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.

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.

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.

9-Amino-20(S)-camptothecin is obtained by nitration of camptothecin (I) with fuming nitric acid in concentrated sulfuric acid yielding the intermediate 9-nitrocamptothecin (II), which is then reduced with H2 over PtO2 in absolute ethanol.

This compound can be obtained in two different ways: 1) By direct nitration of camptothecin (I) with nitric acid in sulfuric acid. 2) By direct nitration of camptothecin (I) with different inorganic nitrates (or mixtures of inorganic nitrates) in sulfuric acid. 3) The reaction of 2,6-dinitrobenzaldehyde (II) with ethylene glycol (III) and p-toluenesulfonic acid in refluxing toluene gives the corresponding ethylene ketal (IV), which is reduced with sodium sulfide in refluxing ehanol/water yielding 2-amino-6-nitrobenzaldehyde ethylene ketal (V). The hydrolysis of (V) with aqueous sulfuric acid affords 2-amino-6-nitrobenzaldehyde (VI), which is finally cyclized with the tricyclic ketone (VII) in refluxing acetic acid (the same cyclization can be performed with the ketal (V) and the ketone (VII).

9-Amino-20(S)-camptothecin is obtained by nitration of camptothecin (I) with fuming nitric acid in concentrated sulfuric acid yielding the intermediate 9-nitrocamptothecin (II), which is then reduced with H2 over PtO2 in absolute ethanol.

The hydroxylation of camptothecin (I) with H2O2 in HOAc gives 10-hydroxycamptothecin (II), which is nitrated with HNO3/H2SO4 to yield 10-hydroxy-9-nitrocamptothecin (III). The sulfonation of (III) with TsCl, DEA and DMAP affords 9-nitro-10-p-toluenesulfonyloxy)camptothecin (IV), which is finally desulfonated and reduced by means of ammonium formate and a Pd(OAc)3/bidentate phosphine ligand catalyst. Other sulfonates such as 1-naphthyl-, phenyl-, 4-fluorophenyl-, 4-nitrophenyl-, 4-methoxyphenyl- or methylsulfonate can be used instead of the reported p-toluenesulfonate.

Treatment of (20S)-camptothecin (I) with HOAc and H2O2 followed by light irradiation in H2SO4 yields hydroxy derivative (II), which is then nitrated by means of HNO3 and H2SO4 to afford compound (III). Sulfonation of (III) by reaction with p-TsCl (IV) in the presence of Et3N and DMAP in CH2Cl2 provides sulfonate (V), which is then subjected to reduction by treatment with Pd(OAc)2, PPh3 and triethylammoniumformate (HCOOH稥t3N) to give 9-aminocamptothecin (VI). Reaction of (VI) with nitrophenyl chloroformate (VII) in dioxane, followed by treatment with intermediate (VIII) and DMAP in acetonitrile, provides (IX). Alternatively, (IX) can also be obtained by first treatment of (VI) with triphosgene followed by reaction with intermediate (VIII) in pyridine and chromatographic purification. Finally, (IX) is treated with potassium trimethyl silanate (KOSiMe3) for methyl ester cleavage and acidified with HCl.

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.