This program will investigate fundamental aspects of heterocycle activation and coupling in the context of a synthetic program designed to prepare potent cytotoxic agents. The targets include FK317 metabolites, N-methylaziridinomitosene B, diazonamide A, and structures containing hindered peptide subunits such as hemiasterlin, an inhibitor of tubulin polymerization. Selected synthetic intermediates will be submitted to the NCI Drug Screening Program, and specific targets in the FK317 and N-methylaziridinomitosene B project will be evaluated for DNA alkylation and crosslinking ability in collaboration with Prof. P. Hopkins (Univ. of Washington). Synthetic efforts in the aziridinomitosene area will exploit recently developed methods for anionic cyclization to prepare FK317 metabolites and to test their role in the activation cascade. Advances in oxazole lithiation will be used to synthesize N-methylaziridinomitosene B and the corresponding hydroquinone. Solvolysis products of the hydroquinone will be identified under controlled pH conditions to resolve mechanistic issues. The Diazonamide A project will focus on synthetic methodology, including the introduction of quaternary carbon with control of absolute configuration in a benzofuranone, ring closure of a hindered peptide in a relatively rigid polycyclic environment, and assembly of an oxazole- and indole-containing biaryl macrocycle. The oxazole activation technology will also be used to assemble heterocyclic structures containing di-oxazoles, tri-oxazoles, and oxazolylindoles. Similar structures often appear in marine natural products. Methodology for high yield coupling of hindered peptides has been developed as part of the diazonamide A project and will be extended to the synthesis of the exceptionally hindered hemiasterlins and related structures.
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