Murraya 1-oxygenated carbazole alkaloids

Clauszoline-K and dausine C (clauszoline-L) have been isolated from the stem bark of the Chinese medidnal plant Clausena excavata [72], Clausine M and dausine N have been found in the root bark of the same plant [73]. The bioassay-guided fractionation of the organic extract of Murraya siamensis, collected in Thailand, led to the isolation of siamenol, which shows HIV-inhibitory activity [74], A simple route to these 7-oxygenated carbazole alkaloids has been developed, based on a highly efficient palladium-catalyzed approach (Scheme 15.21) [75] (Table 15.4). 

A series of 7-oxygenated carbazole alkaloids has been synthesized by us for the first time, including clauszoline-K (117), 3-formyl-7-hydroxycarbazole (119), clau-sine M (120), clausine N (121), and siamenol (124) [148]. Clauszoline-K (117) and clauszoline-L (118) have been isolated by Ito et al. from the stem bark of C. excavata [115]. Wu and co-workers had isolated the same compound 118 one year earlier from the same source and named it clausine C (118) [158]. 3-Formyl-7-hydroxycarbazole (119) was obtained from the root bark of Murraya euchrestifolia [159]. Clausine M (120) and clausine N (121) were isolated from the root bark of C. excavata by Wu et al. [116]. Siamenol (124) was isolated from an extract of M. siamensis and proved to have anti-HIV activity [160]. 

A large number of 2-oxygenated carbazoles has been isolated from natural sources [18, 20]. Mukonidine (149) and clausine L (O-methylmukonidine) (148) have been isolated by Wu et al. from the Chinese medicinal plant C. excavata [173]. 2-Methoxy-3-methylcarbazole (146) was obtained first from the seeds of the Indian medicinal plant Murraya koenigii by Bhattacharyya and co-workers [174]. The isolation of O-methylmukonal (147) was reported by Lange et al. from M. siamen-sis [112]. Two years later, Bhattacharyya found the same compound in the roots of G. pentaphylla and renamed it glycosinine (147) [175]. Clausine V (151), a 2,7-dioxygenated carbazole alkaloid, was extracted from the root bark of C. excavata by Wu and co-workers [116]. 

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