[C:1]([CH2:4][CH2:5][CH2:6][CH2:7][CH:8]1[CH2:12][CH2:11][CH2:10][C:9]1=[O:13])([OH:3])=[O:2].O.[C:15]1(C)C=CC(S(O)(=O)=O)=C[CH:16]=1>C(O)C>[C:1]([CH2:4][CH2:5][CH2:6][CH2:7][CH:8]1[CH2:12][CH2:11][CH2:10][C:9]1=[O:13])([O:3][CH2:15][CH3:16])=[O:2]A stirred solution of 124 g. (0.673 mole) of 2-(4-carboxybutyl)cyclopentan-1-one (Example 2), 800 ml. of ethanol and 1 g. of p-toluenesulfonic acid monohydrate is heated at reflux for 18 hours. The solvent is evaporated and the residue is dissolved in ether. The ether solution is washed with saline, dilute sodium bicarbonate solution and again with saline, dried over magnesium sulfate and evaporated. The oil is distilled under reduced pressure to give 149 g. of a colorless oil, b.p. 106°-109° C. (0.23 mm).
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