Total Synthesis of Diverse Tetramic Acid Bearing cis‐Decalin Natural Products

Abstract We report herein the first total syntheses of four natural antibiotics, vermisporin, PF1052/AB4015‐A, AB4015‐L, AB4015‐B, and one hydrogenated natural product derivative, AB4015‐A2, that all feature a tetramic acid bearing cis ‐decalin ring. The construction of the functionalized cis ‐decalin ring was achieved by a diastereoselective intramolecular Diels‐Alder (IMDA) reaction, which proceeded via a rare endo‐ boat transition state. Through an intramolecular neighboring‐group‐oriented strategy, the sterically hindered epoxy group in vermisporin, PF1052/AB4015‐A and AB4015‐L was installed efficiently. A one‐pot aminolysis/Dieckmann condensation cascade using l ‐amino acid derivatives afforded the desired tetramic acid structure. The total synthesis led to the unambiguous verification of the absolute configuration of these natural products.