Potassium Hydroxide → (1R,2S)-2-methoxycarbonylcyclopropane-1-carboxylic acid

To 150 ml of a methanol solution of 14.68 g (92.8 mmol) of dimethyl cis-1,2-cyclopropanedicarboxylate was added 67 ml of an aqueous solution of 7.52 g (113.9 mmol) of potassium hydroxide under cooling with ice, and the mixture was stirred at room temperature for 24 hours. After completion of the reaction, the solvent was removed by evaporation under reduced pressure, and to the residue was added water. The reaction mixture was washed with diethyl ether. The aqueous layer was adjusted to pH 2 with concentrated hydrochloric acid and extracted with ethyl acetate. The organic layer was dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to give 12.38 g (92.5%) of the title compound as a colorless oily substance.