Dichloromethane → Tetrahydropyranyl ether

6.5 g (49.2 mmol) of methyl ester of (2S,3S)-3-hydroxy-2-methylbutyric acid was dissolved in 20 ml of CHCl3. Thereto were added 9.2 g (0.109 mol) of 3,4-dihydro-α-pyran and 60 mg of p-TsOH.H2O. The mixture was stirred for 2 days at room temperature. After the completion of the reaction, the reaction mixture was mixed with 20 ml of CH2Cl2. The resulting mixture was washed with an aqueous NaHCO3 solution. The organic layer was dried over Na2SO4 and then concentrated under reduced pressure. The residue was subjected to Kugel-rohr distillation to obtain 8.64 g (yield: 81.2%) of a corresponding tetrahydropyranyl ether. 6.91 g of the compound was dissolved in 100 ml of ether, and the solution was added by small portions to a suspension containing 2.28 g (60 mmol) of lithium aluminum hydride, with ice cooling. The reaction mixture was stirred for about 1 hour at 5° C. or below. Thereto was added by small portions 60 ml of water while stirring with ice-cooling, to decompose excess lithium aluminum hydride. The ether layer was collected by decantation, dried and concentrated under reduced pressure to obtain 5.59 g (yield: 98% ) of crude (2R,3S)-2-methyl-3-tetrahydropyranyloxy-1-butanol as an oily material.