Concise Total Syntheses of the 6-7-5 Hamigeran Natural Products

Herein, we reportthe total syntheses of four hamigerannaturalproducts featuring a 6-7-5 tricyclic carbon skeleton.We utilized a palladium-catalyzed intramolecular cyclopropanol ringopening cross-coupling to build the central seven-membered ring anda series of oxidations including a challenging aromatic C-Hoxidation to introduce the peripheral functionalities. This approachenabled us to achieve the first total syntheses of hamigeran C (14steps), debromohamigeran I (12 steps), and hamigeran I (13 steps).Our synthesis also resulted in hamigeran G in 13 steps, which is significantlyshorter than the previously reported one (24 steps, longest linearsequence).

Automated summary

We report the total syntheses of four hamigeran natural products with a 6-7-5 tricyclic carbon skeleton. A palladium-catalyzed intramolecular cyclopropanol ring-opening cross-coupling was used to build the central seven-membered ring, and a series of oxidations, including a challenging aromatic C-H oxidation, were employed to introduce the peripheral functionalities. This approach allowed us to achieve the first total syntheses of hamigeran C (14 steps), debromohamigeran I (12 steps), hamigeran I (13 steps), and hamigeran G (13 steps), significantly shorter than the previously reported longest linear sequence (24 steps).