General Strategy for the Synthesis of Antirhine Alkaloids: Divergent Total Syntheses of (±)-Antirhine, (±)-18,19-Dihydroantirhine, and Their 20-Epimers
2020
Bae, Cheolwoo | Park, Eunjoon | Cho, Cheon-Gyu | Cheon, Cheol-Hong
A general synthetic strategy for antirhine alkaloids was developed in this study. The cyanide-catalyzed imino-Stetter reaction of ethyl 2-aminocinnamate and 4-bromopyridine-2-carboxaldehyde afforded the corresponding indole-3-acetic acid derivative. Subsequent formation of the six-membered C ring followed by trans-selective installation of the two-carbon unit at C-15 provided rapid access to the key intermediate. Stereoselective installation of substituents at C-20 allowed the total syntheses of (±)-antirhine, (±)-18,19-dihydroantirhine, and their 20-epimers, all of the known natural products in the antirhine family.
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