[C:1]([O:5][C:6]([CH2:8][CH2:9][C:10]1([C:17]([O:19]CC)=[O:18])[CH2:15][CH2:14][CH2:13][CH2:12]C1=O)=[O:7])([CH3:4])([CH3:3])[CH3:2].C(=O)([O-])O.[Na+].OO>C(O)(C)(C)C>[C:1]([O:5][C:6]([CH2:8][CH2:9][C:10]1([C:17]([OH:19])=[O:18])[CH2:15][CH2:14][CH2:13][CH2:12]1)=[O:7])([CH3:2])([CH3:3])[CH3:4]To a suspension of 2-[2-(tert-butoxycarbonyl)ethyl]-2-ethoxycarbonylcyclohexanone (see Preparation 10) (1.0 g, 3.35 mmol) and sodium hydrogen carbonate (0.281 g, 3.35 mmol) in tert-butanol (2.0 ml) was added, in four portions over a period of 1.5 hours, a 30% aqueous solution of hydrogen peroxide (4×0.11 ml, 4.0 mmol) at 40° C. The mixture was stirred at 40° C. for 20 hours. A fifth charge of a 30% aqueous solution of hydrogen peroxide (0.11 ml) and a further quantity of sodium hydrogen carbonate (0.281 g, 33.5 mmol) was added, and the mixture stirred at 40° C. for 8 hours. The mixture was partitioned between hexane (40 ml) and 5% aqueous sodium sulphite solution (25 ml) and the layers separated. The hexane layer was washed with dilute aqueous ammonia solution (25 ml of 0.880 ammonia in 200 ml of distilled water, 5×40 ml). The combined aqueous extracts were acidified to pH 2-3 with 5.ON aqueous hydrochloric acid solution and extracted with dichloromethane (3×25 ml). The combined dichloromethane extracts were washed with distilled water (25 ml), dried over magnesium sulphate, filtered and concentrated under reduced pressure to give the title compound as an oil, (0.362 g, 44.6%). Rf. 0.29 (silica, hexane/ethyl acetate 2:1). Analysis %: Found: C, 64.78; H, 9.39; C1H22O4 requires: C, 64.44; H, 9.15.
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