Thiol-disulfide isomerization

Thiol-disulfide isomerization. Disulfide bond formation between Cys residues takes place commonly in the ER during protein biosynthesis. The thiol-disulfide isomerization can occur by either chemical exchange reaction or enzymatic reaction catalyzed by protein disulfide isomerase via mixed disulfide intermediate (protein-S-SG). 

Thiols under mild oxidative conditions are converted to disulfides, and heating (37) with or without an additional oxidizing agent in DMSO gives (38) in 82% yield (76JAP(K)08275). Similarly with iodine, 2,4-pyrimidinedithiol affords an isomeric mixture of sulfur-bridged pyrimidinophanes (39) and (40) (80KGS848). 

The direct sulfenylation of yv.A -dimethylhydrazones via the reaction of the a-lidiio derivative (14) with dimethyl disulfide (Scheme 13) has been reported, and the initially formed product (15) shown to isomerize to the more stable ( )-isomer (16). l ile further transformations have been carried out on compound (16), attempts do not appear to have been made to introduce unsaturation by the elimination of the thiol group. 

A mixture of thiophene and isomeric thienothiophenes (total yield of 85%) was prepared by the gas-phase reaction of dimethyl sulfide, diethyl disulfide, diethyl trisulfide and diethyl tetrasulfide with acetylene (89ZOR2588). It was also found that gaseous allyl 2-thienyl sulfide is transformed into a mixture of thiophene-2-thiol, bis(2-thienyl) sulfide and 2-methylthieno[2,3-i]thiophene at 350-410 °C in the presence of acetylene, the reaction gives these products along with thieno[2,3-i]thiophene (91KGS1312). Thermolysis (at 540 °C) of a mixture of di(prop-l-enyl) sulfide and 2-chloro(or bromo)thiophene affords a mixture of thieno[2,3-Z ]thiophene and thieno[3,2- )]thiophene (91ZOR354). 

Fig. 5.25 Biological NO, chemistry adapted and simplified from Fukuto et al. (2000). Dotted arrow multistep process, Me transition metal ion, RSFl organic sulfide (-SF1 thiol group), RSSH disulfide, ONOO is an isomeric form of the nitrate radical NO3, ONOO (ONOOH) peroxonitrous acid, HON=NOH (H2N2O2) hyponitrous acid, N2O2 (0=N—N—0 ) radical anion of NO dimer, N3O3 (0=N—N—O—NO ) trimer radical anion (not to confuse with Angeli salt N304 [O2N—N—N02] ).

The mechanism of action of cocarboxylase is still very obscure. The suggestion has been offered that the thiol and disulfide forms of thiamine might constitute an oxidation-reduction system. Subsequently, it has been shown in enzyme experiments with yeast that the isomeric thiazole pyrophosphate exhibited full cocarboxylase activity, whereas the disulfide... 

In studying both the electrophilic and nucleophilic nature of the sulfenic acid group, it was found that the sulfenic acid from 106 reacted with thiols (e.g., 2-methylpropane-1-thiol) to give a mixture of the disulfides 152 and 153 (Barton et al., 1970 1971a). The concomitant isomerization of the double bond appeared to be dependent upon both the side chain... 

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