The title compound of Example 4, 1′-biphenyl-4-yl-1-[(3-methylpyridin-2-yl)methyl]-2′-oxo-1′,2′-dihydrospiro[piperidine-4,3′-pyrrolo[2,3-b]pyridine]-5′-carbonitrile, (1 mmol) was combined with anhydrous ethanol (10 mL) and neat sulfuric acid (1 mL) was added drop wise to the solution over 2 minutes. The resulting mixture is heated in a sealed tube to 100° C., allowed to cool to room temperature and combined with ice water. The resulting mixture was extracted with methylene chloride, dried and concentrated. The crude oil is combined with THF (10 mL), water (5 mL) and lithium hydroxide (20 mmol) and heated to 50° C. for 5 h, acidified with 1 m HCl, concentrated and purified by preparative reverse phase HPLC (method C), which provided the title compound, isolated as a salt of trifluoroacetic acid.
