A solution of (3R,4R)-4-(2-hydroxyethyl)-3-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-azetidin-2-one (50 mg) in acetone (3 ml) was added to a solution of 2N Jones reagent (0.284 ml) in acetone (3 ml) at ambient temperature over a period of 30 minutes and the mixture was stirred for 30 minutes. After addition of an excess of isopropyl alcohol to the mixture, the solvent was evaporated off. The residue was dissolved in chloroform and washed with water. The aqueous layer was extracted twice with chloroform. The organic layers were combined, washed with brine, dried over magnesium sulfate and evaporated in vacuo. The residue was dissolved in chloroform (5 ml) and the solution was extracted with 0.1N aqueous solution of sodium bicarbonate (2 ml), 0.05N aqueous solution of sodium bicarbonate (2 ml) and water. The aqueous extracts were combined, acidified with 1N hydrochloric acid and extracted three times with chloroform. The combined chloroform extracts were washed with brine, dried over magnesium sulfate and evaporated to give {(2R,3R)-3-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)-ethyl]-4-oxoazetidin-2-yl}acetic acid (56 mg).
