[OH:1][C:2]1[C:3]([CH3:14])=[C:4]([CH3:13])[C:5]2[O:9][C:8](=O)[S:7][C:6]=2[C:11]=1[CH3:12].[CH:15]([O:17][CH2:18][CH3:19])=[CH2:16].C(Br)Br.C(=O)(O)[O-].[Na+]>CCCCCCCC[N+](CCCCCCCC)(CCCCCCCC)C.[Cl-].CS(O)(=O)=O.O>[CH2:15]([O:17][CH:18]([O:1][C:2]1[C:3]([CH3:14])=[C:4]([CH3:13])[C:5]2[O:9][CH2:8][S:7][C:6]=2[C:11]=1[CH3:12])[CH3:19])[CH3:16]
A mixture of 7.35 g of 5-hydroxy-4,6,7-trimethyl-1,3-benzoxathiole-2-one, 20 ml of ethyl vinyl ether and 20 ml of methylene dibromide was cooled down to -20° C. under a stream of nitrogen, and then 20 mg of methanesulfonic acid were added dropwise, while stirring. After completion of the dropwise addition, the reaction temperature was gradually raised to room temperature, and the mixture was stirred for 3 hours at room temperature. To this reaction mixture were added 30 ml of water, 8.8 g of sodium bicarbonate and 1.0 g of Aliquat 336 (a trade mark for methyltrioctylammonium chloride), and the mixture was heated under reflux for 9 hours, which caused the excess methylene dibromide to vaporize gradually and leave a crude oil. This crude oil was extracted with diethyl ether, and the extract was dried over anhydrous sodium sulfate. The ether was then distilled off, to yield 12 g of an oily substance, which was purified by silica gel column chromatography. From the portion which could be eluted with a 20:1 by volume mixture of petroleum ether and diethyl ether were obtained 5.2 g of the title compound melting at 52°-54° C.
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