Thiols protecting groups

To broaden the scope of this methodology, a study was conducted to elucidate the influence of the substituents (side chain, protecting group, thiol) on the a-proton acidity, also exploring the predictive power of computational chemistry for... 

The dibenzosuberyl ether is prepared from an alcohol and the suberyl chloride in the presence of triethylamine (CH2CI2, 20°, 3 h, 75% yield). It is cleaved by acidic hydrolysis (1 N HCl/dioxane, 20°, 6 h, 80% yield). This group has also been used to protect amines, thiols, and carboxylic acids. The alcohol derivative can be cleaved in the presence of a dibenzosuberylamine. ... 

Silyl-derived protective groups are also used to mask the thiol function. A complete compilation is not given here since silyl derivatives are described in the section on alcohol protection. The formation and cleavage of silyl thioethers proceed analogously to simple alcohols. The Si—S bond is weaker than the Si—O bond, and therefore sulfur derivatives are more susceptible to hydrolysis. For the most part silyl ethers are rarely used to protect the thiol function because of their instability. Silyl ethers have been used for in situ protection of the — SH group during amide formation. ... 

The base-catalyzed reaction of thiothreitol with methyl dithiobenzoate selectively protects a thiol group as an 5-thiobenzoyl derivative in the presence of a hydroxyl group.-... 

At pH 4-5, the reaction is selective for protection of thiol groups in the presence of oc- or e-amino groups. 

These sulfides are prepared from other sulfur protective groups by reaction with the sulfenyl chloride. The Npys group can also be introduced directly by treatment of the thiol with NpysCl. ... 

The dibenzosuberylamine is prepared in quantitative yield from an amine or amino acid and suberyl chloride this chloride has also been used to protect hydroxyl, thiol, and carboxyl groups. Although the dibenzosuberylamine is stable to 5 A HCl/dioxane (22°, 16 h) and to refluxing HBr (1 h), it is completely cleaved by some acids (HCOOH, CH2CI2, 22°, 2 h CE3COOH, CH2CI2, 22°,... 

Nakajima and Okawa prepared cysteine (250 Scheme 3.92) by treating aziridine 127a with dry H2S gas in the presence of a catalytic amount of BF3 Et20 [141]. The resulting thiol 248 was then oxidized with iodine to afford disulfide 249 in 70% overall yield. Removal of the Cbz protecting group afforded cysteine (250). 

Instead of the amide thiol ligands themselves, their S-protected precursors are sometimes used. If the protecting groups are not removed before or during complexation, thioether sulphur is present in the donor set. This confers different... 

SAMSA-fluorescein, 5- [2(and 3)-5-(acetylmercapto)-succinoyl]amino fluorescein, is a fluorescent probe containing a protected sulfhydryl group. In its protected state, the compound is unre-active. The acetyl-protecting group can be removed by treatment with dilute NaOH at pH 10.0 (Figure 9.9). The resulting free sulfhydryl derivative can be used to label thiol-reactive crosslinkers or to couple with sulfhydryl residues on proteins and other molecules. After activating... 

---