[C:1]([O:6][CH2:7][CH2:8][S:9][CH2:10][C:11]([O:13]C(C)(C)C)=[O:12])(=[O:5])[C:2]([CH3:4])=[CH2:3].COC1C=CC(O)=CC=1.C(Cl)(Cl)Cl.CO.CC(O)=O>FC(F)(F)C(O)=O>[C:1]([O:6][CH2:7][CH2:8][S:9][CH2:10][C:11]([OH:13])=[O:12])(=[O:5])[C:2]([CH3:4])=[CH2:3]3 (2 g, 7.7 mmol, 1 eqv.) was slowly dissolved in trifluoroacetic acid (TFA) (10 mL) on ice under nitrogen. A trace amount of hydroquinone monomethyl ether (MEHQ) was added to the reaction mixture to prevent polymerisation. The reaction mixture was allowed to warm to room temperature and the reaction mixture was stirred for 2 hours at 55 C. Completion of the reaction was monitored by TLC(CHCl3/MeOH/HOAc, 9:1:0.1 (v/v), Rf: 0.17). Excess of TFA was removed by evaporation and coevaporation with CH2Cl2 and the residue was purified on a silica gel column (Hex/EtOAc, 4:1 (v/v)). Pure 4 was dried with MgSO4 and filtered through Ø 185 mm whatman filter papers. The filtrate was concentrated in vacuo. 1 g (63% yield) 4 was obtained as a light yellow oil.
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