Sodium Hydroxide → [3-Methyl-5-phenyl-1-(pyrazin-2-yl)-1H-pyrazol-4-yl]acetic acid

0.073 g (1.819 mmol) of 2-molar aqueous sodium hydroxide solution was added to 0.165 g (0.455 mmol) of methyl[3-methyl-5-phenyl-1-(pyrazin-2-yl)-1H-pyrazol-4-yl]acetate (see A3) dissolved in 5 ml of methanol, and the mixture was stirred at 20° C. for 1 h. The methanol was removed under reduced pressure and the residue was poured into a mixture of 10 ml of water and 15 ml of dichloromethane. The aqueous phase was extracted with 15 ml of dichloromethane, acidified with concentrated hydrochloric acid (pH=3) and extracted three times with in each case 15 ml of dichloromethane. Drying of the combined organic phases and removal of the solvent under reduced pressure gave 0.080 g (59.7% of theory) of a colorless foamy solid, melting point 125° C.