DIEA (d 0.742; 0.0410 mL, 0.235 mmol) was added to a solution of 5-phenyl-4-(piperazin-1-yl)-1H-pyrazolo[3,4-b]pyridine dihydrochloride (0.0311 g, 0.0883 mmol, See Example 1), (S)-2-((S)-1-(tert-butoxycarbonyl)pyrrolidin-2-yl)-2-(4-chlorophenyl)acetic acid (0.020 g, 0.0589 mmol, see Example C) and TBTU (0.0227 g, 0.0706 mmol) in DCM (1 mL) and stirred at room temperature for 1 hour. The mixture was directly loaded onto a silica column and purified by chromatography (hexane:ethyl acetate, 1:1) to give (S)-tert-butyl 2-((S)-1-(4-chlorophenyl)-2-oxo-2-(4-(5-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)piperazin-1-yl)ethyl)pyrrolidine-1-carboxylate as a solid. The solid was then dissolved in DCM (1 mL), and TFA (0.2 mL) was added. The mixture was stirred at room temperature for 1 hour and concentrated to dryness. The resulting residue was dissolved in DCM (0.5 mL), and HCl in ether (1 mL, 2N) was added. The resulting solid was collected by filtration to give (S)-2-(4-chlorophenyl)-1-(4-(5-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl)piperazin-1-yl)-2-((S)-pyrrolidin-2-yl)ethanone dihydrochloride (0.008 g, 24%). MS APCI (+) m/z 501.3 detected.
