合成路线1

The reaction of 5-methoxyindole-2-carboxylic acid (I) with thionyl chloride gives the acid chloride (II), which is condensed with dimethylamine to afford the amide (III). Reduction of (III) by LiAlH4 leads to the dimethylamino derivative (IV), which is quaternized by methyl iodide to give (V). The ammonium salt (V) is transformed into the corresponding phosphonium iodide (VI) by means of triphenyl phosphine. The successive steps from (I) to the phosphonium iodide (VI) give an overall yield of 50-60%. The condensation of (VI) with 4-formyl pyridine (VII) gives a mixture of 70% cis-(Z-VIII) and 30% trans-(E-VIII) isomers. The mixture of indolyl-pyridylethylenes (Z-VIII) and (E-VIII) is cyclized to 10-methoxy-7H-pyrido[4,3-c]carbazole (IX) by irradiation for 90 h in a Rayonet photoreactor at 350 nm in the presence of iodine (40% yield). Dimerization of (IX) is achieved by strirring in DMF two equivalents of (IX) with one equivalent of 1,1'-bis(2-chloroethyl)-4,4'-bipiperidine dihydrochloride (X) at 85 C for 18 h and recrystallization in EtOH/H20 (40/60).