[CH3:1][O:2][C:3]1([C:13]([F:16])([F:15])[F:14])[CH2:12][CH2:11][C:6]2(OCC[O:7]2)[CH2:5][CH2:4]1.O.C1(C)C=CC(S(O)(=O)=O)=CC=1>CC(C)=O.O>[CH3:1][O:2][C:3]1([C:13]([F:14])([F:15])[F:16])[CH2:4][CH2:5][C:6](=[O:7])[CH2:11][CH2:12]111.80 g (49.12 mmol) of 8-methoxy-8-(trifluoromethyl)-1,4-dioxaspiro[4.5]decane (Example 9A) were dissolved in 236 ml of acetone and 118 ml of water, 1.50 g (7.86 mmol) of 4-toluenesulphonic acid monohydrate were added and the mixture was heated at reflux overnight. The mixture was then poured into 1.2 l of water and the product was extracted with diethyl ether. The organic phase was washed with water, dried over sodium sulphate and concentrated under reduced pressure. The resulting residue was distilled under reduced pressure (boiling point: 106-110° C. at 40 mbar). This gave 6.86 g (71% of theory) of the title compound as a yellowish oil.
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