反应详情

The crude title compound of 53A was dissolved in anhydrous THF (40 ml). To the reaction was added 10 ml of a solution of 2.0 M aqueous hydrochloric acid (HCl) at 0° C. The mixture was stirred at ambient temperature for two hours. The reaction was subsequently concentrated under vacuum to remove the THF. The reaction was then partitioned between ethyl ether and water. The aqueous layer was washed two more times with ethyl ether. The pH of the aqueous layer was then adjusted to 9 with sodium carbonate (Na2CO3) and the solution is extracted with methylene chloride until virtually no product is left in the methylene chloride (CH2Cl2) layer. The CH2Cl2 extracts were combined, dried over MgSO4, filtered and concentrated under vacuum to give the crude product. The crude product was chromatographed on silica gel with MeOH—CHCl3—NH40H (1:99:0.1) as eluents to afford the title compound of 56B as a white foam, 10.78 g (14.7 mmol, 68% yield for two steps).