Et3N (36.6 μL, 0.263 mmol) and methanesulfonyl chloride (7.46 μL, 0.0964 mmol) were added to a solution of tert-butyl (1-{4-[2-(4-aminophenyl)-9H-imidazo[1,2-d]pyrido[2,3-b][1,4]benzodiazepin-3-yl]phenyl}cyclobutyl)carbamate (50.0 mg, 0.0876 mmol) in DCM (1 mL) at 0° C., and stirred at room temperature. After reaction was completed, the mixture was diluted with sat. NaHCO3 and extracted with CHCl3 (3×). The combined organic layers were dried over anhydrous Na2SO4, and concentrated. The residue was purified by PTLC (CHCl3/MeOH=9:1, CHCl3/EtOAc=1:1) to afford desired product (30.9 mg, 54.4%) as pale yellow solid. 1HNMR (CDCl3) 400 MHz δ: 8.18-8.12 (m, 1H), 8.04-7.97 (m, 1H), 7.63-7.50 (m, 2H), 7.41-7.33 (m, 2H), 7.33-7.23 (m, 2H), 7.19-7.08 (m, 5H), 6.96 (d, J=7.8 Hz, 1H), 6.80 (d, J=7.8 Hz, 1H), 6.60 (dd, J=7.8, 4.6 Hz, 1H), 6.44 (br s, 1H), 5.69-4.98 (m, 1H), 2.98 (s, 3H), 2.63-2.27 (m, 4H), 2.21-2.06 (m, 1H), 1.96-1.82 (m, 1H), 1.38 (br s, 9H).
