合成路线1

Reaction of 5-fluoro-2-hydroxybenzoic acid (VII) with MeOH and H2SO4 gives the corresponding methyl ester (VIII), which is treated with tetramethylammonium nitrate and TFAA to yield 5-fluoro-2-hydroxy-3-nitrobenzoic acid methyl ester (IX). Condensation of the hydroxybenzoate (IX) with the phenylacetylene derivative (X) by means of TF2O, PdCl2(PPh3)2 and TEA affords the diphenylacetylene derivative (XI). Reduction of the NO2 group of (XI) by means of Fe, HCl and NH4Cl provides the aniline derivative (XII), which is cyclized by means of CuI at 100 °C to give the indole derivative (XIII). Condensation of indole (XIII) with N-(2-nitrovinyl)-N,N-dimethylamine (XIV) by means of TFA yields the 3-(2-nitrovinyl)indole derivative (XV), which is reduced with NaBH4 to afford the 3-(2-nitroethyl)indole derivative (XVI). Reductive cyclization of indole (XVI) by means of H2 over RaNi in AcOH provides the tricyclic compound (XVII), which is finally decarboxylated by means of HBr/AcOH (2). Scheme 2.