Murraya koenigii 3-methylcarbazole

The dimeric carbazole alkaloids often occur along with the corresponding monomeric carbazoles in terrestrial plants [7,62] (Scheme 7). Clausenamine-A was obtained by Wu from the stem bark of Clausena excavata [63]. Clausen-amine-A and its synthetic analogs, like bis(O-demethylmurrayafoline-A), show cytotoxic activities against diverse human cancer cell lines [64] and exhibit moderate antimalarial activity [65,66]. Furukawa isolated l,r-bis(2-hy-droxy-3-methylcarbazole) and bismurrayaquinone-A, the first dimeric car-bazolequinone alkaloid found in nature, from Murraya koenigii [67]. 

Furukawa et al. reported the total synthesis of murrayaquinone A (107) by a palladium(II)-mediated oxidative cyclization of the corresponding 2-arylamino-5-methyl-l,4-benzoquinones. 2-Anilino-5-methyl-l,4-benzoquinone (842) was prepared starting from 2-methyl-l,4-benzoquinone 841 and aniline 839, along with the regio-isomeric 2-anilino-6-methyl-l,4-benzoquinone (844). The oxidative cyclization of 2-anilino-5-methyl-l,4-benzoquinone (842) with stoichiometric amounts of palla-dium(ll) acetate provided murrayaquinone A (107) in 64% yield. This method was also applied to the synthesis of 7-methoxy-3-methylcarbazole-l,4-quinone (113) starting from 3-methoxyaniline (840) (623). Seven years later, Chowdhury et al. reported the isolation of 7-methoxy-3-methylcarbazole-l,4-quinone (113) from the stem bark of Murraya koenigii and named it koeniginequinone A (113) (49) (Scheme 5.101). 

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]. 

Preparations from the stem bark of the Indian curry-leaf tree, Murraya koenigii Spreng. (Rutaceae) are used externally to cure skin eruptions. Extraction of the stem bark yielded three compounds, two of which appear to be carbazole derivatives, while the third is as yet of unknown character. Murraj anine, C14H11NO2 (mp 168°) was shown by examination of its spectra and reactions, and by conversion into 3-methylcarbazole and 1-methoxycarbazole, to be either 6-formyl-l-methoxycarbazole or 3-formyl-1-methoxycarbazole (IV), probably the latter (19). This conclusion has now" been confirmed by an unambiguous synthesis (30). 4-Bromo-o-anisidine was converted bj diazotization followed by reduction with stannous chloride into 4-bromo-2-methoxy-])henylh drazine (V). Condensation of V w ith cyclohexanone and cj cli-... 

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