Cysteine sodium tetrathionate

The thiosulfonate derivative was prepared from cysteine to protect the thiol during the native chemical ligation method for peptide synthesis. It is prepared from sodium tetrathionate in DMSO with DIPEA. It can be removed with dithiothreitol. ... 

Perhaps the most widely utilized su henyl derivatives are the S-sulphonates [160] which can be prepared by oxidative sulphitolysis of a disulphide bond with sodium sulphite and sodium tetrathionate at pH 7-9 [161], by the oxidation of disulphides or thiols with sulphite ion and copper(ll) [160], by the use of small amounts of cysteine together with oxygen and sulphite [162], or by the reaction of halides with sodium... 

---