Under Ar, to a soln of the product of Example 242, 3-[8-(2,6-difluoro-phenyl)-4-(4-fluoro-2-methyl-phenyl)-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino]-N-hydroxy-propionamidine (100 mg, 0.20 mmol), and pyridine (0.048 mL, 0.6 mmol), was added 2-ethylhexyl chloroformate (0.039 mL, 0.2 mmol). The mixture was stirred at room temperature for 2 h, then diluted with H2O and extracted with EtOAc. The organic layer was dried over sodium sulfate, filtered and concentrated. The resulting residue was diluted with xylene (10 mL) and heated to reflux for 18 h to give the crude material, which was purified by preparative hplc to give the desired product 28 mg (28%). LC-MS: 495.0 (MH+, m/z), 1.96 (Rt, min).
