CS(O)(=O)=O.[C:6]([C:10]1[C:15]2[CH2:16][CH:17]([CH2:19][CH2:20][CH2:21][CH2:22][CH2:23][CH2:24][CH2:25][CH3:26])[O:18][C:14]=2[CH:13]=[CH:12][C:11]=1[OH:27])([CH3:9])([CH3:8])[CH3:7]>C(O)(C)(C)C.C(Cl)(Cl)Cl>[C:6]([C:10]1[C:15]2[CH2:16][CH:17]([CH2:19][CH2:20][CH2:21][CH2:22][CH2:23][CH2:24][CH2:25][CH3:26])[O:18][C:14]=2[C:13]([C:6]([CH3:9])([CH3:8])[CH3:7])=[CH:12][C:11]=1[OH:27])([CH3:9])([CH3:8])[CH3:7]Under ice-cooling, 1.5 ml of methanesulfonic acid was added dropwise to a solution of 0.51 g of 4-t-butyl-5-hydroxy-2-n-octyl-2,3-dihydrobenzofuran in 0.85 g of t-butyl alcohol and 2 ml of chloroform. After stirring at 0° C. for 15 minutes, the mixture was poured into ice water and extracted with ethyl acetate. The extracted layers were washed with a saturated aqueous sodium bicarbonate solution, dried over anhydrous magnesium sulfate and then concentrated. The concentrate was purified by silica gel column chromatography (in n-hexane) to give 0.35 g of 4,7-di-t-butyl-5-hydroxy-2-n-octyl-2,3-dihydrobenzofuran as a pale yellow oil (yield 58%).
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