Water → 7-(2-Oxo-5-(3-oxooct-1-enyl)-3-(2-tetrahydropyranyloxy)cyclopentyl]heptanoic acid

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Reaction Steps

Chromium trioxide (4.0 g.) (dried over phosphorus pentoxide) was added portionwise to a stirred solution of 2-(7-hydroxyheptyl)-3-(3-oxooct-1-enyl)-5-(2-tetrahydropyranyloxy)cyclopentanol [2.12 g.; prepared as described in Example 2(f)] in dry dimethylformamide (30 ml.), while maintaining the temperature at between 5° and 15° C. A solution of concentrated sulphuric acid (1.4 ml.) in dimethylformamide (40 ml.) was then added and the mixture was stirred at between 5° and 15° C. for a further 90 minutes. Diethyl ether was then added, followed by a minimum quantity of water to produce two readily separable layers. The ethereal layer was separated and stirred with an aqueous 2N sodium carbonate solution. This aqueous layer was then separated, washed with diethyl ether, and then treated with a further quantity of diethyl ether and acidified to pH 4 by the dropwise addition of concentrated hydrochloric acid. The resulting ethereal layer was separated, and the remaining aqueous layer was extracted with a further quantity of diethyl ether. These last two ethereal solutions were then combined, dried over magnesium sulphate, and evaporated to dryness, to give crude 7-[2-oxo-5-(3-oxooct-1-enyl)-3-(2-tetrahydropyranyloxy)cyclopentyl]heptanoic acid (1.03 g.), νmax 1720 cm-1, 1700 cm-1, 1670 cm-1, 1625 cm-1 985 cm-1, which was used as starting material in the following preparation (h) of 7-[2-hydroxy-5-(3-hydroxyoct-1-enyl)-3-(2-tetrahydropyranyloxy)cyclopentyl]heptanoic acid, without further purification being necessary.

Provenance & Evidence