6- Cyano-5-methoxy-12-methylindolo

A 6-cyano-5-methoxy-12-methylindolo[2,3-a]carbazole and 6-cyano-5-methoxyindolo[3-a]carbazole were isolated from the blue-green alga Nostoc sphaericum [95]. These compounds are active against HSV-1. Larsen ct al. [96] isolated three new chlorine-containing P-carbolines, bauerines A-C, from the blue-green alga Dichothrix baueriana. These alkaloids show activity against HSV-2. 

The UV spectrum (/Imax 234, 252,290,338,354, and 372 nm) of 5-cyano-6-methoxy-ll-methylindolo[2,3-fl]carbazole (357) indicated the presence of an indolo[2,3-fljcarbazole framework. The IR sp>ectmm indicated the presence of a sharp band at i max 2200 cm for a nitrile group. The H- and C-NMR spectral data indicated the presence of an aromatic methoxy group ( h 4.21 and 62.0) and an N-methyl group (5h 4.34 and 5q 31.8). Further, a COSY experiment suggested the presence of an... 

The H- and C-NMR spectra of 5-cyano-6-methoxyindolo[2,3-fl]carbazole (358) were very similar to those of 5-cyano-6-methoxy-ll-methylindolo[2,3-fl]carbazole (357), except for the absence of the signals for the N-methyl group at 4.34 and 8c 31.8, and the presence of an additional NH proton signal at 5h 11.41. Based on these spectral data, and the structural similarity to 5-cyano-6-methoxy-ll-methy-lindolo[2,3-fl]carbazole (357), the structure 358 was assigned to 5-cyano-6-methoxy-ll-methylindolo[2,3-fl]carbazole (340) (Scheme 2.93). 

Somei et al. reported the total synthesis of the cytotoxic and antiviral 5-cyano-6-methoxy-ll-methylindolo[2,3-fl]carbazole (357) starting from indigo (1458) (786,787). A reduction of indigo (1458) with tin in acetic acid/acetic anhydride afforded 3-acetoxy-2,2 -bisindolyl (1459) in 88% yield. Heating of 1459 with dichloroacetyl chloride in ethyl acetate under reflux provided 3-acetoxy-3 -dichloroacetyl-2,2 -bisindolyl (1460), which was treated with aqueous ammonia in methanol/DMF at room temperature to give the indolo[2,3-fl] carbazole derivative 1461. N-Methylation... 

The two previous total syntheses of 5-cyano-6-methoxy-ll-methylindolo[2,3-fl] carbazole (357) by Somei et al. started also from indigo, however, gave low overall yields (788). In the following year, the same group reported the syntheses of various indolo[2,3-fl] carbazoles from indigo (789). 

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