[CH3:1][O:2][CH2:3][O:4][C:5]1[CH:10]=[CH:9][CH:8]=[C:7]([O:11][CH2:12][O:13][CH3:14])[CH:6]=1.[Li]CCCC.CCCCCC.Cl[C:27](=[O:33])[C:28]([O:30][CH2:31][CH3:32])=[O:29]>O1CCCC1>[CH3:14][O:13][CH2:12][O:11][C:7]1[CH:8]=[CH:9][CH:10]=[C:5]([O:4][CH2:3][O:2][CH3:1])[C:6]=1[C:27](=[O:33])[C:28]([O:30][CH2:31][CH3:32])=[O:29]
To a solution of 1,3-bis{[(methyloxy)methyl]oxy}benzene (Reference Intermediate 208, 2.19 g) in dry tetrahydrofuran (10 ml) at room temperature BuLi 1.6M in hexane (8.29 ml, 13.26 mmol) was added and the reaction mixture was stirred for 30 minutes at the same temperature. The mixture was cooled to −78° C. and it was added (via cannulation) to a solution of ethyl chloro(oxo)acetate (2.263 g, 16.57 mmol) in dry tetrahydrofuran (10 ml) at −78° C. The reaction mixture was stirred at −78° C. for 30 minutes. The reaction was quenched with an aqueous saturated solution of ammonium chloride (10 ml) and extracted with ethyl acetate (2×30 ml). Combined organic layers were dried over sodium sulphate, filtered and evaporated. The residue was purified by flash chromatography (Biotage system) on silica gel using a 100 g SNAP column and cyclohexane to cyclohexane/ethyl acetate 8:2 as eluent affording the title compound as a light yellow oil (1.75 g).
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