[O:1]1[CH:6]=[CH:5][CH2:4][CH2:3][CH2:2]1.[Br:7][CH2:8][CH2:9][CH2:10][CH2:11][OH:12]>O.C1(C)C=CC(S(O)(=O)=O)=CC=1.ClCCl>[Br:7][CH2:8][CH2:9][CH2:10][CH2:11][O:12][CH:6]1[CH2:5][CH2:4][CH2:3][CH2:2][O:1]13,4-Dihydro-2H-pyran (8.5 mL, 90.96 mmol) was added dropwise to the dichloromethane (20 mL) solution of 1 (10.7 g, 69.93 mmol) and p-toluenesulfonic acid monohydrate (26.5 mg, 0.1372 mmol). The mixture was stirred at room temperature over night. After removing the solvent, the residue was purified by flash chromatography on silica gel with 5:1 hexanes/ethyl acetate as the eluent to yield product 2 as a colorless oil (15.3 g, 92%). 1H NMR (400 MHz, CDCl3): δ 1.48-1.62 (m, 4H), 1.68-1.85 (m, 4H), 1.94-2.02 (m, 2H), 3.40-3.53 (m, 4H), 3.74-3.88 (m, 2H), 4.57-4.59 (m, 1H).
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