Sodium Hydroxide → (E)-3-(3-Methyl-4-oxo-1-n-propyl-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-6-yl)-4-n-propoxycinnamic acid

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Reaction Steps

2N Aqueous sodium hydroxide solution (8.0 ml, 0.016 mol) was added to a solution of (E)-3-(3-methyl-4-oxo-1-n-propyl-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-6-yl)-4-n-propoxycinnamic acid t-butyl ester (Example 12; 1.8 g, 0.004 mol) in methanol (8 ml) and the mixture heated under reflux for 5 hours. The methanol was removed by evaporation under vacuum and the aqueous solution acidified to pH 1 with 2N hydrochloric acid. Exhaustive extraction of the product with 10% methanol in ethyl acetate was followed by drying of the combined extracts (Na2SO4) and evaporation of solvents under vacuum to furnish an off-white solid. Crystallisation from ethyl acetate-methanol afforded the title compound as white crystals (0.18 g, 12%), m.p. 231-232° C. Found: C, 63.52; H, 5.96; N, 14.00. C21H24N4O4 requires C, 63.62; H, 6.10; N, 14.13%.

Provenance & Evidence