Pyranocarbazole alkaloids

In 2004, Cuong ef a. reported the isolation of bisisomahanine (209) from the roots of G. stenocarpa (30). Bisisomahanine was obtained in optically active form (Md 13.1, c 0.25, CHCI3). However, the absolute configuration is not known. This alkaloid represented the first dimeric prenylated pyranocarbazole alkaloid with a 1,1 -linkage (30). 

Nonstructure elucidation of seven pyranocarbazole alkaloids of Murraya koenigii [mahanimbine, koenimbine, (-)-mahanine, koenine, koenigine, koenidine, and ( + )-isomahanimbine] have now been published.Mur-rayacine, a minor alkaloid of the same plant, has been isolated from the roots of Clausena heptaphylla. The stems of another Clausena species, C. anisata Willd., contain atanisatin (1), and the roots contain a second new alkaloid, clausanitin (2). ... 

Dihydrooxepino[3,2-a]carbazole derivatives are formed in moderate to rather high yields on photochemical rearrangement of pyranocarbazole alkaloids, for example mahanimbine <88TL6625>. 

In 1985, Furukawa et al. reported the isolation of pyrayaquinone-A (175) and pyrayaquinone-B (176) from the root bark of M. euchrestifolia (157). Three years later, the same authors reported a further pyranocarbazole-l,4-quinone alkaloid, pyraya-quinone-C (177) from the root bark of the same natural source. The absolute configuration of this isolate is not known (22) (Scheme 2.37). 

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... 

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