Cysteine protection

The related 5-benzyloxymethyl monothioacetal (BOM) has been used for cysteine protection. ... 

Two approaches for solid-phase chemical ligation have been described. Canne et al. have developed an elegant system that utilizes an oxime forming ligation to attach the first peptide to the resin, a selectively cleavable ester link to remove the peptide from the resin as a C-terminal carboxylic acid, and the Acm group to protect the N-terminal cysteine residue)311 A complementary approach has been developed by Brik et al. that utilizes native chemical ligation to attach the first peptide to the solid support, a safety-catch acid labile linker to remove the final polypeptide from the support as a C-terminal amide and either Acm or Msc group for N-terminal cysteine protection)32 ... 

Sprince H, Parker CM, Smith GG. 1978. Ascorbic-acid and cystein protection against aldehyde toxicants of cigaret smoke. Fed Proc 37 247. 

Fig. 33 Optical activity of a chiral ligand-protected gold nanocluster [Au25(SRcys)18]. (a) Optimized geometry, (b) Calculated CD spectrum of the cysteine-protected cluster black), and experimental spectrum for a glutathione-protected cluster (red). Reprinted with permission from [299]. Copyright 2010 American Chemical Society...

Fig. 18 VA top) and VCD bottom) spectra of N-isobutyryl-cysteine protected AuNPs in NaOH/D20. Solutions were made from 7 mg of sample in 50 pL of solution. The dashed (solid) lines correspond to the spectra of the particles covered by the L-enantiomer (D-enantiomer). The VA spectrum of the particles covered with N-isobutyryl-L-cysteine was offset for clarity. Adapted with permission from [155], Copyright (2006) American Chemical Society...

Gautier C, Biirgi T (2005) Vibrational circular dichroism of N-acetyl-L-cysteine protected gold nanoparticles. Chem Commun 5393-5395... 

Gautier C, Biirgi T (2006) Chiral N-isobutyryl-cysteine protected gold nanoparticles preparation, size selection, and optical activity in the UV-vis and infrared. J Am Chem Soc 128 11079-11087... 

Satpute, R.M., Hariharakrishnan, J., Bhattacharya, R. (2008). Alpha-ketoglutarate and V-acetyl cysteine protect PCI 2 cells from cyanide-induced cytotoxicity and altered energy metabolism. Neurotoxicology 29 170-8. 

Historically, the first important cysteine protecting group was the 5-benzyl group, developed by du Vigneaud etal. and used in the classical synthesis of oxytocin,t as well as in the syntheses of a number of cysteine-containing peptides in the first years of solid-phase synthetic methodology.P l This 5-Bzl protection is nowadays used infrequently due to the fact that its removal involves harsh conditions, e.g. sodium in liquid ammoniat or anhydrous hydrogen fluoride at 20°C,t conditions which may lead to side reactions such as elimination... 

For a review on cysteine protection, see F. Cavelier, J. Daunis, R. Jacquier, Bull. Soc. Chim. Fr., 210 (1990) see also reference 22 (peptides) in Chapter 1. L. Moroder, H.-J. Musiol, N. Schaschke, L. Chen, B. Hargittai, and G. Barany, Protection of Functional Groups (Cysteine), in Synthe. h of Peptides and Peptidomemetics M. Goodman, Ed., Houhen-Weyl, 4th ed., Vol. E22a Thieme, Stuttgart, 2002, pp 384-423. 

Cysteine protection. For masking the thiol group of cysteine, the reagent is applied in trifluoroacetic acid/dichloromethane. Deprotection is achieved by palladium-catalyzed reductive deallylation. 

Deblocking cysteine protecting groups. The common S-protecting groups can be cleaved by reaction with 2-nitrophenylsulfenyl chloride in acetic acid followed by reduction of the S-(2-nitrophenylsulfenyl)cysteine residues (equation I). 

Table 1. Cysteine protecting groups compatible with Fmoc/lBu solid-phase peptide synthesis ... 

Mixed disulphides are usuaUy precluded as cysteine protecting groups in the Fmoc/rBu strategy, because such functions are relatively unstable on exposure to piperidine. However, the 5-fcrf-butylmercapto (S -SrBu) group (42) is sufficiently hindered to be compatible its removal is achieved by treatment with either p-mercaptoethanol, dithiothreitol (DTT), tri- -butylphosphine (BU3P), or other reducing agents (5,6). 

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