A 50 ml round-bottomed flask equipped with a septum having a top-mounted argon intake is charged with 180 mg of 5-(2,6-difluorophenyl)-3-{[1-(methylsulphonyl)piperidin-4-yl]amino}-1-{[2-(trimethylsilyl)ethoxy]methyl}-1H-pyrazolo[4,3-c]isoquinoline-7-carbaldehyde oxime in 15 ml of DCM. After cooling to 0° C. using an ice bath, 1.8 ml of TFA are added and the mixture is stirred at RT for 6 h. The mixture is concentrated under RP and the solid obtained is taken up in 50 ml of water and 2 ml of 0.75M aqueous ammonia solution. It is extracted with AcOEt, washed with saturated NaCl solution, dried over MgSO4, filtered and concentrated under RP. Chromatography on silica gel (20-45 μm), eluting with a mixture of DCM and methanol (92.5/7.5 by vol.), gives 63 mg of 5-(2,6-difluorophenyl)-3-{[1-(methylsulphonyl)piperidin-4-yl]amino}-1H-pyrazolo[4,3-c]isoquinoline-7-carbaldehyde oxime (lemon yellow solid). MS (E/I): m/z=500 (M+); 1H NMR: 1.67 (m, 2H); 2.11 (m, 2H); 2.87 (s, 3H); 2.89 (m, 2H); 3.56 (m, 2H); 3.79 (m, 1H); 6.06 (d, J=7.8 Hz, 1H); 7.32 (broad t, J=7.6 Hz, 2H); 7.67 (m, 1H); 7.84 (broad s, 1H); 8.14 (broad d, J=8.5 Hz, 1H); 8.30 (s, 1H); 8.41 (d, J=8.5 Hz, 1H); 11.43 (s, 1H); 12.81 (s, 1H).
