Synthetic and biological investigations of 2-aminoimidazole derived natural products.

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ABSTRACT The purpose of this application is to continue the development of cascade guanidine hydroamination sequences, developed in our laboratory, to prepare highly substituted 2-aminoimidazoles and polyclic guanidine scaffolds and study their rich and diverse biological activities. Specifically, this proposal targets three important structures: (1) We have identified a new class of N2-acyl-2-aminoimidazoles as Zn2+ ionophores that selectively kill breast cancer cells. These compounds cause the active uptake of Zn2+ by cells, leading to Zn2+- dyshomeostasis. Studies will optimize our lead structure (named ZNA) to achieve a complex balance of pKa and pZn (log [Zn2+]free) which underpins this scaffold's activity of inducing zinc dyshomeostasis and lysosomal membrane depolarization. These compounds are active in vivo and are well tolerated, providing an important therapeutic lead for the treatment of breast cancer. Since this mechanism of action is not receptor mediated, these compounds are active against the major breast cancer subtypes including ER, HER2 and PR or triple negative cells. (2) We have developed a powerful cascade hydroamination sequence to construct the bis- guanidine core of (+)-saxitoxin. An extension of this strategy will target the synthesis of zetekitoxin AB (ZTX) a more complex and potent member of the voltage gated sodium channel (Nav) inhibitors that shares this bis- guanidine core. ZTX represents a powerful tool to study ion channel physiology, however, only 0.3 mg of the purified compound exists in human hands. The frog that produces this compound is critically endangered and protected by the Panamanian government. Thus the extreme rarity of this natural product dictates that only total chemical synthesis can provide this compound to the community. (3) Lastly, we will target guadinomine B, a unique carbamoylguanidine containing natural product that we believe is actually the same as NA22598A1, as they are structurally similar and both isolated from Streptomyces spp.. If they are indeed the same, their ascribed activities as an inhibitor of type 3 secretion system mediated pathogenesis (guadinomine B) and inhibition of anchorage independent growth / metastasis (NA22598A1) suggests an overlapping biological target. We advance the hypothesis that this common target is a matrix metalloproteinase (MMP), and that their inhibitory activity relies on Zn2+ chelation by the carbamoylguanidine. If guadinomine B's target is indeed an MMP, this offers a new therapeutic strategy to prevent bacterial pathogenesis, critical to the treatment of human disease (e.g. meningitis, cholera, the plague), either with compounds inspired by these natural products or the abundance of well-developed MMP inhibitors.