Furoannulated carbazole alkaloids

Furoannulated carbazole alkaloids represent a relatively new class of natural products which have been isolated from terrestrial plants [121,122]. The number of members of this family known to date is rather limited. Furoclausine-A (61) along with furoclausine-B was isolated first by Wu and co-workers from the root bark of C. excavata [122]. We have developed an efficient and convergent access to furo [3,2-a]carbazoles via our iron-mediated arylamine cyclization [123, 124]. Retro-synthetic analysis of furoclausine-A (61) suggests 1-methoxycyclohexa-1,4-diene (48) and the arylamine 62 as building blocks (Scheme 16). The latter was obtained by alkylation of 2-methyl-5-nitrophenol (63) with 2-bromo-1,1-diethoxyethane... 

The oxidative cyclization of 5-(2-anilino)-substituted (diene)iron complexes provides access to the carbazole alkaloids hyellazole, 6-chlorohyellazole, carazostatin, 7-methoxy-O-methylmukonal, clausine O, clausine H, and clausine Furoannulated carbazole alkaloids, a rare class of natural carbazols that have been isolated from terrestrial plants, are also available by this method. Scheme 4-128 outlines the key step in the synthesis of furoclausine-A, the construction of the carbazole framework. The annulation of the furan ring is carried out subsequently. Final functional group transformations provide the natural product. ... 

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See also in sourсe #XX -- [ ]

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