[CH3:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]([C:17]2[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=2)(O)[C:9]([O:11]C(C)(C)C)=[O:10])=[CH:4][CH:3]=1.C([SiH](CC)CC)C.FC(F)(F)C(O)=O.C(=O)(O)[O-]>ClCCl.O>[CH3:1][C:2]1[CH:3]=[CH:4][C:5]([CH:8]([C:17]2[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=2)[C:9]([OH:11])=[O:10])=[CH:6][CH:7]=11.49 g (5 mmol) of tert-butyl 2-(4-methyl-phenyl)-2-phenyl-2-hydroxy-acetate are stirred at room temperature in 60 ml of dichloromethane for 3 h with 6.3 ml (40 mmol) of triethylsilane and 12.6 ml (60 mmol) of trifluoroacetic acid. The mixture is diluted with 60 ml of water, adjusted to a pH of 2-3 with saturated aqueous bicarbonate solution and shaken. After removal of the organic phase, the aqueous phase is extracted twice more with dichloromethane. The combined organic phases are dried over sodium sulphate, filtered and concentrated. The product is chromatographed on silica gel 60 using 40-60 petroleum ether/ethyl acetate (6:4).
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