A mixture of 4-{(3S,5R)-3-[(tert-butoxycarbonyl)amino]-5-methylpiperidin-1-yl}-3-({[6-(2,6-difluoro-3-methoxyphenyl)-5-fluoropyridin-2-yl]carbonyl}amino)-6,7-dihydro-5H-cyclopenta[b]pyridin-7-yl acetate (8.0 mg, 0.012 mmol), MeOH (140 μL), THF (71 μL) and 1.0 M aq. NaOH (78 μL, 0.078 mmol) was stirred at room temperature for 20 min. The organic solvents were removed under vacuum and dried to give the crude intermediate, which was dissolved in DCM (0.1 mL), followed by the addition of TFA (0.12 mL, 1.6 mmol). The reaction mixture was stirred at room temperature for 20 min. The solution was then concentrated under reduced pressure and the residue was diluted with MeOH, filtered and purified by preparative LC-MS (XBridge™ preparative C18 5 μm OBD™ column, 30×10 mm, 60 mL/min., eluting with a gradient of MeCN and water with 0.1% NH4OH) to give both diastereoisomers of the title compound as white powders. On analytical HPLC (Waters SunFire™ C18, 2.1×50 mm, 5 μm; flow rate 3 mL/min.; injection volume 2 μL; gradient from 2 to 80% B in 3 minutes (A=water with 0.025% TFA, B=MeCN)) the diastereoisomers had the following properties:
