Et3N (36.6 μL, 0.263 mmol) and phenyl isocyanate (10.4 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). The fractions were concentrated and solidified with CHCl3. The precipitated solids were collected by filtration and washed with CHCl3 to afford desired product (33.5 mg, 55.4%) as cream colored solid. 1HNMR (DMSO-d6) 400 MHz δ: 8.16-8.11 (m, 1H), 8.03-7.99 (m, 1H), 7.54-7.48 (m, 2H), 7.38-7.21 (m, 9H), 7.16-7.05 (m, 4H), 6.95 (d, J=8.2 Hz, 1H), 6.89-6.73 (m, 3H), 6.59 (dd, J=8.0, 4.8 Hz, 1H), 6.29 (s, 1H), 5.19 (s, 1H), 2.61-2.23 (m, 4H), 2.20-2.06 (m, 1H), 1.95-1.80 (m, 1H), 1.49-1.16 (m, 9H).
