Disulfide Formation Strategies in Peptide Synthesis

Abstract

Disulfide bonds play an important role in both proteins and peptides. They cause conformational constraints and increase the stability of such molecules. In nature, disulfide bonds are very common in animal and plant peptide toxins. These disulfide‐rich peptides typically bind very selectively with high affinities to their targets. Disulfide‐rich peptides are of great importance as potential therapeutics. Robust, convenient, and efficient methods are needed in order to prepare disulfide‐rich peptides to facilitate the drug discovery process. This microreview explores new cysteine protecting groups that replace obsolete protecting groups, reduce racemization, or facilitate regioselective disulfide formation, new disulfide formation strategies to assist in the synthesis of complex disulfide‐rich peptides, and the use of selenocysteine to direct disulfide formation.

Characterization of low‐abundance species in the active pharmaceutical ingredient of CIGB‐300: A clinical‐grade anticancer synthetic peptide

“…The ESI‐MS of this fraction was identical to that observed for CIGB‐300, and no other modified species was found (data not shown). As yet, we have not determined the chemical nature of this isomer, but it has been reported that peptides containing cysteine are racemized during coupling by base‐catalysis . We therefore concluded that isomeric species of CIGB‐300 may be eluting in this fraction.…”

Trends to Acid-Labile Cys Protecting Groups: Thp as an Efficient and Non-Aromatic Cys Protecting Group for Fmoc Chemistry

“…In nature, cysteine (Cys) is crucial due to its capacity to confer stability to peptides and proteins, but also constrain the specific conformation of these biomolecules through disulfide bonds [2,3]. In addition, its use has modernized the chemical synthesis of large polypeptides and proteins by Native Chemical Ligation [4].…”

Direct palladium-mediated on-resin disulfide formation from Allocam protected peptides

“…11 Much effort has been devoted to the development of new cysteine protecting groups with the goal of improving the available toolbox for folding disulfide-rich polypeptides. 12 Although some of these groups can be removed while the peptide is on resin and in the presence of related protecting groups, several have practical limitations preventing their widespread use. For example, known photolabile groups are incompatible with piperidine, 13a and reductive removal of protecting groups can interfere with existing disulfide linkages, and sometimes cannot be removed at all.…”

“…A traditional approach to access disulfides on solid support ( 5 ) involves treatment with excess iodine, usually for peptides bearing trityl (Trt), acetamidomethyl (Acm), or 4-methoxytrityl (Mmt) protected cysteines ( 4a ). 15,12a This is a convenient method that cannot always be employed because of issues with oxidation of sensitive amino acids (Met/Trp) or undesired cleavage from the popular TGT and CTC resins. 16 On-resin oxidation of free thiols can be conducted using N -chlorosuccinimide 17 or acidic DMSO ( 4b , HX= HCl or HOAc).…”

“…16 On-resin oxidation of free thiols can be conducted using N -chlorosuccinimide 17 or acidic DMSO ( 4b , HX= HCl or HOAc). 12b A variety of protecting groups ( 4c ) can be cleaved by Tl(tfa) 3 to directly yield the disulfide containing product. This approach is not orthogonal to other cysteine protecting groups or acid-labile side chain protecting groups, and it will also induce cleavage from TGT and CTC resins.…”