7-Acetoxybicyclo[4,3,0]nonan-3-one → 6-Acetoxy-2-carboxybicyclo[3,3,0]octane

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Reaction Steps

Thallic nitrate trihydrate (133 g) was added to a stirred solution of 7-acetoxybicyclo[4,3,0]nonan-3-one (57 g; prepared as described in Reference Example 4) in glacial acetic acid (290 ml). After 30 minutes the resulting solid was filtered off and the filtrate was heated at reflux for 30 minutes. The acetic acid was distilled off under reduced pressure and the residue was neutralised by treatment with aqueous sodium hydroxide solution to pH 5 and then with aqueous sodium bicarbonate solution to neutral. The resulting solution was washed with diethyl ether, and then it was acidified by treatment with concentrated hydrochloric acid and extracted with chloroform. The combined chloroform extracts were washed with saturated aqueous sodium chloride solution, then dried over magnesium sulphate, and concentrated under reduced pressure. The residue was purified by medium pressure, short column chromatography on silica gel, eluting with a mixture of ethyl acetate, hexane, and acetic acid (45:55:1 by volume), to give 6-acetoxy-2-carboxybicyclo[3,3,0]octane (7.55 g), predominantly in the 2β-configuration.

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