10-hydroxy-camptothecin (1.0 kg), dichloromethane (about 13 kg) and isopropanol (about 8 kg) were charged into a suitable reactor. N,N-dimethylmethyleneiminium chloride (0.3-0.5 kg) was added into the reactor. Triethylamine (0.04-0.2 kg) was then added into the resulting mixture at 20-35° C. and stirred at 20-35° C. for at least 12 hours. When the reaction was complete, a mixture of hydrochloric acid (32%, 0.06-0.3 kg) and isopropanol (about 5 kg) was added into the resulting mixture. After the addition was completed, the resulting mixture was stirred, filtered, and then washed with dichloromethane (about 3 kg). The wet solids were dried to give about 1.5 kg of crude topotecan HCl.
