A Unified Strategy for the Syntheses of Angucyclinone Antibiotics: Total Syntheses of Tetrangulol, Kanglemycin M, X-14881-E, and Anhydrolandomycinone

A unified strategy for the syntheses of angucyclinone antibiotics was developed utilizing sequential intramolecular enyne metathesis, Diels-Alder/aromatization, photooxygenation, and one-pot elimination/aromatization reactions. The diversity in this sequence was introduced in the Diels-Alder reaction where a common diene was treated with various appropriately functionalized quinones as the dienophiles to accomplish the total syntheses of tetrangulol, kanglemycin M, X-14881-E, and anhydrolandomycinone in moderate to good overall yields. The requisite diene was synthesized in excellent yield from a known enyne through an intramolecular enyne metathesis. The scope of this flexible and divergent strategy can be extended to the syntheses of similar scaffolds and unnatural aromatic angucyclinones