Thiols, Disulfides and Related Compounds

Table 5.1 Approaches to the assay of thiols, disulfides and related compounds...

Disulfides were shown to be intermediates in the iodine oxidation of 1,3-butadiene-l-thiols and related compounds to form thiophenes (56JOC39). Several simple disulfides were converted to thiophene derivatives under these same conditions (64JOC2372). For example, bis(2-biphenyl) disulfide (13) produced dibenzothiophene (14) in 64% yield when heated with iodine in ethylene glycol for one hour. Treatment of (13) in benzene with aluminum bromide gave (14) in 76% theoretical yield, with an equivalent amount of the thiol, 2-biphenylthiol (62JOC4111). Thus the iodine reagent is more efficient, since it oxidizes the mercaptan, formed by the Friedel-Crafts reaction of disulfide on the adjacent aromatic ring, to disulfide for further reaction, and also serves as a catalyst for the initial reaction. 

In summary, nutritional improvement may result from inactivation of trypsin inhibitors and introduction of new disulfide bonds via sulfhydryl-disulfide interchange and oxidation reaction among added thiols, inhibitors, and structural proteins. Such an approach should be useful for inactivating related disulfide-containing toxic compounds such as lectins (hemagglutinins) and ricin, widely distributed in legumes and castor beans, respectively. 

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