGENATION IN LIQUID AMMONIA O-tcrf-BUTYL-L-SERYL-S-tert-BUTYL-L-CYSTEINE ferr-BUTYL ESTER... 

Triethylamine (8) Ethanamine, N,N-diethyl- (9) (121-44-8) N-Benzyloxycarbonyl-O-te/t-butyl-L-seryl-S-Iert-butyl-L-cysteine fm-butyl ester ( —)... 

Isobutyl chloroformate Formic acid, chloro-, isobutyl ester (8) Carbonochloridic acid, isobutyl ester (9) (543-27-1) S-tcrf-Butyl-L-cysteine ferf-butyl ester L-Cysteine, S-(l,l-dim-ethylethyl), 1,1-dimethylethyl ester (9) ( —) acetate (38024-19-0) hydrochloride (2481-11-0)... 

O-tert-Butyl-L-seryl-S-tert-butyl-L-cysteine terf-butyl ester (—)... 

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