合成路线1

The protection of the OH group of 4-hydroxy-3,5-dimethoxybenzaldehyde (I) with benzyl bromide and K2CO3 DMF gives the benzyl ether (II), which is condensed with ethyl 2-azidoacetate (III) by means of NaOMe in methanol to yield the 2-azido acrylic acid derivative (IV). The cyclization of (IV) in refluxing xylene affords the indole carboxylate (V), which is deprotected by hydrogenation with H2 over PtO2 in THF/methanol to provide 6-hydroxy-5,7-dimethoxy-1H-indole-2-carboxylic acid methyl ester (I). The condensation of (VI) with 1,2-dibromoethane (VII) by means of K2CO3 in DMF gives the 2-bromoethoxy derivative (VIII), which is treated with sodium azide in DMF to yield the 2-azidoethoxy compound (IX). The hydrolysis of the ester group of (IX) with NaOH in THF/water affords the carboxylic acid (X), which is esterified with 4-nitrophenol (XI) by means of DCC and DMAP in dichloromethane to provide the activated ester (XII). The condensation of (XII) with the tetracyclic compound (XIII) by means of NaH in DMF gives the adduct (XIV), which is finally reduced at the azido group with H2 over Pd/C in THF/HOAc to yield the target compound.