C[O:2][C:3](=[O:16])[CH2:4][N:5]1[CH:8]([S:9][CH2:10][CH:11]=[CH2:12])[CH:7]([CH2:13][CH3:14])[C:6]1=[O:15].[OH-].[K+].Cl.C(=O)(O)[O-].[Na+].C(=O)(O)[O-]>C(O)C.O.ClCCl>[CH2:10]([S:9][CH:8]1[N:5]([CH2:4][C:3]([OH:16])=[O:2])[C:6](=[O:15])[CH:7]1[CH2:13][CH3:14])[CH:11]=[CH2:12]To a solution of 3 g of Methyl-(4-allylthio-3-ethylazetidin-2-on-1-yl)acetate in 10 ml of absolute ethanol was added, at room temperature and dropwise over 5 minutes, a solution of 0.90 g of potassium hydroxide in a mixture of 12 ml of ethanol and 1 ml of water. The resulting solution was then poured into 10 ml of dichloromethane, 13 ml of 2M hydrochloric acid and 20 ml of water were added, and the organic phase was separated. The aqueous phase was extracted twice with dichloromethane, and then the combined dichlormethane extracts were re-extracted with aqueous sodium bicarbonate (2.7 mol equivalents in 27 ml) and then discarded. The aqueous bicarbonate layer was then layered with dichloromethane and acidified to pH 1.5 with hydrochloric acid. The aqueous layer was then further extracted with dichloromethane. The combined organic layer was dried over magnesium sulphate and evaporated in vacuo to give the title compound as a colorless crystalline solid. (Yield 2.56 g)
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