Total Synthesis of Bioactive Marine Natural Products

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DESCRIPTION (provided by applicant): The main objective of our research program is the development of new synthetic methods using complex natural products to identify new challenges. Our endeavors in total synthesis and resulting access to natural products will also provide the basis for research in the area of bioorganic chemistry. The new synthetic methods will find further utility in pharmaceutical and medicinal research, serving for the benefit of public health through improved preparation of drugs and bioactive substances. The specific targets pursued in this application are marine toxins containing a spiroimine ring. This is an expanding group of complex marine natural products that presently includes pinnatoxins, pteriatoxins, spirolides, spiro-prorocentrimine, and gymnodimine. The unique spiroimine fragment has been determined to be critical for their bioactivity. Some of these natural products have been implicated in several global seafood intoxication events. The proposed synthetic strategy is general and can be applied for the synthesis of pinnatoxins, spirolides, and gymnodimine. The most challenging part of the target structures is the spiroimine fragment. We developed a method that enables stereoselective Ireland-Claisen rearrangement of alpha-branched allylic esters. Typically, poor diastereoselectivity is observed in these reactions. Employing our method, both diastereomers can be accessed with excellent diastereoselectivity. This is the central method that we use in the synthesis of the spiroimine fragments. We anticipate that our efforts in the area of chemical synthesis of complex natural products will enrich the arsenal of synthetic methods in general, facilitating research in the fields of medicinal chemistry and drug discovery. More specific to this application, the marine toxins featured herein are directly related to the public health issue of seafood intoxication. It is noted that a major problem in the development of precise methods for detection of algal toxins is the lack of pure standards. Thus, the targets of our syntheses will serve as pure standards for the development of detection probes for marine toxins. PUBLIC HEALTH RELEVANCE Developments in organic synthesis have long benefited human health by providing methods for drug discovery and pharmaceutical research. The total synthesis of complex natural products is a major branch of organic chemistry that defines the current state-of-the-art, stimulates innovation and discovery, and identifies new challenges to be addressed. The research proposed in this application will enrich synthetic methodology through total synthesis of complex natural products. In addition, we will develop sensitive immunoassays for the detection of marine toxins in the environment. This will benefit human health by prevention of certain types of seafood intoxication, which has become a global phenomenon.