[CH:1]([N-]C(C)C)(C)C.[Li+].O1CCC[CH2:11][CH:10]1[CH2:15][C:16]([O:18][CH2:19][CH3:20])=[O:17].BrC(Br)C.[O:25]1[CH2:29][CH2:28][CH2:27][CH2:26]1>>[O:25]1[CH2:29][CH2:28][CH:27]([C:15]2([C:16]([O:18][CH2:19][CH3:20])=[O:17])[CH2:10][CH2:11]2)[CH2:26][CH2:1]16.83 mmol of lithium diisopropylamide (2M in tetrahydrofuran) are added dropwise to a solution of 5.69 mmol of ethyl tetrahydropyranylacetate [103260-44-2] in 10 ml of tetrahydrofuran at −78° C. The mixture is stirred at −78° C. for 15 minutes and 7.39 mmol of dibromoethane are added. The reaction mixture is warmed to 0° C. over 15 minutes and then cooled again to −78° C. 6.83 mmol of lithium diisopropylamide (2M in tetrahydrofuran) are again added dropwise to the reaction mixture. It is warmed to room temperature over 2 hours and quenched with 1M HCl. The phases are separated and the aqueous phase is extracted with tert-butyl methyl ether (2×). The combined organic phases are washed with brine, dried with sodium sulphate and evaporated. The title compound is identified by means of the Rf from the residue by flash chromatography (SiO2 60 F).
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