Hydrochloric Acid → 7-[2,3-Dihydroxy-5-(3-hydroxyoct-1-enyl)cyclopentyl]heptanoic acid

A mixture of 7-[2-hydroxy-5-(3-hydroxyoct-1-enyl)-3-(2-tetrahydropyranyloxy)cyclopentyl]heptanoic acid [0.34 g.; prepared as described above in Example 2(h)], ethanol (10 ml.), N aqueous hydrochloric acid (10 ml.) and a cation exchange resin [Dowex resin AG50W-X 8H+ (1.0 g.)] was stirred at 60°-62° C. for 8 hours. The mixture was filtered and the solid was washed with ethanol. The combined filtrate and washings were concentrated in vacuo to remove most of the ethanol, and the residue was extracted twice with diethyl ether. The combined ethereal extracts were extracted with 2N aqueous sodium carbonate solution, and the aqueous extract was acidified to pH 1 by the addition of concentrated hydrochloric acid. The resulting aqueous mixture was extracted with diethyl ether and the ethereal extract was dried over magnesium sulphate and evaporated to dryness. The residue (0.13 g.) was subjected to preparative thin-layer chromotagraphy on silica gel, using a mixture of ethyl acetate, cyclohexane and formic acid (40:40:1 by volume) as the eluent, to give 7-[2,3-dihydroxy-5-(3-hydroxyoct-1-enyl)cyclopentyl]heptanoic acid (0.01 g.), νmax 1700 cm-1, 980 cm-1.