β-turn mimetic: Synthesis of cyclic thioenamino peptides

Following the discovery of callynormine A, a marine metabolite of a new class, the cyclic endiamino peptides, and the synthesis of compounds of this group, we have now prepared an analogue group of compounds, i.e., cyclic thioenamine peptides. The latter peptides contain the α-amino-β- thioacrylamide functionality, a potential new type of β-turn mimic. The superiority of the SH group over the NH₂ group in the reaction with enol-tosylates was demonstrated.