反应详情

To a solution of the ester (5 g, 12.16 mmole) of Step G, in dry tetrahydrofuran (66 mL) is added 1N-LiOH (37 mL, 37 mmole) and the mixture is stirred under nitrogen at room temperature for 2.5 hours (TLC, toluene-MeOH 9:1 ). The tetrahydrofuran is evaporated and the residue is diluted with water, acidified (to pH 6.5) with 10% acetic acid and extracted with ethyl acetate (3x). The extracts are washed with brine, dried (MgSO4) and evaporated to dryness. The crude product (4.94 g, pale yellow solid) is recrystallized from ethyl acetate to provide 3.65 g (75%) of the pure title compound (white solid, m.p. 146°-147° C.).

1. customThe tetrahydrofuran is evaporated
2. additionthe residue is diluted with water
3. extractionextracted with ethyl acetate (3x)
4. washThe extracts are washed with brine
5. dry with materialdried (MgSO4)
6. customevaporated to dryness
7. customThe crude product (4.94 g, pale yellow solid) is recrystallized from ethyl acetate