合成路线1

9-Amino-20(RS)-camptothecin is obtained as follows: The cyclization of cyanoacetamide (I) with 2-ethoxy-4-oxo-2-pentenoic acid ethyl ester (II) by means of K2CO3 in hot DMF gives the intermediate pyridone (III), which without isolation is cyclized again with methyl acrylate (IV) in the same conditions affording the indolizinone (V). The treatment of (V) with concentrated HCl in refluxing acetic acid gives the indolizinedione (VI), which is treated with ethylene glycol and trimethylsilyl chloride in dichloromethane to yield the ethylene ketal (VII). The carboxylation of (VII) with diethyl carbonate and KH in refluxing toluene affords the acetic ester derivative (VIII), which is alkylated with ethyl iodide and potassium tert-butoxide in anhydrous DME to the corresponding butyric ester derivative (IX). The reductive acetylation of (IX) with H2 over RaNi in acetic anhydride gives the acetamide derivative (X), which is treated with NaNO2 in acetic acid to yield the corresponding N-nitroso compound (XI). Thermal degradation of (XI) in refluxing CCl4 affords the acetoxymethyl compound (XII), which is submitted to a oxidative cyclization with O2 in methanol/K2CO3 to give the tetracyclic ketal (XIII). Hydrolysis of the ketal group of (XIII) with 2N H2SO4 in hot DME yields the tricyclic triketone (XIV), which is further cyclized with 2-amino-6-nitrobenzaldehyde (XV) by heating at 160 C to afford 9-nitro-20(RS)-camptothecin (XVI). Finally, this compound is hydrogenated with H2 over Pd/C in ethanol. The title product can also be obtained by direct cyclization of tricyclic triketone (XIV) with 2,6-diaminobenzaldehyde (XVII) in the same conditions.