1 -Hydroxy-3-methylcarbazole isolation

The 3-methylcarbazole origin of the carbazole alkaloids of higher plants and the wider participation of 2-hydroxy-3-methylcarbazole in the formation of pyranocarbazoles, as well as furocarbazoles, has been further substantiated by the isolation of several derivatives of 3-methylcarbazoles, such as mukoenine-A (girinimbilol) (55), heptaphylline (76), furostifoline (224), furoclausine A (225), girinimbine (115), and murrayacine (124). Girinimbilol (55) could be considered the... 

Similarly, 1-hydroxy-3-methylcarbazole (23) and 2-hydroxy-3-methylcarbazole (52) could lead to bis(0-demethylmurrayafoline A) (204) and bis-2-hydroxy-3-methylcarbazole [l,l-bis(2-hydroxy-3-methylcarbazole)] (213), respectively, as shown in Scheme 3.9. Although bis(0-demethylmurrayafoline A) (204) is a non-natural carbazole derivative, the isolation of 2-hydroxy-3-methylcarbazole (52) and bis-2-hydroxy-3-methylcarbazole [l,l-bis(2-hydroxy-3-methylcarbazole)] (213) from M. komigii supports the oxidative dimerization of 2-hydroxy-3-methylcarbazole (52) (Scheme 3.9). 

Continued investigations of this plant uncover still more alkaloids. Mahanimbicine (150) and bicyclomahanimbicine (151) were isolated and their synthesis was achieved from 2-hydroxy-6-methylcarbazole (173). Isomahanimbine (C23H25OX mp 142°) (152) and koenimbidine (C2oH2iOgX mp 225°) (153) had their structures determined largely by NMR spectroscopy and by comparison with alkaloids of known structure (174). 

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