New Methods for Simultaneous Arming and SAR Studies of Natural Products

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DESCRIPTION (provided by applicant): Natural products have immense structural diversity and interact with a wide range of proteins in diverse organisms and, due to structural homology, also in humans. This proposal seeks to develop a toolbox of reagents and reactions that will enable simultaneous arming and structure- activity studies (SAR) of natural products (NPs). The SAR studies may identify potential new activities of the NP derivatives and will also ensure that initial biological activity has not been lost. While not a Specific Aim of this grant given the scope of this RFA, the arming aspect leads to NP derivatives that are equipped for subsequent conjugation to various tags via Sharpless-Huisgen cycloadditions, enabling biological studies such as mechanism of action (MOA) studies (including off-targets) and provide useful probes for basic cell biology. The long-term objective is to develop a more systemized approach to mine the rich potential of NPs as activators/inactivators of cellular pathways contributing to chemical genetics. The team includes a synthetic organic chemist (D. Romo), an analytical chemist (G. Vigh), a bioorganic/biosynthetic chemist (C. Watanabe), and a biochemist/molecular biologist (J. Liu, Johns Hopkins). We propose to further develop a set of chemo- and site selective reactions employing bifunctional reagents to obtain NP derivatives that are also useful cellular probes. These studies will contribute to a fundamental understanding of the chemo- and site selectivity of various reactions in the context of complex NPs. We have established collaborations with synthetic, biosynthetic, and isolation chemists and they have provided or agreed to provide ~25 bioactive NPs for the proposed studies. Primary reactions to be studied are Rh(II)-promoted O-H insertion reactions, C-H aminations and alkene aziridinations with metal nitrenoids, and mild aryl halogenations. After an initial site non-selective step, we will employ robust/versatile NP derivative purification methods, re- assay the resulting pure derivatives (SAR studies), and determine the most appropriate site for tag attachment, i.e. find the derivatives that retain the greatest bioactivity. We will also screen for potential novel bioactivities of the NP derivatives in various cellular assays and make quantities available to the Molecular Libraries Small Molecule Repository. The subsequent development of both chemo and site-selective versions of the initial reactions will rely on screening various chiral metal complexes, and robust methods for reaction monitoring (LC-MSn) and semi-preparative HPLC purification, to modulate site-selectivity via a type of "double asymmetric synthesis." PUBLIC HEALTH RELEVANCE: The long-term objective of this project is the development of a more systematized approach to mine the rich potential of natural products as activators and inactivators of cellular pathways. Natural products have a rich history as tools for identification of novel therapeutic targets for human disease and as lead structures for drug development. Results from these studies will be directly relevant to human disease including diabetes, inflammation, and cancer since novel methods are proposed for derivatization of natural products (this proposal) pertinent to these disease. Subsequent SAR studies (this proposal) will be pursued to identify potential new bioactivities and suitable sites for probe attachment enabling subsequent mode of action studies (not in this proposal) relevant to these diseases.