The 10-hydroxy camptothecin (800 mg; 2.2 mmol) is suspended in water (24 ml). Iron (II) sulfate heptahydrate (250 mg, 0.85 millimoles) is added to the suspension and then followed by the addition of propionaldehyde (3 ml). The reaction mixture is then cooled in an ice bath and concentrated sulfuric acid (1 ml) and trifluoroacetic acid (24 ml) are added. After stirring the homogeneous solution for 15 minutes, potassium persulfate (3.5 g; 6 mol equivalent) is added, and the mixture is slowly warmed to room temperature. After approximately 15 hours, the reaction mixture is diluted with water and the product is extracted using excess chloroform. The crude product is washed thrice with 5% methanol in ether and dried to obtain 806 mg of the desired compound. 1H NMR (300 MHz; DMSO-d6): 0.87 δ (3H, t, J=7 Hz); 1.62 δ (3H, t, J=7 Hz); 1.85 δ (2H, 1q, J=5 Hz); 3.18 δ (2H, q, J=5 Hz); 5.19 δ (2H, m); 5.40 δ (2H, s); 6.51 δ (1H, bs); 7.23 δ (2H, m); 7.39 δ (1H, d, J=10 Hz); 8.01 δ (1H, d, J=9Hz) 13C NMR: δ7.3, 13.6, 22.4, 29.8, 72.0, 95.8, 102.7, 117.9, 120.4, 124.8, 144.6, 145.3, 156.5, 158.3, 200.1 FAB MS: 403 (M+1)+
