[C:1](=O)([O-])[O-].[K+].[K+].[CH3:7][O:8][C:9]1[CH:10]=[C:11]2[C:19](=[CH:20][CH:21]=1)[NH:18][C:17]1[CH2:16][CH2:15][CH2:14][C:13](=[O:22])[C:12]2=1.S(OC)(OC)(=O)=O.O>CC(C)=O>[CH3:7][O:8][C:9]1[CH:10]=[C:11]2[C:19](=[CH:20][CH:21]=1)[N:18]([CH3:1])[C:17]1[CH2:16][CH2:15][CH2:14][C:13](=[O:22])[C:12]2=1Anhydrous potassium carbonate (2.24 g) was added to a solution of the product of Stage (i) (3 g) in acetone (30 ml) at room temperature and stirred for 30 min. Dimethyl sulphate (1.6 ml) was added and the mixture was heated to reflux for 4 h. The resulting solution was poured into water (150 ml) and the resulting precipitate filtered off to give the title compound as a solid (2.5 g), m.p. 150°-151°.
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