[OH:1][CH:2]([CH:9]([CH3:13])[CH2:10][CH2:11][CH3:12])[CH:3]([CH3:8])[C:4]([O:6][CH3:7])=[O:5].[O:14]1[CH:19]=[CH:18][CH2:17][CH2:16][CH2:15]1.C(Cl)Cl>O1CCCC1.C1(C)C=CC(S([O-])(=O)=O)=CC=1.[NH+]1C=CC=CC=1>[CH3:8][CH:3]([CH:2]([O:1][CH:15]1[CH2:16][CH2:17][CH2:18][CH2:19][O:14]1)[CH:9]([CH3:13])[CH2:10][CH2:11][CH3:12])[C:4]([O:6][CH3:7])=[O:5]200 mg (1.06 mmol) of methyl (+)-3-hydroxy-2,4-dimethylheptanoate was dissolved in 4 ml of tetrahydrofuran, and 134 mg (1.59 mmol) of dihydropyran and 1 mg of pyridinium p-toluenesulfonate were added, and the mixture was reacted overnight at room temperature. Since TLC showed that the starting materials still remained, 5 mg of pyridinium p-toluenesulfonate and 3 ml of methylene chloride were added, and the reaction was further carried out overnight at room temperature. The reaction mixture was extracted with ether. The ethereal layer was washed with a saturated aqueous solution of sodium hydrogencarbonate and then with an aqueous solution of sodium chloride, and dried over anhydrous sodium sulfate, filtered, and concentrated to give 350 mg of crude methyl (+)-2,4-dimethyl-3-tetrahydropyranyloxy-1heptanoate (6).
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