Water → 2-[1-(2-Fluorobenzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]-6-methyl-7,9-dihydro-8H-purin-8-one

Under an argon atmosphere, 245 mg (0.60 mmol) of the compound from example 69A were initially charged in tetrahydrofuran (2.6 ml) and cooled to 0° C., and 0.90 ml (0.90 mmol) of bis(trimethylsilyl)sodium amide (1.0 M in tetrahydrofuran) was added dropwise. The mixture was stirred at 0° C. for 1 h and then at RT overnight. Subsequently, the mixture was stirred at 60° C. for 8 h. Thereafter, water was added and the reaction mixture was concentrated. The residue was extracted twice with ethyl acetate, and the collected organic phases were washed with water and saturated aqueous sodium chloride solution, dried over magnesium sulfate, filtered and concentrated. This gave 110 mg (85% purity, 41% of theory) of the title compound in solid form. A solid likewise precipitated out of the aqueous phase, which was filtered off, washed with water and dried under high vacuum. This gave a further 100 mg (44% of theory) of the title compound.