Chemical and Ribosomal Synthesis of Topologically Controlled Bicyclic and Tricyclic Peptide Scaffolds Primed by Selenoether Formation.

Bicyclic and tricyclic peptides have emerged as promising candidates for the development of protein binders and new therapeutics. However, convenient and efficient strategies that can generate topologically controlled bicyclic and tricyclic peptide scaffolds from fully-unprotected peptides are still much in demand, particularly for those amenable to the design of biosynthetic libraries. In this work, we report a reliable chemical and ribosomal synthesis of topologically controlled bicyclic and tricyclic peptide scaffolds. Our strategy involves the combination of selenoether cyclization followed by disulfide or thioether cyclization, yielding desirable bicyclic and tricyclic peptides. This work thus lays the foundation for developing peptide libraries with controlled topology of multicyclic scaffolds for in vitro display techniques.

Peptide Macrocycles Developed from Precisely Regulated Multiple Cyclization of Unprotected Peptides.

Peptide macrocycles have been attractive scaffolds for the development of ligands and inhibitors to proteins, which have the potential of being developed as potent drugs. Novel strategies for peptide macrocyclization should be of particular interest to peptide drug design and discovery. Herein, an efficient strategy for designing and synthesizing macrocyclic peptides, which relies on the precisely regulated and efficient one-pot cyclization of unprotected peptides with 2,3,5,6-tetrafluoroterephthalonitrile (4F-2CN), is reported. The peptide bicycles can be considered as novel structurally hyperconstrained peptide macrocycles constrained with a rigidifying ring-closing moiety, consisting of an N-terminal 6-membered ring and C-terminal 13-membered ring fused with the benzene ring of 4F-2CN. These novel macrocyclic peptide scaffolds would be intriguing and promising scaffolds for developing macrocyclic peptide inhibitors and targeting ligands for many proteins.

Synthesis of α,ß-Unsaturated N-Sulfonyl Imides through Zinc-Catalyzed Intermolecular Oxidation of N-Sulfonyl Ynamides.

A novel zinc-catalyzed intermolecular oxidation of N-sulfonyl ynamides has been developed. A variety of functionalized α,ß-unsaturated N-sulfonyl imides are readily accessed by utilizing this approach, thus providing a viable alternative to synthetically useful α,ß-unsaturated imides. Importantly, the reaction is proposed to proceed by a vinyligous E2-type elimination pathway, but not metal carbene pathway.