Carboxymethyl thioethers

Carboxylic acids, protection of, 224-276 as amides and hydrazides, 270-276 as esters, 227-270 Reactivity Chart 6, 433-436 S-Carboxymethyl thioethers, to protect thiophenols, 294-295 Catechols, protection of, 170-174 as cyclic acetals and ketals, 170-172 as cyclic esters, 173-174 Reactivity Chart 4, 425-428 CBZ, see Benzyl carbamates Chloroacetamides, to protect amines, 352-353... 

Hydrogen peroxide/sulfuric acid Ar. halogenomereaptans Protection of sulfhydryl groups as carboxymethyl thioethers... 

Cl5H25C0N6O2S3, ((Benzyl 2-carboxymethyl thioether)-0,S)bis(ethyl-enediamine)cobalt(lII) thiocyanate, 44B, 812 Cl sHaoNijOi i,PtSb2, (R)-Propylenediamine-N,N -dimethylethylenediamine-platinum(II) di-ju-(+)-tartrato(4-)-bis(antimonate(III)) dihydrate, 42B, 732... 

The H- and N-isoforms of Ras support the first (isoprenoid) hydrophobic modification by additional thioester formation with palmitoylic acids [18]. At physiological temperature (37°C) the dissociation of doubly modified lipo-peptides with an isoprenyl thioether and a palmitoyl thioester is very slow and characterized by half-times in the order of 50 h. Here, the relative effect of the carboxymethylation is significantly reduced. Palmitoyl groups with their C16 alkane chain length contribute more efficiently to membrane anchoring than the farnesyl modification. 

Similar Sjj2 mechanism takes place when H atoms react with two other thioethers, each containing either carbonyl or carboxyl groups. The pulse radiolysis of acidic aqueous solutions of 2-(methylthio)-ethanoic acid and S-ethylthioacetone yielded carboxymethyl radicals, CHjCOOH, and acetylmethyl radicals, CH2-C(=0)-CH3, respectively. Support for this assignment was given by DFT calculations and radical scavenging experiments with trrt-butanol. DFT calculations indicated that the thermochemistry of the Sjj2 reactions should be feasible with AG between -29 and -33 kcal mol" in both cases. 

Zahn et al. [58, 59] have reported that thioglycolate can accelerate the rate of formation of thioether residues (lanthionyl) in wool fiber. Therefore, one might expect to find trace quantities of this amino acid in hair permanent-waved in an alkaline medium. Chao et al. [60] have demonstrated small quantities of lanthionine and carboxymethyl thiocysteine in hair reduced by thioglycolic acid. 

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