Disulfide bond, selective cleavage

The simplest approach is offered by parallel homodimers which require only two orthogonal protecting groups. After deprotection of one thiol group mild oxidation by one of the methods discussed in Section 6.1.1.1 or following direct selective oxidative cleavage of one S-protected cysteine residue by the methods described in Section 6.1.1.2, the second disulfide bond has to be produced by selective procedures compatible with the presence of a disulfide as described in Section 6.1.2. 

The thiols, mercaptoethanol and diethiothreitol, have been used extensively for the reductive cleavage of disulfide bonds and for the maintenance of a reductive environment in the isolation and characterization of specific soybean proteins (2). However, these reagents have not been used for the preparation of protein products for food. The odor and flavor of the low-molecular-weight thiol compounds are not compatible with usage in a broad range of food items, yet these substances contribute to the desirable odor and flavor of selected foods. 

A series of trisubstituted alkenes containing (Z)-allylthio moieties as the key structural units, that is, sodium (Z)-allyl thiosulfates 338, symmetrical di[(Z)-allyl] sulfides 343 and di[(Z)-allyl] disulfides 339 and unsymmetrical diallyl sulfides 341 have been prepared in moderate to good yields via chemical transformations from the acetates of MBH adducts. In addition, it was found that the Sm and a trace amount of I2 could be used for the selective cleavage of the S-S or C-S bonds in sodium (Z)-allyl thiosulfates 338, depending on the substituents (alkyl or aryl group), to give the corresponding... 

Moreover, novel redox-responsive polycationic hydrogels of AAf-diethylacrylamide (DEAAm) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) were successfully synthesized by cross-linking reactions via quaternary ammonium compounds with a disulfide. The ability of the polymer netwoik to enclose and release substances by reductive cleavage or oxidative formation of disulfide bonds was shown exemplarily using different dyes. The redox-responsive character was proven by oscillatory rheological measurements and different material properties of polycationic polymer discs were also investigated. Because of its polycationic structure, this polymeric system could be a promising compound for complexation of DNA-like substances. Its ability for selective release in reductive environments, like tumor tissues, could possibly be used in medical applications or in chemotherapy [162]. 

Thus, oxidation reactions are possible under very mild conditions and with high selectivities. Therefore, this method is especially useful for oxidative deprotections. For example, the oxidative cleavage of the carbon-sulfur bond is easily possible according to Eq. (103). In this way, disulfides and follow-up products of carbenium... 

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