[CH3:1][O:2][C:3]1([C:9]#[C:10][CH2:11][OH:12])[CH2:8][CH2:7][O:6][CH2:5][CH2:4]1.COCCO[AlH2-]OCCOC.[Na+]>C1COCC1>[CH3:1][O:2][C:3]1(/[CH:9]=[CH:10]/[CH2:11][OH:12])[CH2:8][CH2:7][O:6][CH2:5][CH2:4]1A solution of 4-methoxy-4-(3-hydroxyprop-1-ynyl)tetrahydropyran (10.8 g, 44.9 mmol), prepared as in step 3, in dry THF (100 mL) was cooled to -75° C., and RED-AL (sodium bis(2-methoxyethoxy)aluminum hydride, Aldrich Chemical Co., 20 mL of 3.4M solution in toluene, 68 mmol) was added under a dry argon atmosphere. The cooling bath was removed and the reaction was warmed to 0° C. and quenched by addition of crushed ice and saturated aqueous NH4Cl. The resulting two-phase mixture was extracted with ethyl acetate (4×90 mL). The combined organic layers were dried over MgSO4, filtered, and concentrated in vacuo. Purification by chromatography on silica gel (100 g, 10% ethyl acetate: hexanes) provided 4-methoxy-4-(3-hydroxy -trans-prop-1-enyl)tetrahydropyran(3.71 g, 34 %) as a colorless oil.
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