Natural bridged biaryls synthesis

The bis-carbazole alkaloids typically contain previously known monomeric carbazoles as structural subunits. To date, bis-carbazole alkaloids have been isolated from plants of two genera of the family Rutaceae, Murraya and Clausena, and are linked either by a methylene unit, a bisbenzylic ether bridge, a bond joining one aromatic portion directly to an annotated dihydropyran unit, or by a biaryl bond. Many reviews have appeared on the monomeric carbazole alkaloids. However, in these articles only a few bis-carbazole alkaloids were listed (3,5-7). For the first time, in 1992, Furukawa et al. compiled all of the bis-carbazole alkaloids that were known to the end of 1992 (158). Taster and Bringmann summarized to the end of 2001, the occurrence, stereochemistry, synthesis, and biological activity of the bis-carbazoles linked through a biaryl bond (159). We compiled to the mid of 2002, the occurrence, stereochemistry, synthesis, and the biological activity of all classes of bis-carbazoles (8). In this section, we cover the total syntheses of the natural bis-carbazole alkaloids reported since 1990. 

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