反应详情

A solution of the product of Example 1 Step 1 (48.0 g, 0.2 mol) in tetrahydrofuran (1 L) at −78° C. under argon atmosphere was treated dropwise with n-butyl lithium (138 ml, 1.6M in hexanes, 0.22 mol). After stirring at −78° C. for 30 minutes trimethyl borate (49 ml, 0.44 mol) was added and the solution warmed to room temperature and stirred for 16 hours. The mixture was concentrated in vacuo, acidified to pH1 with 5N hydrochloric acid and stirred at room temperature for 1 hour. The mixture was then basified with 40% sodium hydroxide and the solution washed three times with diethyl ether. The aqueous phase was re-acidified to pH 1 and the mixture was extracted five times with ethyl acetate. The organic extracts were combined washed with brine, dried and evaporated in vacuo. The residue was triturated with hexane, filtered, washed with hexane and then a small amount of ether to afford the title compound (23.6 g, 58%); MS(AP−) m/e 204 [M−H]−.

1. additionwas added
2. concentrationThe mixture was concentrated in vacuo
3. stirringstirred at room temperature for 1 hour
4. washthe solution washed three times with diethyl ether
5. extractionthe mixture was extracted five times with ethyl acetate
6. washThe organic extracts were combined washed with brine
7. customdried
8. customevaporated in vacuo
9. customThe residue was triturated with hexane
10. filtrationfiltered
11. washwashed with hexane