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Total Synthesis of the Neuronal Cell‐Protecting Carbazole Alkaloids Carbazomadurin A and ( S )‐(+)‐Carbazomadurin B
Author(s) -
Hieda Yuhzo,
Choshi Tominari,
Fujioka Haruto,
Hibino Satoshi
Publication year - 2013
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201301059
Subject(s) - carbazole , chemistry , alkoxy group , indole test , total synthesis , stereochemistry , medicinal chemistry , combinatorial chemistry , organic chemistry , alkyl
Abstract The total syntheses of the neuronal cell‐protecting carbazole alkaloids carbazomadurin A and ( S )‐(+)‐carbazomadurin B were achieved. The key step of the synthesis of the polysubstituted carbazole rings included an allene‐mediated electrocyclic reaction of the 6π‐electron system that involved the indole 2,3‐bond. The cleavage of the alkoxy groups of the resulting 3‐ethoxy‐8‐isopropoxycarbazole successfully gave the 3,8‐dihydroxycarbazole, which was converted into the 3,8‐bis(OSEM)‐carbazole (SEM = 2‐trimethylsilylethoxymethyl). A Suzuki–Miyaura cross‐coupling reaction of the 3,8‐bis(OSEM)‐carbazole with the corresponding alkenyl pinacol borates afforded the 1‐alkenylcarbazoles, which were treated with tetra‐ n ‐butylammonium fluoride (TBAF) followed by reduction with NaBH 4 to provide carbazomadurin A and ( S )‐(+)‐carbazomadurin B, respectively.