3-Formyl-2-methoxycarbazole

In 1991, McChesney and El-Feraly described the isolation and structural elucidation of 3-formyl-6-methoxycarbazole (97) from the roots of C. lansium (23). The roots of this ornamental tree are used in traditional medicine in Taiwan to treat bronchitis and malaria (23). In 2005, Franzblau et al. isolated the same natural product from the stem bark of Micromelum hirsutum (103). They reported that 3-formyl-6-methoxycarbazole (97) shows in vitro anti-TB activity against the H37RV strain of Mycobacterium tuberculosis. 

During the course of photoformylation studies on methoxycarbazoles with chloroform, Chowdhury and Saha reported the synthesis of 3-formyl-6-methoxy-carbazole (97) starting from 3-methoxycarbazole (1003) (656). In this transformation, the desired 3-formyl-6-methoxycarbazole (97) was obtained in only 10% yield, along with the other major regioisomeric formyl carbazoles, 1004 (14%)... 

Oxidation of 3-formyl-6-methoxycarbazole (97) with manganese dioxide and potassium cyanide in methanol afforded methyl 6-methoxycarbazole-3-carboxylate (104). Regioselective bromination of 97 afforded the 5-bromocarbazole 1031. Cleavage of the methyl ether to 1032, followed by nickel-mediated prenylation, provided micromeline (100) (547) (Scheme 5.154). 

The structures of several carbazoles and pyranocarbazoles have been confirmed by synthesis these include lansine [2-hydroxy-3-formyl-6-methoxycarbazole - a... 

The relay compound 1025 required for the synthesis of all of these 7-oxygenated carbazole alkaloids was obtained starting from commercially available 4-bromo-toluene (1023) and m-anisidine (840) in two steps and 72% overall yield. Buchwald-Hartwig amination of 4-bromotoluene (1023) with m-anisidine (840) furnished quantitatively the corresponding diarylamine 1024. Oxidative cyclization of 1024 using catalytic amounts of palladium(ll) acetate afforded 3-methyl-7-methoxycarbazole (1025). Oxidation of 1025 with DDQ led to clauszoline-K (98), which, on cleavage of the methyl ether using boron tribromide, afforded 3-formyl-7-hydroxycarbazole (99) (546) (Scheme 5.149). 

Clausena harmandiana Pierre (root bark) Rutaceae Heptaphylline (54) 2-Hydroxy-3-formyl-7-methoxycarbazole (55) 7-Methoxyheptaphylline (55)... 

The known alkaloid heptaphylline has been isolated from the roots of Clausena harmandiana Pierre (Rutaceae) along with two new carbazole alkaloids identified as 2-hydroxy-3-formyl-7-methoxycarbazole (58) and 7-methoxyheptaphylline (59). The H- and l3C-NMR spectra have been analyzed and used to position the various functional groups (54,55). Other carbazole alkaloids isolated from the roots of Murraya siamensis Craib are identified as murrayanine, girinimbine, and mukonal, which occur together with heptaphylline and compounds 58 and 59 (56-55). Three new alkaloids have also been isolated from M. siamensis and named 3-formyl-2,7-dimethoxycarbazole (60), 3-formyl-2-methoxylcarbazole (O-methylmukonal) (61), and 7-methoxymurrayacine (62) (59). From the roots of Rauwolfia serpentina, the new alkaloid indobine (63) (60), the benzyl ester, and indobinine (64) (61), the cyclohexyl ester of indolepropionic acid, have been isolated and identified. 

Non-tryptamines.—The number of carbazole derivatives isolated from the Rutaceae is now fourteen. Besides the tricyclic compounds murrayanine " (3-formyl-l-methoxycarbazole), glycozoline " (3-methoxy-6-methylcarbazole), glycozolidine " (2,4-dimethoxy-6-methylcarbazole), and (from Clausena hepta-phylla) heptaphylline (1), tetra- and penta-cyclic carbazoles have been obtained from Murraya koenigU3 ... 

Formyl-1-methoxycarbazole (murrayanine) and 3-methylcarbazole (for the first time from natural sources) have been isolated from Clausena heptaphylla Heptazolidine/ a new alkaloid from the same source, has been given the structure (44). Its dihydro-derivative has a u.v. absorption said to be similar to that of 2,3-dimethoxycarbazole. 

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-... 

The characteristic ultraviolet absorption spectra of carbazole, 3-methyl-, formyl- and methoxycarbazoles (18) continue to be useful in structure elucidation studies. Uv absorption data of the alkaloids reported after 1977 are detailed in Table 2. 

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