Other Methods for Carbocyclic Construction: 6,11-Epoxyisodaucane (Tanino), Magellanine (Yao), Nemorosonol (Ohyoshi/Kigoshi), Antroalbocin (Kalesse), Cochlearol B (Schindler), Emerione A (Miller)
6,11-Epoxyisodaucane (3) was isolated from the liverwort Tritomaria polita. In the course of the synthesis of 3, a key step of which was the decyanative cyclization of the epoxide 1 to the ketone 2, Keiji Tanino of Hokkaido University corrected the structure (Org. Lett. 2022, 24, 7939. DOI: 10.1021/acs.orglett.2c03068).
The tetracyclic alkaloid magellanine (6) was isolated from the club moss Lycopodium magellanicum. Zhu-Jun Yao of Nanjing University assembled the carbocyclic skeleton of 6 by the diastereoselective intramolecular Michael cyclization of 4 to 5 (J. Org. Chem. 2022, 87, 8685. DOI: 10.1021/acs.joc.2c00871).
Nemorosonol (9), isolated from the Brazilian tree Clusia nemorosa, shows antibiotic activity. En route to 9, Takayuki Ohyoshi and Hideo Kigoshi of the University of Tsukuba reduced the enol lactone 7 with Dibal, leading to the aldol product 8 (Org. Lett. 2022, 24, 4635. DOI: 10.1021/acs.orglett.2c01745).
Antroalbocin (12), isolated from the fungus Antrodiella albocinnamomea, also showed antibiotic activity. Markus Kalesse of the Gottfried Wilhelm Leibniz University Hannover irradiated the enone 10 to give first the β,γ-unsaturated ketone, that underwent 1,3-acyl migration to 11. Diastereoselective reduction completed the synthesis of 12 (Org. Lett. 2022, 24, 5812. DOI: 10.1021/acs.orglett.2c02347).
Cochlearol B (15) was isolated from the fruiting body of the fungus Ganoderma cochlear, used in traditional Chinese medicine. Corinna S. Schindler of the University of Michigan showed that the Ir photocatalyst was essential for the efficient cyclization of 13 to 14 (Angew. Chem. Int. Ed. 2022, 61, e202201213. DOI: 10.1002/anie.202201213).
Emerione A (18), isolated from the fungus Emericella nidulans, inhibits NO production in lipopolysaccharide-induced RAW264.7 cells. Aubry K. Miller of the German Cancer Research Center prepared 17 by the gentle warming of the pentaene 16. Selective epoxidation completed the synthesis of 18 (Angew. Chem. Int. Ed. 2022, 61, e202205878. DOI: 10.1002/anie.202205878).