Experimental procedure
A solution of triacetate 15 (13 mg, 0.024 mmol) and PhH (4.7 mL, 0.005 M) was prepared, to which 2,6-di-t-butylpyridine (10.7 µL, 0.047 mmol, 2 equiv) and MgBr2•Et2O (6.7 mg, 0.026 mmol, 1.1 equiv, dissolved in 0.26 mL MeCN) were added. This reaction was stirred at 78 °C. The reaction was then cooled to room temperature after 1.5 hours, and filtered through Celite. The extract was then rinsed with two portions of EtOAc (2 x 2 mL). A yellow residue appeared after concentration in vacuo, which was dissolved in butanone and water (1:1, 2.4 mL, 0.01 M). Pyridinium p-toluenesulfonate (PPTS, 20 mg, 0.12 mmol, 5 equiv) was added and the mixture was stirred at 90 °C for 2 hours. The reaction was once again cooled to room temperature and K2CO3 was added. 5 hours later the reaction was concentrated in vacuo and any residue was dissolved in CH2Cl2 (2 mL) and sat. aq. NaCl (1 mL) was added. The aqueous layer was extracted 5 times using CH2Cl2 (5 equiv., 3 mL), and the organics were passed through Na2SO4, and concentrated in vacuo. The residue was purified using preparatory thin layer chromatography, yielding (+)-cortistatinone (8).
|
|
||
|
|||