Experimental Section for Steps 22-23

 

The addition for vinylmagnesium bromide(H2C=CH2MgBr) to ketone 22 was realized in the presence of anhydrous cerium chloride (CeCl3) in tetrahydrofuran (THF) at -78 �C to produce alcohol 23 in 96% yield.

 

A suspension of CeCl3 (0.044 g, 0.18 mmol) in dry THF (0.6 mL) was stirred at 0 �C for 2 h.  Ketone 22 (0.03 g, 0.06 mmol) was dissolved in THF (0.2 mL), cannulated into the CeCl3 suspension and stirred for 15 h at room temperature.  The solution was cooled to -78 �C and vinylmagnesium bromide 0.9 M (0.2 mL, 0.18 mmol) was added dropwise. The reaction was stirred for 30 min at -78 �C.  Saturated NH4Cl (aq) was added.  The aqueous layer was extracted 3 times with dichloromethane (3 � 20 mL).  The organic layer was dried over anhydrous MgSO4 and filtered and the solvent was evaporated using rotary evaporation.  The crude product was purified by flash silica column chromatography (20%  EtOAc/ hexanes) to afford 30 mg of 23 (96% yield) as a colorless oil.