A mixture of methyl 8-methylsulfonyl-8-methoxycarbonyl-12-acetoxy-13-(3-trifluoromethylphenoxy)tridecanoate (5.82 g., 0.01 mole), sodium chloride (0.59 g., 0.01 mole), dimethylsulfoxide (8 ml.), and water (0.2 ml.) is heated in an oil bath at 185° C. for 10 hours under nitrogen. The reaction mixture is then concentrated in vacuo on a steam bath. The dark-colored residue is diluted with water, acidified with 6N hydrochloric acid, and extracted with ether. The ether extracts are washed with water, dried with anhydrous magnesium sulfate, and concentrated in vacuo to give the title compound (9.90 g., 0.019 mole, 94%).
