Synthesis of DNA‐Encoded Disulfide‐ and Thioether‐Cyclized Peptides

Abstract

DNA‐encoded chemical library technologies enable the screening of large combinatorial libraries of chemically and structurally diverse molecules, including short cyclic peptides. A challenge in the combinatorial synthesis of cyclic peptides is the final step, the cyclization of linear peptides that typically suffers from incomplete reactions and large variability between substrates. Several efficient peptide cyclization strategies rely on the modification of thiol groups, such as the formation of disulfide or thioether bonds between cysteines. In this work, we established a strategy and reaction conditions for the efficient chemical synthesis of cyclic peptide–DNA conjugates based on linking the side chains of cysteines. We tested two different thiol‐protecting groups and found that tert‐butylthio (S‐tBu) works best for incorporating a pair of cysteines, and we show that the DNA‐linked peptides can be efficiently cyclized through disulfide and thioether bond formation. In combination with established procedures for DNA encoding, the strategy for incorporation of cysteines may be readily applied for the generation and screening of disulfide‐ and thioether‐cyclized peptide libraries.

Constructing Head-to-Tail Cyclic Peptide DNA-Encoded Libraries Using Two-Directional Synthesis Strategy

“…An affinity selection of this library against p300 identified two potential inhibitors with single-digit micromolar activity. In addition, the on-DNA Ru-promoted ring-closing metathesis , and thioether cyclization reaction are also viable to be employed to prepare DNA-encode macrocyclic libraries.…”

“…13−16 In 2021, Lu, Chen, and co-workers 17 potential inhibitors with single-digit micromolar activity. In addition, the on-DNA Ru-promoted ring-closing metathesis 18,19 and thioether cyclization reaction 20 are also viable to be employed to prepare DNA-encode macrocyclic libraries. The overall goal in DEL campaigns is to obtain as much selection information as possible to understand the structurebinding relationship (SBR) for hits identification and further optimization.…”

Plant antimicrobial peptides: structures, functions, and applications

“…It has been found that disulfide bonds and hydrogen bonds contribute to the stability of native-folded AMPs, and both types of bonds affect the activity of AMPs by influencing their folding stability (Ranade et al 2020;Vila-Perelló et al 2005). In addition to the chemical bonds mentioned in previous sections, a few others have been reported, such as thioether bonds, which are required for peptide maturation (Pham et al 2020;Wieckowski et al 2015). However, the structure-activity relationship between these chemical bonds and AMPs is not clear.…”

Macrocyclic DNA-encoded chemical libraries: a historical perspective

“…Another study on thioether formation was published by Heinis and coworkers describing the formation of macrocycles on DNA in solution by thioether formation. 89 Two tert-butylthio (S-tBu) protected cysteines were incorporated into peptides and subsequently deprotected in aqueous solution. Disulfide bond formation readily occurred, and the addition of symmetrical bis-electrophiles lead to the creation of thioether bonds via nucleophilic substitution or 1,4-addition.…”