Carboxymethyl thioethers groups

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

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. 

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