合成路线1

Tetrahydropyridine (II), obtained by NaBH4 reduction of the 1-benzylpyridinium salt (I), was condensed with 5-methoxyindole (III) in refluxing 50% AcOH to produce, through a biomimetic sequence, the aminoethyl carbazole compound (IV). Catalytic debenzylation of (IV) led to the primary amine (V), which was converted to the oxalic acid mono-amide (VI) upon heating with diethyl oxalate. Cyclization of amide (VI) in the presence of POCl3 under Vilsmeier conditions furnished the pyridocarbazole tetracyclic system (VII). Dehydrogenation of (VII) over Pd/C in boiling diphenyl ether led to a mixture of the desired aromatized compound (VIII) and the decarbethoxylated byproduct (IX), which were separated by column chromatography. N-Methylation of the pyrrole ring of (VIII) to give (X) was performed by using dimethyl carbonate in DMF in the presence of K2CO3 and crown ether. Reaction of ester (X) with 2-(dimethylamino)ethylamine (XI) at 115 C gave amide (XII). Finally, the desired 9-hydroxy derivative was obtained by methyl ether cleavage in (XII) employing boron tribromide. Alternatively, the title compound was obtained by demethylation of ether (X) and subsequent reaction with 2-(dimethylamino)ethylamine (XI).