C[C@@H:2]([C@@H:9]1[C@@]2(C)CC[C@@H]3[C@@]4(C)CC[C@@H](O)C[C@H]4[C@@H](O)C[C@H]3[C@@H]2CC1)[CH2:3][CH2:4][C:5]([O:7][CH3:8])=[O:6].[O:30]1C=[CH:34][CH2:33][CH2:32][CH2:31]1.CO>O1CCOCC1.C1(C)C=CC(S(O)(=O)=O)=CC=1>[O:30]1[CH2:31][CH2:32][CH2:33][CH2:34][CH:8]1[O:7][CH:5]1[CH2:4][CH2:3][CH2:2][CH2:9][O:6]1
To a solution of 100.0 g (0.2557 mole) of methyl hyodeoxycholate and 5.68 g of p-toluenesulfonic acid in 2000 ml of p-dioxane was added 153.7 g (1.62 mole, 148.6 ml) of dihydropyran over a period of 30 min under argon atmosphere. After stirring overnight at room temperature, the pH of the solution was adjusted to approximately pH 8 by the addition of 55 ml of 50/50 methanol/29% ammonium hydroxide. The solution was concentrated to a yellow oil under reduced pressure and the residue stirred in heptane 4 hr, then filtered to remove the precipitated p-toluenesulfonic acid. The filtrate was heated with charcoal, filtered, and evaporated to yield 116.8 g (80%) of the di-tetrahydropyranyl ether as a colorless viscous oil.
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