This proposal describes a highly unified, enantioselective strategy to the complex, bioactive marine alkaloids palau'amine, axinellamine, and styloguanidine from a common cyclopentane intermediate bearing either a cyclic urea-hydantoin or bis-cyclic guanidines heterocycles. This strategy is suggestive of one possible biogenesis of these natural products and in order to study the various hypotheses posited in the literature, we propose the synthesis of 15N-labelled putative biosynthetic precursors to be subjected to cell-free acetone preparations from producing marine sponges in collaboration with Prof. Ted Molinski (UCSD). A novel method for imidazolone annulation and amino-imidazoline annulation of alkenes will be further developed useful for heterocycle synthesis beyond the current targets. The synthetic strategies proposed and completed (in the case of gymnodimine and now agelastatins) will be put to work to enable synthesis of appropriate conjugates of these natural products to enable a molecular level understanding of the bioacitivites exhibited by these anticancer agents and also begin to unravel the biosynthesis of higher order pyrrole-2-aminoimidazoIe alkaloids. In the case of gymnodimine, further SAR studies and mice toxicity will establish the potential of this natural product as both a cellular probe and as a public health hazard. The biomechanistic studies are enabled by continued productive collaborations with Prof. Jun Liu (Johns Hopkins).
The natural products targeted in this proposal all possess potent biological effects including antibacterial, immunosuppressive, neuoronal, and antitumor effects thus having potential for the treatment of human disease including bacterial infection, inflammation, nervous system disorders, and cancer. We propose unique, concise synthetic strategies to prepare these natural products and derivatives to address questions regarding the molecular details of their interactions in cells and improve supply. Subsequent mode of action studies of these compounds including cellular target elucidation will contribute to fundamental studies in cell biology and define the potential of these natural products as drug leads. In addition, the studies proposed will begin to shed light on the biosynthetic pathways used by the marine sponges that produce these complex natural products enabling alternative means to prepare these potential drug leads on scale.
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