Biocompatible and Selective Generation of Bicyclic Peptides**

Abstract

Bicyclic peptides possess superior properties for drug discovery; however, their chemical synthesis is not straightforward and often neither biocompatible nor fully orthogonal to all canonical amino acids. The selective reaction between 1,2-aminothiols and 2,6dicyanopyridine allows direct access to complex bicyclic peptides in high yield. The process can be fully automated using standard solid-phase peptide synthesis. Bicyclization occurs in water at physiological pH within minutes and without the need for a catalyst. The use of various linkers allows tailored bicyclic peptides with qualities such as plasma stability, conformational preorganization, and high target affinity. We demonstrate this for a bicyclic inhibitor of the Zika virus protease NS2B-NS3 as well as for bicyclic versions of the α-helical antimicrobial peptide aurein 1.2.

Biocompatible strategies for peptide macrocyclisation

“…207 Additionally, dicyanopyridine reagents can be employed for peptide stapling or to generate bicyclic peptides. 37,208 Cpa can also be selectively incorporated into proteins. 209…”

The Cyanopyridine–Aminothiol Click Reaction: Expanding Horizons in Chemical Biology

“…Consequently, additional cysteine residues are well tolerated within the peptide macrocycle, as demonstrated for cyclic, stapled and bicyclic peptides (Figure 1). 10, [12][13] Figure 1 Macrocyclic, stapled and bicyclic peptides with additional cysteine residues that remain unaffected by the cyanopyridine-nitrile click reaction.…”

N-terminal cysteine as minimalistic handle for dual, site-selective bioconjugation: application to an anti-HER2 affibody reveals synergy of two conjugated drugs

“…13 Thanks to the binuclophilic nature of its 1,2-aminothiol group, NCys have been largely exploited for chemoselective ligations that engage both nitrogen and sulfur atoms. Reported NCys-directed strategies include reaction with aldehydes to yield thiazolidines, [14][15][16][17][18][19] with nitriles to yield thiazolines, [20][21][22][23][24][25] and with N-hydroxy succinimide (NHS) acrylates to yield 1,4-thiazepan-5-ones. 26 With a focus on NCys-directed dual functionalization, we have been interested by ligation methods that would harness the 1,2aminothiol group while restoring the thiol functionality, thus enabling for the introduction of a second cargo at the same site.…”