COC1C=C(OC)C=CC=1C[N:6]1[C@H:9]([S:10]([C:13]([CH3:16])([CH3:15])[CH3:14])(=[O:12])=[O:11])[C@@H:8]([CH2:17][OH:18])[C:7]1=[O:19].S(OOS([O-])(=O)=O)([O-])(=O)=O.[K+].[K+].P([O-])([O-])(O)=O.[K+].[K+]>C(#N)C>[OH:18][CH2:17][C@@H:8]1[C@@H:9]([S:10]([C:13]([CH3:15])([CH3:14])[CH3:16])(=[O:12])=[O:11])[NH:6][C:7]1=[O:19]A solution of 74 mg (0.2 mmol) of 1-(2,4-dimethoxybenzyl)-3-(S)-hydroxymethyl-4-(R)-tert.butylsulphonyl-2-azetidinone (see Example 20), 486 mg (1.8 mmol) of potassium peroxydisulphate and 174 mg (1.0 mmol) of dipotassium hydrogen phosphate in 4 ml of acetonitrile is stirred for 2 hours at 65° under a reflux condenser, the resulting reaction mixture is freed from acetonitrile under reduced pressure and the aqueous residue is extracted with ethyl acetate. After drying of the organic phase over Na2SO4 and concentration by evaporation in vacuo, a residue is obtained from which the title compound is obtained in the form of colourless crystals by adding a little methylene chloride and ether.
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