Bioactive isonitrile-containing metabolites are among the best small-molecule leads for addressing the 300-500 million infections and 1-3 million deaths caused annually by malaria. Unfortunately few isonitrile-based synthetic methods exist that maintain the isonitrile functionality which is preventing direct, rapid access to bioactive isonitrile-containing carbocycles. This proposal aims to develop new connectivity methods, access isonitriles having new structural diversity, reveal fundamental reactivity patterns in alkylations and conjugate additions, and establish the essential principles for performing transition metal catalysis with isonitriles. As such the proposal fits into the mandate of NIAID for advances leading to rapid synthesis of disease treatments, particularly malaria. This proposal launches a new initiative to address the dearth of isonitrile-based synthetic methods. Three complementary developments will be explored to develop new methods (a) for alkylating isonitriles through deprotonations with mixed metal bases, (b) a new exchange process in which an activated isonitrile is converted into a metalated isonitrile, an alkeneisonitrile, or an alkyneisonitrile, and (c) for developing transition metal catalysts capable of promoting reactions without irreversibly binding the isonitrile functionality. Preliminary results demonstrate the viability of two different, but complementary, alkylation strategies to access bioactive isonitriles. The long term goal is to develop these methods into robust syntheses of isonitriles using NMR analyses and alkylation selectivities to probe the nature of the reactive intermediates. Another strategy addresses the long-standing challenge of developing transition metal catalysts capable of processing the carbon architecture without irreversibly binding to the isonitrile group. The approach is to develop catalysts for non-polar reactions, such as the Diels-Alder cycloaddition, and then apply the understanding to more challenging conjugate addition reactions. If successful, this will allow researchers to rapidly access isonitriles with diverse substitution patterns. In summary, if successful the proposal will provide a new strategy for rapidly assembling substituted isonitriles ideally suited to diverse biomedical applications. Developing a robust route to these extremely valuable building blocks should facilitate their use in pharmaceutical synthesis and provide fundamental insight for developing additional isonitrile-based methods.
Isonitriles are functionalities primed for conversion to peptide mimics, bioactive heterocycles, and binding to radioactive metals used in tumor imaging. The proposal describes the synthesis of diverse isonitriles to address their limited availability and simultaneously advance fundamental bond forming reactions with this functionality.
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