Preparation of 14-nitrocamptothecin derivatives by reactions of camptothecin with nitronium tetrafluoroborate in acidic solvents

The new camptothecin derivatives (20S)-20-O-acetyl-14-nitrocamptothecin 7 and 5-hydroxy-14-nitrocamptothecin 8 are prepared by the reactions of camptothecin 1 with nitronium tetrafluoroborate 9 in acetic anhydride and trifluoroacetic acid, respectively. When acetic acid is used as reaction solvent, the esterification product (20S)-20-O-acetylcamptothecin 6 is obtained.