To a solution of 36 mg (0.082 mmol) of 6-(4-benzyl-phenyl)-7-cyclohexyl-pyrazolo[1,5-a]pyrimidine-3-carboxylic acid ethyl ester in 3 mL of tetrahydrofuran was added 0.5 mL (0.5 mmol) of 1 M LiOH solution, and the resulting mixture was heated at reflux overnight. The reaction mixture was then acidified with 1 M HCl solution to pH=2, and extracted with ethyl acetate. The combined organic extracts were dried over sodium sulfate, and concentrated to give a residue which was purified via reverse-phase chromatography to afford (after lyophilization) 7 mg (21% yield) of 6-(4-benzyl-phenyl)-7-cyclohexyl-pyrazolo[1,5-a]pyrimidine-3-carboxylic acid as a solid (90% purity, entry 444) as indicated by 1H NMR; LC-MS—calcd for C26H25N3O2 [M++H]+: 412.19, found: 412.3.
