Biologically Inspired Total Synthesis of Ulbactin F, an Iron-Binding Natural Product

Abstract

Natural products from environmental microbiomes provide exquisite templates for elucidating biological activity in the search for new drugs. A recently discovered marine Brevibacillus sp. metabolite, ulbactin F, was found to inhibit tumor cell migration and invasion at IC₅₀ < 3 μM. Herein, we disclose the first total synthesis of ulbactin F and epi-ulbactin F, which was modeled after the biosynthetic pathway. The scaffold bears structural similarity to siderophores of human pathogens but contains a novel tricyclic ring system derived from cysteine. We have found that ulbactin F forms low-affinity metal complexes, with a preference for Fe³⁺ and Cu²⁺, which may hint both at its environmental role and its antimetastatic mechanism of action.