Discovery, Genome-Guided Structure Elucidation, and Total Synthesis of Terukufazoline A, a Macrocyclic Docosapeptide, from a Marine Cyanobacterium

The structure elucidation of large molecules remains a central challenge in natural products chemistry. This challenge has been addressed through spectroscopic methods as well as degradative and synthetic approaches, which have provided effective solutions. Recent advances in genome analysis have enabled an orthogonal approach to structure elucidation based on biosynthetic gene information. In this study, we report the structure elucidation of an unprecedentedly large cyanobactin, terukufazoline A ( 1 ), through integration of spectroscopic analysis, metagenome-guided biosynthetic information, chemical degradation, and total synthesis. Terukufazolines A ( 1 ) and B ( 2 ) were discovered from an undescribed marine cyanobacterium, and the intractable NMR and tandem MS data for 1 prompted us to incorporate biosynthetic gene information. Metagenomic analysis identified the cyanobactin biosynthetic gene cluster, whose core peptide sequence enabled the assignment of the amino acid sequence of 1 . The absolute configuration was established by degradation-based analyses, and the proposed structures were verified by convergent total syntheses of 1 and 2 .